h261 decoder by (Maarten Daniels <maarten.daniels at student dot luc dot ac dot be>)

Originally committed as revision 3176 to svn://svn.ffmpeg.org/ffmpeg/trunk

10 files changed, 1153 insertions, 1 deletions

diff --git a/libavcodec/Makefile b/libavcodec/Makefile
index 64b3b132ed..cc7d289870 100644
--- a/libavcodec/Makefile
+++ b/libavcodec/Makefile
@@ -55,7 +55,7 @@ ASM_OBJS=
 
 # codecs which are patented in some non free countries like the us
 ifeq ($(CONFIG_RISKY),yes)
-OBJS+= h263.o msmpeg4.o h263dec.o svq1.o rv10.o wmadec.o indeo3.o
+OBJS+= h263.o h261.o msmpeg4.o h263dec.o svq1.o rv10.o wmadec.o indeo3.o
 endif
 
 ifeq ($(HAVE_XVMC_ACCEL),yes)
diff --git a/libavcodec/allcodecs.c b/libavcodec/allcodecs.c
index 31fd8f6a0d..fcedfc34f1 100644
--- a/libavcodec/allcodecs.c
+++ b/libavcodec/allcodecs.c
@@ -84,6 +84,7 @@ void avcodec_register_all(void)
 #ifdef CONFIG_DECODERS
 #ifdef CONFIG_RISKY
     register_avcodec(&h263_decoder);
+    register_avcodec(&h261_decoder);
     register_avcodec(&mpeg4_decoder);
     register_avcodec(&msmpeg4v1_decoder);
     register_avcodec(&msmpeg4v2_decoder);
@@ -213,6 +214,7 @@ PCM_CODEC(CODEC_ID_ADPCM_EA, adpcm_g726);
     /* parsers */ 
     av_register_codec_parser(&mpegvideo_parser);
     av_register_codec_parser(&mpeg4video_parser);
+    av_register_codec_parser(&h261_parser);
     av_register_codec_parser(&h263_parser);
     av_register_codec_parser(&h264_parser);
 
diff --git a/libavcodec/avcodec.h b/libavcodec/avcodec.h
index 21966a803a..457c990db6 100644
--- a/libavcodec/avcodec.h
+++ b/libavcodec/avcodec.h
@@ -34,6 +34,7 @@ enum CodecID {
     CODEC_ID_MPEG1VIDEO,
     CODEC_ID_MPEG2VIDEO, /* prefered ID for MPEG Video 1 or 2 decoding */
     CODEC_ID_MPEG2VIDEO_XVMC,
+    CODEC_ID_H261,
     CODEC_ID_H263,
     CODEC_ID_RV10,
     CODEC_ID_RV20,
@@ -1724,6 +1725,7 @@ extern AVCodec zlib_encoder;
 extern AVCodec svq1_encoder;
 
 extern AVCodec h263_decoder;
+extern AVCodec h261_decoder;
 extern AVCodec mpeg4_decoder;
 extern AVCodec msmpeg4v1_decoder;
 extern AVCodec msmpeg4v2_decoder;
@@ -2124,6 +2126,7 @@ void av_parser_close(AVCodecParserContext *s);
 
 extern AVCodecParser mpegvideo_parser;
 extern AVCodecParser mpeg4video_parser;
+extern AVCodecParser h261_parser;
 extern AVCodecParser h263_parser;
 extern AVCodecParser h264_parser;
 extern AVCodecParser mpegaudio_parser;
diff --git a/libavcodec/dsputil.c b/libavcodec/dsputil.c
index b1252251ad..63fb32e426 100644
--- a/libavcodec/dsputil.c
+++ b/libavcodec/dsputil.c
@@ -2360,6 +2360,36 @@ static void h263_h_loop_filter_c(uint8_t *src, int stride, int qscale){
     }
 }
 
+static void h261_v_loop_filter_c(uint8_t *dest,uint8_t *src, int stride){
+    int i,j,xy,yz;
+    int res;
+    for(i=0; i<8; i++){
+        for(j=1; j<7; j++){
+            xy = j * stride + i;
+            yz = j * 8 + i;
+            res = (int)src[yz-1*8] + ((int)(src[yz+0*8]) * 2) + (int)src[yz+1*8];
+            res +=2;
+            res >>=2;
+            dest[xy] = (uint8_t)res;
+        }
+    }
+}
+
+static void h261_h_loop_filter_c(uint8_t *dest,uint8_t *src, int stride){
+    int i,j,xy,yz;
+    int res;    
+    for(i=1; i<7; i++){
+        for(j=0; j<8; j++){
+            xy = j * stride + i;
+            yz = j * 8 + i;
+            res = (int)src[yz-1] + ((int)(src[yz]) *2) + (int)src[yz+1];
+            res+=2;
+            res>>=2;
+            dest[xy] = (uint8_t)res;
+        }
+    }
+}
+
 static inline int pix_abs16_c(void *v, uint8_t *pix1, uint8_t *pix2, int line_size, int h)
 {
     int s, i;
@@ -3295,6 +3325,9 @@ void dsputil_init(DSPContext* c, AVCodecContext *avctx)
     c->h263_h_loop_filter= h263_h_loop_filter_c;
     c->h263_v_loop_filter= h263_v_loop_filter_c;
     
+    c->h261_h_loop_filter= h261_h_loop_filter_c;
+    c->h261_v_loop_filter= h261_v_loop_filter_c;
+    
     c->try_8x8basis= try_8x8basis_c;
     c->add_8x8basis= add_8x8basis_c;
 
diff --git a/libavcodec/dsputil.h b/libavcodec/dsputil.h
index 0d42fe1089..16f70b428b 100644
--- a/libavcodec/dsputil.h
+++ b/libavcodec/dsputil.h
@@ -261,6 +261,9 @@ typedef struct DSPContext {
     void (*h263_v_loop_filter)(uint8_t *src, int stride, int qscale);
     void (*h263_h_loop_filter)(uint8_t *src, int stride, int qscale);
 
+    void (*h261_v_loop_filter)(uint8_t *dest,uint8_t *src, int stride);
+    void (*h261_h_loop_filter)(uint8_t *dest,uint8_t *src, int stride);
+
     /* (I)DCT */
     void (*fdct)(DCTELEM *block/* align 16*/);
     void (*fdct248)(DCTELEM *block/* align 16*/);
diff --git a/libavcodec/h261.c b/libavcodec/h261.c
new file mode 100644
index 0000000000..236fd8a3ca
--- /dev/null
+++ b/libavcodec/h261.c
@@ -0,0 +1,875 @@
+/*
+ * H261 decoder
+ * Copyright (c) 2002-2004 Michael Niedermayer <michaelni@gmx.at>
+ * Copyright (c) 2004 Maarten Daniels
+ *
+ * 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
+ */
+
+/**
+ * @file h261.c
+ * h261codec.
+ */
+
+#include "common.h"
+#include "dsputil.h"
+#include "avcodec.h"
+#include "mpegvideo.h"
+#include "h261data.h"
+
+
+#define H261_MBA_VLC_BITS 9
+#define H261_MTYPE_VLC_BITS 6
+#define H261_MV_VLC_BITS 7
+#define H261_CBP_VLC_BITS 9
+#define TCOEFF_VLC_BITS 9
+
+#define MAX_MBA 33
+#define IS_FIL(a)    ((a)&MB_TYPE_H261_FIL)
+
+/**
+ * H261Context
+ */
+typedef struct H261Context{
+    MpegEncContext s;
+
+    int current_mba;
+    int mba_diff;
+    int mtype;
+    int current_mv_x;
+    int current_mv_y;
+    int gob_number;
+    int loop_filter;
+    int bits_left; //8 - nr of bits left of the following frame in the last byte in this frame
+    int last_bits; //bits left of the following frame in the last byte in this frame
+}H261Context;
+
+void ff_h261_loop_filter(H261Context * h){
+    MpegEncContext * const s = &h->s;
+    int i;
+    const int linesize  = s->linesize;
+    const int uvlinesize= s->uvlinesize;
+    uint8_t *dest_y = s->dest[0];
+    uint8_t *dest_cb= s->dest[1];
+    uint8_t *dest_cr= s->dest[2];
+    uint8_t *src;
+
+    CHECKED_ALLOCZ((src),sizeof(uint8_t) * 64 );
+
+    for(i=0; i<8;i++)
+        memcpy(src+i*8,dest_y+i*linesize,sizeof(uint8_t) * 8 );
+    s->dsp.h261_v_loop_filter(dest_y, src, linesize);
+    s->dsp.h261_h_loop_filter(dest_y, src, linesize);
+
+    for(i=0; i<8;i++)
+        memcpy(src+i*8,dest_y+i*linesize + 8,sizeof(uint8_t) * 8 );
+    s->dsp.h261_v_loop_filter(dest_y + 8, src, linesize);
+    s->dsp.h261_h_loop_filter(dest_y + 8, src, linesize);
+
+    for(i=0; i<8;i++)
+        memcpy(src+i*8,dest_y+(i+8)*linesize,sizeof(uint8_t) * 8 );
+    s->dsp.h261_v_loop_filter(dest_y + 8 * linesize, src, linesize);
+    s->dsp.h261_h_loop_filter(dest_y + 8 * linesize, src, linesize);
+
+    for(i=0; i<8;i++)
+        memcpy(src+i*8,dest_y+(i+8)*linesize + 8,sizeof(uint8_t) * 8 );
+    s->dsp.h261_v_loop_filter(dest_y + 8 * linesize + 8, src, linesize);
+    s->dsp.h261_h_loop_filter(dest_y + 8 * linesize + 8, src, linesize);
+
+    for(i=0; i<8;i++)
+        memcpy(src+i*8,dest_cb+i*uvlinesize,sizeof(uint8_t) * 8 );
+    s->dsp.h261_v_loop_filter(dest_cb, src, uvlinesize);
+    s->dsp.h261_h_loop_filter(dest_cb, src, uvlinesize);
+
+    for(i=0; i<8;i++)
+        memcpy(src+i*8,dest_cr+i*uvlinesize,sizeof(uint8_t) * 8 );
+    s->dsp.h261_v_loop_filter(dest_cr, src, uvlinesize);
+    s->dsp.h261_h_loop_filter(dest_cr, src, uvlinesize);
+
+fail:
+    av_free(src);
+
+    return;
+}
+
+static int h261_decode_block(H261Context *h, DCTELEM *block,
+                             int n, int coded);
+static int h261_decode_mb(H261Context *h,
+                      DCTELEM block[6][64]);
+void ff_set_qscale(MpegEncContext * s, int qscale);
+
+/***********************************************/
+/* decoding */
+
+static VLC h261_mba_vlc;
+static VLC h261_mtype_vlc;
+static VLC h261_mv_vlc;
+static VLC h261_cbp_vlc;
+
+void init_vlc_rl(RLTable *rl);
+
+static void h261_decode_init_vlc(H261Context *h){
+    static int done = 0;
+
+    if(!done){
+        done = 1;
+        init_vlc(&h261_mba_vlc, H261_MBA_VLC_BITS, 34,
+                 h261_mba_bits, 1, 1,
+                 h261_mba_code, 1, 1);
+        init_vlc(&h261_mtype_vlc, H261_MTYPE_VLC_BITS, 10,
+                 h261_mtype_bits, 1, 1,
+                 h261_mtype_code, 1, 1);
+        init_vlc(&h261_mv_vlc, H261_MV_VLC_BITS, 17,
+                 &h261_mv_tab[0][1], 2, 1,
+                 &h261_mv_tab[0][0], 2, 1);
+        init_vlc(&h261_cbp_vlc, H261_CBP_VLC_BITS, 63,
+                 &h261_cbp_tab[0][1], 2, 1,
+                 &h261_cbp_tab[0][0], 2, 1);
+        init_rl(&h261_rl_tcoeff);
+        init_vlc_rl(&h261_rl_tcoeff);
+    }
+}
+
+static int h261_decode_init(AVCodecContext *avctx){
+    H261Context *h= avctx->priv_data;
+    MpegEncContext * const s = &h->s;
+
+    // set defaults
+    MPV_decode_defaults(s);
+    s->avctx = avctx;
+
+    s->width = s->avctx->width;
+    s->height = s->avctx->height;
+    s->codec_id = s->avctx->codec->id;
+
+    s->out_format = FMT_H261;
+    s->low_delay= 1;
+    avctx->pix_fmt= PIX_FMT_YUV420P;
+
+    s->codec_id= avctx->codec->id;
+
+    h261_decode_init_vlc(h);
+
+    h->bits_left = 0;
+    h->last_bits = 0;
+    
+    return 0;
+}
+
+/**
+ * decodes the group of blocks header or slice header.
+ * @return <0 if an error occured
+ */
+static int h261_decode_gob_header(H261Context *h){
+    unsigned int val;
+    MpegEncContext * const s = &h->s;
+    
+    /* Check for GOB Start Code */
+    val = show_bits(&s->gb, 15);
+    if(val)
+        return -1;
+
+    /* We have a GBSC */
+    skip_bits(&s->gb, 16);
+
+    h->gob_number = get_bits(&s->gb, 4); /* GN */
+    s->qscale = get_bits(&s->gb, 5); /* GQUANT */
+
+    /* GEI */
+    while (get_bits1(&s->gb) != 0) {
+        skip_bits(&s->gb, 8);
+    }
+
+    if(s->qscale==0)
+        return -1;
+
+    // For the first transmitted macroblock in a GOB, MBA is the absolute address. For
+    // subsequent macroblocks, MBA is the difference between the absolute addresses of
+    // the macroblock and the last transmitted macroblock.
+    h->current_mba = 0;
+    h->mba_diff = 0;
+
+    return 0;
+}
+
+/**
+ * decodes the group of blocks / video packet header.
+ * @return <0 if no resync found
+ */
+static int ff_h261_resync(H261Context *h){
+    MpegEncContext * const s = &h->s;
+    int left, ret;
+
+    if(show_bits(&s->gb, 15)==0){
+        ret= h261_decode_gob_header(h);
+        if(ret>=0)
+            return 0;
+    }
+    //ok, its not where its supposed to be ...
+    s->gb= s->last_resync_gb;
+    align_get_bits(&s->gb);
+    left= s->gb.size_in_bits - get_bits_count(&s->gb);
+
+    for(;left>15+1+4+5; left-=8){
+        if(show_bits(&s->gb, 15)==0){
+            GetBitContext bak= s->gb;
+
+            ret= h261_decode_gob_header(h);
+            if(ret>=0)
+                return 0;
+
+            s->gb= bak;
+        }
+        skip_bits(&s->gb, 8);
+    }
+
+    return -1;
+}
+
+/**
+ * decodes a skipped macroblock, called when when mba_diff > 1.
+ * @return 0
+ */
+static int h261_decode_mb_skipped(H261Context *h,
+                                  DCTELEM block[6][64])
+{
+    MpegEncContext * const s = &h->s;
+    int i;
+    const int xy = s->mb_x + s->mb_y * s->mb_stride;
+    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->current_picture.mb_type[xy]= MB_TYPE_SKIP | MB_TYPE_16x16 | MB_TYPE_L0;
+    s->mv[0][0][0] = 0;
+    s->mv[0][0][1] = 0;
+    s->mb_skiped = 1;
+    return 0;
+}
+
+static int h261_decode_mb(H261Context *h,
+                          DCTELEM block[6][64])
+{
+    MpegEncContext * const s = &h->s;
+    int i, cbp, mv_x_diff, mv_y_diff, sign, xy;
+
+    cbp = 63;
+    // Read mba
+    do{
+        h->mba_diff = get_vlc2(&s->gb, h261_mba_vlc.table, H261_MBA_VLC_BITS, 2)+1;
+    }
+    while( h->mba_diff == MAX_MBA + 1 ); // stuffing
+
+    if ( h->mba_diff < 0 )
+        return -1;
+
+    h->current_mba += h->mba_diff;
+
+    if ( h->current_mba > MAX_MBA )
+        return -1;
+    
+    s->mb_x= ((h->gob_number-1) % 2) * 11 + ((h->current_mba-1) % 11);
+    s->mb_y= ((h->gob_number-1) / 2) * 3 + ((h->current_mba-1) / 11);
+
+    xy = s->mb_x + s->mb_y * s->mb_stride;
+
+    ff_init_block_index(s);
+    ff_update_block_index(s);
+
+    // Read mtype
+    int old_mtype = h->mtype;
+    h->mtype = get_vlc2(&s->gb, h261_mtype_vlc.table, H261_MTYPE_VLC_BITS, 2);
+    h->mtype = h261_mtype_map[h->mtype];
+
+    if (IS_FIL (h->mtype))
+        h->loop_filter = 1;
+
+    // Read mquant
+    if ( IS_QUANT ( h->mtype ) ){
+        s->qscale = get_bits(&s->gb, 5);
+    }
+
+    s->mb_intra = IS_INTRA4x4(h->mtype);
+
+    // Read mv
+    if ( IS_16X16 ( h->mtype ) ){
+        // Motion vector data is included for all MC macroblocks. MVD is obtained from the macroblock vector by subtracting the
+        // vector of the preceding macroblock. For this calculation the vector of the preceding macroblock is regarded as zero in the
+        // following three situations:
+        // 1) evaluating MVD for macroblocks 1, 12 and 23;
+        // 2) evaluating MVD for macroblocks in which MBA does not represent a difference of 1;
+        // 3) MTYPE of the previous macroblock was not MC.
+        if ( ( h->current_mba == 1 ) || ( h->current_mba == 12 ) || ( h->current_mba == 23 ) ||
+             ( h->mba_diff != 1) || ( !IS_16X16 ( old_mtype ) ))
+        {
+            h->current_mv_x = 0;
+            h->current_mv_y = 0;
+        }
+
+        mv_x_diff = get_vlc2(&s->gb, h261_mv_vlc.table, H261_MV_VLC_BITS, 2);
+        mv_x_diff = mvmap[mv_x_diff];
+
+        if(mv_x_diff != 0){
+            sign = get_bits1(&s->gb);
+
+            if(!sign)
+                mv_x_diff= -mv_x_diff;
+        }
+
+        mv_y_diff = get_vlc2(&s->gb, h261_mv_vlc.table, H261_MV_VLC_BITS, 2);
+        mv_y_diff = mvmap[mv_y_diff];
+
+        if(mv_y_diff != 0){
+            sign = get_bits1(&s->gb);
+
+            if(!sign)
+                mv_y_diff= -mv_y_diff;
+        }
+
+        //mv's are in the range -15...15
+        if((h->current_mv_x + mv_x_diff > -16) && (h->current_mv_x + mv_x_diff < 16) )
+            h->current_mv_x += mv_x_diff;
+        else
+            h->current_mv_x += (mv_x_diff + (mv_x_diff > 0 ? -32 : 32));
+
+        if((h->current_mv_y + mv_y_diff > -16) && (h->current_mv_y + mv_y_diff < 16) )
+            h->current_mv_y += mv_y_diff;
+        else
+            h->current_mv_y += (mv_y_diff + (mv_y_diff>0 ? -32 : 32));
+    }
+
+    // Read cbp
+    if ( HAS_CBP( h->mtype ) ){
+        cbp = get_vlc2(&s->gb, h261_cbp_vlc.table, H261_CBP_VLC_BITS, 2) + 1;
+    }
+
+    if(s->mb_intra){
+        s->current_picture.mb_type[xy]= MB_TYPE_INTRA;
+        goto intra;
+    }
+
+    //set motion vectors
+    s->mv_dir = MV_DIR_FORWARD;
+    s->mv_type = MV_TYPE_16X16;
+    s->current_picture.mb_type[xy]= MB_TYPE_16x16 | MB_TYPE_L0;
+    if(IS_16X16 ( h->mtype )){
+        s->mv[0][0][0] = h->current_mv_x * 2;//gets divided by 2 in motion compensation
+        s->mv[0][0][1] = h->current_mv_y * 2;
+    }
+    else{
+        h->current_mv_x = s->mv[0][0][0] = 0;
+        h->current_mv_x = s->mv[0][0][1] = 0;
+    }
+
+intra:
+    /* decode each block */
+    if(s->mb_intra || HAS_CBP(h->mtype)){
+        for (i = 0; i < 6; i++) {
+            if (h261_decode_block(h, block[i], i, cbp&32) < 0){
+                return -1;
+            }
+            cbp+=cbp;
+        }
+    }
+
+    /* per-MB end of slice check */
+    {
+        int v= show_bits(&s->gb, 15);
+
+        if(get_bits_count(&s->gb) + 15 > s->gb.size_in_bits){
+            v>>= get_bits_count(&s->gb) + 15 - s->gb.size_in_bits;
+        }
+
+        if(v==0){
+            return SLICE_END;
+        }
+    }
+    return SLICE_OK;
+}
+
+/**
+ * decodes a macroblock
+ * @return <0 if an error occured
+ */
+static int h261_decode_block(H261Context * h, DCTELEM * block,
+                             int n, int coded)
+{
+    MpegEncContext * const s = &h->s;
+    int code, level, i, j, run;
+    RLTable *rl = &h261_rl_tcoeff;
+    const uint8_t *scan_table;
+    
+    // For the variable length encoding there are two code tables, one being used for
+    // the first transmitted LEVEL in INTER, INTER+MC and INTER+MC+FIL blocks, the second
+    // for all other LEVELs except the first one in INTRA blocks which is fixed length
+    // coded with 8 bits.
+    // NOTE: the two code tables only differ in one VLC so we handle that manually.
+    scan_table = s->intra_scantable.permutated;
+    if (s->mb_intra){
+        /* DC coef */
+        level = get_bits(&s->gb, 8);
+        // 0 (00000000b) and -128 (10000000b) are FORBIDDEN
+        if((level&0x7F) == 0){
+            av_log(s->avctx, AV_LOG_ERROR, "illegal dc %d at %d %d\n", level, s->mb_x, s->mb_y);
+            return -1;
+        }
+        // The code 1000 0000 is not used, the reconstruction level of 1024 being coded as 1111 1111.
+        if (level == 255)
+            level = 128;
+        block[0] = level;
+        i = 1;
+    }else if(coded){
+        // Run  Level   Code
+        // EOB                  Not possible for first level when cbp is available (that's why the table is different)
+        // 0    1               1s
+        // *    *               0*
+        int check = show_bits(&s->gb, 2);
+        i = 0;
+        if ( check & 0x2 ){
+            skip_bits(&s->gb, 2);
+            block[0] = ( check & 0x1 ) ? -1 : 1;
+            i = 1;
+        }
+    }else{
+        i = 0;
+    }
+    if(!coded){
+        s->block_last_index[n] = i - 1;
+        return 0;
+    }
+    for(;;){
+        code = get_vlc2(&s->gb, rl->vlc.table, TCOEFF_VLC_BITS, 2);
+        if (code < 0){
+            av_log(s->avctx, AV_LOG_ERROR, "illegal ac vlc code at %dx%d\n", s->mb_x, s->mb_y);
+            return -1;
+        }
+        if (code == rl->n) {
+            /* escape */
+            // The remaining combinations of (run, level) are encoded with a 20-bit word consisting of 6 bits escape, 6 bits run and 8 bits level.
+            run = get_bits(&s->gb, 6);
+            level = (int8_t)get_bits(&s->gb, 8);
+        }else if(code == 0){
+            break;
+        }else{
+            run = rl->table_run[code];
+            level = rl->table_level[code];
+            if (get_bits1(&s->gb))
+                level = -level;
+        }
+        i += run;
+        if (i >= 64){
+            av_log(s->avctx, AV_LOG_ERROR, "run overflow at %dx%d\n", s->mb_x, s->mb_y);
+            return -1;
+        }
+        j = scan_table[i];
+        block[j] = level;
+        i++;
+    }
+    s->block_last_index[n] = i;
+    return 0;
+}
+
+/**
+ * decodes the H261 picture header.
+ * @return <0 if no startcode found
+ */
+int h261_decode_picture_header(H261Context *h){
+    MpegEncContext * const s = &h->s;
+    int format, i;
+    static int h261_framecounter = 0;
+    uint32_t startcode;
+    align_get_bits(&s->gb);
+
+    startcode = (h->last_bits << (12 - (8-h->bits_left))) | get_bits(&s->gb, 20-8 - (8- h->bits_left));
+
+    for(i= s->gb.size_in_bits - get_bits_count(&s->gb); i>24; i-=1){
+        startcode = ((startcode << 1) | get_bits(&s->gb, 1)) & 0x000FFFFF;
+
+        if(startcode == 0x10)
+            break;
+    }
+
+    if (startcode != 0x10){
+        av_log(s->avctx, AV_LOG_ERROR, "Bad picture start code\n");
+        return -1;
+    }
+
+    /* temporal reference */
+    s->picture_number = get_bits(&s->gb, 5); /* picture timestamp */
+
+    /* PTYPE starts here */
+    skip_bits1(&s->gb); /* split screen off */
+    skip_bits1(&s->gb); /* camera  off */
+    skip_bits1(&s->gb); /* freeze picture release off */
+
+    format = get_bits1(&s->gb);
+
+    //only 2 formats possible
+    if (format == 0){//QCIF
+        s->width = 176;
+        s->height = 144;
+        s->mb_width = 11;
+        s->mb_height = 9;
+    }else{//CIF
+        s->width = 352;
+        s->height = 288;
+        s->mb_width = 22;
+        s->mb_height = 18;
+    }
+
+    s->mb_num = s->mb_width * s->mb_height;
+
+    skip_bits1(&s->gb); /* still image mode off */
+    skip_bits1(&s->gb); /* Reserved */
+
+    /* PEI */
+    while (get_bits1(&s->gb) != 0){
+        skip_bits(&s->gb, 8);
+    }
+
+    //h261 has no I-FRAMES, pass the test in MPV_frame_start in mpegvideo.c
+    if(h261_framecounter > 1)
+        s->pict_type = P_TYPE;
+    else
+        s->pict_type = I_TYPE;
+
+    h261_framecounter++;
+
+    h->gob_number = 0;
+    return 0;
+}
+
+static int h261_decode_gob(H261Context *h){
+    MpegEncContext * const s = &h->s;
+    int i;
+    
+    ff_set_qscale(s, s->qscale);
+    while(h->current_mba <= MAX_MBA)
+    {
+        int ret;
+        /* DCT & quantize */
+        s->dsp.clear_blocks(s->block[0]);
+        ret= h261_decode_mb(h, s->block);
+        if(ret<0){
+            const int xy= s->mb_x + s->mb_y*s->mb_stride;
+            if(ret==SLICE_END){
+                MPV_decode_mb(s, s->block);
+                if(h->loop_filter){
+                    ff_h261_loop_filter(h);
+                }
+                h->loop_filter = 0;
+                for(i=1; i<h->mba_diff; i++){
+                    s->mb_x= ((h->gob_number-1) % 2) * 11 + ((h->current_mba-1-i) % 11);
+                    s->mb_y= ((h->gob_number-1) / 2) * 3 + ((h->current_mba-1-i) / 11);
+                    ff_init_block_index(s);
+                    ff_update_block_index(s);
+                    s->dsp.clear_blocks(s->block[0]);
+                    ret= h261_decode_mb_skipped(h, s->block);
+                    MPV_decode_mb(s, s->block);
+                }
+                
+                return 0;
+            }else if(ret==SLICE_NOEND){
+                av_log(s->avctx, AV_LOG_ERROR, "Slice mismatch at MB: %d\n", xy);
+                return -1;
+            }
+            av_log(s->avctx, AV_LOG_ERROR, "Error at MB: %d\n", xy);
+            return -1;
+        }
+        MPV_decode_mb(s, s->block);
+        if(h->loop_filter){
+            ff_h261_loop_filter(h);
+        }
+
+        h->loop_filter = 0;
+        for(i=1; i<h->mba_diff; i++){
+            s->mb_x= ((h->gob_number-1) % 2) * 11 + ((h->current_mba-1-i) % 11);
+            s->mb_y= ((h->gob_number-1) / 2) * 3 + ((h->current_mba-1-i) / 11);
+            ff_init_block_index(s);
+            ff_update_block_index(s);
+            s->dsp.clear_blocks(s->block[0]);
+            ret= h261_decode_mb_skipped(h, s->block);
+            MPV_decode_mb(s, s->block);
+        }
+    }
+    
+    return -1;
+}
+
+static int h261_find_frame_end(ParseContext *pc, AVCodecContext* avctx, const uint8_t *buf, int buf_size){
+    int vop_found, i, j, bits_left, last_bits;
+    uint32_t state;
+
+    H261Context *h = avctx->priv_data;
+
+    if(h){
+        bits_left = h->bits_left;
+        last_bits = h->last_bits;
+    }
+    else{
+        bits_left = 0;
+        last_bits = 0;
+    }
+
+    vop_found= pc->frame_start_found;
+    state= pc->state;
+    if(bits_left!=0 && !vop_found)
+        state = state << (8-bits_left) | last_bits;
+    i=0;
+    if(!vop_found){
+        for(i=0; i<buf_size; i++){
+            state= (state<<8) | buf[i];
+            for(j=0; j<8; j++){
+                if(( (  (state<<j)  |  (buf[i]>>(8-j))  )>>(32-20) == 0x10 )&&(((state >> (17-j)) & 0x4000) == 0x0)){
+                    i++;
+                    vop_found=1;
+                    break;
+                }
+            }
+            if(vop_found)
+                    break;    
+        }
+    }
+    if(vop_found){
+        for(; i<buf_size; i++){
+            if(avctx->flags & CODEC_FLAG_TRUNCATED)//XXX ffplay workaround, someone a better solution?
+                state= (state<<8) | buf[i];
+            for(j=0; j<8; j++){
+                if(( (  (state<<j)  |  (buf[i]>>(8-j))  )>>(32-20) == 0x10 )&&(((state >> (17-j)) & 0x4000) == 0x0)){
+                    pc->frame_start_found=0;
+                    pc->state=-1;
+                    return i-3;
+                }
+            }
+        }
+    }
+
+    pc->frame_start_found= vop_found;
+    pc->state= state;
+    return END_NOT_FOUND;
+}
+
+static int h261_parse(AVCodecParserContext *s,
+                      AVCodecContext *avctx,
+                      uint8_t **poutbuf, int *poutbuf_size, 
+                      const uint8_t *buf, int buf_size)
+{
+    ParseContext *pc = s->priv_data;
+    int next;
+    
+    next= h261_find_frame_end(pc,avctx, buf, buf_size);
+    if (ff_combine_frame(pc, next, (uint8_t **)&buf, &buf_size) < 0) {
+        *poutbuf = NULL;
+        *poutbuf_size = 0;
+        return buf_size;
+    }
+    *poutbuf = (uint8_t *)buf;
+    *poutbuf_size = buf_size;
+    return next;
+}
+
+/**
+ * returns the number of bytes consumed for building the current frame
+ */
+static int get_consumed_bytes(MpegEncContext *s, int buf_size){
+    int pos= (get_bits_count(&s->gb)+7)>>3;
+
+    if(s->flags&CODEC_FLAG_TRUNCATED){
+        pos -= s->parse_context.last_index;
+        if(pos<0) pos=0;// padding is not really read so this might be -1
+        return pos;
+    }else{
+        if(pos==0) pos=1; //avoid infinite loops (i doubt thats needed but ...)
+        if(pos+10>buf_size) pos=buf_size; // oops ;)
+
+        return pos;
+    }
+}
+
+static int h261_decode_frame(AVCodecContext *avctx,
+                             void *data, int *data_size,
+                             uint8_t *buf, int buf_size)
+{
+    H261Context *h= avctx->priv_data;
+    MpegEncContext *s = &h->s;
+    int ret;
+    AVFrame *pict = data;
+
+#ifdef PRINT_FRAME_TIME
+uint64_t time= rdtsc();
+#endif
+#ifdef DEBUG
+    printf("*****frame %d size=%d\n", avctx->frame_number, buf_size);
+    printf("bytes=%x %x %x %x\n", buf[0], buf[1], buf[2], buf[3]);
+#endif
+    s->flags= avctx->flags;
+    s->flags2= avctx->flags2;
+
+    /* no supplementary picture */
+    if (buf_size == 0) {
+        /* special case for last picture */
+        if (s->low_delay==0 && s->next_picture_ptr) {
+            *pict= *(AVFrame*)s->next_picture_ptr;
+            s->next_picture_ptr= NULL;
+
+            *data_size = sizeof(AVFrame);
+        }
+
+        return 0;
+    }
+
+    if(s->flags&CODEC_FLAG_TRUNCATED){
+        int next;
+
+        next= h261_find_frame_end(&s->parse_context,avctx, buf, buf_size);
+
+        if( ff_combine_frame(&s->parse_context, next, &buf, &buf_size) < 0 )
+            return buf_size;
+    }
+
+
+retry:
+
+    if(s->bitstream_buffer_size && buf_size<20){
+        init_get_bits(&s->gb, s->bitstream_buffer, s->bitstream_buffer_size*8);
+    }else
+        init_get_bits(&s->gb, buf, buf_size*8);
+    s->bitstream_buffer_size=0;
+
+    if(!s->context_initialized){
+        if (MPV_common_init(s) < 0) //we need the idct permutaton for reading a custom matrix
+            return -1;
+    }
+
+    //we need to set current_picture_ptr before reading the header, otherwise we cant store anyting im there
+    if(s->current_picture_ptr==NULL || s->current_picture_ptr->data[0]){
+        int i= ff_find_unused_picture(s, 0);
+        s->current_picture_ptr= &s->picture[i];
+    }
+
+    ret = h261_decode_picture_header(h);
+
+    if(ret==FRAME_SKIPED) return get_consumed_bytes(s, buf_size);
+
+    /* skip if the header was thrashed */
+    if (ret < 0){
+        av_log(s->avctx, AV_LOG_ERROR, "header damaged\n");
+        return -1;
+    }
+
+    if (s->width != avctx->width || s->height != avctx->height){
+        ParseContext pc= s->parse_context; //FIXME move these demuxng hack to avformat
+        s->parse_context.buffer=0;
+        MPV_common_end(s);
+        s->parse_context= pc;
+    }
+    if (!s->context_initialized) {
+        avctx->width = s->width;
+        avctx->height = s->height;
+
+        goto retry;
+    }
+
+    // for hurry_up==5
+    s->current_picture.pict_type= s->pict_type;
+    s->current_picture.key_frame= s->pict_type == I_TYPE;
+
+    /* skip everything if we are in a hurry>=5 */
+    if(avctx->hurry_up>=5) return get_consumed_bytes(s, buf_size);
+
+    if(MPV_frame_start(s, avctx) < 0)
+        return -1;
+
+    ff_er_frame_start(s);
+
+    /* decode each macroblock */
+    s->mb_x=0;
+    s->mb_y=0;
+
+    while(h->gob_number < (s->mb_height==18 ? 12 : 5)){
+        if(ff_h261_resync(h)<0)
+            break;
+        h261_decode_gob(h);
+    }
+    MPV_frame_end(s);
+
+    // h261 doesn't have byte aligned codes
+    // store the bits of the next frame that are left in the last byte
+    // in the H261Context and remember the number of stored bits
+    {
+        int bitsleft;
+        int current_pos= get_bits_count(&s->gb)>>3;
+        bitsleft =  (current_pos<<3) - get_bits_count(&s->gb);
+        h->bits_left = - bitsleft;
+        if(bitsleft > 0)
+            h->last_bits= get_bits(&s->gb, 8 - h->bits_left);
+        else
+            h->last_bits = 0;
+    }
+
+assert(s->current_picture.pict_type == s->current_picture_ptr->pict_type);
+assert(s->current_picture.pict_type == s->pict_type);
+    if(s->low_delay){
+        *pict= *(AVFrame*)&s->current_picture;
+        ff_print_debug_info(s, pict);
+    }else{
+        *pict= *(AVFrame*)&s->last_picture;
+        if(pict)
+            ff_print_debug_info(s, pict);
+    }
+
+    /* Return the Picture timestamp as the frame number */
+    /* we substract 1 because it is added on utils.c    */
+    avctx->frame_number = s->picture_number - 1;
+
+    /* dont output the last pic after seeking */
+    if(s->last_picture_ptr || s->low_delay)
+        *data_size = sizeof(AVFrame);
+#ifdef PRINT_FRAME_TIME
+printf("%Ld\n", rdtsc()-time);
+#endif
+
+return get_consumed_bytes(s, buf_size);
+}
+
+static int h261_decode_end(AVCodecContext *avctx)
+{
+    H261Context *h= avctx->priv_data;
+    MpegEncContext *s = &h->s;
+
+    MPV_common_end(s);
+    return 0;
+}
+
+AVCodec h261_decoder = {
+    "h261",
+    CODEC_TYPE_VIDEO,
+    CODEC_ID_H261,
+    sizeof(H261Context),
+    h261_decode_init,
+    NULL,
+    h261_decode_end,
+    h261_decode_frame,
+    CODEC_CAP_TRUNCATED,
+};
+
+AVCodecParser h261_parser = {
+    { CODEC_ID_H261 },
+    sizeof(ParseContext),
+    NULL,
+    h261_parse,
+    ff_parse_close,
+};
diff --git a/libavcodec/h261data.h b/libavcodec/h261data.h
new file mode 100644
index 0000000000..2f6b5c7eec
--- /dev/null
+++ b/libavcodec/h261data.h
@@ -0,0 +1,134 @@
+/**
+ * @file h261data.h
+ * H.261 tables.
+ */
+#define MB_TYPE_H261_FIL 0x800000
+
+// H.261 VLC table for macroblock addressing
+const uint8_t h261_mba_code[34] = {
+     1,  3,  2,  3,
+     2,  3,  2,  7,
+     6, 11, 10,  9,
+     8,  7,  6, 23,
+    22, 21, 20, 19,
+    18, 35, 34, 33,
+    32, 31, 30, 29,
+    28, 27, 26, 25,
+    24,
+    15             //(MBA stuffing)
+};
+
+const uint8_t h261_mba_bits[34] = {
+     1,  3,  3,  4,
+     4,  5,  5,  7,
+     7,  8,  8,  8,
+     8,  8,  8, 10,
+    10, 10, 10, 10,
+    10, 11, 11, 11,
+    11, 11, 11, 11,
+    11, 11, 11, 11,
+    11,
+    11            //(MBA stuffing)
+};
+
+//H.261 VLC table for macroblock type
+const uint8_t h261_mtype_code[10] = {
+    1,  1,  1,  1,
+    1,  1,  1,  1,
+    1,  1
+};
+
+const uint8_t h261_mtype_bits[10] = {
+    4,  7,  1,  5,
+    9,  8, 10,  3,
+    2,  6
+};
+
+static const int h261_mtype_map[10]= {
+        MB_TYPE_INTRA4x4,
+        MB_TYPE_INTRA4x4  |  MB_TYPE_QUANT,
+                                               MB_TYPE_CBP,
+                             MB_TYPE_QUANT  |  MB_TYPE_CBP,
+                                                               MB_TYPE_16x16,
+                                               MB_TYPE_CBP  |  MB_TYPE_16x16,
+                             MB_TYPE_QUANT  |  MB_TYPE_CBP  |  MB_TYPE_16x16,
+                                                               MB_TYPE_16x16  |  MB_TYPE_H261_FIL,
+                                               MB_TYPE_CBP  |  MB_TYPE_16x16  |  MB_TYPE_H261_FIL,
+                             MB_TYPE_QUANT  |  MB_TYPE_CBP  |  MB_TYPE_16x16  |  MB_TYPE_H261_FIL
+};
+
+//H.261 VLC table for motion vectors
+const uint8_t h261_mv_tab[17][2] = {
+    {1,1}, {1,2}, {1,3}, {1,4}, {3,6}, {5,7}, {4,7}, {3,7},
+    {11,9}, {10,9}, {9,9}, {17,10}, {16,10}, {15,10}, {14,10}, {13,10}, {12,10}
+};
+
+static const int mvmap[17] =
+{
+    0, -1, -2, -3, -4, -5, -6, -7, -8, -9, -10, -11, -12, -13, -14, -15, 16
+};
+
+//H.261 VLC table for coded block pattern
+const uint8_t h261_cbp_tab[63][2] =
+{
+    {11,5}, {9,5}, {13,6}, {13,4}, {23,7}, {19,7}, {31,8}, {12,4},
+    {22,7}, {18,7}, {30,8}, {19,5}, {27,8}, {23,8}, {19,8}, {11,4},
+    {21,7}, {17,7}, {29,8}, {17,5}, {25,8}, {21,8}, {17,8}, {15,6},
+    {15,8}, {13,8}, {3,9}, {15,5}, {11,8}, {7,8}, {7,9}, {10,4},
+    {20,7}, {16,7}, {28,8}, {14,6}, {14,8}, {12,8}, {2,9}, {16,5},
+    {24,8}, {20,8}, {16,8}, {14,5}, {10,8}, {6,8}, {6,9}, {18,5},
+    {26,8}, {22,8}, {18,8}, {13,5}, {9,8}, {5,8}, {5,9}, {12,5},
+    {8,8}, {4,8}, {4,9}, {7,3}, {10,5}, {8,5}, {12,6}
+};
+
+//H.261 VLC table for transform coefficients
+const uint16_t h261_tcoeff_vlc[65][2] = {
+{ 0x2, 2 }, { 0x3, 2 },{ 0x4, 4 },{ 0x5, 5 },
+{ 0x6, 7 },{ 0x26, 8 },{ 0x21, 8 },{ 0xa, 10 },
+{ 0x1d, 12 },{ 0x18, 12 },{ 0x13, 12 },{ 0x10 , 12 },
+{ 0x1a, 13},{ 0x19, 13 }, { 0x18, 13 }, { 0x17, 13 },
+{ 0x3, 3 }, { 0x6, 6 }, { 0x25 , 8 }, { 0xc, 10 },
+{ 0x1b, 12 }, { 0x16, 13 }, { 0x15, 13 }, { 0x5, 4},
+{ 0x4, 7}, { 0xb, 10 }, { 0x14, 12 }, { 0x14, 13 },
+{ 0x7, 5 }, { 0x24, 8 }, { 0x1c, 12 }, { 0x13, 13 },
+{ 0x6, 5 }, { 0xf, 10 }, { 0x12, 12}, { 0x7, 6},
+{ 0x9 , 10 }, { 0x12, 13 }, { 0x5, 6 }, { 0x1e, 12 },
+{ 0x4, 6 }, { 0x15, 12 }, { 0x7, 7 }, { 0x11, 12},
+{ 0x5, 7 }, { 0x11, 13 }, { 0x27, 8 }, { 0x10, 13 },
+{ 0x23, 8 }, { 0x22, 8 }, { 0x20, 8 }, { 0xe , 10 },
+{ 0xd, 10 }, { 0x8, 10 },{ 0x1f, 12 }, { 0x1a, 12 },
+{ 0x19, 12 }, { 0x17, 12 }, { 0x16, 12}, { 0x1f, 13},
+{ 0x1e, 13 }, { 0x1d, 13 }, { 0x1c, 13}, { 0x1b, 13},
+{ 0x1, 6 }                                             //escape
+};
+
+const int8_t h261_tcoeff_level[64] = {
+    0,  1,  2,  3,  4,  5,  6,  7,
+    8,  9, 10, 11, 12, 13, 14, 15,
+    1,  2,  3,  4,  5,  6,  7,  1,
+    2,  3,  4,  5,  1,  2,  3,  4,
+    1,  2,  3,  1,  2,  3,  1,  2,
+    1,  2,  1,  2,  1,  2,  1,  2,
+    1,  1,  1,  1,  1,  1,  1,  1,
+    1,  1,  1,  1,  1,  1,  1,  1
+};
+
+const int8_t h261_tcoeff_run[64] = {
+    0,
+    0,  0,  0,  0,  0,  0,  0,  0,
+    0,  0,  0,  0,  0,  0,  0,  1,
+    1,  1,  1,  1,  1,  1,  2,  2,
+    2,  2,  2,  3,  3,  3,  3,  4,
+    4,  4,  5,  5,  5,  6,  6,  7,
+    7,  8,  8,  9,  9, 10, 10, 11,
+   12, 13, 14, 15, 16, 17, 18, 19,
+   20, 21, 22, 23, 24, 25, 26
+};
+
+static RLTable h261_rl_tcoeff = {
+    64,
+    64,
+    h261_tcoeff_vlc,
+    h261_tcoeff_run,
+    h261_tcoeff_level,
+};
diff --git a/libavcodec/mpegvideo.c b/libavcodec/mpegvideo.c
index 069194d182..e0b5d0ec6e 100644
--- a/libavcodec/mpegvideo.c
+++ b/libavcodec/mpegvideo.c
@@ -53,6 +53,10 @@ static void dct_unquantize_h263_intra_c(MpegEncContext *s,
                                   DCTELEM *block, int n, int qscale);
 static void dct_unquantize_h263_inter_c(MpegEncContext *s, 
                                   DCTELEM *block, int n, int qscale);
+static void dct_unquantize_h261_intra_c(MpegEncContext *s, 
+                                  DCTELEM *block, int n, int qscale);
+static void dct_unquantize_h261_inter_c(MpegEncContext *s, 
+                                  DCTELEM *block, int n, int qscale);
 static void draw_edges_c(uint8_t *buf, int wrap, int width, int height, int w);
 #ifdef CONFIG_ENCODERS
 static int dct_quantize_c(MpegEncContext *s, DCTELEM *block, int n, int qscale, int *overflow);
@@ -215,6 +219,8 @@ int DCT_common_init(MpegEncContext *s)
 {
     s->dct_unquantize_h263_intra = dct_unquantize_h263_intra_c;
     s->dct_unquantize_h263_inter = dct_unquantize_h263_inter_c;
+    s->dct_unquantize_h261_intra = dct_unquantize_h261_intra_c;
+    s->dct_unquantize_h261_inter = dct_unquantize_h261_inter_c;
     s->dct_unquantize_mpeg1_intra = dct_unquantize_mpeg1_intra_c;
     s->dct_unquantize_mpeg1_inter = dct_unquantize_mpeg1_inter_c;
     s->dct_unquantize_mpeg2_intra = dct_unquantize_mpeg2_intra_c;
@@ -1454,6 +1460,9 @@ alloc:
     }else if(s->out_format == FMT_H263){
         s->dct_unquantize_intra = s->dct_unquantize_h263_intra;
         s->dct_unquantize_inter = s->dct_unquantize_h263_inter;
+    }else if(s->out_format == FMT_H261){
+        s->dct_unquantize_intra = s->dct_unquantize_h261_intra;
+        s->dct_unquantize_inter = s->dct_unquantize_h261_inter;
     }else{
         s->dct_unquantize_intra = s->dct_unquantize_mpeg1_intra;
         s->dct_unquantize_inter = s->dct_unquantize_mpeg1_inter;
@@ -2494,6 +2503,12 @@ if(s->quarter_sample)
             uvsrc_x = src_x>>1;
             uvsrc_y = src_y>>1;
         }
+    }else if(s->out_format == FMT_H261){//even chroma mv's are full pel in H261
+        mx = motion_x / 4;
+        my = motion_y / 4;
+        uvdxy = 0;
+        uvsrc_x = s->mb_x*8 + mx;
+        uvsrc_y = s->mb_y*8 + my;
     } else {
         mx = motion_x / 2;
         my = motion_y / 2;
@@ -5782,6 +5797,59 @@ static void dct_unquantize_h263_inter_c(MpegEncContext *s,
     }
 }
 
+static void dct_unquantize_h261_intra_c(MpegEncContext *s, 
+                                  DCTELEM *block, int n, int qscale)
+{
+    int i, level, odd;
+    int nCoeffs;
+    
+    assert(s->block_last_index[n]>=0);
+    
+    if (n < 4) 
+        block[0] = block[0] * s->y_dc_scale;
+    else
+        block[0] = block[0] * s->c_dc_scale;
+    odd = qscale & 0x1;
+    nCoeffs= s->inter_scantable.raster_end[ s->block_last_index[n] ];
+
+    for(i=1; i<=nCoeffs; i++){
+        level = block[i];
+        if (level){
+            if (level < 0){
+                level = qscale * ((level << 1) - 1) + (~odd);
+            }else{
+                level = qscale * ((level << 1) + 1) - (~odd);
+            }
+        }
+        block[i] = level;
+    }
+}
+
+static void dct_unquantize_h261_inter_c(MpegEncContext *s, 
+                                  DCTELEM *block, int n, int qscale)
+{
+    int i, level, odd;
+    int nCoeffs;
+    
+    assert(s->block_last_index[n]>=0);
+    
+    odd = qscale & 0x1;
+    
+    nCoeffs= s->inter_scantable.raster_end[ s->block_last_index[n] ];
+
+    for(i=0; i<=nCoeffs; i++){
+        level = block[i];
+        if (level){
+            if (level < 0){
+                level = qscale * ((level << 1) - 1) + (~odd);
+            }else{
+                level = qscale * ((level << 1) + 1) - (~odd);
+            }
+        }
+        block[i] = level;
+    }
+}
+
 static const AVOption mpeg4_options[] =
 {
     AVOPTION_CODEC_INT("bitrate", "desired video bitrate", bit_rate, 4, 240000000, 800000),
diff --git a/libavcodec/mpegvideo.h b/libavcodec/mpegvideo.h
index 715fb6d927..d4c7064f46 100644
--- a/libavcodec/mpegvideo.h
+++ b/libavcodec/mpegvideo.h
@@ -32,6 +32,7 @@
 
 enum OutputFormat {
     FMT_MPEG1,
+    FMT_H261,
     FMT_H263,
     FMT_MJPEG, 
     FMT_H264,
@@ -703,6 +704,10 @@ typedef struct MpegEncContext {
                            DCTELEM *block/*align 16*/, int n, int qscale);
     void (*dct_unquantize_h263_inter)(struct MpegEncContext *s, 
                            DCTELEM *block/*align 16*/, int n, int qscale);
+    void (*dct_unquantize_h261_intra)(struct MpegEncContext *s, 
+                           DCTELEM *block/*align 16*/, int n, int qscale);
+    void (*dct_unquantize_h261_inter)(struct MpegEncContext *s, 
+                           DCTELEM *block/*align 16*/, int n, int qscale);
     void (*dct_unquantize_intra)(struct MpegEncContext *s, // unquantizer to use (mpeg4 can use both)
                            DCTELEM *block/*align 16*/, int n, int qscale);
     void (*dct_unquantize_inter)(struct MpegEncContext *s, // unquantizer to use (mpeg4 can use both)
diff --git a/libavformat/raw.c b/libavformat/raw.c
index fbdbb7aa1c..35b07159b6 100644
--- a/libavformat/raw.c
+++ b/libavformat/raw.c
@@ -259,6 +259,21 @@ static int h263_probe(AVProbeData *p)
     return 0;
 }
 
+static int h261_probe(AVProbeData *p)
+{
+    int code;
+    const uint8_t *d;
+
+    if (p->buf_size < 6)
+        return 0;
+    d = p->buf;
+    code = (d[0] << 12) | (d[1] << 4) | (d[2] >> 4);
+    if (code == 0x10) {
+        return 50;
+    }
+    return 0;
+}
+
 AVInputFormat ac3_iformat = {
     "ac3",
     "raw ac3",
@@ -285,6 +300,18 @@ AVOutputFormat ac3_oformat = {
 };
 #endif //CONFIG_ENCODERS
 
+AVInputFormat h261_iformat = {
+    "h261",
+    "raw h261",
+    0,
+    h261_probe,
+    video_read_header,
+    raw_read_partial_packet,
+    raw_read_close,
+    .extensions = "h261",
+    .value = CODEC_ID_H261,
+};
+
 AVInputFormat h263_iformat = {
     "h263",
     "raw h263",
@@ -586,6 +613,8 @@ int raw_init(void)
     av_register_input_format(&ac3_iformat);
     av_register_output_format(&ac3_oformat);
 
+    av_register_input_format(&h261_iformat);
+
     av_register_input_format(&h263_iformat);
     av_register_output_format(&h263_oformat);