h263dec.c

ffmpeg的完整源代码和作者自己写的文档。不但有在Linux的工程哦

        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
         * lets 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) && defined(CONFIG_GPL)
    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 == I_TYPE;

    /* skip B-frames if we don't have reference frames */
    if(s->last_picture_ptr==NULL && (s->pict_type==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==B_TYPE) 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);
    /* 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==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==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==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 (s->msmpeg4_version==5){
        if(!ENABLE_WMV2_DECODER || ff_wmv2_decode_secondary_picture_header(s) < 0)
            return -1;
    }

    /* 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==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;
        }
    }

    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 == 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 substract 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,
};

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,
};

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,
};

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,
};

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,
};

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,
};

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,
};

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
};