first pass at a new VP3 video decoder

Originally committed as revision 1831 to svn://svn.ffmpeg.org/ffmpeg/trunk

1 files changed, 2325 insertions, 0 deletions

diff --git a/libavcodec/vp3.c b/libavcodec/vp3.c
new file mode 100644
index 0000000000..a1ada883ca
--- /dev/null
+++ b/libavcodec/vp3.c
@@ -0,0 +1,2325 @@
+/*
+ *
+ * Copyright (C) 2003 the ffmpeg project
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+ *
+ * VP3 Video Decoder by Mike Melanson (melanson@pcisys.net)
+ *
+ */
+
+/**
+ * @file vp3.c
+ * On2 VP3 Video Decoder
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+
+#include "common.h"
+#include "avcodec.h"
+#include "dsputil.h"
+#include "mpegvideo.h"
+#include "dsputil.h"
+#include "bswap.h"
+
+#include "vp3data.h"
+
+#define FRAGMENT_PIXELS 8
+
+/* 
+ * Debugging Variables
+ * 
+ * Define one or more of the following compile-time variables to 1 to obtain
+ * elaborate information about certain aspects of the decoding process.
+ *
+ * DEBUG_VP3: high-level decoding flow
+ * DEBUG_INIT: initialization parameters
+ * DEBUG_DEQUANTIZERS: display how the dequanization tables are built
+ * DEBUG_BLOCK_CODING: unpacking the superblock/macroblock/fragment coding
+ * DEBUG_MODES: unpacking the coding modes for individual fragments
+ * DEBUG_VECTORS: display the motion vectors
+ * DEBUG_TOKEN: display exhaustive information about each DCT token
+ * DEBUG_VLC: display the VLCs as they are extracted from the stream
+ * DEBUG_DC_PRED: display the process of reversing DC prediction
+ * DEBUG_IDCT: show every detail of the IDCT process
+ */
+
+#define DEBUG_VP3 0
+#define DEBUG_INIT 0
+#define DEBUG_DEQUANTIZERS 0
+#define DEBUG_BLOCK_CODING 0
+#define DEBUG_MODES 0
+#define DEBUG_VECTORS 0
+#define DEBUG_TOKEN 0
+#define DEBUG_VLC 0
+#define DEBUG_DC_PRED 0
+#define DEBUG_IDCT 0
+
+#if DEBUG_VP3
+#define debug_vp3 printf
+#else
+static inline void debug_vp3(const char *format, ...) { }
+#endif
+
+#if DEBUG_INIT
+#define debug_init printf
+#else
+static inline void debug_init(const char *format, ...) { }
+#endif
+
+#if DEBUG_DEQUANTIZERS
+#define debug_dequantizers printf 
+#else
+static inline void debug_dequantizers(const char *format, ...) { } 
+#endif
+
+#if DEBUG_BLOCK_CODING
+#define debug_block_coding printf 
+#else
+static inline void debug_block_coding(const char *format, ...) { } 
+#endif
+
+#if DEBUG_MODES
+#define debug_modes printf 
+#else
+static inline void debug_modes(const char *format, ...) { } 
+#endif
+
+#if DEBUG_VECTORS
+#define debug_vectors printf 
+#else
+static inline void debug_vectors(const char *format, ...) { } 
+#endif
+
+#if DEBUG_TOKEN 
+#define debug_token printf 
+#else
+static inline void debug_token(const char *format, ...) { } 
+#endif
+
+#if DEBUG_VLC
+#define debug_vlc printf 
+#else
+static inline void debug_vlc(const char *format, ...) { } 
+#endif
+
+#if DEBUG_DC_PRED
+#define debug_dc_pred printf 
+#else
+static inline void debug_dc_pred(const char *format, ...) { } 
+#endif
+
+#if DEBUG_IDCT
+#define debug_idct printf 
+#else
+static inline void debug_idct(const char *format, ...) { } 
+#endif
+
+typedef struct Vp3Fragment {
+    DCTELEM coeffs[64];
+    int coding_method;
+    int coeff_count;
+    int last_coeff;
+    int motion_x;
+    int motion_y;
+    /* address of first pixel taking into account which plane the fragment
+     * lives on as well as the plane stride */
+    int first_pixel;
+    /* this is the macroblock that the fragment belongs to */
+    int macroblock;
+} Vp3Fragment;
+
+#define SB_NOT_CODED        0
+#define SB_PARTIALLY_CODED  1
+#define SB_FULLY_CODED      2
+
+#define MODE_INTER_NO_MV      0
+#define MODE_INTRA            1
+#define MODE_INTER_PLUS_MV    2
+#define MODE_INTER_LAST_MV    3
+#define MODE_INTER_PRIOR_LAST 4
+#define MODE_USING_GOLDEN     5
+#define MODE_GOLDEN_MV        6
+#define MODE_INTER_FOURMV     7
+#define CODING_MODE_COUNT     8
+
+/* special internal mode */
+#define MODE_COPY             8
+
+/* There are 6 preset schemes, plus a free-form scheme */
+static int ModeAlphabet[7][CODING_MODE_COUNT] =
+{
+    /* this is the custom scheme */
+    { 0, 0, 0, 0, 0, 0, 0, 0 },
+
+    /* scheme 1: Last motion vector dominates */
+    {    MODE_INTER_LAST_MV,    MODE_INTER_PRIOR_LAST,  
+         MODE_INTER_PLUS_MV,    MODE_INTER_NO_MV,
+         MODE_INTRA,            MODE_USING_GOLDEN,      
+         MODE_GOLDEN_MV,        MODE_INTER_FOURMV },
+
+    /* scheme 2 */
+    {    MODE_INTER_LAST_MV,    MODE_INTER_PRIOR_LAST,  
+         MODE_INTER_NO_MV,      MODE_INTER_PLUS_MV,
+         MODE_INTRA,            MODE_USING_GOLDEN,      
+         MODE_GOLDEN_MV,        MODE_INTER_FOURMV },
+
+    /* scheme 3 */
+    {    MODE_INTER_LAST_MV,    MODE_INTER_PLUS_MV,     
+         MODE_INTER_PRIOR_LAST, MODE_INTER_NO_MV,
+         MODE_INTRA,            MODE_USING_GOLDEN,      
+         MODE_GOLDEN_MV,        MODE_INTER_FOURMV },
+
+    /* scheme 4 */
+    {    MODE_INTER_LAST_MV,    MODE_INTER_PLUS_MV,     
+         MODE_INTER_NO_MV,      MODE_INTER_PRIOR_LAST,
+         MODE_INTRA,            MODE_USING_GOLDEN,      
+         MODE_GOLDEN_MV,        MODE_INTER_FOURMV },
+
+    /* scheme 5: No motion vector dominates */
+    {    MODE_INTER_NO_MV,      MODE_INTER_LAST_MV,     
+         MODE_INTER_PRIOR_LAST, MODE_INTER_PLUS_MV,
+         MODE_INTRA,            MODE_USING_GOLDEN,      
+         MODE_GOLDEN_MV,        MODE_INTER_FOURMV },
+
+    /* scheme 6 */
+    {    MODE_INTER_NO_MV,      MODE_USING_GOLDEN,      
+         MODE_INTER_LAST_MV,    MODE_INTER_PRIOR_LAST,
+         MODE_INTER_PLUS_MV,    MODE_INTRA,             
+         MODE_GOLDEN_MV,        MODE_INTER_FOURMV },
+
+};
+
+#define MIN_DEQUANT_VAL 2
+
+typedef struct Vp3DecodeContext {
+    AVCodecContext *avctx;
+    int width, height;
+    unsigned char *current_picture[3]; /* picture structure */
+    int linesize[3];
+    AVFrame golden_frame;
+    AVFrame last_frame;
+    AVFrame current_frame;
+    int keyframe;
+    DSPContext dsp;
+
+    int quality_index;
+    int last_quality_index;
+
+    int superblock_count;
+    int superblock_width;
+    int superblock_height;
+    int u_superblock_start;
+    int v_superblock_start;
+    unsigned char *superblock_coding;
+
+    int macroblock_count;
+    int macroblock_width;
+    int macroblock_height;
+
+    int fragment_count;
+    int fragment_width;
+    int fragment_height;
+
+    Vp3Fragment *all_fragments;
+    int u_fragment_start;
+    int v_fragment_start;
+
+    /* this is a list of indices into the all_fragments array indicating
+     * which of the fragments are coded */
+    int *coded_fragment_list;
+    int coded_fragment_list_index;
+    int pixel_addresses_inited;
+
+    VLC dc_vlc[16];
+    VLC ac_vlc_1[16];
+    VLC ac_vlc_2[16];
+    VLC ac_vlc_3[16];
+    VLC ac_vlc_4[16];
+
+    int16_t intra_y_dequant[64];
+    int16_t intra_c_dequant[64];
+    int16_t inter_dequant[64];
+
+    /* This table contains superblock_count * 16 entries. Each set of 16
+     * numbers corresponds to the fragment indices 0..15 of the superblock.
+     * An entry will be -1 to indicate that no entry corresponds to that
+     * index. */
+    int *superblock_fragments;
+
+    /* This table contains superblock_count * 4 entries. Each set of 4
+     * numbers corresponds to the macroblock indices 0..3 of the superblock.
+     * An entry will be -1 to indicate that no entry corresponds to that
+     * index. */
+    int *superblock_macroblocks;
+
+    /* This table contains macroblock_count * 6 entries. Each set of 6
+     * numbers corresponds to the fragment indices 0..5 which comprise
+     * the macroblock (4 Y fragments and 2 C fragments). */
+    int *macroblock_fragments;
+    /* This is an array of flags indicating whether a particular 
+     * macroblock is coded. */
+    unsigned char *macroblock_coded;
+
+} Vp3DecodeContext;
+
+/************************************************************************
+ * VP3 specific functions
+ ************************************************************************/
+
+/*
+ * This function sets up all of the various blocks mappings:
+ * superblocks <-> fragments, macroblocks <-> fragments,
+ * superblocks <-> macroblocks
+ */
+static void init_block_mapping(Vp3DecodeContext *s) 
+{
+    int i, j;
+    signed int hilbert_walk_y[16];
+    signed int hilbert_walk_c[16];
+    signed int hilbert_walk_mb[4];
+
+    int current_fragment = 0;
+    int current_width = 0;
+    int current_height = 0;
+    int right_edge = 0;
+    int bottom_edge = 0;
+    int superblock_row_inc = 0;
+    int *hilbert = NULL;
+    int mapping_index = 0;
+
+    int current_macroblock;
+    int c_fragment;
+
+    signed char travel_width[16] = {
+         1,  1,  0, -1, 
+         0,  0,  1,  0,
+         1,  0,  1,  0,
+         0, -1,  0,  1
+    };
+
+    signed char travel_height[16] = {
+         0,  0,  1,  0,
+         1,  1,  0, -1,
+         0,  1,  0, -1,
+        -1,  0, -1,  0
+    };
+
+    signed char travel_width_mb[4] = {
+         1,  0,  1,  0
+    };
+
+    signed char travel_height_mb[4] = {
+         0,  1,  0, -1
+    };
+
+    debug_vp3("  vp3: initialize block mapping tables\n");
+
+    /* figure out hilbert pattern per these frame dimensions */
+    hilbert_walk_y[0]  = 1;
+    hilbert_walk_y[1]  = 1;
+    hilbert_walk_y[2]  = s->fragment_width;
+    hilbert_walk_y[3]  = -1;
+    hilbert_walk_y[4]  = s->fragment_width;
+    hilbert_walk_y[5]  = s->fragment_width;
+    hilbert_walk_y[6]  = 1;
+    hilbert_walk_y[7]  = -s->fragment_width;
+    hilbert_walk_y[8]  = 1;
+    hilbert_walk_y[9]  = s->fragment_width;
+    hilbert_walk_y[10]  = 1;
+    hilbert_walk_y[11] = -s->fragment_width;
+    hilbert_walk_y[12] = -s->fragment_width;
+    hilbert_walk_y[13] = -1;
+    hilbert_walk_y[14] = -s->fragment_width;
+    hilbert_walk_y[15] = 1;
+
+    hilbert_walk_c[0]  = 1;
+    hilbert_walk_c[1]  = 1;
+    hilbert_walk_c[2]  = s->fragment_width / 2;
+    hilbert_walk_c[3]  = -1;
+    hilbert_walk_c[4]  = s->fragment_width / 2;
+    hilbert_walk_c[5]  = s->fragment_width / 2;
+    hilbert_walk_c[6]  = 1;
+    hilbert_walk_c[7]  = -s->fragment_width / 2;
+    hilbert_walk_c[8]  = 1;
+    hilbert_walk_c[9]  = s->fragment_width / 2;
+    hilbert_walk_c[10]  = 1;
+    hilbert_walk_c[11] = -s->fragment_width / 2;
+    hilbert_walk_c[12] = -s->fragment_width / 2;
+    hilbert_walk_c[13] = -1;
+    hilbert_walk_c[14] = -s->fragment_width / 2;
+    hilbert_walk_c[15] = 1;
+
+    hilbert_walk_mb[0] = 1;
+    hilbert_walk_mb[1] = s->macroblock_width;
+    hilbert_walk_mb[2] = 1;
+    hilbert_walk_mb[3] = -s->macroblock_width;
+
+    /* iterate through each superblock (all planes) and map the fragments */
+    for (i = 0; i < s->superblock_count; i++) {
+        debug_init("    superblock %d (u starts @ %d, v starts @ %d)\n",
+            i, s->u_superblock_start, s->v_superblock_start);
+
+        /* time to re-assign the limits? */
+        if (i == 0) {
+
+            /* start of Y superblocks */
+            right_edge = s->fragment_width;
+            bottom_edge = s->fragment_height;
+            current_width = 0;
+            current_height = 0;
+            superblock_row_inc = 3 * s->fragment_width;
+            hilbert = hilbert_walk_y;
+
+            /* the first operation for this variable is to advance by 1 */
+            current_fragment = -1;
+
+        } else if (i == s->u_superblock_start) {
+
+            /* start of U superblocks */
+            right_edge = s->fragment_width / 2;
+            bottom_edge = s->fragment_height / 2;
+            current_width = 0;
+            current_height = 0;
+            superblock_row_inc = 3 * (s->fragment_width / 2);
+            hilbert = hilbert_walk_c;
+
+            /* the first operation for this variable is to advance by 1 */
+            current_fragment = s->u_fragment_start - 1;
+
+        } else if (i == s->v_superblock_start) {
+
+            /* start of V superblocks */
+            right_edge = s->fragment_width / 2;
+            bottom_edge = s->fragment_height / 2;
+            current_width = 0;
+            current_height = 0;
+            superblock_row_inc = 3 * (s->fragment_width / 2);
+            hilbert = hilbert_walk_c;
+
+            /* the first operation for this variable is to advance by 1 */
+            current_fragment = s->v_fragment_start - 1;
+
+        }
+
+        if (current_width >= right_edge) {
+            /* reset width and move to next superblock row */
+            current_width = 0;
+            current_height += 4;
+
+            /* fragment is now at the start of a new superblock row */
+            current_fragment += superblock_row_inc;
+        }
+
+        /* iterate through all 16 fragments in a superblock */
+        for (j = 0; j < 16; j++) {
+            current_fragment += hilbert[j];
+            current_height += travel_height[j];
+
+            /* check if the fragment is in bounds */
+            if ((current_width <= right_edge) &&
+                (current_height < bottom_edge)) {
+                s->superblock_fragments[mapping_index] = current_fragment;
+                debug_init("    mapping fragment %d to superblock %d, position %d\n", 
+                    s->superblock_fragments[mapping_index], i, j);
+            } else {
+                s->superblock_fragments[mapping_index] = -1;
+                debug_init("    superblock %d, position %d has no fragment\n", 
+                    i, j);
+            }
+
+            current_width += travel_width[j];
+            mapping_index++;
+        }
+    }
+
+    /* initialize the superblock <-> macroblock mapping; iterate through
+     * all of the Y plane superblocks to build this mapping */
+    right_edge = s->macroblock_width;
+    bottom_edge = s->macroblock_height;
+    current_width = 0;
+    current_height = 0;
+    superblock_row_inc = s->macroblock_width;
+    hilbert = hilbert_walk_mb;
+    mapping_index = 0;
+    current_macroblock = -1;
+    for (i = 0; i < s->u_superblock_start; i++) {
+
+        if (current_width >= right_edge) {
+            /* reset width and move to next superblock row */
+            current_width = 0;
+            current_height += 2;
+
+            /* macroblock is now at the start of a new superblock row */
+            current_macroblock += superblock_row_inc;
+        }
+
+        /* iterate through each potential macroblock in the superblock */
+        for (j = 0; j < 4; j++) {
+            current_macroblock += hilbert_walk_mb[j];
+            current_height += travel_height_mb[j];
+
+            /* check if the macroblock is in bounds */
+            if ((current_width <= right_edge) &&
+                (current_height < bottom_edge)) {
+                s->superblock_macroblocks[mapping_index] = current_macroblock;
+                debug_init("    mapping macroblock %d to superblock %d, position %d\n",
+                    s->superblock_macroblocks[mapping_index], i, j);
+            } else {
+                s->superblock_macroblocks[mapping_index] = -1;
+                debug_init("    superblock %d, position %d has no macroblock\n",
+                    i, j);
+            }
+
+            current_width += travel_width_mb[j];
+            mapping_index++;
+        }
+    }
+
+    /* initialize the macroblock <-> fragment mapping */
+    current_fragment = 0;
+    current_macroblock = 0;
+    mapping_index = 0;
+    for (i = 0; i < s->fragment_height; i += 2) {
+
+        for (j = 0; j < s->fragment_width; j += 2) {
+
+            debug_init("    macroblock %d contains fragments: ", current_macroblock);
+            s->all_fragments[current_fragment].macroblock = current_macroblock;
+            s->macroblock_fragments[mapping_index++] = current_fragment;
+            debug_init("%d ", current_fragment);
+
+            if (j + 1 < s->fragment_width) {
+                s->all_fragments[current_fragment + 1].macroblock = current_macroblock;
+                s->macroblock_fragments[mapping_index++] = current_fragment + 1;
+                debug_init("%d ", current_fragment + 1);
+            } else
+                s->macroblock_fragments[mapping_index++] = -1;
+
+            if (i + 1 < s->fragment_height) {
+                s->all_fragments[current_fragment + s->fragment_width].macroblock = 
+                    current_macroblock;
+                s->macroblock_fragments[mapping_index++] = 
+                    current_fragment + s->fragment_width;
+                debug_init("%d ", current_fragment + s->fragment_width);
+            } else
+                s->macroblock_fragments[mapping_index++] = -1;
+
+            if ((j + 1 < s->fragment_width) && (i + 1 < s->fragment_height)) {
+                s->all_fragments[current_fragment + s->fragment_width + 1].macroblock = 
+                    current_macroblock;
+                s->macroblock_fragments[mapping_index++] = 
+                    current_fragment + s->fragment_width + 1;
+                debug_init("%d ", current_fragment + s->fragment_width + 1);
+            } else
+                s->macroblock_fragments[mapping_index++] = -1;
+
+            /* C planes */
+            c_fragment = s->u_fragment_start + 
+                (i * s->fragment_width / 4) + (j / 2);
+        s->all_fragments[c_fragment].macroblock = s->macroblock_count;
+            s->macroblock_fragments[mapping_index++] = c_fragment;
+            debug_init("%d ", c_fragment);
+
+            c_fragment = s->v_fragment_start + 
+                (i * s->fragment_width / 4) + (j / 2);
+        s->all_fragments[c_fragment].macroblock = s->macroblock_count;
+            s->macroblock_fragments[mapping_index++] = c_fragment;
+            debug_init("%d ", c_fragment);
+
+            debug_init("\n");
+
+            if (j + 2 <= s->fragment_width)
+                current_fragment += 2;
+            else 
+                current_fragment++;
+            current_macroblock++;
+        }
+
+        current_fragment += s->fragment_width;
+    }
+}
+
+/*
+ * This function unpacks a single token (which should be in the range 0..31)
+ * and returns a zero run (number of zero coefficients in current DCT matrix
+ * before next non-zero coefficient), the next DCT coefficient, and the
+ * number of consecutive, non-EOB'd DCT blocks to EOB.
+ */
+static void unpack_token(GetBitContext *gb, int token, int *zero_run,
+                         DCTELEM *coeff, int *eob_run) 
+{
+    int sign;
+
+    *zero_run = 0;
+    *eob_run = 0;
+    *coeff = 0;
+
+    debug_token("    vp3 token %d: ", token);
+    switch (token) {
+
+    case 0:
+        debug_token("DCT_EOB_TOKEN, EOB next block\n");
+        *eob_run = 1;
+        break;
+
+    case 1:
+        debug_token("DCT_EOB_PAIR_TOKEN, EOB next 2 blocks\n");
+        *eob_run = 2;
+        break;
+
+    case 2:
+        debug_token("DCT_EOB_TRIPLE_TOKEN, EOB next 3 blocks\n");
+        *eob_run = 3;
+        break;
+
+    case 3:
+        debug_token("DCT_REPEAT_RUN_TOKEN, ");
+        *eob_run = get_bits(gb, 2) + 4;
+        debug_token("EOB the next %d blocks\n", *eob_run);
+        break;
+
+    case 4:
+        debug_token("DCT_REPEAT_RUN2_TOKEN, ");
+        *eob_run = get_bits(gb, 3) + 8;
+        debug_token("EOB the next %d blocks\n", *eob_run);
+        break;
+
+    case 5:
+        debug_token("DCT_REPEAT_RUN3_TOKEN, ");
+        *eob_run = get_bits(gb, 4) + 16;
+        debug_token("EOB the next %d blocks\n", *eob_run);
+        break;
+
+    case 6:
+        debug_token("DCT_REPEAT_RUN4_TOKEN, ");
+        *eob_run = get_bits(gb, 12);
+        debug_token("EOB the next %d blocks\n", *eob_run);
+        break;
+
+    case 7:
+        debug_token("DCT_SHORT_ZRL_TOKEN, ");
+        /* note that this token actually indicates that (3 extra bits) + 1 0s
+         * should be output; this case specifies a run of (3 EBs) 0s and a
+         * coefficient of 0. */
+        *zero_run = get_bits(gb, 3);
+        *coeff = 0;
+        debug_token("skip the next %d positions in output matrix\n", *zero_run + 1);
+        break;
+
+    case 8:
+        debug_token("DCT_ZRL_TOKEN, ");
+        /* note that this token actually indicates that (6 extra bits) + 1 0s
+         * should be output; this case specifies a run of (6 EBs) 0s and a
+         * coefficient of 0. */
+        *zero_run = get_bits(gb, 6);
+        *coeff = 0;
+        debug_token("skip the next %d positions in output matrix\n", *zero_run + 1);
+        break;
+
+    case 9:
+        debug_token("ONE_TOKEN, output 1\n");
+        *coeff = 1;
+        break;
+
+    case 10:
+        debug_token("MINUS_ONE_TOKEN, output -1\n");
+        *coeff = -1;
+        break;
+
+    case 11:
+        debug_token("TWO_TOKEN, output 2\n");
+        *coeff = 2;
+        break;
+
+    case 12:
+        debug_token("MINUS_TWO_TOKEN, output -2\n");
+        *coeff = -2;
+        break;
+
+    case 13:
+    case 14:
+    case 15:
+    case 16:
+        debug_token("LOW_VAL_TOKENS, ");
+        if (get_bits(gb, 1))
+            *coeff = -(3 + (token - 13));
+        else
+            *coeff = 3 + (token - 13);
+        debug_token("output %d\n", *coeff);
+        break;
+
+    case 17:
+        debug_token("DCT_VAL_CATEGORY3, ");
+        sign = get_bits(gb, 1);
+        *coeff = 7 + get_bits(gb, 1);
+        if (sign)
+            *coeff = -(*coeff);
+        debug_token("output %d\n", *coeff);
+        break;
+
+    case 18:
+        debug_token("DCT_VAL_CATEGORY4, ");
+        sign = get_bits(gb, 1);
+        *coeff = 9 + get_bits(gb, 2);
+        if (sign)
+            *coeff = -(*coeff);
+        debug_token("output %d\n", *coeff);
+        break;
+
+    case 19:
+        debug_token("DCT_VAL_CATEGORY5, ");
+        sign = get_bits(gb, 1);
+        *coeff = 13 + get_bits(gb, 3);
+        if (sign)
+            *coeff = -(*coeff);
+        debug_token("output %d\n", *coeff);
+        break;
+
+    case 20:
+        debug_token("DCT_VAL_CATEGORY6, ");
+        sign = get_bits(gb, 1);
+        *coeff = 21 + get_bits(gb, 4);
+        if (sign)
+            *coeff = -(*coeff);
+        debug_token("output %d\n", *coeff);
+        break;
+
+    case 21:
+        debug_token("DCT_VAL_CATEGORY7, ");
+        sign = get_bits(gb, 1);
+        *coeff = 37 + get_bits(gb, 5);
+        if (sign)
+            *coeff = -(*coeff);
+        debug_token("output %d\n", *coeff);
+        break;
+
+    case 22:
+        debug_token("DCT_VAL_CATEGORY8, ");
+        sign = get_bits(gb, 1);
+        *coeff = 69 + get_bits(gb, 9);
+        if (sign)
+            *coeff = -(*coeff);
+        debug_token("output %d\n", *coeff);
+        break;
+
+    case 23:
+    case 24:
+    case 25:
+    case 26:
+    case 27:
+        debug_token("DCT_RUN_CATEGORY1, ");
+        *zero_run = token - 22;
+        if (get_bits(gb, 1))
+            *coeff = -1;
+        else
+            *coeff = 1;
+        debug_token("output %d 0s, then %d\n", *zero_run, *coeff);
+        break;
+
+    case 28:
+        debug_token("DCT_RUN_CATEGORY1B, ");
+        if (get_bits(gb, 1))
+            *coeff = -1;
+        else
+            *coeff = 1;
+        *zero_run = 6 + get_bits(gb, 2);
+        debug_token("output %d 0s, then %d\n", *zero_run, *coeff);
+        break;
+
+    case 29:
+        debug_token("DCT_RUN_CATEGORY1C, ");
+        if (get_bits(gb, 1))
+            *coeff = -1;
+        else
+            *coeff = 1;
+        *zero_run = 10 + get_bits(gb, 3);
+        debug_token("output %d 0s, then %d\n", *zero_run, *coeff);
+        break;
+
+    case 30:
+        debug_token("DCT_RUN_CATEGORY2, ");
+        sign = get_bits(gb, 1);
+        *coeff = 2 + get_bits(gb, 1);
+        if (sign)
+            *coeff = -(*coeff);
+        *zero_run = 1;
+        debug_token("output %d 0s, then %d\n", *zero_run, *coeff);
+        break;
+
+    case 31:
+        debug_token("DCT_RUN_CATEGORY2, ");
+        sign = get_bits(gb, 1);
+        *coeff = 2 + get_bits(gb, 1);
+        if (sign)
+            *coeff = -(*coeff);
+        *zero_run = 2 + get_bits(gb, 1);
+        debug_token("output %d 0s, then %d\n", *zero_run, *coeff);
+        break;
+
+    default:
+        printf ("  vp3: help! Got a bad token: %d > 31\n", token);
+        break;
+
+  }
+}
+
+/*
+ * This function wipes out all of the fragment data.
+ */
+static void init_frame(Vp3DecodeContext *s, GetBitContext *gb)
+{
+    int i;
+
+    /* zero out all of the fragment information */
+    s->coded_fragment_list_index = 0;
+    for (i = 0; i < s->fragment_count; i++) {
+        memset(s->all_fragments[i].coeffs, 0, 64 * sizeof(DCTELEM));
+        s->all_fragments[i].coeff_count = 0;
+        s->all_fragments[i].last_coeff = 0;
+    }
+}
+
+/*
+ * This function sets of the dequantization tables used for a particular
+ * frame.
+ */
+static void init_dequantizer(Vp3DecodeContext *s)
+{
+
+    int quality_scale = vp31_quality_threshold[s->quality_index];
+    int dc_scale_factor = vp31_dc_scale_factor[s->quality_index];
+    int i, j;
+
+    debug_vp3("  vp3: initializing dequantization tables\n");
+
+    /* 
+     * Scale dequantizers:
+     *
+     *   quantizer * sf
+     *   --------------
+     *        100
+     *
+     * where sf = dc_scale_factor for DC quantizer
+     *           or quality_scale for AC quantizer
+     *
+     * Then, saturate the result to a lower limit of MIN_DEQUANT_VAL.
+     */
+#define SCALER 1
+
+    /* scale DC quantizers */
+    s->intra_y_dequant[0] = vp31_intra_y_dequant[0] * dc_scale_factor / 100;
+    if (s->intra_y_dequant[0] < MIN_DEQUANT_VAL * 2)
+        s->intra_y_dequant[0] = MIN_DEQUANT_VAL * 2;
+    s->intra_y_dequant[0] *= SCALER;
+
+    s->intra_c_dequant[0] = vp31_intra_c_dequant[0] * dc_scale_factor / 100;
+    if (s->intra_c_dequant[0] < MIN_DEQUANT_VAL * 2)
+        s->intra_c_dequant[0] = MIN_DEQUANT_VAL * 2;
+    s->intra_c_dequant[0] *= SCALER;
+
+    s->inter_dequant[0] = vp31_inter_dequant[0] * dc_scale_factor / 100;
+    if (s->inter_dequant[0] < MIN_DEQUANT_VAL * 4)
+        s->inter_dequant[0] = MIN_DEQUANT_VAL * 4;
+    s->inter_dequant[0] *= SCALER;
+
+    /* scale AC quantizers, zigzag at the same time in preparation for
+     * the dequantization phase */
+    for (i = 1; i < 64; i++) {
+
+        j = quant_index[i];
+
+        s->intra_y_dequant[j] = vp31_intra_y_dequant[i] * quality_scale / 100;
+        if (s->intra_y_dequant[j] < MIN_DEQUANT_VAL)
+            s->intra_y_dequant[j] = MIN_DEQUANT_VAL;
+        s->intra_y_dequant[j] *= SCALER;
+
+        s->intra_c_dequant[j] = vp31_intra_c_dequant[i] * quality_scale / 100;
+        if (s->intra_c_dequant[j] < MIN_DEQUANT_VAL)
+            s->intra_c_dequant[j] = MIN_DEQUANT_VAL;
+        s->intra_c_dequant[j] *= SCALER;
+
+        s->inter_dequant[j] = vp31_inter_dequant[i] * quality_scale / 100;
+        if (s->inter_dequant[j] < MIN_DEQUANT_VAL * 2)
+            s->inter_dequant[j] = MIN_DEQUANT_VAL * 2;
+        s->inter_dequant[j] *= SCALER;
+    }
+
+    /* print debug information as requested */
+    debug_dequantizers("intra Y dequantizers:\n");
+    for (i = 0; i < 8; i++) {
+      for (j = i * 8; j < i * 8 + 8; j++) {
+        debug_dequantizers(" %4d,", s->intra_y_dequant[j]);
+      }
+      debug_dequantizers("\n");
+    }
+    debug_dequantizers("\n");
+
+    debug_dequantizers("intra C dequantizers:\n");
+    for (i = 0; i < 8; i++) {
+      for (j = i * 8; j < i * 8 + 8; j++) {
+        debug_dequantizers(" %4d,", s->intra_c_dequant[j]);
+      }
+      debug_dequantizers("\n");
+    }
+    debug_dequantizers("\n");
+
+    debug_dequantizers("interframe dequantizers:\n");
+    for (i = 0; i < 8; i++) {
+      for (j = i * 8; j < i * 8 + 8; j++) {
+        debug_dequantizers(" %4d,", s->inter_dequant[j]);
+      }
+      debug_dequantizers("\n");
+    }
+    debug_dequantizers("\n");
+}
+
+/*
+ * This function is used to fetch runs of 1s or 0s from the bitstream for
+ * use in determining which superblocks are fully and partially coded.
+ *
+ *  Codeword                RunLength
+ *  0                       1
+ *  10x                     2-3
+ *  110x                    4-5
+ *  1110xx                  6-9
+ *  11110xxx                10-17
+ *  111110xxxx              18-33
+ *  111111xxxxxxxxxxxx      34-4129
+ */
+static int get_superblock_run_length(GetBitContext *gb)
+{
+
+    if (get_bits(gb, 1) == 0)
+        return 1;
+
+    else if (get_bits(gb, 1) == 0)
+        return (2 + get_bits(gb, 1));
+
+    else if (get_bits(gb, 1) == 0)
+        return (4 + get_bits(gb, 1));
+
+    else if (get_bits(gb, 1) == 0)
+        return (6 + get_bits(gb, 2));
+
+    else if (get_bits(gb, 1) == 0)
+        return (10 + get_bits(gb, 3));
+
+    else if (get_bits(gb, 1) == 0)
+        return (18 + get_bits(gb, 4));
+
+    else
+        return (34 + get_bits(gb, 12));
+
+}
+
+/*
+ * This function is used to fetch runs of 1s or 0s from the bitstream for
+ * use in determining which particular fragments are coded.
+ *
+ * Codeword                RunLength
+ * 0x                      1-2
+ * 10x                     3-4
+ * 110x                    5-6
+ * 1110xx                  7-10
+ * 11110xx                 11-14
+ * 11111xxxx               15-30
+ */
+static int get_fragment_run_length(GetBitContext *gb)
+{
+
+    if (get_bits(gb, 1) == 0)
+        return (1 + get_bits(gb, 1));
+
+    else if (get_bits(gb, 1) == 0)
+        return (3 + get_bits(gb, 1));
+
+    else if (get_bits(gb, 1) == 0)
+        return (5 + get_bits(gb, 1));
+
+    else if (get_bits(gb, 1) == 0)
+        return (7 + get_bits(gb, 2));
+
+    else if (get_bits(gb, 1) == 0)
+        return (11 + get_bits(gb, 2));
+
+    else
+        return (15 + get_bits(gb, 4));
+
+}
+
+/*
+ * This function decodes a VLC from the bitstream and returns a number
+ * that ranges from 0..7. The number indicates which of the 8 coding
+ * modes to use.
+ *
+ *  VLC       Number
+ *  0            0
+ *  10           1
+ *  110          2
+ *  1110         3
+ *  11110        4
+ *  111110       5
+ *  1111110      6
+ *  1111111      7
+ *
+ */
+static int get_mode_code(GetBitContext *gb)
+{
+
+    if (get_bits(gb, 1) == 0)
+        return 0;
+
+    else if (get_bits(gb, 1) == 0)
+        return 1;
+
+    else if (get_bits(gb, 1) == 0)
+        return 2;
+
+    else if (get_bits(gb, 1) == 0)
+        return 3;
+
+    else if (get_bits(gb, 1) == 0)
+        return 4;
+
+    else if (get_bits(gb, 1) == 0)
+        return 5;
+
+    else if (get_bits(gb, 1) == 0)
+        return 6;
+
+    else
+        return 7;
+
+}
+
+/*
+ * This function extracts a motion vector from the bitstream using a VLC
+ * scheme. 3 bits are fetched from the bitstream and 1 of 8 actions is
+ * taken depending on the value on those 3 bits:
+ *
+ *  0: return 0
+ *  1: return 1
+ *  2: return -1
+ *  3: if (next bit is 1) return -2, else return 2
+ *  4: if (next bit is 1) return -3, else return 3
+ *  5: return 4 + (next 2 bits), next bit is sign
+ *  6: return 8 + (next 3 bits), next bit is sign
+ *  7: return 16 + (next 4 bits), next bit is sign
+ */
+static int get_motion_vector_vlc(GetBitContext *gb)
+{
+    int bits;
+
+    bits = get_bits(gb, 3);
+
+    switch(bits) {
+
+    case 0:
+        bits = 0;
+        break;
+
+    case 1:
+        bits = 1;
+        break;
+
+    case 2:
+        bits = -1;
+        break;
+
+    case 3:
+        if (get_bits(gb, 1) == 0)
+            bits = 2;
+        else
+            bits = -2;
+        break;
+
+    case 4:
+        if (get_bits(gb, 1) == 0)
+            bits = 3;
+        else
+            bits = -3;
+        break;
+
+    case 5:
+        bits = 4 + get_bits(gb, 2);
+        if (get_bits(gb, 1) == 1)
+            bits = -bits;
+        break;
+
+    case 6:
+        bits = 8 + get_bits(gb, 3);
+        if (get_bits(gb, 1) == 1)
+            bits = -bits;
+        break;
+
+    case 7:
+        bits = 16 + get_bits(gb, 4);
+        if (get_bits(gb, 1) == 1)
+            bits = -bits;
+        break;
+
+    }
+
+    return bits;
+}
+
+/*
+ * This function fetches a 5-bit number from the stream followed by
+ * a sign and calls it a motion vector.
+ */
+static int get_motion_vector_fixed(GetBitContext *gb)
+{
+
+    int bits;
+
+    bits = get_bits(gb, 5);
+
+    if (get_bits(gb, 1) == 1)
+        bits = -bits;
+
+    return bits;
+}
+
+/*
+ * This function unpacks all of the superblock/macroblock/fragment coding 
+ * information from the bitstream.
+ */
+static void unpack_superblocks(Vp3DecodeContext *s, GetBitContext *gb)
+{
+    int bit = 0;
+    int current_superblock = 0;
+    int current_run = 0;
+    int decode_fully_flags = 0;
+    int decode_partial_blocks = 0;
+
+    int i, j;
+    int current_fragment;
+
+    debug_vp3("  vp3: unpacking superblock coding\n");
+
+    if (s->keyframe) {
+
+        debug_vp3("    keyframe-- all superblocks are fully coded\n");
+        memset(s->superblock_coding, SB_FULLY_CODED, s->superblock_count);
+
+    } else {
+
+        /* unpack the list of partially-coded superblocks */
+        bit = get_bits(gb, 1);
+        /* toggle the bit because as soon as the first run length is 
+         * fetched the bit will be toggled again */
+        bit ^= 1;
+        while (current_superblock < s->superblock_count) {
+            if (current_run == 0) {
+                bit ^= 1;
+                current_run = get_superblock_run_length(gb);
+                debug_block_coding("      setting superblocks %d..%d to %s\n",
+                    current_superblock,
+                    current_superblock + current_run - 1,
+                    (bit) ? "partially coded" : "not coded");
+
+                /* if any of the superblocks are not partially coded, flag
+                 * a boolean to decode the list of fully-coded superblocks */
+                if (bit == 0)
+                    decode_fully_flags = 1;
+            } else {
+
+                /* make a note of the fact that there are partially coded
+                 * superblocks */
+                decode_partial_blocks = 1;
+
+            }
+            s->superblock_coding[current_superblock++] = 
+                (bit) ? SB_PARTIALLY_CODED : SB_NOT_CODED;
+            current_run--;
+        }
+
+        /* unpack the list of fully coded superblocks if any of the blocks were
+         * not marked as partially coded in the previous step */
+        if (decode_fully_flags) {
+
+            current_superblock = 0;
+            current_run = 0;
+            bit = get_bits(gb, 1);
+            /* toggle the bit because as soon as the first run length is 
+             * fetched the bit will be toggled again */
+            bit ^= 1;
+            while (current_superblock < s->superblock_count) {
+
+                /* skip any superblocks already marked as partially coded */
+                if (s->superblock_coding[current_superblock] == SB_NOT_CODED) {
+
+                    if (current_run == 0) {
+                        bit ^= 1;
+                        current_run = get_superblock_run_length(gb);
+                    }
+
+                    debug_block_coding("      setting superblock %d to %s\n",
+                        current_superblock,
+                        (bit) ? "fully coded" : "not coded");
+                    s->superblock_coding[current_superblock] = 
+                        (bit) ? SB_FULLY_CODED : SB_NOT_CODED;
+                    current_run--;
+                }
+                current_superblock++;
+            }
+        }
+
+        /* if there were partial blocks, initialize bitstream for
+         * unpacking fragment codings */
+        if (decode_partial_blocks) {
+
+            current_run = 0;
+            bit = get_bits(gb, 1);
+            /* toggle the bit because as soon as the first run length is 
+             * fetched the bit will be toggled again */
+            bit ^= 1;
+        }
+    }
+
+    /* figure out which fragments are coded; iterate through each
+     * superblock (all planes) */
+    s->coded_fragment_list_index = 0;
+    memset(s->macroblock_coded, 0, s->macroblock_count);
+    for (i = 0; i < s->superblock_count; i++) {
+
+        /* iterate through all 16 fragments in a superblock */
+        for (j = 0; j < 16; j++) {
+
+            /* if the fragment is in bounds, check its coding status */
+            current_fragment = s->superblock_fragments[i * 16 + j];
+            if (current_fragment != -1) {
+                if (s->superblock_coding[i] == SB_NOT_CODED) {
+
+                    /* copy all the fragments from the prior frame */
+                    s->all_fragments[current_fragment].coding_method = 
+                        MODE_COPY;
+
+                } else if (s->superblock_coding[i] == SB_PARTIALLY_CODED) {
+
+                    /* fragment may or may not be coded; this is the case
+                     * that cares about the fragment coding runs */
+                    if (current_run == 0) {
+                        bit ^= 1;
+                        current_run = get_fragment_run_length(gb);
+                    }
+
+                    if (bit) {
+                        /* mode will be decoded in the next phase */
+                        s->all_fragments[current_fragment].coding_method = 
+                            MODE_INTER_NO_MV;
+                        s->coded_fragment_list[s->coded_fragment_list_index++] = 
+                            current_fragment;
+                        s->macroblock_coded[s->all_fragments[current_fragment].macroblock] = 1;
+                        debug_block_coding("      superblock %d is partially coded, fragment %d is coded\n",
+                            i, current_fragment);
+                    } else {
+                        /* not coded; copy this fragment from the prior frame */
+                        s->all_fragments[current_fragment].coding_method =
+                            MODE_COPY;
+                        debug_block_coding("      superblock %d is partially coded, fragment %d is not coded\n",
+                            i, current_fragment);
+                    }
+
+                    current_run--;
+
+                } else {
+
+                    /* fragments are fully coded in this superblock; actual
+                     * coding will be determined in next step */
+                    s->all_fragments[current_fragment].coding_method = 
+                        MODE_INTER_NO_MV;
+                    s->coded_fragment_list[s->coded_fragment_list_index++] = 
+                        current_fragment;
+                    s->macroblock_coded[s->all_fragments[current_fragment].macroblock] = 1;
+                    debug_block_coding("      superblock %d is fully coded, fragment %d is coded\n",
+                        i, current_fragment);
+                }
+            }
+        }
+    }
+}
+
+/*
+ * This function unpacks all the coding mode data for individual macroblocks
+ * from the bitstream.
+ */
+static void unpack_modes(Vp3DecodeContext *s, GetBitContext *gb)
+{
+    int i, j, k;
+    int scheme;
+    int current_macroblock;
+    int current_fragment;
+    int coding_mode;
+
+    debug_vp3("  vp3: unpacking encoding modes\n");
+
+    if (s->keyframe) {
+        debug_vp3("    keyframe-- all blocks are coded as INTRA\n");
+
+        for (i = 0; i < s->fragment_count; i++)
+            s->all_fragments[i].coding_method = MODE_INTRA;
+
+    } else {
+
+        /* fetch the mode coding scheme for this frame */
+        scheme = get_bits(gb, 3);
+        debug_modes("    using mode alphabet %d\n", scheme);
+
+        /* is it a custom coding scheme? */
+        if (scheme == 0) {
+            debug_modes("    custom mode alphabet ahead:\n");
+            for (i = 0; i < 8; i++)
+                ModeAlphabet[0][i] = get_bits(gb, 3);
+        }
+
+        for (i = 0; i < 8; i++)
+            debug_modes("      mode[%d][%d] = %d\n", scheme, i, 
+                ModeAlphabet[scheme][i]);
+
+        /* iterate through all of the macroblocks that contain 1 or more
+         * coded fragments */
+        for (i = 0; i < s->u_superblock_start; i++) {
+
+            for (j = 0; j < 4; j++) {
+                current_macroblock = s->superblock_macroblocks[i * 4 + j];
+                if ((current_macroblock == -1) ||
+                    (!s->macroblock_coded[current_macroblock]))
+                    continue;
+
+                /* mode 7 means get 3 bits for each coding mode */
+                if (scheme == 7)
+                    coding_mode = get_bits(gb, 3);
+                else
+                    coding_mode = ModeAlphabet[scheme][get_mode_code(gb)];
+
+                for (k = 0; k < 6; k++) {
+                    current_fragment = 
+                        s->macroblock_fragments[current_macroblock * 6 + k];
+                    if (s->all_fragments[current_fragment].coding_method != 
+                        MODE_COPY)
+                        s->all_fragments[current_fragment].coding_method =
+                            coding_mode;
+                }
+
+                debug_modes("    coding method for macroblock starting @ fragment %d = %d\n",
+                    s->macroblock_fragments[current_macroblock * 6], coding_mode);
+            }
+        }
+    }
+
+}
+
+/*
+ * This function unpacks all the motion vectors for the individual
+ * macroblocks from the bitstream.
+ */
+static void unpack_vectors(Vp3DecodeContext *s, GetBitContext *gb)
+{
+    int i, j, k;
+    int coding_mode;
+    int motion_x[6];
+    int motion_y[6];
+    int last_motion_x = 0;
+    int last_motion_y = 0;
+    int prior_last_motion_x = 0;
+    int prior_last_motion_y = 0;
+    int current_macroblock;
+    int current_fragment;
+
+    debug_vp3("  vp3: unpacking motion vectors\n");
+
+    if (s->keyframe) {
+
+        debug_vp3("    keyframe-- there are no motion vectors\n");
+
+    } else {
+
+        memset(motion_x, 0, 6 * sizeof(int));
+        memset(motion_y, 0, 6 * sizeof(int));
+
+        /* coding mode 0 is the VLC scheme; 1 is the fixed code scheme */
+        coding_mode = get_bits(gb, 1);
+        debug_vectors("    using %s scheme for unpacking motion vectors\n",
+            (coding_mode == 0) ? "VLC" : "fixed-length");
+
+        /* iterate through all of the macroblocks that contain 1 or more
+         * coded fragments */
+        for (i = 0; i < s->u_superblock_start; i++) {
+
+            for (j = 0; j < 4; j++) {
+                current_macroblock = s->superblock_macroblocks[i * 4 + j];
+                if ((current_macroblock == -1) ||
+                    (!s->macroblock_coded[current_macroblock]))
+                    continue;
+
+                current_fragment = s->macroblock_fragments[current_macroblock * 6];
+                switch (s->all_fragments[current_fragment].coding_method) {
+
+                case MODE_INTER_PLUS_MV:
+                case MODE_GOLDEN_MV:
+                    /* all 6 fragments use the same motion vector */
+                    if (coding_mode == 0) {
+                        motion_x[0] = get_motion_vector_vlc(gb);
+                        motion_y[0] = get_motion_vector_vlc(gb);
+                    } else {
+                        motion_x[0] = get_motion_vector_fixed(gb);
+                        motion_y[0] = get_motion_vector_fixed(gb);
+                    }
+                    for (k = 1; k < 6; k++) {
+                        motion_x[k] = motion_x[0];
+                        motion_y[k] = motion_y[0];
+                    }
+
+                    /* vector maintenance, only on MODE_INTER_PLUS_MV */
+                    if (s->all_fragments[current_fragment].coding_method ==
+                        MODE_INTER_PLUS_MV) {
+                        prior_last_motion_x = last_motion_x;
+                        prior_last_motion_y = last_motion_y;
+                        last_motion_x = motion_x[0];
+                        last_motion_y = motion_y[0];
+                    }
+                    break;
+
+                case MODE_INTER_FOURMV:
+                    /* fetch 4 vectors from the bitstream, one for each
+                     * Y fragment, then average for the C fragment vectors */
+                    motion_x[4] = motion_y[4] = 0;
+                    for (k = 0; k < 4; k++) {
+                        if (coding_mode == 0) {
+                            motion_x[k] = get_motion_vector_vlc(gb);
+                            motion_y[k] = get_motion_vector_vlc(gb);
+                        } else {
+                            motion_x[k] = get_motion_vector_fixed(gb);
+                            motion_y[k] = get_motion_vector_fixed(gb);
+                        }
+                        motion_x[4] += motion_x[k];
+                        motion_y[4] += motion_y[k];
+                    }
+
+                    if (motion_x[4] >= 0) 
+                        motion_x[4] = (motion_x[4] + 2) / 4;
+                    else
+                        motion_x[4] = (motion_x[4] - 2) / 4;
+                    motion_x[5] = motion_x[4];
+
+                    if (motion_y[4] >= 0) 
+                        motion_y[4] = (motion_y[4] + 2) / 4;
+                    else
+                        motion_y[4] = (motion_y[4] - 2) / 4;
+                    motion_y[5] = motion_y[4];
+
+                    /* vector maintenance; vector[3] is treated as the
+                     * last vector in this case */
+                    prior_last_motion_x = last_motion_x;
+                    prior_last_motion_y = last_motion_y;
+                    last_motion_x = motion_x[3];
+                    last_motion_y = motion_y[3];
+                    break;
+
+                case MODE_INTER_LAST_MV:
+                    /* all 6 fragments use the last motion vector */
+                    motion_x[0] = last_motion_x;
+                    motion_y[0] = last_motion_y;
+                    for (k = 1; k < 6; k++) {
+                        motion_x[k] = motion_x[0];
+                        motion_y[k] = motion_y[0];
+                    }
+
+                    /* no vector maintenance (last vector remains the
+                     * last vector) */
+                    break;
+
+                case MODE_INTER_PRIOR_LAST:
+                    /* all 6 fragments use the motion vector prior to the
+                     * last motion vector */
+                    motion_x[0] = prior_last_motion_x;
+                    motion_y[0] = prior_last_motion_y;
+                    for (k = 1; k < 6; k++) {
+                        motion_x[k] = motion_x[0];
+                        motion_y[k] = motion_y[0];
+                    }
+
+                    /* vector maintenance */
+                    prior_last_motion_x = last_motion_x;
+                    prior_last_motion_y = last_motion_y;
+                    last_motion_x = motion_x[0];
+                    last_motion_y = motion_y[0];
+                    break;
+                }
+
+                /* assign the motion vectors to the correct fragments */
+                debug_vectors("    vectors for macroblock starting @ fragment %d (coding method %d):\n",
+                    current_fragment,
+                    s->all_fragments[current_fragment].coding_method);
+                for (k = 0; k < 6; k++) {
+                    current_fragment = 
+                        s->macroblock_fragments[current_macroblock * 6 + k];
+                    s->all_fragments[current_fragment].motion_x = motion_x[k];
+                    s->all_fragments[current_fragment].motion_x = motion_y[k];
+                    debug_vectors("    vector %d: fragment %d = (%d, %d)\n",
+                        k, current_fragment, motion_x[k], motion_y[k]);
+                }
+            }
+        }
+    }
+}
+
+/* 
+ * This function is called by unpack_dct_coeffs() to extract the VLCs from
+ * the bitstream. The VLCs encode tokens which are used to unpack DCT
+ * data. This function unpacks all the VLCs for either the Y plane or both
+ * C planes, and is called for DC coefficients or different AC coefficient
+ * levels (since different coefficient types require different VLC tables.
+ *
+ * This function returns a residual eob run. E.g, if a particular token gave
+ * instructions to EOB the next 5 fragments and there were only 2 fragments
+ * left in the current fragment range, 3 would be returned so that it could
+ * be passed into the next call to this same function.
+ */
+static int unpack_vlcs(Vp3DecodeContext *s, GetBitContext *gb,
+                        VLC *table, int coeff_index,
+                        int first_fragment, int last_fragment,
+                        int eob_run)
+{
+    int i;
+    int token;
+    int zero_run;
+    DCTELEM coeff;
+    Vp3Fragment *fragment;
+
+    for (i = first_fragment; i < last_fragment; i++) {
+
+        fragment = &s->all_fragments[s->coded_fragment_list[i]];
+        if (fragment->coeff_count > coeff_index)
+            continue;
+
+        if (!eob_run) {
+            /* decode a VLC into a token */
+            token = get_vlc2(gb, table->table, 5, 3);
+            debug_vlc(" token = %2d, ", token);
+            /* use the token to get a zero run, a coefficient, and an eob run */
+            unpack_token(gb, token, &zero_run, &coeff, &eob_run);
+        }
+
+        if (!eob_run) {
+            fragment->coeff_count += zero_run;
+            if (fragment->coeff_count < 64)
+                fragment->coeffs[fragment->coeff_count++] = coeff;
+            debug_vlc(" fragment %d coeff = %d\n",
+                s->coded_fragment_list[i], fragment->coeffs[coeff_index]);
+        } else {
+            fragment->last_coeff = fragment->coeff_count;
+            fragment->coeff_count = 64;
+            debug_vlc(" fragment %d eob with %d coefficients\n", 
+                s->coded_fragment_list[i], fragment->last_coeff);
+            eob_run--;
+        }
+    }
+
+    return eob_run;
+}
+
+/*
+ * This function unpacks all of the DCT coefficient data from the
+ * bitstream.
+ */
+static void unpack_dct_coeffs(Vp3DecodeContext *s, GetBitContext *gb)
+{
+    int i;
+    int dc_y_table;
+    int dc_c_table;
+    int ac_y_table;
+    int ac_c_table;
+    int residual_eob_run = 0;
+
+    /* for the binary search */
+    int left, middle, right, found;
+    /* this indicates the first fragment of the color plane data */
+    int plane_split = 0;
+
+    debug_vp3("  vp3: unpacking DCT coefficients\n");
+
+    /* find the plane split (the first color plane fragment) using a binary 
+     * search; test the boundaries first */
+    if (s->coded_fragment_list_index == 0)
+        return;
+    if (s->u_fragment_start <= s->coded_fragment_list[0])
+        plane_split = 0;  /* this means no Y fragments */
+    else if (s->coded_fragment_list[s->coded_fragment_list_index - 1] >
+        s->u_fragment_start) {
+
+        left = 0;
+        right = s->coded_fragment_list_index - 1;
+        found = 0;
+        do {
+            middle = (left + right + 1) / 2;
+            if ((s->coded_fragment_list[middle] >= s->u_fragment_start) &&
+                (s->coded_fragment_list[middle - 1] < s->u_fragment_start))
+                found = 1;
+            else if (s->coded_fragment_list[middle] < s->u_fragment_start)
+                left = middle;
+            else
+                right = middle;
+        } while (!found);
+
+        plane_split = middle;
+    }
+
+    debug_vp3("  plane split @ index %d (fragment %d)\n", plane_split,
+        s->coded_fragment_list[plane_split]);
+
+    /* fetch the DC table indices */
+    dc_y_table = get_bits(gb, 4);
+    dc_c_table = get_bits(gb, 4);
+
+    /* unpack the Y plane DC coefficients */
+    debug_vp3("  vp3: unpacking Y plane DC coefficients using table %d\n",
+        dc_y_table);
+    residual_eob_run = unpack_vlcs(s, gb, &s->dc_vlc[dc_y_table], 0, 
+        0, plane_split, residual_eob_run);
+
+    /* unpack the C plane DC coefficients */
+    debug_vp3("  vp3: unpacking C plane DC coefficients using table %d\n",
+        dc_c_table);
+    residual_eob_run = unpack_vlcs(s, gb, &s->dc_vlc[dc_c_table], 0,
+        plane_split, s->coded_fragment_list_index, residual_eob_run);
+
+    /* fetch the level 1 AC table indices */
+    ac_y_table = get_bits(gb, 4);
+    ac_c_table = get_bits(gb, 4);
+
+    /* unpack the level 1 AC coefficients (coeffs 1-5) */
+    for (i = 1; i <= 5; i++) {
+
+        debug_vp3("  vp3: unpacking level %d Y plane AC coefficients using table %d\n",
+            i, ac_y_table);
+        residual_eob_run = unpack_vlcs(s, gb, &s->ac_vlc_1[ac_y_table], i, 
+            0, plane_split, residual_eob_run);
+
+        debug_vp3("  vp3: unpacking level %d C plane AC coefficients using table %d\n",
+            i, ac_c_table);
+        residual_eob_run = unpack_vlcs(s, gb, &s->ac_vlc_1[ac_c_table], i, 
+            plane_split, s->coded_fragment_list_index, residual_eob_run);
+    }
+
+    /* unpack the level 2 AC coefficients (coeffs 6-14) */
+    for (i = 6; i <= 14; i++) {
+
+        debug_vp3("  vp3: unpacking level %d Y plane AC coefficients using table %d\n",
+            i, ac_y_table);
+        residual_eob_run = unpack_vlcs(s, gb, &s->ac_vlc_2[ac_y_table], i, 
+            0, plane_split, residual_eob_run);
+
+        debug_vp3("  vp3: unpacking level %d C plane AC coefficients using table %d\n",
+            i, ac_c_table);
+        residual_eob_run = unpack_vlcs(s, gb, &s->ac_vlc_2[ac_c_table], i, 
+            plane_split, s->coded_fragment_list_index, residual_eob_run);
+    }
+
+    /* unpack the level 3 AC coefficients (coeffs 15-27) */
+    for (i = 15; i <= 27; i++) {
+
+        debug_vp3("  vp3: unpacking level %d Y plane AC coefficients using table %d\n",
+            i, ac_y_table);
+        residual_eob_run = unpack_vlcs(s, gb, &s->ac_vlc_3[ac_y_table], i, 
+            0, plane_split, residual_eob_run);
+
+        debug_vp3("  vp3: unpacking level %d C plane AC coefficients using table %d\n",
+            i, ac_c_table);
+        residual_eob_run = unpack_vlcs(s, gb, &s->ac_vlc_3[ac_c_table], i, 
+            plane_split, s->coded_fragment_list_index, residual_eob_run);
+    }
+
+    /* unpack the level 4 AC coefficients (coeffs 28-63) */
+    for (i = 28; i <= 63; i++) {
+
+        debug_vp3("  vp3: unpacking level %d Y plane AC coefficients using table %d\n",
+            i, ac_y_table);
+        residual_eob_run = unpack_vlcs(s, gb, &s->ac_vlc_4[ac_y_table], i, 
+            0, plane_split, residual_eob_run);
+
+        debug_vp3("  vp3: unpacking level %d C plane AC coefficients using table %d\n",
+            i, ac_c_table);
+        residual_eob_run = unpack_vlcs(s, gb, &s->ac_vlc_4[ac_c_table], i, 
+            plane_split, s->coded_fragment_list_index, residual_eob_run);
+    }
+}
+
+/*
+ * This function reverses the DC prediction for each coded fragment in
+ * the frame. Much of this function is adapted directly from the original 
+ * VP3 source code.
+ */
+#define COMPATIBLE_FRAME(x) \
+  (compatible_frame[s->all_fragments[x].coding_method] == current_frame_type)
+#define FRAME_CODED(x) (s->all_fragments[x].coding_method != MODE_COPY)
+#define HIGHBITDUPPED(X) (((signed short) X)  >> 15)
+static inline int iabs (int x) { return ((x < 0) ? -x : x); }
+
+static void reverse_dc_prediction(Vp3DecodeContext *s,
+                                  int first_fragment,
+                                  int fragment_width,
+                                  int fragment_height) 
+{
+
+#define PUL 8
+#define PU 4
+#define PUR 2
+#define PL 1
+
+    int x, y;
+    int i = first_fragment;
+
+    /*
+     * Fragment prediction groups:
+     *
+     * 32222222226
+     * 10000000004
+     * 10000000004
+     * 10000000004
+     * 10000000004
+     *
+     * Note: Groups 5 and 7 do not exist as it would mean that the 
+     * fragment's x coordinate is both 0 and (width - 1) at the same time.
+     */
+    int predictor_group;
+    short predicted_dc;
+
+    /* validity flags for the left, up-left, up, and up-right fragments */
+    int fl, ful, fu, fur;
+
+    /* DC values for the left, up-left, up, and up-right fragments */
+    int vl, vul, vu, vur;
+
+    /* indices for the left, up-left, up, and up-right fragments */
+    int l, ul, u, ur;
+
+    /* 
+     * The 6 fields mean:
+     *   0: up-left multiplier
+     *   1: up multiplier
+     *   2: up-right multiplier
+     *   3: left multiplier
+     *   4: mask
+     *   5: right bit shift divisor (e.g., 7 means >>=7, a.k.a. div by 128)
+     */
+    int predictor_transform[16][6] = {
+        {  0,  0,  0,  0,   0,  0 },
+        {  0,  0,  0,  1,   0,  0 },        // PL
+        {  0,  0,  1,  0,   0,  0 },        // PUR
+        {  0,  0, 53, 75, 127,  7 },        // PUR|PL
+        {  0,  1,  0,  0,   0,  0 },        // PU
+        {  0,  1,  0,  1,   1,  1 },        // PU|PL
+        {  0,  1,  0,  0,   0,  0 },        // PU|PUR
+        {  0,  0, 53, 75, 127,  7 },        // PU|PUR|PL
+        {  1,  0,  0,  0,   0,  0 },        // PUL
+        {  0,  0,  0,  1,   0,  0 },        // PUL|PL
+        {  1,  0,  1,  0,   1,  1 },        // PUL|PUR
+        {  0,  0, 53, 75, 127,  7 },        // PUL|PUR|PL
+        {  0,  1,  0,  0,   0,  0 },        // PUL|PU
+        {-26, 29,  0, 29,  31,  5 },        // PUL|PU|PL
+        {  3, 10,  3,  0,  15,  4 },        // PUL|PU|PUR
+        {-26, 29,  0, 29,  31,  5 }         // PUL|PU|PUR|PL
+    };
+
+    /* This table shows which types of blocks can use other blocks for
+     * prediction. For example, INTRA is the only mode in this table to
+     * have a frame number of 0. That means INTRA blocks can only predict
+     * from other INTRA blocks. There are 2 golden frame coding types; 
+     * blocks encoding in these modes can only predict from other blocks
+     * that were encoded with these 1 of these 2 modes. */
+    unsigned char compatible_frame[8] = {
+        1,    /* MODE_INTER_NO_MV */
+        0,    /* MODE_INTRA */
+        1,    /* MODE_INTER_PLUS_MV */
+        1,    /* MODE_INTER_LAST_MV */
+        1,    /* MODE_INTER_PRIOR_MV */
+        2,    /* MODE_USING_GOLDEN */
+        2,    /* MODE_GOLDEN_MV */
+        1     /* MODE_INTER_FOUR_MV */
+    };
+    int current_frame_type;
+
+    /* there is a last DC predictor for each of the 3 frame types */
+    short last_dc[3];
+
+    int transform = 0;
+
+    debug_vp3("  vp3: reversing DC prediction\n");
+
+    vul = vu = vur = vl = 0;
+    last_dc[0] = last_dc[1] = last_dc[2] = 0;
+
+    /* for each fragment row... */
+    for (y = 0; y < fragment_height; y++) {
+
+        /* for each fragment in a row... */
+        for (x = 0; x < fragment_width; x++, i++) {
+
+            /* reverse prediction if this block was coded */
+            if (s->all_fragments[i].coding_method != MODE_COPY) {
+
+                current_frame_type = 
+                    compatible_frame[s->all_fragments[i].coding_method];
+                predictor_group = (x == 0) + ((y == 0) << 1) +
+                    ((x + 1 == fragment_width) << 2);
+                debug_dc_pred(" frag %d: group %d, orig DC = %d, ",
+                    i, predictor_group, s->all_fragments[i].coeffs[0]);
+
+                switch (predictor_group) {
+
+                case 0:
+                    /* main body of fragments; consider all 4 possible
+                     * fragments for prediction */
+
+                    /* calculate the indices of the predicting fragments */
+                    ul = i - fragment_width - 1;
+                    u = i - fragment_width;
+                    ur = i - fragment_width + 1;
+                    l = i - 1;
+
+                    /* fetch the DC values for the predicting fragments */
+                    vul = s->all_fragments[ul].coeffs[0];
+                    vu = s->all_fragments[u].coeffs[0];
+                    vur = s->all_fragments[ur].coeffs[0];
+                    vl = s->all_fragments[l].coeffs[0];
+
+                    /* figure out which fragments are valid */
+                    ful = FRAME_CODED(ul) && COMPATIBLE_FRAME(ul);
+                    fu = FRAME_CODED(u) && COMPATIBLE_FRAME(u);
+                    fur = FRAME_CODED(ur) && COMPATIBLE_FRAME(ur);
+                    fl = FRAME_CODED(l) && COMPATIBLE_FRAME(l);
+
+                    /* decide which predictor transform to use */
+                    transform = (fl*PL) | (fu*PU) | (ful*PUL) | (fur*PUR);
+
+                    break;
+
+                case 1:
+                    /* left column of fragments, not including top corner;
+                     * only consider up and up-right fragments */
+
+                    /* calculate the indices of the predicting fragments */
+                    u = i - fragment_width;
+                    ur = i - fragment_width + 1;
+
+                    /* fetch the DC values for the predicting fragments */
+                    vu = s->all_fragments[u].coeffs[0];
+                    vur = s->all_fragments[ur].coeffs[0];
+
+                    /* figure out which fragments are valid */
+                    fur = FRAME_CODED(ur) && COMPATIBLE_FRAME(ur);
+                    fu = FRAME_CODED(u) && COMPATIBLE_FRAME(u);
+
+                    /* decide which predictor transform to use */
+                    transform = (fu*PU) | (fur*PUR);
+
+                    break;
+
+                case 2:
+                case 6:
+                    /* top row of fragments, not including top-left frag;
+                     * only consider the left fragment for prediction */
+
+                    /* calculate the indices of the predicting fragments */
+                    l = i - 1;
+
+                    /* fetch the DC values for the predicting fragments */
+                    vl = s->all_fragments[l].coeffs[0];
+
+                    /* figure out which fragments are valid */
+                    fl = FRAME_CODED(l) && COMPATIBLE_FRAME(l);
+
+                    /* decide which predictor transform to use */
+                    transform = (fl*PL);
+
+                    break;
+
+                case 3:
+                    /* top-left fragment */
+
+                    /* nothing to predict from in this case */
+                    transform = 0;
+
+                    break;
+
+                case 4:
+                    /* right column of fragments, not including top corner;
+                     * consider up-left, up, and left fragments for
+                     * prediction */
+
+                    /* calculate the indices of the predicting fragments */
+                    ul = i - fragment_width - 1;
+                    u = i - fragment_width;
+                    l = i - 1;
+
+                    /* fetch the DC values for the predicting fragments */
+                    vul = s->all_fragments[ul].coeffs[0];
+                    vu = s->all_fragments[u].coeffs[0];
+                    vl = s->all_fragments[l].coeffs[0];
+
+                    /* figure out which fragments are valid */
+                    ful = FRAME_CODED(ul) && COMPATIBLE_FRAME(ul);
+                    fu = FRAME_CODED(u) && COMPATIBLE_FRAME(u);
+                    fl = FRAME_CODED(l) && COMPATIBLE_FRAME(l);
+
+                    /* decide which predictor transform to use */
+                    transform = (fl*PL) | (fu*PU) | (ful*PUL);
+
+                    break;
+
+                }
+
+                debug_dc_pred("transform = %d, ", transform);
+
+                if (transform == 0) {
+
+                    /* if there were no fragments to predict from, use last
+                     * DC saved */
+                    s->all_fragments[i].coeffs[0] += last_dc[current_frame_type];
+                    debug_dc_pred("from last DC (%d) = %d\n", 
+                        current_frame_type, s->all_fragments[i].coeffs[0]);
+
+                } else {
+
+                    /* apply the appropriate predictor transform */
+                    predicted_dc =
+                        (predictor_transform[transform][0] * vul) +
+                        (predictor_transform[transform][1] * vu) +
+                        (predictor_transform[transform][2] * vur) +
+                        (predictor_transform[transform][3] * vl);
+
+                    /* if there is a shift value in the transform, add
+                     * the sign bit before the shift */
+                    if (predictor_transform[transform][5] != 0) {
+                        predicted_dc += ((predicted_dc >> 15) & 
+                            predictor_transform[transform][4]);
+                        predicted_dc >>= predictor_transform[transform][5];
+                    }
+
+                    /* check for outranging on the [ul u l] and
+                     * [ul u ur l] predictors */
+                    if ((transform == 13) || (transform == 15)) {
+                        if (iabs(predicted_dc - vu) > 128)
+                            predicted_dc = vu;
+                        else if (iabs(predicted_dc - vl) > 128)
+                            predicted_dc = vl;
+                        else if (iabs(predicted_dc - vul) > 128)
+                            predicted_dc = vul;
+                    }
+
+                    /* at long last, apply the predictor */
+                    s->all_fragments[i].coeffs[0] += predicted_dc;
+                    debug_dc_pred("from pred DC = %d\n", 
+                    s->all_fragments[i].coeffs[0]);
+                }
+
+                /* save the DC */
+                last_dc[current_frame_type] = s->all_fragments[i].coeffs[0];
+            }
+        }
+    }
+}
+
+/*
+ * This function performs the final rendering of each fragment's data
+ * onto the output frame.
+ */
+static void render_fragments(Vp3DecodeContext *s,
+                             int first_fragment,
+                             int fragment_width,
+                             int fragment_height,
+                             int plane /* 0 = Y, 1 = U, 2 = V */) 
+{
+    int x, y;
+    int m, n;
+    int i = first_fragment;
+    int j;
+    int16_t *dequantizer;
+    DCTELEM dequant_block[64];
+    unsigned char *output_plane;
+    unsigned char *last_plane;
+    unsigned char *golden_plane;
+    int stride;
+
+    debug_vp3("  vp3: rendering final fragments for %s\n",
+        (plane == 0) ? "Y plane" : (plane == 1) ? "U plane" : "V plane");
+
+    /* set up plane-specific parameters */
+    if (plane == 0) {
+        dequantizer = s->intra_y_dequant;
+        output_plane = s->current_frame.data[0];
+        last_plane = s->current_frame.data[0];
+        golden_plane = s->current_frame.data[0];
+        stride = -s->current_frame.linesize[0];
+    } else if (plane == 1) {
+        dequantizer = s->intra_c_dequant;
+        output_plane = s->current_frame.data[1];
+        last_plane = s->current_frame.data[1];
+        golden_plane = s->current_frame.data[1];
+        stride = -s->current_frame.linesize[1];
+    } else {
+        dequantizer = s->intra_c_dequant;
+        output_plane = s->current_frame.data[2];
+        last_plane = s->current_frame.data[2];
+        golden_plane = s->current_frame.data[2];
+        stride = -s->current_frame.linesize[2];
+    }
+
+    /* for each fragment row... */
+    for (y = 0; y < fragment_height; y++) {
+
+        /* for each fragment in a row... */
+        for (x = 0; x < fragment_width; x++, i++) {
+
+            /* transform if this block was coded */
+            if (s->all_fragments[i].coding_method == MODE_INTRA) {
+                /* dequantize the DCT coefficients */
+                for (j = 0; j < 64; j++)
+                    dequant_block[dequant_index[j]] =
+                        s->all_fragments[i].coeffs[j] *
+                        dequantizer[j];
+                dequant_block[0] += 1024;
+
+                debug_idct("fragment %d:\n", i);
+                debug_idct("dequantized block:\n");
+                for (m = 0; m < 8; m++) {
+                    for (n = 0; n < 8; n++) {
+                        debug_idct(" %5d", dequant_block[m * 8 + n]);
+                    }
+                    debug_idct("\n");
+                }
+                debug_idct("\n");
+
+                /* invert DCT and place in final output */
+                s->dsp.idct_put(
+                    output_plane + s->all_fragments[i].first_pixel,
+                    stride, dequant_block);
+
+/*
+                debug_idct("idct block:\n");
+                for (m = 0; m < 8; m++) {
+                    for (n = 0; n < 8; n++) {
+                        debug_idct(" %3d", pixels[m * 8 + n]);
+                    }
+                    debug_idct("\n");
+                }
+                debug_idct("\n");
+*/
+            } else if (s->all_fragments[i].coding_method == MODE_COPY) {
+
+                /* copy directly from the previous frame */
+                for (m = 0; m < 8; m++)
+                    memcpy(
+                        output_plane + s->all_fragments[i].first_pixel + stride * m,
+                        last_plane + s->all_fragments[i].first_pixel + stride * m,
+                        8);
+
+            } else {
+
+                /* carry out the motion compensation */
+
+            }
+        }
+    }
+
+    emms_c();
+
+}
+
+/* 
+ * This function computes the first pixel addresses for each fragment.
+ * This function needs to be invoked after the first frame is allocated
+ * so that it has access to the plane strides.
+ */
+static void vp3_calculate_pixel_addresses(Vp3DecodeContext *s) 
+{
+
+    int i, x, y;
+
+    /* figure out the first pixel addresses for each of the fragments */
+    /* Y plane */
+    i = 0;
+    for (y = s->fragment_height; y > 0; y--) {
+        for (x = 0; x < s->fragment_width; x++) {
+            s->all_fragments[i++].first_pixel = 
+                s->golden_frame.linesize[0] * y * FRAGMENT_PIXELS -
+                    s->golden_frame.linesize[0] +
+                    x * FRAGMENT_PIXELS;
+            debug_init("  fragment %d, first pixel @ %d\n", 
+                i-1, s->all_fragments[i-1].first_pixel);
+        }
+    }
+
+    /* U plane */
+    i = s->u_fragment_start;
+    for (y = s->fragment_height / 2; y > 0; y--) {
+        for (x = 0; x < s->fragment_width / 2; x++) {
+            s->all_fragments[i++].first_pixel = 
+                s->golden_frame.linesize[1] * y * FRAGMENT_PIXELS -
+                    s->golden_frame.linesize[1] +
+                    x * FRAGMENT_PIXELS;
+            debug_init("  fragment %d, first pixel @ %d\n", 
+                i-1, s->all_fragments[i-1].first_pixel);
+        }
+    }
+
+    /* V plane */
+    i = s->v_fragment_start;
+    for (y = s->fragment_height / 2; y > 0; y--) {
+        for (x = 0; x < s->fragment_width / 2; x++) {
+            s->all_fragments[i++].first_pixel = 
+                s->golden_frame.linesize[2] * y * FRAGMENT_PIXELS -
+                    s->golden_frame.linesize[2] +
+                    x * FRAGMENT_PIXELS;
+            debug_init("  fragment %d, first pixel @ %d\n", 
+                i-1, s->all_fragments[i-1].first_pixel);
+        }
+    }
+}
+
+/*
+ * This is the ffmpeg/libavcodec API init function.
+ */
+static int vp3_decode_init(AVCodecContext *avctx)
+{
+    Vp3DecodeContext *s = avctx->priv_data;
+    int i;
+
+    s->avctx = avctx;
+    s->width = avctx->width;
+    s->height = avctx->height;
+    avctx->pix_fmt = PIX_FMT_YUV420P;
+    avctx->has_b_frames = 0;
+    dsputil_init(&s->dsp, avctx);
+
+    /* initialize to an impossible value which will force a recalculation
+     * in the first frame decode */
+    s->quality_index = -1;
+
+    s->superblock_width = (s->width + 31) / 32;
+    s->superblock_height = (s->height + 31) / 32;
+    s->superblock_count = s->superblock_width * s->superblock_height * 3 / 2;
+    s->u_superblock_start = s->superblock_width * s->superblock_height;
+    s->v_superblock_start = s->superblock_width * s->superblock_height * 5 / 4;
+    s->superblock_coding = av_malloc(s->superblock_count);
+
+    s->macroblock_width = (s->width + 15) / 16;
+    s->macroblock_height = (s->height + 15) / 16;
+    s->macroblock_count = s->macroblock_width * s->macroblock_height;
+
+    s->fragment_width = s->width / FRAGMENT_PIXELS;
+    s->fragment_height = s->height / FRAGMENT_PIXELS;
+
+    /* fragment count covers all 8x8 blocks for all 3 planes */
+    s->fragment_count = s->fragment_width * s->fragment_height * 3 / 2;
+    s->u_fragment_start = s->fragment_width * s->fragment_height;
+    s->v_fragment_start = s->fragment_width * s->fragment_height * 5 / 4;
+
+    debug_init("  width: %d x %d\n", s->width, s->height);
+    debug_init("  superblocks: %d x %d, %d total\n",
+        s->superblock_width, s->superblock_height, s->superblock_count);
+    debug_init("  macroblocks: %d x %d, %d total\n",
+        s->macroblock_width, s->macroblock_height, s->macroblock_count);
+    debug_init("  %d fragments, %d x %d, u starts @ %d, v starts @ %d\n",
+        s->fragment_count,
+        s->fragment_width,
+        s->fragment_height,
+        s->u_fragment_start,
+        s->v_fragment_start);
+
+    s->all_fragments = av_malloc(s->fragment_count * sizeof(Vp3Fragment));
+    s->coded_fragment_list = av_malloc(s->fragment_count * sizeof(int));
+    s->pixel_addresses_inited = 0;
+
+    /* init VLC tables */
+    for (i = 0; i < 16; i++) {
+
+        /* Dc histograms */
+        init_vlc(&s->dc_vlc[i], 5, 32,
+            &dc_bias[i][0][1], 4, 2,
+            &dc_bias[i][0][0], 4, 2);
+
+        /* level 1 AC histograms */
+        init_vlc(&s->ac_vlc_1[i], 5, 32,
+            &ac_bias_0[i][0][1], 4, 2,
+            &ac_bias_0[i][0][0], 4, 2);
+
+        /* level 2 AC histograms */
+        init_vlc(&s->ac_vlc_2[i], 5, 32,
+            &ac_bias_1[i][0][1], 4, 2,
+            &ac_bias_1[i][0][0], 4, 2);
+
+        /* level 3 AC histograms */
+        init_vlc(&s->ac_vlc_3[i], 5, 32,
+            &ac_bias_2[i][0][1], 4, 2,
+            &ac_bias_2[i][0][0], 4, 2);
+
+        /* level 4 AC histograms */
+        init_vlc(&s->ac_vlc_4[i], 5, 32,
+            &ac_bias_3[i][0][1], 4, 2,
+            &ac_bias_3[i][0][0], 4, 2);
+    }
+
+    /* build quantization table */
+    for (i = 0; i < 64; i++)
+        quant_index[dequant_index[i]] = i;
+
+    /* work out the block mapping tables */
+    s->superblock_fragments = av_malloc(s->superblock_count * 16 * sizeof(int));
+    s->superblock_macroblocks = av_malloc(s->superblock_count * 4 * sizeof(int));
+    s->macroblock_fragments = av_malloc(s->macroblock_count * 6 * sizeof(int));
+    s->macroblock_coded = av_malloc(s->macroblock_count + 1);
+    init_block_mapping(s);
+
+    return 0;
+}
+
+/*
+ * This is the ffmpeg/libavcodec API frame decode function.
+ */
+static int vp3_decode_frame(AVCodecContext *avctx, 
+                            void *data, int *data_size,
+                            uint8_t *buf, int buf_size)
+{
+    Vp3DecodeContext *s = avctx->priv_data;
+    GetBitContext gb;
+    static int counter = 0;
+
+    *data_size = 0;
+
+    init_get_bits(&gb, buf, buf_size * 8);
+
+    s->keyframe = get_bits(&gb, 1);
+    s->keyframe ^= 1;
+    skip_bits(&gb, 1);
+    s->last_quality_index = s->quality_index;
+    s->quality_index = get_bits(&gb, 6);
+    if (s->quality_index != s->last_quality_index)
+        init_dequantizer(s);
+
+    debug_vp3(" VP3 frame #%d: Q index = %d", counter, s->quality_index);
+    counter++;
+
+    if (s->keyframe) {
+        /* release the previous golden frame and get a new one */
+        if (counter > 1)
+            avctx->release_buffer(avctx, &s->golden_frame);
+
+        s->golden_frame.reference = 0;
+        if(avctx->get_buffer(avctx, &s->golden_frame) < 0) {
+            printf("vp3: get_buffer() failed\n");
+            return -1;
+        }
+
+        /* last frame is hereby invalidated */
+        avctx->release_buffer(avctx, &s->last_frame);
+
+        /* golden frame is also the current frame */
+        s->current_frame = s->golden_frame;
+
+        /* time to figure out pixel addresses? */
+        if (!s->pixel_addresses_inited)
+            vp3_calculate_pixel_addresses(s);
+
+    } else {
+
+        /* allocate a new current frame */
+        s->current_frame.reference = 0;
+        if(avctx->get_buffer(avctx, &s->current_frame) < 0) {
+            printf("vp3: get_buffer() failed\n");
+            return -1;
+        }
+
+    }
+
+    if (s->keyframe) {
+      debug_vp3(", keyframe\n");
+      /* skip the other 2 header bytes for now */
+      skip_bits(&gb, 16);
+    } else
+      debug_vp3("\n");
+
+    init_frame(s, &gb);
+
+    unpack_superblocks(s, &gb);
+    unpack_modes(s, &gb);
+    unpack_vectors(s, &gb);
+    unpack_dct_coeffs(s, &gb);
+
+    reverse_dc_prediction(s, 0, s->fragment_width, s->fragment_height);
+    reverse_dc_prediction(s, s->u_fragment_start,
+        s->fragment_width / 2, s->fragment_height / 2);
+    reverse_dc_prediction(s, s->v_fragment_start,
+        s->fragment_width / 2, s->fragment_height / 2);
+
+    render_fragments(s, 0, s->fragment_width, s->fragment_height, 0);
+    render_fragments(s, s->u_fragment_start,
+        s->fragment_width / 2, s->fragment_height / 2, 1);
+    render_fragments(s, s->v_fragment_start,
+        s->fragment_width / 2, s->fragment_height / 2, 2);
+
+
+    *data_size=sizeof(AVFrame);
+    *(AVFrame*)data= s->current_frame;
+
+    /* release the last frame, if it was allocated */
+    avctx->release_buffer(avctx, &s->last_frame);
+
+    /* shuffle frames */
+    s->last_frame = s->current_frame;
+
+    return buf_size;
+}
+
+/*
+ * This is the ffmpeg/libavcodec API module cleanup function.
+ */
+static int vp3_decode_end(AVCodecContext *avctx)
+{
+    Vp3DecodeContext *s = avctx->priv_data;
+
+    av_free(s->all_fragments);
+    av_free(s->coded_fragment_list);
+    av_free(s->superblock_fragments);
+    av_free(s->superblock_macroblocks);
+    av_free(s->macroblock_fragments);
+    av_free(s->macroblock_coded);
+
+    /* release all frames */
+    avctx->release_buffer(avctx, &s->golden_frame);
+    avctx->release_buffer(avctx, &s->last_frame);
+    avctx->release_buffer(avctx, &s->current_frame);
+
+    return 0;
+}
+
+AVCodec vp3_decoder = {
+    "vp3",
+    CODEC_TYPE_VIDEO,
+    CODEC_ID_VP3,
+    sizeof(Vp3DecodeContext),
+    vp3_decode_init,
+    NULL,
+    vp3_decode_end,
+    vp3_decode_frame,
+    0,
+    NULL
+};