PeerStreamer

/*

 * H.263 decoder

 * Copyright (c) 2001 Fabrice Bellard.

 * Copyright (c) 2002-2004 Michael Niedermayer <michaelni@gmx.at>

 *

 * 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 h263dec.c

 * H.263 decoder.

 */

#include "avcodec.h"

#include "dsputil.h"

#include "mpegvideo.h"

#include "h263_parser.h"

#include "mpeg4video_parser.h"

#include "msmpeg4.h"

//#define DEBUG

//#define PRINT_FRAME_TIME

av_cold int ff_h263_decode_init(AVCodecContext *avctx)

{

    MpegEncContext *s = avctx->priv_data;

    s->avctx = avctx;

    s->out_format = FMT_H263;

    s->width  = avctx->coded_width;

    s->height = avctx->coded_height;

    s->workaround_bugs= avctx->workaround_bugs;

    // set defaults

    MPV_decode_defaults(s);

    s->quant_precision=5;

    s->decode_mb= ff_h263_decode_mb;

    s->low_delay= 1;

    avctx->pix_fmt= PIX_FMT_YUV420P;

    s->unrestricted_mv= 1;

    /* select sub codec */

    switch(avctx->codec->id) {

    case CODEC_ID_H263:

        s->unrestricted_mv= 0;

        break;

    case CODEC_ID_MPEG4:

        s->decode_mb= ff_mpeg4_decode_mb;

        s->time_increment_bits = 4; /* default value for broken headers */

        s->h263_pred = 1;

        s->low_delay = 0; //default, might be overriden in the vol header during header parsing

        break;

    case CODEC_ID_MSMPEG4V1:

        s->h263_msmpeg4 = 1;

        s->h263_pred = 1;

        s->msmpeg4_version=1;

        break;

    case CODEC_ID_MSMPEG4V2:

        s->h263_msmpeg4 = 1;

        s->h263_pred = 1;

        s->msmpeg4_version=2;

        break;

    case CODEC_ID_MSMPEG4V3:

        s->h263_msmpeg4 = 1;

        s->h263_pred = 1;

        s->msmpeg4_version=3;

        break;

    case CODEC_ID_WMV1:

        s->h263_msmpeg4 = 1;

        s->h263_pred = 1;

        s->msmpeg4_version=4;

        break;

    case CODEC_ID_WMV2:

        s->h263_msmpeg4 = 1;

        s->h263_pred = 1;

        s->msmpeg4_version=5;

        break;

    case CODEC_ID_VC1:

    case CODEC_ID_WMV3:

        s->h263_msmpeg4 = 1;

        s->h263_pred = 1;

        s->msmpeg4_version=6;

        break;

    case CODEC_ID_H263I:

        break;

    case CODEC_ID_FLV1:

        s->h263_flv = 1;

        break;

    default:

        return -1;

    }

    s->codec_id= avctx->codec->id;

    /* for h263, we allocate the images after having read the header */

    if (avctx->codec->id != CODEC_ID_H263 && avctx->codec->id != CODEC_ID_MPEG4)

        if (MPV_common_init(s) < 0)

            return -1;

    if (ENABLE_MSMPEG4_DECODER && s->h263_msmpeg4)

        ff_msmpeg4_decode_init(s);

    else

        h263_decode_init_vlc(s);

    return 0;

}

av_cold int ff_h263_decode_end(AVCodecContext *avctx)

{

    MpegEncContext *s = avctx->priv_data;

    MPV_common_end(s);

    return 0;

}

/**

 * 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->divx_packed){

        //we would have to scan through the whole buf to handle the weird reordering ...

        return buf_size;

    }else 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 that is needed but ...)

        if(pos+10>buf_size) pos=buf_size; // oops ;)

        return pos;

    }

}

static int decode_slice(MpegEncContext *s){

    const int part_mask= s->partitioned_frame ? (AC_END|AC_ERROR) : 0x7F;

    const int mb_size= 16>>s->avctx->lowres;

    s->last_resync_gb= s->gb;

    s->first_slice_line= 1;

    s->resync_mb_x= s->mb_x;

    s->resync_mb_y= s->mb_y;

    ff_set_qscale(s, s->qscale);

    if(s->partitioned_frame){

        const int qscale= s->qscale;

        if(s->codec_id==CODEC_ID_MPEG4){

            if(ff_mpeg4_decode_partitions(s) < 0)

                return -1;

        }

        /* restore variables which were modified */

        s->first_slice_line=1;

        s->mb_x= s->resync_mb_x;

        s->mb_y= s->resync_mb_y;

        ff_set_qscale(s, qscale);

    }

    for(; s->mb_y < s->mb_height; s->mb_y++) {

        /* per-row end of slice checks */

        if(s->msmpeg4_version){

            if(s->resync_mb_y + s->slice_height == s->mb_y){

                ff_er_add_slice(s, s->resync_mb_x, s->resync_mb_y, s->mb_x-1, s->mb_y, AC_END|DC_END|MV_END);

                return 0;

            }

        }

        if(s->msmpeg4_version==1){

            s->last_dc[0]=

            s->last_dc[1]=

            s->last_dc[2]= 128;

        }

        ff_init_block_index(s);

        for(; s->mb_x < s->mb_width; s->mb_x++) {

            int ret;

            ff_update_block_index(s);

            if(s->resync_mb_x == s->mb_x && s->resync_mb_y+1 == s->mb_y){

                s->first_slice_line=0;

            }

            /* DCT & quantize */

            s->mv_dir = MV_DIR_FORWARD;

            s->mv_type = MV_TYPE_16X16;

//            s->mb_skipped = 0;

//printf("%d %d %06X\n", ret, get_bits_count(&s->gb), show_bits(&s->gb, 24));

            ret= s->decode_mb(s, s->block);

            if (s->pict_type!=FF_B_TYPE)

                ff_h263_update_motion_val(s);

            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(s->loop_filter)

                        ff_h263_loop_filter(s);

//printf("%d %d %d %06X\n", s->mb_x, s->mb_y, s->gb.size*8 - get_bits_count(&s->gb), show_bits(&s->gb, 24));

                    ff_er_add_slice(s, s->resync_mb_x, s->resync_mb_y, s->mb_x, s->mb_y, (AC_END|DC_END|MV_END)&part_mask);

                    s->padding_bug_score--;

                    if(++s->mb_x >= s->mb_width){

                        s->mb_x=0;

                        ff_draw_horiz_band(s, s->mb_y*mb_size, mb_size);

                        s->mb_y++;

                    }

                    return 0;

                }else if(ret==SLICE_NOEND){

                    av_log(s->avctx, AV_LOG_ERROR, "Slice mismatch at MB: %d\n", xy);

                    ff_er_add_slice(s, s->resync_mb_x, s->resync_mb_y, s->mb_x+1, s->mb_y, (AC_END|DC_END|MV_END)&part_mask);

                    return -1;

                }

                av_log(s->avctx, AV_LOG_ERROR, "Error at MB: %d\n", xy);

                ff_er_add_slice(s, s->resync_mb_x, s->resync_mb_y, s->mb_x, s->mb_y, (AC_ERROR|DC_ERROR|MV_ERROR)&part_mask);

                return -1;

            }

            MPV_decode_mb(s, s->block);

            if(s->loop_filter)

                ff_h263_loop_filter(s);

        }

        ff_draw_horiz_band(s, s->mb_y*mb_size, mb_size);

        s->mb_x= 0;

    }

    assert(s->mb_x==0 && s->mb_y==s->mb_height);

    /* try to detect the padding bug */

    if(      s->codec_id==CODEC_ID_MPEG4

       &&   (s->workaround_bugs&FF_BUG_AUTODETECT)

       &&    s->gb.size_in_bits - get_bits_count(&s->gb) >=0

       &&    s->gb.size_in_bits - get_bits_count(&s->gb) < 48

//       &&   !s->resync_marker

       &&   !s->data_partitioning){

        const int bits_count= get_bits_count(&s->gb);

        const int bits_left = s->gb.size_in_bits - bits_count;

        if(bits_left==0){

            s->padding_bug_score+=16;

        } else if(bits_left != 1){

            int v= show_bits(&s->gb, 8);

            v|= 0x7F >> (7-(bits_count&7));

            if(v==0x7F && bits_left<=8)

                s->padding_bug_score--;

            else if(v==0x7F && ((get_bits_count(&s->gb)+8)&8) && bits_left<=16)

                s->padding_bug_score+= 4;

            else

                s->padding_bug_score++;

        }

    }

    if(s->workaround_bugs&FF_BUG_AUTODETECT){

        if(s->padding_bug_score > -2 && !s->data_partitioning /*&& (s->divx_version || !s->resync_marker)*/)

            s->workaround_bugs |=  FF_BUG_NO_PADDING;

        else

            s->workaround_bugs &= ~FF_BUG_NO_PADDING;

    }

    // handle formats which don't have unique end markers

    if(s->msmpeg4_version || (s->workaround_bugs&FF_BUG_NO_PADDING)){ //FIXME perhaps solve this more cleanly

        int left= s->gb.size_in_bits - get_bits_count(&s->gb);

        int max_extra=7;

        /* no markers in M$ crap */

        if(s->msmpeg4_version && s->pict_type==FF_I_TYPE)

            max_extra+= 17;

        /* buggy padding but the frame should still end approximately at the bitstream end */

        if((s->workaround_bugs&FF_BUG_NO_PADDING) && s->error_resilience>=3)

            max_extra+= 48;

        else if((s->workaround_bugs&FF_BUG_NO_PADDING))

            max_extra+= 256*256*256*64;

        if(left>max_extra){

            av_log(s->avctx, AV_LOG_ERROR, "discarding %d junk bits at end, next would be %X\n", left, show_bits(&s->gb, 24));

        }

        else if(left<0){

            av_log(s->avctx, AV_LOG_ERROR, "overreading %d bits\n", -left);

        }else

            ff_er_add_slice(s, s->resync_mb_x, s->resync_mb_y, s->mb_x-1, s->mb_y, AC_END|DC_END|MV_END);

        return 0;

    }

    av_log(s->avctx, AV_LOG_ERROR, "slice end not reached but screenspace end (%d left %06X, score= %d)\n",

            s->gb.size_in_bits - get_bits_count(&s->gb),

            show_bits(&s->gb, 24), s->padding_bug_score);

    ff_er_add_slice(s, s->resync_mb_x, s->resync_mb_y, s->mb_x, s->mb_y, (AC_END|DC_END|MV_END)&part_mask);

    return -1;

}

int ff_h263_decode_frame(AVCodecContext *avctx,

                             void *data, int *data_size,

                             const uint8_t *buf, int buf_size)

{

    MpegEncContext *s = avctx->priv_data;

    int ret;

    AVFrame *pict = data;

#ifdef PRINT_FRAME_TIME

uint64_t time= rdtsc();

#endif

#ifdef DEBUG

    av_log(avctx, AV_LOG_DEBUG, "*****frame %d size=%d\n", avctx->frame_number, buf_size);

    if(buf_size>0)

        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;

    /* 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;

        if(ENABLE_MPEG4_DECODER && s->codec_id==CODEC_ID_MPEG4){

            next= ff_mpeg4_find_frame_end(&s->parse_context, buf, buf_size);

        }else if(ENABLE_H263_DECODER && s->codec_id==CODEC_ID_H263){

            next= ff_h263_find_frame_end(&s->parse_context, buf, buf_size);

        }else{

            av_log(s->avctx, AV_LOG_ERROR, "this codec does not support truncated bitstreams\n");

            return -1;

        }

        if( ff_combine_frame(&s->parse_context, next, (const uint8_t **)&buf, &buf_size) < 0 )

            return buf_size;

    }

retry:

    if(s->bitstream_buffer_size && (s->divx_packed || buf_size<20)){ //divx 5.01+/xvid frame reorder

        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 cannot store anyting in 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];

    }

    /* let's go :-) */

    if (ENABLE_WMV2_DECODER && s->msmpeg4_version==5) {

        ret= ff_wmv2_decode_picture_header(s);

    } else if (ENABLE_MSMPEG4_DECODER && s->msmpeg4_version) {

        ret = msmpeg4_decode_picture_header(s);

    } else if (s->h263_pred) {

        if(s->avctx->extradata_size && s->picture_number==0){

            GetBitContext gb;

            init_get_bits(&gb, s->avctx->extradata, s->avctx->extradata_size*8);

            ret = ff_mpeg4_decode_picture_header(s, &gb);

        }

        ret = ff_mpeg4_decode_picture_header(s, &s->gb);

        if(s->flags& CODEC_FLAG_LOW_DELAY)

            s->low_delay=1;

    } else if (s->codec_id == CODEC_ID_H263I) {

        ret = intel_h263_decode_picture_header(s);

    } else if (s->h263_flv) {

        ret = flv_h263_decode_picture_header(s);

    } else {

        ret = h263_decode_picture_header(s);

    }

    if(ret==FRAME_SKIPPED) 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;

    }

    avctx->has_b_frames= !s->low_delay;

    if(s->xvid_build==0 && s->divx_version==0 && s->lavc_build==0){

        if(s->stream_codec_tag == ff_get_fourcc("XVID") ||

           s->codec_tag == ff_get_fourcc("XVID") || s->codec_tag == ff_get_fourcc("XVIX") ||

           s->codec_tag == ff_get_fourcc("RMP4"))

            s->xvid_build= -1;

#if 0

        if(s->codec_tag == ff_get_fourcc("DIVX") && s->vo_type==0 && s->vol_control_parameters==1

           && s->padding_bug_score > 0 && s->low_delay) // XVID with modified fourcc

            s->xvid_build= -1;

#endif

    }

    if(s->xvid_build==0 && s->divx_version==0 && s->lavc_build==0){

        if(s->codec_tag == ff_get_fourcc("DIVX") && s->vo_type==0 && s->vol_control_parameters==0)

            s->divx_version= 400; //divx 4

    }

    if(s->xvid_build && s->divx_version){

        s->divx_version=

        s->divx_build= 0;

    }

    if(s->workaround_bugs&FF_BUG_AUTODETECT){

        if(s->codec_tag == ff_get_fourcc("XVIX"))

            s->workaround_bugs|= FF_BUG_XVID_ILACE;

        if(s->codec_tag == ff_get_fourcc("UMP4")){

            s->workaround_bugs|= FF_BUG_UMP4;

        }

        if(s->divx_version>=500 && s->divx_build<1814){

            s->workaround_bugs|= FF_BUG_QPEL_CHROMA;

        }

        if(s->divx_version>502 && s->divx_build<1814){

            s->workaround_bugs|= FF_BUG_QPEL_CHROMA2;

        }

        if(s->xvid_build && s->xvid_build<=3)

            s->padding_bug_score= 256*256*256*64;

        if(s->xvid_build && s->xvid_build<=1)

            s->workaround_bugs|= FF_BUG_QPEL_CHROMA;

        if(s->xvid_build && s->xvid_build<=12)

            s->workaround_bugs|= FF_BUG_EDGE;

        if(s->xvid_build && s->xvid_build<=32)

            s->workaround_bugs|= FF_BUG_DC_CLIP;

#define SET_QPEL_FUNC(postfix1, postfix2) \

    s->dsp.put_ ## postfix1 = ff_put_ ## postfix2;\

    s->dsp.put_no_rnd_ ## postfix1 = ff_put_no_rnd_ ## postfix2;\

    s->dsp.avg_ ## postfix1 = ff_avg_ ## postfix2;

        if(s->lavc_build && s->lavc_build<4653)

            s->workaround_bugs|= FF_BUG_STD_QPEL;

        if(s->lavc_build && s->lavc_build<4655)

            s->workaround_bugs|= FF_BUG_DIRECT_BLOCKSIZE;

        if(s->lavc_build && s->lavc_build<4670){

            s->workaround_bugs|= FF_BUG_EDGE;

        }

        if(s->lavc_build && s->lavc_build<=4712)

            s->workaround_bugs|= FF_BUG_DC_CLIP;

        if(s->divx_version)

            s->workaround_bugs|= FF_BUG_DIRECT_BLOCKSIZE;

//printf("padding_bug_score: %d\n", s->padding_bug_score);

        if(s->divx_version==501 && s->divx_build==20020416)

            s->padding_bug_score= 256*256*256*64;

        if(s->divx_version && s->divx_version<500){

            s->workaround_bugs|= FF_BUG_EDGE;

        }

        if(s->divx_version)

            s->workaround_bugs|= FF_BUG_HPEL_CHROMA;

#if 0

        if(s->divx_version==500)

            s->padding_bug_score= 256*256*256*64;

        /* very ugly XVID padding bug detection FIXME/XXX solve this differently

         * Let us hope this at least works.

         */

        if(   s->resync_marker==0 && s->data_partitioning==0 && s->divx_version==0

           && s->codec_id==CODEC_ID_MPEG4 && s->vo_type==0)

            s->workaround_bugs|= FF_BUG_NO_PADDING;

        if(s->lavc_build && s->lavc_build<4609) //FIXME not sure about the version num but a 4609 file seems ok

            s->workaround_bugs|= FF_BUG_NO_PADDING;

#endif

    }

    if(s->workaround_bugs& FF_BUG_STD_QPEL){

        SET_QPEL_FUNC(qpel_pixels_tab[0][ 5], qpel16_mc11_old_c)

        SET_QPEL_FUNC(qpel_pixels_tab[0][ 7], qpel16_mc31_old_c)

        SET_QPEL_FUNC(qpel_pixels_tab[0][ 9], qpel16_mc12_old_c)

        SET_QPEL_FUNC(qpel_pixels_tab[0][11], qpel16_mc32_old_c)

        SET_QPEL_FUNC(qpel_pixels_tab[0][13], qpel16_mc13_old_c)

        SET_QPEL_FUNC(qpel_pixels_tab[0][15], qpel16_mc33_old_c)

        SET_QPEL_FUNC(qpel_pixels_tab[1][ 5], qpel8_mc11_old_c)

        SET_QPEL_FUNC(qpel_pixels_tab[1][ 7], qpel8_mc31_old_c)

        SET_QPEL_FUNC(qpel_pixels_tab[1][ 9], qpel8_mc12_old_c)

        SET_QPEL_FUNC(qpel_pixels_tab[1][11], qpel8_mc32_old_c)

        SET_QPEL_FUNC(qpel_pixels_tab[1][13], qpel8_mc13_old_c)

        SET_QPEL_FUNC(qpel_pixels_tab[1][15], qpel8_mc33_old_c)

    }

    if(avctx->debug & FF_DEBUG_BUGS)

        av_log(s->avctx, AV_LOG_DEBUG, "bugs: %X lavc_build:%d xvid_build:%d divx_version:%d divx_build:%d %s\n",

               s->workaround_bugs, s->lavc_build, s->xvid_build, s->divx_version, s->divx_build,

               s->divx_packed ? "p" : "");

#if 0 // dump bits per frame / qp / complexity

{

    static FILE *f=NULL;

    if(!f) f=fopen("rate_qp_cplx.txt", "w");

    fprintf(f, "%d %d %f\n", buf_size, s->qscale, buf_size*(double)s->qscale);

}

#endif

#if defined(HAVE_MMX)

    if(s->codec_id == CODEC_ID_MPEG4 && s->xvid_build && avctx->idct_algo == FF_IDCT_AUTO && (mm_flags & MM_MMX)){

        avctx->idct_algo= FF_IDCT_XVIDMMX;

        avctx->coded_width= 0; // force reinit

//        dsputil_init(&s->dsp, avctx);

        s->picture_number=0;

    }

#endif

        /* After H263 & mpeg4 header decode we have the height, width,*/

        /* and other parameters. So then we could init the picture   */

        /* FIXME: By the way H263 decoder is evolving it should have */

        /* an H263EncContext                                         */

    if (   s->width  != avctx->coded_width

        || s->height != avctx->coded_height) {

        /* H.263 could change picture size any time */

        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;

    }

    if((s->codec_id==CODEC_ID_H263 || s->codec_id==CODEC_ID_H263P))

        s->gob_index = ff_h263_get_gob_height(s);

    // for hurry_up==5

    s->current_picture.pict_type= s->pict_type;

    s->current_picture.key_frame= s->pict_type == FF_I_TYPE;

    /* skip B-frames if we don't have reference frames */

    if(s->last_picture_ptr==NULL && (s->pict_type==FF_B_TYPE || s->dropable)) return get_consumed_bytes(s, buf_size);

    /* skip b frames if we are in a hurry */

    if(avctx->hurry_up && s->pict_type==FF_B_TYPE) return get_consumed_bytes(s, buf_size);

    if(   (avctx->skip_frame >= AVDISCARD_NONREF && s->pict_type==FF_B_TYPE)

       || (avctx->skip_frame >= AVDISCARD_NONKEY && s->pict_type!=FF_I_TYPE)

       ||  avctx->skip_frame >= AVDISCARD_ALL)

        return get_consumed_bytes(s, buf_size);

    /* skip everything if we are in a hurry>=5 */

    if(avctx->hurry_up>=5) return get_consumed_bytes(s, buf_size);

    if(s->next_p_frame_damaged){

        if(s->pict_type==FF_B_TYPE)

            return get_consumed_bytes(s, buf_size);

        else

            s->next_p_frame_damaged=0;

    }

    if((s->avctx->flags2 & CODEC_FLAG2_FAST) && s->pict_type==FF_B_TYPE){

        s->me.qpel_put= s->dsp.put_2tap_qpel_pixels_tab;

        s->me.qpel_avg= s->dsp.avg_2tap_qpel_pixels_tab;

    }else if((!s->no_rounding) || s->pict_type==FF_B_TYPE){

        s->me.qpel_put= s->dsp.put_qpel_pixels_tab;

        s->me.qpel_avg= s->dsp.avg_qpel_pixels_tab;

    }else{

        s->me.qpel_put= s->dsp.put_no_rnd_qpel_pixels_tab;

        s->me.qpel_avg= s->dsp.avg_qpel_pixels_tab;

    }

    if(MPV_frame_start(s, avctx) < 0)

        return -1;

#ifdef DEBUG

    av_log(avctx, AV_LOG_DEBUG, "qscale=%d\n", s->qscale);

#endif

    ff_er_frame_start(s);

    //the second part of the wmv2 header contains the MB skip bits which are stored in current_picture->mb_type

    //which is not available before MPV_frame_start()

    if (ENABLE_WMV2_DECODER && s->msmpeg4_version==5){

        ret = ff_wmv2_decode_secondary_picture_header(s);

        if(ret<0) return ret;

        if(ret==1) goto intrax8_decoded;

    }

    /* decode each macroblock */

    s->mb_x=0;

    s->mb_y=0;

    decode_slice(s);

    while(s->mb_y<s->mb_height){

        if(s->msmpeg4_version){

            if(s->slice_height==0 || s->mb_x!=0 || (s->mb_y%s->slice_height)!=0 || get_bits_count(&s->gb) > s->gb.size_in_bits)

                break;

        }else{

            if(ff_h263_resync(s)<0)

                break;

        }

        if(s->msmpeg4_version<4 && s->h263_pred)

            ff_mpeg4_clean_buffers(s);

        decode_slice(s);

    }

    if (s->h263_msmpeg4 && s->msmpeg4_version<4 && s->pict_type==FF_I_TYPE)

        if(!ENABLE_MSMPEG4_DECODER || msmpeg4_decode_ext_header(s, buf_size) < 0){

            s->error_status_table[s->mb_num-1]= AC_ERROR|DC_ERROR|MV_ERROR;

        }

    /* divx 5.01+ bistream reorder stuff */

    if(s->codec_id==CODEC_ID_MPEG4 && s->bitstream_buffer_size==0 && s->divx_packed){

        int current_pos= get_bits_count(&s->gb)>>3;

        int startcode_found=0;

        if(buf_size - current_pos > 5){

            int i;

            for(i=current_pos; i<buf_size-3; i++){

                if(buf[i]==0 && buf[i+1]==0 && buf[i+2]==1 && buf[i+3]==0xB6){

                    startcode_found=1;

                    break;

                }

            }

        }

        if(s->gb.buffer == s->bitstream_buffer && buf_size>20){ //xvid style

            startcode_found=1;

            current_pos=0;

        }

        if(startcode_found){

            s->bitstream_buffer= av_fast_realloc(

                s->bitstream_buffer,

                &s->allocated_bitstream_buffer_size,

                buf_size - current_pos + FF_INPUT_BUFFER_PADDING_SIZE);

            memcpy(s->bitstream_buffer, buf + current_pos, buf_size - current_pos);

            s->bitstream_buffer_size= buf_size - current_pos;

        }

    }

intrax8_decoded:

    ff_er_frame_end(s);

    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);

    if (s->pict_type == FF_B_TYPE || s->low_delay) {

        *pict= *(AVFrame*)s->current_picture_ptr;

    } else if (s->last_picture_ptr != NULL) {

        *pict= *(AVFrame*)s->last_picture_ptr;

    }

    if(s->last_picture_ptr || s->low_delay){

        *data_size = sizeof(AVFrame);

        ff_print_debug_info(s, pict);

    }

    /* Return the Picture timestamp as the frame number */

    /* we subtract 1 because it is added on utils.c     */

    avctx->frame_number = s->picture_number - 1;

#ifdef PRINT_FRAME_TIME

av_log(avctx, AV_LOG_DEBUG, "%"PRId64"\n", rdtsc()-time);

#endif

    return get_consumed_bytes(s, buf_size);

}

AVCodec mpeg4_decoder = {

    "mpeg4",

    CODEC_TYPE_VIDEO,

    CODEC_ID_MPEG4,

    sizeof(MpegEncContext),

    ff_h263_decode_init,

    NULL,

    ff_h263_decode_end,

    ff_h263_decode_frame,

    CODEC_CAP_DRAW_HORIZ_BAND | CODEC_CAP_DR1 | CODEC_CAP_TRUNCATED | CODEC_CAP_DELAY,

    .flush= ff_mpeg_flush,

    .long_name= NULL_IF_CONFIG_SMALL("MPEG-4 part 2"),

};

AVCodec h263_decoder = {

    "h263",

    CODEC_TYPE_VIDEO,

    CODEC_ID_H263,

    sizeof(MpegEncContext),

    ff_h263_decode_init,

    NULL,

    ff_h263_decode_end,

    ff_h263_decode_frame,

    CODEC_CAP_DRAW_HORIZ_BAND | CODEC_CAP_DR1 | CODEC_CAP_TRUNCATED | CODEC_CAP_DELAY,

    .flush= ff_mpeg_flush,

    .long_name= NULL_IF_CONFIG_SMALL("H.263"),

};

AVCodec msmpeg4v1_decoder = {

    "msmpeg4v1",

    CODEC_TYPE_VIDEO,

    CODEC_ID_MSMPEG4V1,

    sizeof(MpegEncContext),

    ff_h263_decode_init,

    NULL,

    ff_h263_decode_end,

    ff_h263_decode_frame,

    CODEC_CAP_DRAW_HORIZ_BAND | CODEC_CAP_DR1,

    .long_name= NULL_IF_CONFIG_SMALL("MPEG-4 part 2 Microsoft variant version 1"),

};

AVCodec msmpeg4v2_decoder = {

    "msmpeg4v2",

    CODEC_TYPE_VIDEO,

    CODEC_ID_MSMPEG4V2,

    sizeof(MpegEncContext),

    ff_h263_decode_init,

    NULL,

    ff_h263_decode_end,

    ff_h263_decode_frame,

    CODEC_CAP_DRAW_HORIZ_BAND | CODEC_CAP_DR1,

    .long_name= NULL_IF_CONFIG_SMALL("MPEG-4 part 2 Microsoft variant version 2"),

};

AVCodec msmpeg4v3_decoder = {

    "msmpeg4",

    CODEC_TYPE_VIDEO,

    CODEC_ID_MSMPEG4V3,

    sizeof(MpegEncContext),

    ff_h263_decode_init,

    NULL,

    ff_h263_decode_end,

    ff_h263_decode_frame,

    CODEC_CAP_DRAW_HORIZ_BAND | CODEC_CAP_DR1,

    .long_name= NULL_IF_CONFIG_SMALL("MPEG-4 part 2 Microsoft variant version 3"),

};

AVCodec wmv1_decoder = {

    "wmv1",

    CODEC_TYPE_VIDEO,

    CODEC_ID_WMV1,

    sizeof(MpegEncContext),

    ff_h263_decode_init,

    NULL,

    ff_h263_decode_end,

    ff_h263_decode_frame,

    CODEC_CAP_DRAW_HORIZ_BAND | CODEC_CAP_DR1,

    .long_name= NULL_IF_CONFIG_SMALL("Windows Media Video 7"),

};

AVCodec h263i_decoder = {

    "h263i",

    CODEC_TYPE_VIDEO,

    CODEC_ID_H263I,

    sizeof(MpegEncContext),

    ff_h263_decode_init,

    NULL,

    ff_h263_decode_end,

    ff_h263_decode_frame,

    CODEC_CAP_DRAW_HORIZ_BAND | CODEC_CAP_DR1,

    .long_name = NULL_IF_CONFIG_SMALL("H.263i"),

};

AVCodec flv_decoder = {

    "flv",

    CODEC_TYPE_VIDEO,

    CODEC_ID_FLV1,

    sizeof(MpegEncContext),

    ff_h263_decode_init,

    NULL,

    ff_h263_decode_end,

    ff_h263_decode_frame,

    CODEC_CAP_DRAW_HORIZ_BAND | CODEC_CAP_DR1,

    .long_name= NULL_IF_CONFIG_SMALL("Flash Video"),

};