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

/*
 * H.263 decoder
 * Copyright (c) 2001 Fabrice Bellard.
 * Copyright (c) 2002-2004 Michael Niedermayer <[e-mail]>
 *
 * 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

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;
}

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!=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==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,
                             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(s->codec_id==CODEC_ID_MPEG4){
            next= ff_mpeg4_find_frame_end(&s->parse_context, buf, buf_size);
        }else if(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);