Initial revision

Originally committed as revision 5 to svn://svn.ffmpeg.org/ffmpeg/trunk

1 files changed, 931 insertions, 0 deletions

diff --git a/libavcodec/msmpeg4.c b/libavcodec/msmpeg4.c
new file mode 100644
index 0000000000..044d964ee5
--- /dev/null
+++ b/libavcodec/msmpeg4.c
@@ -0,0 +1,931 @@
+/*
+ * MSMPEG4 backend for ffmpeg encoder and decoder
+ * Copyright (c) 2001 Gerard Lantau.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program 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 General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+ */
+#include <stdlib.h>
+#include <stdio.h>
+#include "common.h"
+#include "dsputil.h"
+#include "mpegvideo.h"
+
+/*
+ * You can also call this codec : MPEG4 with a twist ! 
+ *
+ * TODO: 
+ *        - (encoding) select best mv table (two choices)
+ *        - (encoding) select best vlc/dc table 
+ *        - (decoding) handle slice indication
+ */
+//#define DEBUG
+
+/* motion vector table */
+typedef struct MVTable {
+    int n;
+    const UINT16 *table_mv_code;
+    const UINT8 *table_mv_bits;
+    const UINT8 *table_mvx;
+    const UINT8 *table_mvy;
+    UINT16 *table_mv_index; /* encoding: convert mv to index in table_mv */
+    VLC vlc;                /* decoding: vlc */
+} MVTable;
+
+static void msmpeg4_encode_block(MpegEncContext * s, DCTELEM * block, int n);
+static int msmpeg4_decode_block(MpegEncContext * s, DCTELEM * block,
+                                int n, int coded);
+static int msmpeg4_decode_dc(MpegEncContext * s, int n, int *dir_ptr);
+static int msmpeg4_decode_motion(MpegEncContext * s, 
+                                 int *mx_ptr, int *my_ptr);
+
+#ifdef DEBUG
+int intra_count = 0;
+int frame_count = 0;
+#endif
+/* XXX: move it to mpegvideo.h */
+
+static int init_done = 0;
+
+#include "msmpeg4data.h"
+
+#ifdef STATS
+
+const char *st_names[ST_NB] = {
+    "unknown",
+    "dc",
+    "intra_ac",
+    "inter_ac",
+    "intra_mb",
+    "inter_mb",
+    "mv",
+};
+
+int st_current_index = 0;
+unsigned int st_bit_counts[ST_NB];
+unsigned int st_out_bit_counts[ST_NB];
+
+#define set_stat(var) st_current_index = var;
+
+void print_stats(void)
+{
+    unsigned int total;
+    int i;
+
+    printf("Input:\n");
+    total = 0;
+    for(i=0;i<ST_NB;i++)
+        total += st_bit_counts[i];
+    if (total == 0)
+        total = 1;
+    for(i=0;i<ST_NB;i++) {
+        printf("%-10s : %10.1f %5.1f%%\n", 
+               st_names[i], 
+               (double)st_bit_counts[i] / 8.0, 
+               (double)st_bit_counts[i] * 100.0 / total);
+    }
+    printf("%-10s : %10.1f %5.1f%%\n",
+           "total", 
+           (double)total / 8.0, 
+           100.0);
+
+    printf("Output:\n");
+    total = 0;
+    for(i=0;i<ST_NB;i++)
+        total += st_out_bit_counts[i];
+    if (total == 0)
+        total = 1;
+    for(i=0;i<ST_NB;i++) {
+        printf("%-10s : %10.1f %5.1f%%\n", 
+               st_names[i], 
+               (double)st_out_bit_counts[i] / 8.0, 
+               (double)st_out_bit_counts[i] * 100.0 / total);
+    }
+    printf("%-10s : %10.1f %5.1f%%\n",
+           "total", 
+           (double)total / 8.0, 
+           100.0);
+}
+
+#else
+
+#define set_stat(var)
+
+#endif
+
+/* build the table which associate a (x,y) motion vector to a vlc */
+static void init_mv_table(MVTable *tab)
+{
+    int i, x, y;
+
+    tab->table_mv_index = malloc(sizeof(UINT16) * 4096);
+    /* mark all entries as not used */
+    for(i=0;i<4096;i++)
+        tab->table_mv_index[i] = tab->n;
+    
+    for(i=0;i<tab->n;i++) {
+        x = tab->table_mvx[i];
+        y = tab->table_mvy[i];
+        tab->table_mv_index[(x << 6) | y] = i;
+    }
+}
+
+static void code012(PutBitContext *pb, int n)
+{
+    if (n == 0) {
+        put_bits(pb, 1, 0);
+    } else {
+        put_bits(pb, 1, 1);
+        put_bits(pb, 1, (n >= 2));
+    }
+}
+
+/* write MSMPEG4 V3 compatible frame header */
+void msmpeg4_encode_picture_header(MpegEncContext * s, int picture_number)
+{
+    int i;
+
+    align_put_bits(&s->pb);
+
+    put_bits(&s->pb, 2, s->pict_type - 1);
+
+    put_bits(&s->pb, 5, s->qscale);
+
+    s->rl_table_index = 2;
+    s->rl_chroma_table_index = 1; /* only for I frame */
+    s->dc_table_index = 1;
+    s->mv_table_index = 1; /* only if P frame */
+    s->use_skip_mb_code = 1; /* only if P frame */
+    
+    if (s->pict_type == I_TYPE) {
+        put_bits(&s->pb, 5, 0x17); /* indicate only one "slice" */
+
+        code012(&s->pb, s->rl_chroma_table_index);
+        code012(&s->pb, s->rl_table_index);
+
+        put_bits(&s->pb, 1, s->dc_table_index);
+        s->no_rounding = 1;
+    } else {
+        put_bits(&s->pb, 1, s->use_skip_mb_code);
+        
+        s->rl_chroma_table_index = s->rl_table_index;
+        code012(&s->pb, s->rl_table_index);
+
+        put_bits(&s->pb, 1, s->dc_table_index);
+
+        put_bits(&s->pb, 1, s->mv_table_index);
+        s->no_rounding ^= 1;
+    }
+
+    if (!init_done) {
+        /* init various encoding tables */
+        init_done = 1;
+        init_mv_table(&mv_tables[0]);
+        init_mv_table(&mv_tables[1]);
+        for(i=0;i<NB_RL_TABLES;i++)
+            init_rl(&rl_table[i]);
+    }
+
+#ifdef DEBUG
+    intra_count = 0;
+    printf("*****frame %d:\n", frame_count++);
+#endif
+}
+
+/* predict coded block */
+static inline int coded_block_pred(MpegEncContext * s, int n, UINT8 **coded_block_ptr)
+{
+    int x, y, wrap, pred, a, b, c;
+
+    x = 2 * s->mb_x + 1 + (n & 1);
+    y = 2 * s->mb_y + 1 + ((n & 2) >> 1);
+    wrap = s->mb_width * 2 + 2;
+
+    /* B C
+     * A X 
+     */
+    a = s->coded_block[(x - 1) + (y) * wrap];
+    b = s->coded_block[(x - 1) + (y - 1) * wrap];
+    c = s->coded_block[(x) + (y - 1) * wrap];
+    
+    if (b == c) {
+        pred = a;
+    } else {
+        pred = c;
+    }
+    
+    /* store value */
+    *coded_block_ptr = &s->coded_block[(x) + (y) * wrap];
+
+    return pred;
+}
+
+static void msmpeg4_encode_motion(MpegEncContext * s, 
+                                  int mx, int my)
+{
+    int code;
+    MVTable *mv;
+
+    /* modulo encoding */
+    /* WARNING : you cannot reach all the MVs even with the modulo
+       encoding. This is a somewhat strange compromise they took !!!  */
+    if (mx <= -64)
+        mx += 64;
+    else if (mx >= 64)
+        mx -= 64;
+    if (my <= -64)
+        my += 64;
+    else if (my >= 64)
+        my -= 64;
+    
+    mx += 32;
+    my += 32;
+#if 0
+    if ((unsigned)mx >= 64 ||
+        (unsigned)my >= 64) 
+        fprintf(stderr, "error mx=%d my=%d\n", mx, my);
+#endif
+    mv = &mv_tables[s->mv_table_index];
+
+    code = mv->table_mv_index[(mx << 6) | my];
+    set_stat(ST_MV);
+    put_bits(&s->pb, 
+             mv->table_mv_bits[code], 
+             mv->table_mv_code[code]);
+    if (code == mv->n) {
+        /* escape : code litterally */
+        put_bits(&s->pb, 6, mx);
+        put_bits(&s->pb, 6, my);
+    }
+}
+
+void msmpeg4_encode_mb(MpegEncContext * s, 
+                       DCTELEM block[6][64],
+                       int motion_x, int motion_y)
+{
+    int cbp, coded_cbp, i;
+    int pred_x, pred_y;
+    UINT8 *coded_block;
+
+    if (!s->mb_intra) {
+	/* compute cbp */
+        set_stat(ST_INTER_MB);
+	cbp = 0;
+	for (i = 0; i < 6; i++) {
+	    if (s->block_last_index[i] >= 0)
+		cbp |= 1 << (5 - i);
+	}
+	if (s->use_skip_mb_code && (cbp | motion_x | motion_y) == 0) {
+	    /* skip macroblock */
+	    put_bits(&s->pb, 1, 1);
+	    return;
+	}
+        if (s->use_skip_mb_code)
+            put_bits(&s->pb, 1, 0);	/* mb coded */
+        
+        put_bits(&s->pb, 
+                 table_mb_non_intra[cbp + 64][1], 
+                 table_mb_non_intra[cbp + 64][0]);
+
+        /* motion vector */
+        h263_pred_motion(s, 0, &pred_x, &pred_y);
+        msmpeg4_encode_motion(s, motion_x - pred_x, 
+                              motion_y - pred_y);
+    } else {
+	/* compute cbp */
+	cbp = 0;
+        coded_cbp = 0;
+	for (i = 0; i < 6; i++) {
+            int val, pred;
+            val = (s->block_last_index[i] >= 1);
+            cbp |= val << (5 - i);
+            if (i < 4) {
+                /* predict value for close blocks only for luma */
+                pred = coded_block_pred(s, i, &coded_block);
+                *coded_block = val;
+                val = val ^ pred;
+            }
+            coded_cbp |= val << (5 - i);
+	}
+#if 0
+        if (coded_cbp)
+            printf("cbp=%x %x\n", cbp, coded_cbp);
+#endif
+
+	if (s->pict_type == I_TYPE) {
+            set_stat(ST_INTRA_MB);
+            put_bits(&s->pb, 
+                     table_mb_intra[coded_cbp][1], table_mb_intra[coded_cbp][0]);
+        } else {
+            if (s->use_skip_mb_code)
+                put_bits(&s->pb, 1, 0);	/* mb coded */
+            put_bits(&s->pb, 
+                     table_mb_non_intra[cbp][1], 
+                     table_mb_non_intra[cbp][0]);
+        }
+        set_stat(ST_INTRA_MB);
+        put_bits(&s->pb, 1, 0);	/* no AC prediction yet */
+    }
+
+    for (i = 0; i < 6; i++) {
+        msmpeg4_encode_block(s, block[i], i);
+    }
+}
+
+
+/* strongly inspirated from MPEG4, but not exactly the same ! */
+void msmpeg4_dc_scale(MpegEncContext * s)
+{
+    int scale;
+
+    if (s->qscale < 5)
+        scale = 8;
+    else if (s->qscale < 9)
+        scale = 2 * s->qscale;
+    else 
+        scale = s->qscale + 8;
+    s->y_dc_scale = scale;
+    s->c_dc_scale = (s->qscale + 13) / 2;
+}
+
+/* dir = 0: left, dir = 1: top prediction */
+static int msmpeg4_pred_dc(MpegEncContext * s, int n, 
+                           UINT16 **dc_val_ptr, int *dir_ptr)
+{
+    int a, b, c, x, y, wrap, pred, scale;
+    UINT16 *dc_val;
+
+    /* find prediction */
+    if (n < 4) {
+	x = 2 * s->mb_x + 1 + (n & 1);
+	y = 2 * s->mb_y + 1 + ((n & 2) >> 1);
+	wrap = s->mb_width * 2 + 2;
+	dc_val = s->dc_val[0];
+	scale = s->y_dc_scale;
+    } else {
+	x = s->mb_x + 1;
+	y = s->mb_y + 1;
+	wrap = s->mb_width + 2;
+	dc_val = s->dc_val[n - 4 + 1];
+	scale = s->c_dc_scale;
+    }
+
+    /* B C
+     * A X 
+     */
+    a = dc_val[(x - 1) + (y) * wrap];
+    b = dc_val[(x - 1) + (y - 1) * wrap];
+    c = dc_val[(x) + (y - 1) * wrap];
+
+    /* XXX: the following solution consumes divisions, but it does not
+       necessitate to modify mpegvideo.c. The problem comes from the
+       fact they decided to store the quantized DC (which would lead
+       to problems if Q could vary !) */
+    a = (a + (scale >> 1)) / scale;
+    b = (b + (scale >> 1)) / scale;
+    c = (c + (scale >> 1)) / scale;
+
+    /* XXX: WARNING: they did not choose the same test as MPEG4. This
+       is very important ! */
+    if (abs(a - b) <= abs(b - c)) {
+	pred = c;
+        *dir_ptr = 1;
+    } else {
+	pred = a;
+        *dir_ptr = 0;
+    }
+
+    /* update predictor */
+    *dc_val_ptr = &dc_val[(x) + (y) * wrap];
+    return pred;
+}
+
+#define DC_MAX 119
+
+static void msmpeg4_encode_dc(MpegEncContext * s, int level, int n, int *dir_ptr)
+{
+    int sign, code;
+    int pred;
+    UINT16 *dc_val;
+
+    pred = msmpeg4_pred_dc(s, n, &dc_val, dir_ptr);
+
+    /* update predictor */
+    if (n < 4) {
+        *dc_val = level * s->y_dc_scale;
+    } else {
+        *dc_val = level * s->c_dc_scale;
+    }
+
+    /* do the prediction */
+    level -= pred;
+
+    sign = 0;
+    if (level < 0) {
+        level = -level;
+        sign = 1;
+    }
+    
+    code = level;
+    if (code > DC_MAX) 
+        code = DC_MAX;
+
+    if (s->dc_table_index == 0) {
+        if (n < 4) {
+            put_bits(&s->pb, table0_dc_lum[code][1], table0_dc_lum[code][0]);
+        } else {
+            put_bits(&s->pb, table0_dc_chroma[code][1], table0_dc_chroma[code][0]);
+        }
+    } else {
+        if (n < 4) {
+            put_bits(&s->pb, table1_dc_lum[code][1], table1_dc_lum[code][0]);
+        } else {
+            put_bits(&s->pb, table1_dc_chroma[code][1], table1_dc_chroma[code][0]);
+        }
+    }
+        
+    if (code == DC_MAX)
+        put_bits(&s->pb, 8, level);
+        
+    if (level != 0) {
+        put_bits(&s->pb, 1, sign);
+    }
+}
+
+/* Encoding of a block. Very similar to MPEG4 except for a different
+   escape coding (same as H263) and more vlc tables.
+ */
+static void msmpeg4_encode_block(MpegEncContext * s, DCTELEM * block, int n)
+{
+    int level, run, last, i, j, last_index;
+    int last_non_zero, sign, slevel;
+    int code, run_diff, dc_pred_dir;
+    const RLTable *rl;
+
+    if (s->mb_intra) {
+        set_stat(ST_DC);
+        msmpeg4_encode_dc(s, block[0], n, &dc_pred_dir);
+        i = 1;
+        if (n < 4) {
+            rl = &rl_table[s->rl_table_index];
+        } else {
+            rl = &rl_table[3 + s->rl_chroma_table_index];
+        }
+        run_diff = 0;
+        set_stat(ST_INTRA_AC);
+    } else {
+        i = 0;
+        rl = &rl_table[3 + s->rl_table_index];
+        run_diff = 1;
+        set_stat(ST_INTER_AC);
+    }
+
+    /* AC coefs */
+    last_index = s->block_last_index[n];
+    last_non_zero = i - 1;
+    for (; i <= last_index; i++) {
+	j = zigzag_direct[i];
+	level = block[j];
+	if (level) {
+	    run = i - last_non_zero - 1;
+	    last = (i == last_index);
+	    sign = 0;
+	    slevel = level;
+	    if (level < 0) {
+		sign = 1;
+		level = -level;
+	    }
+            code = get_rl_index(rl, last, run, level);
+            put_bits(&s->pb, rl->table_vlc[code][1], rl->table_vlc[code][0]);
+            if (code == rl->n) {
+                int level1, run1;
+
+                level1 = level - rl->max_level[last][run];
+                if (level1 < 1) 
+                    goto esc2;
+                code = get_rl_index(rl, last, run, level1);
+                if (code == rl->n) {
+                esc2:
+                    put_bits(&s->pb, 1, 0);
+                    if (level > MAX_LEVEL)
+                        goto esc3;
+                    run1 = run - rl->max_run[last][level] - run_diff;
+                    if (run1 < 0)
+                        goto esc3;
+                    code = get_rl_index(rl, last, run1, level);
+                    if (code == rl->n) {
+                    esc3:
+                        /* third escape */
+                        put_bits(&s->pb, 1, 0);
+                        put_bits(&s->pb, 1, last);
+                        put_bits(&s->pb, 6, run);
+                        put_bits(&s->pb, 8, slevel & 0xff);
+                    } else {
+                        /* second escape */
+                        put_bits(&s->pb, 1, 1);
+                        put_bits(&s->pb, rl->table_vlc[code][1], rl->table_vlc[code][0]);
+                        put_bits(&s->pb, 1, sign);
+                    }
+                } else {
+                    /* first escape */
+                    put_bits(&s->pb, 1, 1);
+                    put_bits(&s->pb, rl->table_vlc[code][1], rl->table_vlc[code][0]);
+                    put_bits(&s->pb, 1, sign);
+                }
+            } else {
+                put_bits(&s->pb, 1, sign);
+            }
+	    last_non_zero = i;
+	}
+    }
+}
+
+/****************************************/
+/* decoding stuff */
+
+static VLC mb_non_intra_vlc;
+static VLC mb_intra_vlc;
+static VLC dc_lum_vlc[2];
+static VLC dc_chroma_vlc[2];
+
+/* init all vlc decoding tables */
+int msmpeg4_decode_init_vlc(MpegEncContext *s)
+{
+    int i;
+    MVTable *mv;
+
+    for(i=0;i<NB_RL_TABLES;i++) {
+        init_rl(&rl_table[i]);
+        init_vlc_rl(&rl_table[i]);
+    }
+    for(i=0;i<2;i++) {
+        mv = &mv_tables[i];
+        init_vlc(&mv->vlc, 9, mv->n + 1, 
+                 mv->table_mv_bits, 1, 1,
+                 mv->table_mv_code, 2, 2);
+    }
+
+    init_vlc(&dc_lum_vlc[0], 9, 120, 
+             &table0_dc_lum[0][1], 8, 4,
+             &table0_dc_lum[0][0], 8, 4);
+    init_vlc(&dc_chroma_vlc[0], 9, 120, 
+             &table0_dc_chroma[0][1], 8, 4,
+             &table0_dc_chroma[0][0], 8, 4);
+    init_vlc(&dc_lum_vlc[1], 9, 120, 
+             &table1_dc_lum[0][1], 8, 4,
+             &table1_dc_lum[0][0], 8, 4);
+    init_vlc(&dc_chroma_vlc[1], 9, 120, 
+             &table1_dc_chroma[0][1], 8, 4,
+             &table1_dc_chroma[0][0], 8, 4);
+
+    init_vlc(&mb_non_intra_vlc, 9, 128, 
+             &table_mb_non_intra[0][1], 8, 4,
+             &table_mb_non_intra[0][0], 8, 4);
+    init_vlc(&mb_intra_vlc, 9, 128, 
+             &table_mb_intra[0][1], 4, 2,
+             &table_mb_intra[0][0], 4, 2);
+    return 0;
+}
+
+static int decode012(GetBitContext *gb)
+{
+    int n;
+    n = get_bits(gb, 1);
+    if (n == 0)
+        return 0;
+    else
+        return get_bits(gb, 1) + 1;
+}
+
+int msmpeg4_decode_picture_header(MpegEncContext * s)
+{
+    int code;
+
+    s->pict_type = get_bits(&s->gb, 2) + 1;
+    if (s->pict_type != I_TYPE &&
+        s->pict_type != P_TYPE)
+        return -1;
+
+    s->qscale = get_bits(&s->gb, 5);
+
+    if (s->pict_type == I_TYPE) {
+        code = get_bits(&s->gb, 5); 
+        /* 0x17: one slice, 0x18: three slices */
+        /* XXX: implement it */
+        if (code < 0x17)
+            return -1;
+        s->slice_height = s->mb_height / (code - 0x16);
+        s->rl_chroma_table_index = decode012(&s->gb);
+        s->rl_table_index = decode012(&s->gb);
+
+        s->dc_table_index = get_bits(&s->gb, 1);
+        s->no_rounding = 1;
+    } else {
+        s->use_skip_mb_code = get_bits(&s->gb, 1);
+        
+        s->rl_table_index = decode012(&s->gb);
+        s->rl_chroma_table_index = s->rl_table_index;
+
+        s->dc_table_index = get_bits(&s->gb, 1);
+
+        s->mv_table_index = get_bits(&s->gb, 1);
+        s->no_rounding ^= 1;
+    }
+#ifdef DEBUG
+    printf("*****frame %d:\n", frame_count++);
+#endif
+    return 0;
+}
+
+void memsetw(short *tab, int val, int n)
+{
+    int i;
+    for(i=0;i<n;i++)
+        tab[i] = val;
+}
+
+int msmpeg4_decode_mb(MpegEncContext *s, 
+                      DCTELEM block[6][64])
+{
+    int cbp, code, i;
+    int pred, val;
+    UINT8 *coded_val;
+
+    /* special slice handling */
+    if (s->mb_x == 0) {
+        if ((s->mb_y % s->slice_height) == 0) {
+            int wrap;
+            /* reset DC pred (set previous line to 1024) */
+            wrap = 2 * s->mb_width + 2;
+            memsetw(&s->dc_val[0][(1) + (2 * s->mb_y) * wrap], 
+                    1024, 2 * s->mb_width);
+            wrap = s->mb_width + 2;
+            memsetw(&s->dc_val[1][(1) + (s->mb_y) * wrap], 
+                    1024, s->mb_width);
+            memsetw(&s->dc_val[2][(1) + (s->mb_y) * wrap], 
+                    1024, s->mb_width);
+
+            s->first_slice_line = 1;
+        } else {
+            s->first_slice_line = 0; 
+        }
+    }
+
+    if (s->pict_type == P_TYPE) {
+        set_stat(ST_INTER_MB);
+        if (s->use_skip_mb_code) {
+            if (get_bits(&s->gb, 1)) {
+                /* skip mb */
+                s->mb_intra = 0;
+                for(i=0;i<6;i++)
+                    s->block_last_index[i] = -1;
+                s->mv_dir = MV_DIR_FORWARD;
+                s->mv_type = MV_TYPE_16X16;
+                s->mv[0][0][0] = 0;
+                s->mv[0][0][1] = 0;
+                return 0;
+            }
+        }
+        
+        code = get_vlc(&s->gb, &mb_non_intra_vlc);
+        if (code < 0)
+            return -1;
+        if (code & 0x40)
+            s->mb_intra = 0;
+        else
+            s->mb_intra = 1;
+            
+        cbp = code & 0x3f;
+    } else {
+        set_stat(ST_INTRA_MB);
+        s->mb_intra = 1;
+        code = get_vlc(&s->gb, &mb_intra_vlc);
+        if (code < 0)
+            return -1;
+        /* predict coded block pattern */
+        cbp = 0;
+        for(i=0;i<6;i++) {
+            val = ((code >> (5 - i)) & 1);
+            if (i < 4) {
+                pred = coded_block_pred(s, i, &coded_val);
+                val = val ^ pred;
+                *coded_val = val;
+            }
+            cbp |= val << (5 - i);
+        }
+    }
+
+    if (!s->mb_intra) {
+        int mx, my;
+        set_stat(ST_MV);
+        h263_pred_motion(s, 0, &mx, &my);
+        if (msmpeg4_decode_motion(s, &mx, &my) < 0)
+            return -1;
+        s->mv_dir = MV_DIR_FORWARD;
+        s->mv_type = MV_TYPE_16X16;
+        s->mv[0][0][0] = mx;
+        s->mv[0][0][1] = my;
+    } else {
+        set_stat(ST_INTRA_MB);
+        s->ac_pred = get_bits(&s->gb, 1);
+    }
+
+    for (i = 0; i < 6; i++) {
+        if (msmpeg4_decode_block(s, block[i], i, (cbp >> (5 - i)) & 1) < 0)
+            return -1;
+    }
+    return 0;
+}
+
+static int msmpeg4_decode_block(MpegEncContext * s, DCTELEM * block,
+                              int n, int coded)
+{
+    int code, level, i, j, last, run, run_diff;
+    int dc_pred_dir;
+    RLTable *rl;
+    const UINT8 *scan_table;
+
+    if (s->mb_intra) {
+	/* DC coef */
+        set_stat(ST_DC);
+        level = msmpeg4_decode_dc(s, n, &dc_pred_dir);
+        if (level < 0)
+            return -1;
+        block[0] = level;
+        if (n < 4) {
+            rl = &rl_table[s->rl_table_index];
+        } else {
+            rl = &rl_table[3 + s->rl_chroma_table_index];
+        }
+        run_diff = 0;
+	i = 1;
+        if (!coded) {
+            goto not_coded;
+        }
+        if (s->ac_pred) {
+            if (dc_pred_dir == 0) 
+                scan_table = ff_alternate_vertical_scan; /* left */
+            else
+                scan_table = ff_alternate_horizontal_scan; /* top */
+        } else {
+            scan_table = zigzag_direct;
+        }
+        set_stat(ST_INTRA_AC);
+    } else {
+	i = 0;
+        rl = &rl_table[3 + s->rl_table_index];
+        run_diff = 1;
+        if (!coded) {
+            s->block_last_index[n] = i - 1;
+            return 0;
+        }
+        scan_table = zigzag_direct;
+        set_stat(ST_INTER_AC);
+    }
+
+    for(;;) {
+        code = get_vlc(&s->gb, &rl->vlc);
+        if (code < 0)
+            return -1;
+        if (code == rl->n) {
+            /* escape */
+            if (get_bits(&s->gb, 1) == 0) {
+                if (get_bits(&s->gb, 1) == 0) {
+                    /* third escape */
+                    last = get_bits(&s->gb, 1);
+                    run = get_bits(&s->gb, 6);
+                    level = get_bits(&s->gb, 8);
+                    level = (level << 24) >> 24; /* sign extend */
+                } else {
+                    /* second escape */
+                    code = get_vlc(&s->gb, &rl->vlc);
+                    if (code < 0 || code >= rl->n)
+                        return -1;
+                    run = rl->table_run[code];
+                    level = rl->table_level[code];
+                    last = code >= rl->last;
+                    run += rl->max_run[last][level] + run_diff;
+                    if (get_bits(&s->gb, 1))
+                        level = -level;
+                }
+            } else {
+                /* first escape */
+                code = get_vlc(&s->gb, &rl->vlc);
+                if (code < 0 || code >= rl->n)
+                    return -1;
+                run = rl->table_run[code];
+                level = rl->table_level[code];
+                last = code >= rl->last;
+                level += rl->max_level[last][run];
+                if (get_bits(&s->gb, 1))
+                    level = -level;
+            }
+        } else {
+            run = rl->table_run[code];
+            level = rl->table_level[code];
+            last = code >= rl->last;
+            if (get_bits(&s->gb, 1))
+                level = -level;
+        }
+        i += run;
+        if (i >= 64)
+            return -1;
+	j = scan_table[i];
+        block[j] = level;
+        i++;
+        if (last)
+            break;
+    }
+ not_coded:
+    if (s->mb_intra) {
+        mpeg4_pred_ac(s, block, n, dc_pred_dir);
+        if (s->ac_pred) {
+            i = 64; /* XXX: not optimal */
+        }
+    }
+    s->block_last_index[n] = i - 1;
+
+    return 0;
+}
+
+static int msmpeg4_decode_dc(MpegEncContext * s, int n, int *dir_ptr)
+{
+    int level, pred;
+    UINT16 *dc_val;
+
+    if (n < 4) {
+        level = get_vlc(&s->gb, &dc_lum_vlc[s->dc_table_index]);
+    } else {
+        level = get_vlc(&s->gb, &dc_chroma_vlc[s->dc_table_index]);
+    }
+    if (level < 0)
+        return -1;
+
+    if (level == DC_MAX) {
+        level = get_bits(&s->gb, 8);
+        if (get_bits(&s->gb, 1))
+            level = -level;
+    } else if (level != 0) {
+        if (get_bits(&s->gb, 1))
+            level = -level;
+    }
+
+    pred = msmpeg4_pred_dc(s, n, &dc_val, dir_ptr);
+    level += pred;
+
+    /* update predictor */
+    if (n < 4) {
+        *dc_val = level * s->y_dc_scale;
+    } else {
+        *dc_val = level * s->c_dc_scale;
+    }
+
+    return level;
+}
+
+static int msmpeg4_decode_motion(MpegEncContext * s, 
+                                 int *mx_ptr, int *my_ptr)
+{
+    MVTable *mv;
+    int code, mx, my;
+
+    mv = &mv_tables[s->mv_table_index];
+
+    code = get_vlc(&s->gb, &mv->vlc);
+    if (code < 0)
+        return -1;
+    if (code == mv->n) {
+        mx = get_bits(&s->gb, 6);
+        my = get_bits(&s->gb, 6);
+    } else {
+        mx = mv->table_mvx[code];
+        my = mv->table_mvy[code];
+    }
+
+    mx += *mx_ptr - 32;
+    my += *my_ptr - 32;
+    /* WARNING : they do not do exactly modulo encoding */
+    if (mx <= -64)
+        mx += 64;
+    else if (mx >= 64)
+        mx -= 64;
+
+    if (my <= -64)
+        my += 64;
+    else if (my >= 64)
+        my -= 64;
+    *mx_ptr = mx;
+    *my_ptr = my;
+    return 0;
+}