Split the h261.c file into separate files for the encoder, decoder and common stuff.

Originally committed as revision 9090 to svn://svn.ffmpeg.org/ffmpeg/trunk

5 files changed, 1034 insertions, 941 deletions

diff --git a/libavcodec/Makefile b/libavcodec/Makefile
index 6701a4e146..f696cdf717 100644
--- a/libavcodec/Makefile
+++ b/libavcodec/Makefile
@@ -83,8 +83,8 @@ OBJS-$(CONFIG_FOURXM_DECODER)          += 4xm.o
 OBJS-$(CONFIG_FRAPS_DECODER)           += fraps.o
 OBJS-$(CONFIG_GIF_DECODER)             += gifdec.o lzw.o
 OBJS-$(CONFIG_GIF_ENCODER)             += gif.o
-OBJS-$(CONFIG_H261_DECODER)            += h261.o
-OBJS-$(CONFIG_H261_ENCODER)            += h261.o
+OBJS-$(CONFIG_H261_DECODER)            += h261dec.o h261.o
+OBJS-$(CONFIG_H261_ENCODER)            += h261enc.o h261.o
 OBJS-$(CONFIG_H263_DECODER)            += h263dec.o
 OBJS-$(CONFIG_H264_DECODER)            += h264.o
 OBJS-$(CONFIG_H264_ENCODER)            += h264enc.o h264dsp.o
diff --git a/libavcodec/h261.c b/libavcodec/h261.c
index 042e683f90..1cf1e48992 100644
--- a/libavcodec/h261.c
+++ b/libavcodec/h261.c
@@ -1,5 +1,5 @@
 /*
- * H261 decoder
+ * H261 common code
  * Copyright (c) 2002-2004 Michael Niedermayer <michaelni@gmx.at>
  * Copyright (c) 2004 Maarten Daniels
  *
@@ -27,37 +27,12 @@
 
 #include "dsputil.h"
 #include "avcodec.h"
-#include "mpegvideo.h"
+#include "h261.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 MBA_STUFFING 33
-#define MBA_STARTCODE 34
 #define IS_FIL(a)    ((a)&MB_TYPE_H261_FIL)
 
-/**
- * H261Context
- */
-typedef struct H261Context{
-    MpegEncContext s;
-
-    int current_mba;
-    int previous_mba;
-    int mba_diff;
-    int mtype;
-    int current_mv_x;
-    int current_mv_y;
-    int gob_number;
-    int gob_start_code_skipped; // 1 if gob start code is already read before gob header is read
-}H261Context;
-
-static uint8_t static_rl_table_store[2][2*MAX_RUN + MAX_LEVEL + 3];
+uint8_t ff_h261_rl_table_store[2][2*MAX_RUN + MAX_LEVEL + 3];
 
 void ff_h261_loop_filter(MpegEncContext *s){
     H261Context * h= (H261Context*)s;
@@ -78,914 +53,3 @@ void ff_h261_loop_filter(MpegEncContext *s){
     s->dsp.h261_loop_filter(dest_cr, uvlinesize);
 }
 
-int ff_h261_get_picture_format(int width, int height){
-    // QCIF
-    if (width == 176 && height == 144)
-        return 0;
-    // CIF
-    else if (width == 352 && height == 288)
-        return 1;
-    // ERROR
-    else
-        return -1;
-}
-
-static void h261_encode_block(H261Context * h, DCTELEM * block,
-                              int n);
-static int h261_decode_block(H261Context *h, DCTELEM *block,
-                             int n, int coded);
-
-void ff_h261_encode_picture_header(MpegEncContext * s, int picture_number){
-    H261Context * h = (H261Context *) s;
-    int format, temp_ref;
-
-    align_put_bits(&s->pb);
-
-    /* Update the pointer to last GOB */
-    s->ptr_lastgob = pbBufPtr(&s->pb);
-
-    put_bits(&s->pb, 20, 0x10); /* PSC */
-
-    temp_ref= s->picture_number * (int64_t)30000 * s->avctx->time_base.num /
-                         (1001 * (int64_t)s->avctx->time_base.den); //FIXME maybe this should use a timestamp
-    put_bits(&s->pb, 5, temp_ref & 0x1f); /* TemporalReference */
-
-    put_bits(&s->pb, 1, 0); /* split screen off */
-    put_bits(&s->pb, 1, 0); /* camera  off */
-    put_bits(&s->pb, 1, 0); /* freeze picture release off */
-
-    format = ff_h261_get_picture_format(s->width, s->height);
-
-    put_bits(&s->pb, 1, format); /* 0 == QCIF, 1 == CIF */
-
-    put_bits(&s->pb, 1, 0); /* still image mode */
-    put_bits(&s->pb, 1, 0); /* reserved */
-
-    put_bits(&s->pb, 1, 0); /* no PEI */
-    if(format == 0)
-        h->gob_number = -1;
-    else
-        h->gob_number = 0;
-    h->current_mba = 0;
-}
-
-/**
- * Encodes a group of blocks header.
- */
-static void h261_encode_gob_header(MpegEncContext * s, int mb_line){
-    H261Context * h = (H261Context *)s;
-    if(ff_h261_get_picture_format(s->width, s->height) == 0){
-        h->gob_number+=2; // QCIF
-    }
-    else{
-        h->gob_number++; // CIF
-    }
-    put_bits(&s->pb, 16, 1); /* GBSC */
-    put_bits(&s->pb, 4, h->gob_number); /* GN */
-    put_bits(&s->pb, 5, s->qscale); /* GQUANT */
-    put_bits(&s->pb, 1, 0); /* no GEI */
-    h->current_mba = 0;
-    h->previous_mba = 0;
-    h->current_mv_x=0;
-    h->current_mv_y=0;
-}
-
-void ff_h261_reorder_mb_index(MpegEncContext* s){
-    int index= s->mb_x + s->mb_y*s->mb_width;
-
-    if(index % 33 == 0)
-        h261_encode_gob_header(s,0);
-
-    /* for CIF the GOB's are fragmented in the middle of a scanline
-       that's why we need to adjust the x and y index of the macroblocks */
-    if(ff_h261_get_picture_format(s->width,s->height) == 1){ // CIF
-        s->mb_x =     index % 11 ; index /= 11;
-        s->mb_y =     index %  3 ; index /=  3;
-        s->mb_x+= 11*(index %  2); index /=  2;
-        s->mb_y+=  3*index;
-
-        ff_init_block_index(s);
-        ff_update_block_index(s);
-    }
-}
-
-static void h261_encode_motion(H261Context * h, int val){
-    MpegEncContext * const s = &h->s;
-    int sign, code;
-    if(val==0){
-        code = 0;
-        put_bits(&s->pb,h261_mv_tab[code][1],h261_mv_tab[code][0]);
-    }
-    else{
-        if(val > 15)
-            val -=32;
-        if(val < -16)
-            val+=32;
-        sign = val < 0;
-        code = sign ? -val : val;
-        put_bits(&s->pb,h261_mv_tab[code][1],h261_mv_tab[code][0]);
-        put_bits(&s->pb,1,sign);
-    }
-}
-
-static inline int get_cbp(MpegEncContext * s,
-                      DCTELEM block[6][64])
-{
-    int i, cbp;
-    cbp= 0;
-    for (i = 0; i < 6; i++) {
-        if (s->block_last_index[i] >= 0)
-            cbp |= 1 << (5 - i);
-    }
-    return cbp;
-}
-void ff_h261_encode_mb(MpegEncContext * s,
-         DCTELEM block[6][64],
-         int motion_x, int motion_y)
-{
-    H261Context * h = (H261Context *)s;
-    int mvd, mv_diff_x, mv_diff_y, i, cbp;
-    cbp = 63; // avoid warning
-    mvd = 0;
-
-    h->current_mba++;
-    h->mtype = 0;
-
-    if (!s->mb_intra){
-        /* compute cbp */
-        cbp= get_cbp(s, block);
-
-        /* mvd indicates if this block is motion compensated */
-        mvd = motion_x | motion_y;
-
-        if((cbp | mvd | s->dquant ) == 0) {
-            /* skip macroblock */
-            s->skip_count++;
-            h->current_mv_x=0;
-            h->current_mv_y=0;
-            return;
-        }
-    }
-
-    /* MB is not skipped, encode MBA */
-    put_bits(&s->pb, h261_mba_bits[(h->current_mba-h->previous_mba)-1], h261_mba_code[(h->current_mba-h->previous_mba)-1]);
-
-    /* calculate MTYPE */
-    if(!s->mb_intra){
-        h->mtype++;
-
-        if(mvd || s->loop_filter)
-            h->mtype+=3;
-        if(s->loop_filter)
-            h->mtype+=3;
-        if(cbp || s->dquant)
-            h->mtype++;
-        assert(h->mtype > 1);
-    }
-
-    if(s->dquant)
-        h->mtype++;
-
-    put_bits(&s->pb, h261_mtype_bits[h->mtype], h261_mtype_code[h->mtype]);
-
-    h->mtype = h261_mtype_map[h->mtype];
-
-    if(IS_QUANT(h->mtype)){
-        ff_set_qscale(s,s->qscale+s->dquant);
-        put_bits(&s->pb, 5, s->qscale);
-    }
-
-    if(IS_16X16(h->mtype)){
-        mv_diff_x = (motion_x >> 1) - h->current_mv_x;
-        mv_diff_y = (motion_y >> 1) - h->current_mv_y;
-        h->current_mv_x = (motion_x >> 1);
-        h->current_mv_y = (motion_y >> 1);
-        h261_encode_motion(h,mv_diff_x);
-        h261_encode_motion(h,mv_diff_y);
-    }
-
-    h->previous_mba = h->current_mba;
-
-    if(HAS_CBP(h->mtype)){
-        assert(cbp>0);
-        put_bits(&s->pb,h261_cbp_tab[cbp-1][1],h261_cbp_tab[cbp-1][0]);
-    }
-    for(i=0; i<6; i++) {
-        /* encode each block */
-        h261_encode_block(h, block[i], i);
-    }
-
-    if ( ( h->current_mba == 11 ) || ( h->current_mba == 22 ) || ( h->current_mba == 33 ) || ( !IS_16X16 ( h->mtype ) )){
-        h->current_mv_x=0;
-        h->current_mv_y=0;
-    }
-}
-
-void ff_h261_encode_init(MpegEncContext *s){
-    static int done = 0;
-
-    if (!done) {
-        done = 1;
-        init_rl(&h261_rl_tcoeff, static_rl_table_store);
-    }
-
-    s->min_qcoeff= -127;
-    s->max_qcoeff=  127;
-    s->y_dc_scale_table=
-    s->c_dc_scale_table= ff_mpeg1_dc_scale_table;
-}
-
-
-/**
- * encodes a 8x8 block.
- * @param block the 8x8 block
- * @param n block index (0-3 are luma, 4-5 are chroma)
- */
-static void h261_encode_block(H261Context * h, DCTELEM * block, int n){
-    MpegEncContext * const s = &h->s;
-    int level, run, last, i, j, last_index, last_non_zero, sign, slevel, code;
-    RLTable *rl;
-
-    rl = &h261_rl_tcoeff;
-    if (s->mb_intra) {
-        /* DC coef */
-        level = block[0];
-        /* 255 cannot be represented, so we clamp */
-        if (level > 254) {
-            level = 254;
-            block[0] = 254;
-        }
-        /* 0 cannot be represented also */
-        else if (level < 1) {
-            level = 1;
-            block[0] = 1;
-        }
-        if (level == 128)
-            put_bits(&s->pb, 8, 0xff);
-        else
-            put_bits(&s->pb, 8, level);
-        i = 1;
-    } else if((block[0]==1 || block[0] == -1) && (s->block_last_index[n] > -1)){
-        //special case
-        put_bits(&s->pb,2,block[0]>0 ? 2 : 3 );
-        i = 1;
-    } else {
-        i = 0;
-    }
-
-    /* AC coefs */
-    last_index = s->block_last_index[n];
-    last_non_zero = i - 1;
-    for (; i <= last_index; i++) {
-        j = s->intra_scantable.permutated[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, 0 /*no last in H.261, EOB is used*/, run, level);
-            if(run==0 && level < 16)
-            code+=1;
-            put_bits(&s->pb, rl->table_vlc[code][1], rl->table_vlc[code][0]);
-            if (code == rl->n) {
-                put_bits(&s->pb, 6, run);
-                assert(slevel != 0);
-                assert(level <= 127);
-                put_bits(&s->pb, 8, slevel & 0xff);
-            } else {
-                put_bits(&s->pb, 1, sign);
-            }
-            last_non_zero = i;
-        }
-    }
-    if(last_index > -1){
-        put_bits(&s->pb, rl->table_vlc[0][1], rl->table_vlc[0][0]);// END OF BLOCK
-    }
-}
-
-/***********************************************/
-/* decoding */
-
-static VLC h261_mba_vlc;
-static VLC h261_mtype_vlc;
-static VLC h261_mv_vlc;
-static VLC h261_cbp_vlc;
-
-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, 35,
-                 h261_mba_bits, 1, 1,
-                 h261_mba_code, 1, 1, 1);
-        init_vlc(&h261_mtype_vlc, H261_MTYPE_VLC_BITS, 10,
-                 h261_mtype_bits, 1, 1,
-                 h261_mtype_code, 1, 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, 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, 1);
-        init_rl(&h261_rl_tcoeff, static_rl_table_store);
-        init_vlc_rl(&h261_rl_tcoeff, 1);
-    }
-}
-
-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->coded_width;
-    s->height = s->avctx->coded_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->gob_start_code_skipped = 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;
-
-    if ( !h->gob_start_code_skipped ){
-        /* 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_start_code_skipped = 0;
-
-    h->gob_number = get_bits(&s->gb, 4); /* GN */
-    s->qscale = get_bits(&s->gb, 5); /* GQUANT */
-
-    /* Check if gob_number is valid */
-    if (s->mb_height==18){ //cif
-        if ((h->gob_number<=0) || (h->gob_number>12))
-            return -1;
-    }
-    else{ //qcif
-        if ((h->gob_number!=1) && (h->gob_number!=3) && (h->gob_number!=5))
-            return -1;
-    }
-
-    /* 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 ( h->gob_start_code_skipped ){
-        ret= h261_decode_gob_header(h);
-        if(ret>=0)
-            return 0;
-    }
-    else{
-        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 skipped macroblocks
- * @return 0
- */
-static int h261_decode_mb_skipped(H261Context *h, int mba1, int mba2 )
-{
-    MpegEncContext * const s = &h->s;
-    int i;
-
-    s->mb_intra = 0;
-
-    for(i=mba1; i<mba2; i++){
-        int j, xy;
-
-        s->mb_x= ((h->gob_number-1) % 2) * 11 + i % 11;
-        s->mb_y= ((h->gob_number-1) / 2) * 3 + i / 11;
-        xy = s->mb_x + s->mb_y * s->mb_stride;
-        ff_init_block_index(s);
-        ff_update_block_index(s);
-
-        for(j=0;j<6;j++)
-            s->block_last_index[j] = -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_skipped = 1;
-        h->mtype &= ~MB_TYPE_H261_FIL;
-
-        MPV_decode_mb(s, s->block);
-    }
-
-    return 0;
-}
-
-static int decode_mv_component(GetBitContext *gb, int v){
-    int mv_diff = get_vlc2(gb, h261_mv_vlc.table, H261_MV_VLC_BITS, 2);
-
-    /* check if mv_diff is valid */
-    if ( mv_diff < 0 )
-        return v;
-
-    mv_diff = mvmap[mv_diff];
-
-    if(mv_diff && !get_bits1(gb))
-        mv_diff= -mv_diff;
-
-    v += mv_diff;
-    if     (v <=-16) v+= 32;
-    else if(v >= 16) v-= 32;
-
-    return v;
-}
-
-static int h261_decode_mb(H261Context *h){
-    MpegEncContext * const s = &h->s;
-    int i, cbp, xy;
-
-    cbp = 63;
-    // Read mba
-    do{
-        h->mba_diff = get_vlc2(&s->gb, h261_mba_vlc.table, H261_MBA_VLC_BITS, 2);
-
-        /* Check for slice end */
-        /* NOTE: GOB can be empty (no MB data) or exist only of MBA_stuffing */
-        if (h->mba_diff == MBA_STARTCODE){ // start code
-            h->gob_start_code_skipped = 1;
-            return SLICE_END;
-        }
-    }
-    while( h->mba_diff == MBA_STUFFING ); // stuffing
-
-    if ( h->mba_diff < 0 ){
-        if ( get_bits_count(&s->gb) + 7 >= s->gb.size_in_bits )
-            return SLICE_END;
-
-        av_log(s->avctx, AV_LOG_ERROR, "illegal mba at %d %d\n", s->mb_x, s->mb_y);
-        return SLICE_ERROR;
-    }
-
-    h->mba_diff += 1;
-    h->current_mba += h->mba_diff;
-
-    if ( h->current_mba > MBA_STUFFING )
-        return SLICE_ERROR;
-
-    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
-    h->mtype = get_vlc2(&s->gb, h261_mtype_vlc.table, H261_MTYPE_VLC_BITS, 2);
-    h->mtype = h261_mtype_map[h->mtype];
-
-    // Read mquant
-    if ( IS_QUANT ( h->mtype ) ){
-        ff_set_qscale(s, 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))
-        {
-            h->current_mv_x = 0;
-            h->current_mv_y = 0;
-        }
-
-        h->current_mv_x= decode_mv_component(&s->gb, h->current_mv_x);
-        h->current_mv_y= decode_mv_component(&s->gb, h->current_mv_y);
-    }else{
-        h->current_mv_x = 0;
-        h->current_mv_y = 0;
-    }
-
-    // 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;
-    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;
-
-intra:
-    /* decode each block */
-    if(s->mb_intra || HAS_CBP(h->mtype)){
-        s->dsp.clear_blocks(s->block[0]);
-        for (i = 0; i < 6; i++) {
-            if (h261_decode_block(h, s->block[i], i, cbp&32) < 0){
-                return SLICE_ERROR;
-            }
-            cbp+=cbp;
-        }
-    }else{
-        for (i = 0; i < 6; i++)
-            s->block_last_index[i]= -1;
-    }
-
-    MPV_decode_mb(s, s->block);
-
-    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 = get_sbits(&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-1;
-    return 0;
-}
-
-/**
- * decodes the H261 picture header.
- * @return <0 if no startcode found
- */
-static int h261_decode_picture_header(H261Context *h){
-    MpegEncContext * const s = &h->s;
-    int format, i;
-    uint32_t startcode= 0;
-
-    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 */
-    i= get_bits(&s->gb, 5); /* picture timestamp */
-    if(i < (s->picture_number&31))
-        i += 32;
-    s->picture_number = (s->picture_number&~31) + i;
-
-    s->avctx->time_base= (AVRational){1001, 30000};
-    s->current_picture.pts= s->picture_number;
-
-
-    /* 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, but if we pass I_TYPE for the first frame, the codec crashes if it does
-    // not contain all I-blocks (e.g. when a packet is lost)
-    s->pict_type = P_TYPE;
-
-    h->gob_number = 0;
-    return 0;
-}
-
-static int h261_decode_gob(H261Context *h){
-    MpegEncContext * const s = &h->s;
-
-    ff_set_qscale(s, s->qscale);
-
-    /* decode mb's */
-    while(h->current_mba <= MBA_STUFFING)
-    {
-        int ret;
-        /* DCT & quantize */
-        ret= h261_decode_mb(h);
-        if(ret<0){
-            if(ret==SLICE_END){
-                h261_decode_mb_skipped(h, h->current_mba, 33);
-                return 0;
-            }
-            av_log(s->avctx, AV_LOG_ERROR, "Error at MB: %d\n", s->mb_x + s->mb_y*s->mb_stride);
-            return -1;
-        }
-
-        h261_decode_mb_skipped(h, h->current_mba-h->mba_diff, h->current_mba-1);
-    }
-
-    return -1;
-}
-
-/**
- * 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)>>3;
-    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 DEBUG
-    av_log(avctx, AV_LOG_DEBUG, "*****frame %d size=%d\n", avctx->frame_number, buf_size);
-    av_log(avctx, AV_LOG_DEBUG, "bytes=%x %x %x %x\n", buf[0], buf[1], buf[2], buf[3]);
-#endif
-    s->flags= avctx->flags;
-    s->flags2= avctx->flags2;
-
-    h->gob_start_code_skipped=0;
-
-retry:
-
-    init_get_bits(&s->gb, buf, buf_size*8);
-
-    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);
-
-    /* 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->coded_width || s->height != avctx->coded_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) {
-        avcodec_set_dimensions(avctx, s->width, 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(  (avctx->skip_frame >= AVDISCARD_NONREF && s->pict_type==B_TYPE)
-       ||(avctx->skip_frame >= AVDISCARD_NONKEY && s->pict_type!=I_TYPE)
-       || avctx->skip_frame >= AVDISCARD_ALL)
-        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);
-
-assert(s->current_picture.pict_type == s->current_picture_ptr->pict_type);
-assert(s->current_picture.pict_type == s->pict_type);
-    *pict= *(AVFrame*)s->current_picture_ptr;
-    ff_print_debug_info(s, pict);
-
-    *data_size = sizeof(AVFrame);
-
-    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;
-}
-
-#ifdef CONFIG_ENCODERS
-AVCodec h261_encoder = {
-    "h261",
-    CODEC_TYPE_VIDEO,
-    CODEC_ID_H261,
-    sizeof(H261Context),
-    MPV_encode_init,
-    MPV_encode_picture,
-    MPV_encode_end,
-    .pix_fmts= (enum PixelFormat[]){PIX_FMT_YUV420P, -1},
-};
-#endif
-
-AVCodec h261_decoder = {
-    "h261",
-    CODEC_TYPE_VIDEO,
-    CODEC_ID_H261,
-    sizeof(H261Context),
-    h261_decode_init,
-    NULL,
-    h261_decode_end,
-    h261_decode_frame,
-    CODEC_CAP_DR1,
-};
diff --git a/libavcodec/h261.h b/libavcodec/h261.h
new file mode 100644
index 0000000000..b0ce1bb991
--- /dev/null
+++ b/libavcodec/h261.h
@@ -0,0 +1,45 @@
+/*
+ * H261 decoder
+ * Copyright (c) 2002-2004 Michael Niedermayer <michaelni@gmx.at>
+ * Copyright (c) 2004 Maarten Daniels
+ *
+ * This file is part of FFmpeg.
+ *
+ * FFmpeg 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 2.1 of the License, or (at your option) any later version.
+ *
+ * FFmpeg 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 FFmpeg; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+/**
+ * @file h261.c
+ * h261codec.
+ */
+
+#include "mpegvideo.h"
+
+/**
+ * H261Context
+ */
+typedef struct H261Context{
+    MpegEncContext s;
+
+    int current_mba;
+    int previous_mba;
+    int mba_diff;
+    int mtype;
+    int current_mv_x;
+    int current_mv_y;
+    int gob_number;
+    int gob_start_code_skipped; // 1 if gob start code is already read before gob header is read
+}H261Context;
+
diff --git a/libavcodec/h261dec.c b/libavcodec/h261dec.c
new file mode 100644
index 0000000000..f6d4d9c014
--- /dev/null
+++ b/libavcodec/h261dec.c
@@ -0,0 +1,650 @@
+/*
+ * H261 decoder
+ * Copyright (c) 2002-2004 Michael Niedermayer <michaelni@gmx.at>
+ * Copyright (c) 2004 Maarten Daniels
+ *
+ * This file is part of FFmpeg.
+ *
+ * FFmpeg 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 2.1 of the License, or (at your option) any later version.
+ *
+ * FFmpeg 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 FFmpeg; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+/**
+ * @file h261dec.c
+ * H.261 decoder.
+ */
+
+#include "dsputil.h"
+#include "avcodec.h"
+#include "mpegvideo.h"
+#include "h261data.h"
+#include "h261.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 MBA_STUFFING 33
+#define MBA_STARTCODE 34
+
+extern uint8_t ff_h261_rl_table_store[2][2*MAX_RUN + MAX_LEVEL + 3];
+
+static VLC h261_mba_vlc;
+static VLC h261_mtype_vlc;
+static VLC h261_mv_vlc;
+static VLC h261_cbp_vlc;
+
+static int h261_decode_block(H261Context * h, DCTELEM * block, int n, int coded);
+
+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, 35,
+                 h261_mba_bits, 1, 1,
+                 h261_mba_code, 1, 1, 1);
+        init_vlc(&h261_mtype_vlc, H261_MTYPE_VLC_BITS, 10,
+                 h261_mtype_bits, 1, 1,
+                 h261_mtype_code, 1, 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, 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, 1);
+        init_rl(&h261_rl_tcoeff, ff_h261_rl_table_store);
+        init_vlc_rl(&h261_rl_tcoeff, 1);
+    }
+}
+
+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->coded_width;
+    s->height = s->avctx->coded_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->gob_start_code_skipped = 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;
+
+    if ( !h->gob_start_code_skipped ){
+        /* 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_start_code_skipped = 0;
+
+    h->gob_number = get_bits(&s->gb, 4); /* GN */
+    s->qscale = get_bits(&s->gb, 5); /* GQUANT */
+
+    /* Check if gob_number is valid */
+    if (s->mb_height==18){ //cif
+        if ((h->gob_number<=0) || (h->gob_number>12))
+            return -1;
+    }
+    else{ //qcif
+        if ((h->gob_number!=1) && (h->gob_number!=3) && (h->gob_number!=5))
+            return -1;
+    }
+
+    /* 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 ( h->gob_start_code_skipped ){
+        ret= h261_decode_gob_header(h);
+        if(ret>=0)
+            return 0;
+    }
+    else{
+        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 skipped macroblocks
+ * @return 0
+ */
+static int h261_decode_mb_skipped(H261Context *h, int mba1, int mba2 )
+{
+    MpegEncContext * const s = &h->s;
+    int i;
+
+    s->mb_intra = 0;
+
+    for(i=mba1; i<mba2; i++){
+        int j, xy;
+
+        s->mb_x= ((h->gob_number-1) % 2) * 11 + i % 11;
+        s->mb_y= ((h->gob_number-1) / 2) * 3 + i / 11;
+        xy = s->mb_x + s->mb_y * s->mb_stride;
+        ff_init_block_index(s);
+        ff_update_block_index(s);
+
+        for(j=0;j<6;j++)
+            s->block_last_index[j] = -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_skipped = 1;
+        h->mtype &= ~MB_TYPE_H261_FIL;
+
+        MPV_decode_mb(s, s->block);
+    }
+
+    return 0;
+}
+
+static int decode_mv_component(GetBitContext *gb, int v){
+    int mv_diff = get_vlc2(gb, h261_mv_vlc.table, H261_MV_VLC_BITS, 2);
+
+    /* check if mv_diff is valid */
+    if ( mv_diff < 0 )
+        return v;
+
+    mv_diff = mvmap[mv_diff];
+
+    if(mv_diff && !get_bits1(gb))
+        mv_diff= -mv_diff;
+
+    v += mv_diff;
+    if     (v <=-16) v+= 32;
+    else if(v >= 16) v-= 32;
+
+    return v;
+}
+
+static int h261_decode_mb(H261Context *h){
+    MpegEncContext * const s = &h->s;
+    int i, cbp, xy;
+
+    cbp = 63;
+    // Read mba
+    do{
+        h->mba_diff = get_vlc2(&s->gb, h261_mba_vlc.table, H261_MBA_VLC_BITS, 2);
+
+        /* Check for slice end */
+        /* NOTE: GOB can be empty (no MB data) or exist only of MBA_stuffing */
+        if (h->mba_diff == MBA_STARTCODE){ // start code
+            h->gob_start_code_skipped = 1;
+            return SLICE_END;
+        }
+    }
+    while( h->mba_diff == MBA_STUFFING ); // stuffing
+
+    if ( h->mba_diff < 0 ){
+        if ( get_bits_count(&s->gb) + 7 >= s->gb.size_in_bits )
+            return SLICE_END;
+
+        av_log(s->avctx, AV_LOG_ERROR, "illegal mba at %d %d\n", s->mb_x, s->mb_y);
+        return SLICE_ERROR;
+    }
+
+    h->mba_diff += 1;
+    h->current_mba += h->mba_diff;
+
+    if ( h->current_mba > MBA_STUFFING )
+        return SLICE_ERROR;
+
+    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
+    h->mtype = get_vlc2(&s->gb, h261_mtype_vlc.table, H261_MTYPE_VLC_BITS, 2);
+    h->mtype = h261_mtype_map[h->mtype];
+
+    // Read mquant
+    if ( IS_QUANT ( h->mtype ) ){
+        ff_set_qscale(s, 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))
+        {
+            h->current_mv_x = 0;
+            h->current_mv_y = 0;
+        }
+
+        h->current_mv_x= decode_mv_component(&s->gb, h->current_mv_x);
+        h->current_mv_y= decode_mv_component(&s->gb, h->current_mv_y);
+    }else{
+        h->current_mv_x = 0;
+        h->current_mv_y = 0;
+    }
+
+    // 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;
+    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;
+
+intra:
+    /* decode each block */
+    if(s->mb_intra || HAS_CBP(h->mtype)){
+        s->dsp.clear_blocks(s->block[0]);
+        for (i = 0; i < 6; i++) {
+            if (h261_decode_block(h, s->block[i], i, cbp&32) < 0){
+                return SLICE_ERROR;
+            }
+            cbp+=cbp;
+        }
+    }else{
+        for (i = 0; i < 6; i++)
+            s->block_last_index[i]= -1;
+    }
+
+    MPV_decode_mb(s, s->block);
+
+    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 = get_sbits(&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-1;
+    return 0;
+}
+
+/**
+ * decodes the H261 picture header.
+ * @return <0 if no startcode found
+ */
+static int h261_decode_picture_header(H261Context *h){
+    MpegEncContext * const s = &h->s;
+    int format, i;
+    uint32_t startcode= 0;
+
+    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 */
+    i= get_bits(&s->gb, 5); /* picture timestamp */
+    if(i < (s->picture_number&31))
+        i += 32;
+    s->picture_number = (s->picture_number&~31) + i;
+
+    s->avctx->time_base= (AVRational){1001, 30000};
+    s->current_picture.pts= s->picture_number;
+
+
+    /* 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, but if we pass I_TYPE for the first frame, the codec crashes if it does
+    // not contain all I-blocks (e.g. when a packet is lost)
+    s->pict_type = P_TYPE;
+
+    h->gob_number = 0;
+    return 0;
+}
+
+static int h261_decode_gob(H261Context *h){
+    MpegEncContext * const s = &h->s;
+
+    ff_set_qscale(s, s->qscale);
+
+    /* decode mb's */
+    while(h->current_mba <= MBA_STUFFING)
+    {
+        int ret;
+        /* DCT & quantize */
+        ret= h261_decode_mb(h);
+        if(ret<0){
+            if(ret==SLICE_END){
+                h261_decode_mb_skipped(h, h->current_mba, 33);
+                return 0;
+            }
+            av_log(s->avctx, AV_LOG_ERROR, "Error at MB: %d\n", s->mb_x + s->mb_y*s->mb_stride);
+            return -1;
+        }
+
+        h261_decode_mb_skipped(h, h->current_mba-h->mba_diff, h->current_mba-1);
+    }
+
+    return -1;
+}
+
+/**
+ * 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)>>3;
+    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 DEBUG
+    av_log(avctx, AV_LOG_DEBUG, "*****frame %d size=%d\n", avctx->frame_number, buf_size);
+    av_log(avctx, AV_LOG_DEBUG, "bytes=%x %x %x %x\n", buf[0], buf[1], buf[2], buf[3]);
+#endif
+    s->flags= avctx->flags;
+    s->flags2= avctx->flags2;
+
+    h->gob_start_code_skipped=0;
+
+retry:
+
+    init_get_bits(&s->gb, buf, buf_size*8);
+
+    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);
+
+    /* 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->coded_width || s->height != avctx->coded_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) {
+        avcodec_set_dimensions(avctx, s->width, 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(  (avctx->skip_frame >= AVDISCARD_NONREF && s->pict_type==B_TYPE)
+       ||(avctx->skip_frame >= AVDISCARD_NONKEY && s->pict_type!=I_TYPE)
+       || avctx->skip_frame >= AVDISCARD_ALL)
+        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);
+
+assert(s->current_picture.pict_type == s->current_picture_ptr->pict_type);
+assert(s->current_picture.pict_type == s->pict_type);
+    *pict= *(AVFrame*)s->current_picture_ptr;
+    ff_print_debug_info(s, pict);
+
+    *data_size = sizeof(AVFrame);
+
+    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_DR1,
+};
diff --git a/libavcodec/h261enc.c b/libavcodec/h261enc.c
new file mode 100644
index 0000000000..a92060a4bb
--- /dev/null
+++ b/libavcodec/h261enc.c
@@ -0,0 +1,334 @@
+/*
+ * H261 encoder
+ * Copyright (c) 2002-2004 Michael Niedermayer <michaelni@gmx.at>
+ * Copyright (c) 2004 Maarten Daniels
+ *
+ * This file is part of FFmpeg.
+ *
+ * FFmpeg 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 2.1 of the License, or (at your option) any later version.
+ *
+ * FFmpeg 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 FFmpeg; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+/**
+ * @file h261enc.c
+ * H.261 encoder.
+ */
+
+#include "dsputil.h"
+#include "avcodec.h"
+#include "mpegvideo.h"
+#include "h261data.h"
+#include "h261.h"
+
+extern uint8_t ff_h261_rl_table_store[2][2*MAX_RUN + MAX_LEVEL + 3];
+
+static void h261_encode_block(H261Context * h, DCTELEM * block,
+                              int n);
+
+int ff_h261_get_picture_format(int width, int height){
+    // QCIF
+    if (width == 176 && height == 144)
+        return 0;
+    // CIF
+    else if (width == 352 && height == 288)
+        return 1;
+    // ERROR
+    else
+        return -1;
+}
+
+void ff_h261_encode_picture_header(MpegEncContext * s, int picture_number){
+    H261Context * h = (H261Context *) s;
+    int format, temp_ref;
+
+    align_put_bits(&s->pb);
+
+    /* Update the pointer to last GOB */
+    s->ptr_lastgob = pbBufPtr(&s->pb);
+
+    put_bits(&s->pb, 20, 0x10); /* PSC */
+
+    temp_ref= s->picture_number * (int64_t)30000 * s->avctx->time_base.num /
+                         (1001 * (int64_t)s->avctx->time_base.den); //FIXME maybe this should use a timestamp
+    put_bits(&s->pb, 5, temp_ref & 0x1f); /* TemporalReference */
+
+    put_bits(&s->pb, 1, 0); /* split screen off */
+    put_bits(&s->pb, 1, 0); /* camera  off */
+    put_bits(&s->pb, 1, 0); /* freeze picture release off */
+
+    format = ff_h261_get_picture_format(s->width, s->height);
+
+    put_bits(&s->pb, 1, format); /* 0 == QCIF, 1 == CIF */
+
+    put_bits(&s->pb, 1, 0); /* still image mode */
+    put_bits(&s->pb, 1, 0); /* reserved */
+
+    put_bits(&s->pb, 1, 0); /* no PEI */
+    if(format == 0)
+        h->gob_number = -1;
+    else
+        h->gob_number = 0;
+    h->current_mba = 0;
+}
+
+/**
+ * Encodes a group of blocks header.
+ */
+static void h261_encode_gob_header(MpegEncContext * s, int mb_line){
+    H261Context * h = (H261Context *)s;
+    if(ff_h261_get_picture_format(s->width, s->height) == 0){
+        h->gob_number+=2; // QCIF
+    }
+    else{
+        h->gob_number++; // CIF
+    }
+    put_bits(&s->pb, 16, 1); /* GBSC */
+    put_bits(&s->pb, 4, h->gob_number); /* GN */
+    put_bits(&s->pb, 5, s->qscale); /* GQUANT */
+    put_bits(&s->pb, 1, 0); /* no GEI */
+    h->current_mba = 0;
+    h->previous_mba = 0;
+    h->current_mv_x=0;
+    h->current_mv_y=0;
+}
+
+void ff_h261_reorder_mb_index(MpegEncContext* s){
+    int index= s->mb_x + s->mb_y*s->mb_width;
+
+    if(index % 33 == 0)
+        h261_encode_gob_header(s,0);
+
+    /* for CIF the GOB's are fragmented in the middle of a scanline
+       that's why we need to adjust the x and y index of the macroblocks */
+    if(ff_h261_get_picture_format(s->width,s->height) == 1){ // CIF
+        s->mb_x =     index % 11 ; index /= 11;
+        s->mb_y =     index %  3 ; index /=  3;
+        s->mb_x+= 11*(index %  2); index /=  2;
+        s->mb_y+=  3*index;
+
+        ff_init_block_index(s);
+        ff_update_block_index(s);
+    }
+}
+
+static void h261_encode_motion(H261Context * h, int val){
+    MpegEncContext * const s = &h->s;
+    int sign, code;
+    if(val==0){
+        code = 0;
+        put_bits(&s->pb,h261_mv_tab[code][1],h261_mv_tab[code][0]);
+    }
+    else{
+        if(val > 15)
+            val -=32;
+        if(val < -16)
+            val+=32;
+        sign = val < 0;
+        code = sign ? -val : val;
+        put_bits(&s->pb,h261_mv_tab[code][1],h261_mv_tab[code][0]);
+        put_bits(&s->pb,1,sign);
+    }
+}
+
+static inline int get_cbp(MpegEncContext * s,
+                      DCTELEM block[6][64])
+{
+    int i, cbp;
+    cbp= 0;
+    for (i = 0; i < 6; i++) {
+        if (s->block_last_index[i] >= 0)
+            cbp |= 1 << (5 - i);
+    }
+    return cbp;
+}
+void ff_h261_encode_mb(MpegEncContext * s,
+         DCTELEM block[6][64],
+         int motion_x, int motion_y)
+{
+    H261Context * h = (H261Context *)s;
+    int mvd, mv_diff_x, mv_diff_y, i, cbp;
+    cbp = 63; // avoid warning
+    mvd = 0;
+
+    h->current_mba++;
+    h->mtype = 0;
+
+    if (!s->mb_intra){
+        /* compute cbp */
+        cbp= get_cbp(s, block);
+
+        /* mvd indicates if this block is motion compensated */
+        mvd = motion_x | motion_y;
+
+        if((cbp | mvd | s->dquant ) == 0) {
+            /* skip macroblock */
+            s->skip_count++;
+            h->current_mv_x=0;
+            h->current_mv_y=0;
+            return;
+        }
+    }
+
+    /* MB is not skipped, encode MBA */
+    put_bits(&s->pb, h261_mba_bits[(h->current_mba-h->previous_mba)-1], h261_mba_code[(h->current_mba-h->previous_mba)-1]);
+
+    /* calculate MTYPE */
+    if(!s->mb_intra){
+        h->mtype++;
+
+        if(mvd || s->loop_filter)
+            h->mtype+=3;
+        if(s->loop_filter)
+            h->mtype+=3;
+        if(cbp || s->dquant)
+            h->mtype++;
+        assert(h->mtype > 1);
+    }
+
+    if(s->dquant)
+        h->mtype++;
+
+    put_bits(&s->pb, h261_mtype_bits[h->mtype], h261_mtype_code[h->mtype]);
+
+    h->mtype = h261_mtype_map[h->mtype];
+
+    if(IS_QUANT(h->mtype)){
+        ff_set_qscale(s,s->qscale+s->dquant);
+        put_bits(&s->pb, 5, s->qscale);
+    }
+
+    if(IS_16X16(h->mtype)){
+        mv_diff_x = (motion_x >> 1) - h->current_mv_x;
+        mv_diff_y = (motion_y >> 1) - h->current_mv_y;
+        h->current_mv_x = (motion_x >> 1);
+        h->current_mv_y = (motion_y >> 1);
+        h261_encode_motion(h,mv_diff_x);
+        h261_encode_motion(h,mv_diff_y);
+    }
+
+    h->previous_mba = h->current_mba;
+
+    if(HAS_CBP(h->mtype)){
+        assert(cbp>0);
+        put_bits(&s->pb,h261_cbp_tab[cbp-1][1],h261_cbp_tab[cbp-1][0]);
+    }
+    for(i=0; i<6; i++) {
+        /* encode each block */
+        h261_encode_block(h, block[i], i);
+    }
+
+    if ( ( h->current_mba == 11 ) || ( h->current_mba == 22 ) || ( h->current_mba == 33 ) || ( !IS_16X16 ( h->mtype ) )){
+        h->current_mv_x=0;
+        h->current_mv_y=0;
+    }
+}
+
+void ff_h261_encode_init(MpegEncContext *s){
+    static int done = 0;
+
+    if (!done) {
+        done = 1;
+        init_rl(&h261_rl_tcoeff, ff_h261_rl_table_store);
+    }
+
+    s->min_qcoeff= -127;
+    s->max_qcoeff=  127;
+    s->y_dc_scale_table=
+    s->c_dc_scale_table= ff_mpeg1_dc_scale_table;
+}
+
+
+/**
+ * encodes a 8x8 block.
+ * @param block the 8x8 block
+ * @param n block index (0-3 are luma, 4-5 are chroma)
+ */
+static void h261_encode_block(H261Context * h, DCTELEM * block, int n){
+    MpegEncContext * const s = &h->s;
+    int level, run, last, i, j, last_index, last_non_zero, sign, slevel, code;
+    RLTable *rl;
+
+    rl = &h261_rl_tcoeff;
+    if (s->mb_intra) {
+        /* DC coef */
+        level = block[0];
+        /* 255 cannot be represented, so we clamp */
+        if (level > 254) {
+            level = 254;
+            block[0] = 254;
+        }
+        /* 0 cannot be represented also */
+        else if (level < 1) {
+            level = 1;
+            block[0] = 1;
+        }
+        if (level == 128)
+            put_bits(&s->pb, 8, 0xff);
+        else
+            put_bits(&s->pb, 8, level);
+        i = 1;
+    } else if((block[0]==1 || block[0] == -1) && (s->block_last_index[n] > -1)){
+        //special case
+        put_bits(&s->pb,2,block[0]>0 ? 2 : 3 );
+        i = 1;
+    } else {
+        i = 0;
+    }
+
+    /* AC coefs */
+    last_index = s->block_last_index[n];
+    last_non_zero = i - 1;
+    for (; i <= last_index; i++) {
+        j = s->intra_scantable.permutated[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, 0 /*no last in H.261, EOB is used*/, run, level);
+            if(run==0 && level < 16)
+            code+=1;
+            put_bits(&s->pb, rl->table_vlc[code][1], rl->table_vlc[code][0]);
+            if (code == rl->n) {
+                put_bits(&s->pb, 6, run);
+                assert(slevel != 0);
+                assert(level <= 127);
+                put_bits(&s->pb, 8, slevel & 0xff);
+            } else {
+                put_bits(&s->pb, 1, sign);
+            }
+            last_non_zero = i;
+        }
+    }
+    if(last_index > -1){
+        put_bits(&s->pb, rl->table_vlc[0][1], rl->table_vlc[0][0]);// END OF BLOCK
+    }
+}
+
+AVCodec h261_encoder = {
+    "h261",
+    CODEC_TYPE_VIDEO,
+    CODEC_ID_H261,
+    sizeof(H261Context),
+    MPV_encode_init,
+    MPV_encode_picture,
+    MPV_encode_end,
+    .pix_fmts= (enum PixelFormat[]){PIX_FMT_YUV420P, -1},
+};
+