mpeg12.c

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            v = get_bits(&s->gb, 8);
            j= s->dsp.idct_permutation[ ff_zigzag_direct[i] ];
            s->chroma_intra_matrix[j] = v;
        }
    }
    if (get_bits1(&s->gb)) {
        for(i=0;i<64;i++) {
            v = get_bits(&s->gb, 8);
            j= s->dsp.idct_permutation[ ff_zigzag_direct[i] ];
            s->chroma_inter_matrix[j] = v;
        }
    }
}

static void mpeg_decode_picture_coding_extension(MpegEncContext *s)
{
    s->full_pel[0] = s->full_pel[1] = 0;
    s->mpeg_f_code[0][0] = get_bits(&s->gb, 4);
    s->mpeg_f_code[0][1] = get_bits(&s->gb, 4);
    s->mpeg_f_code[1][0] = get_bits(&s->gb, 4);
    s->mpeg_f_code[1][1] = get_bits(&s->gb, 4);
    s->intra_dc_precision = get_bits(&s->gb, 2);
    s->picture_structure = get_bits(&s->gb, 2);
    s->top_field_first = get_bits1(&s->gb);
    s->frame_pred_frame_dct = get_bits1(&s->gb);
    s->concealment_motion_vectors = get_bits1(&s->gb);
    s->q_scale_type = get_bits1(&s->gb);
    s->intra_vlc_format = get_bits1(&s->gb);
    s->alternate_scan = get_bits1(&s->gb);
    s->repeat_first_field = get_bits1(&s->gb);
    s->chroma_420_type = get_bits1(&s->gb);
    s->progressive_frame = get_bits1(&s->gb);

    if(s->picture_structure == PICT_FRAME){
        s->first_field=0;
        s->v_edge_pos= 16*s->mb_height;
    }else{
        s->first_field ^= 1;
        s->v_edge_pos=  8*s->mb_height;
        memset(s->mbskip_table, 0, s->mb_stride*s->mb_height);
    }

    if(s->alternate_scan){
        ff_init_scantable(s->dsp.idct_permutation, &s->inter_scantable  , ff_alternate_vertical_scan);
        ff_init_scantable(s->dsp.idct_permutation, &s->intra_scantable  , ff_alternate_vertical_scan);
    }else{
        ff_init_scantable(s->dsp.idct_permutation, &s->inter_scantable  , ff_zigzag_direct);
        ff_init_scantable(s->dsp.idct_permutation, &s->intra_scantable  , ff_zigzag_direct);
    }

    /* composite display not parsed */
    dprintf(s->avctx, "intra_dc_precision=%d\n", s->intra_dc_precision);
    dprintf(s->avctx, "picture_structure=%d\n", s->picture_structure);
    dprintf(s->avctx, "top field first=%d\n", s->top_field_first);
    dprintf(s->avctx, "repeat first field=%d\n", s->repeat_first_field);
    dprintf(s->avctx, "conceal=%d\n", s->concealment_motion_vectors);
    dprintf(s->avctx, "intra_vlc_format=%d\n", s->intra_vlc_format);
    dprintf(s->avctx, "alternate_scan=%d\n", s->alternate_scan);
    dprintf(s->avctx, "frame_pred_frame_dct=%d\n", s->frame_pred_frame_dct);
    dprintf(s->avctx, "progressive_frame=%d\n", s->progressive_frame);
}

static void mpeg_decode_extension(AVCodecContext *avctx,
                                  const uint8_t *buf, int buf_size)
{
    Mpeg1Context *s1 = avctx->priv_data;
    MpegEncContext *s = &s1->mpeg_enc_ctx;
    int ext_type;

    init_get_bits(&s->gb, buf, buf_size*8);

    ext_type = get_bits(&s->gb, 4);
    switch(ext_type) {
    case 0x1:
        mpeg_decode_sequence_extension(s1);
        break;
    case 0x2:
        mpeg_decode_sequence_display_extension(s1);
        break;
    case 0x3:
        mpeg_decode_quant_matrix_extension(s);
        break;
    case 0x7:
        mpeg_decode_picture_display_extension(s1);
        break;
    case 0x8:
        mpeg_decode_picture_coding_extension(s);
        break;
    }
}

static void exchange_uv(MpegEncContext *s){
    short * tmp = s->pblocks[4];
    s->pblocks[4] = s->pblocks[5];
    s->pblocks[5] = tmp;
}

static int mpeg_field_start(MpegEncContext *s){
    AVCodecContext *avctx= s->avctx;
    Mpeg1Context *s1 = (Mpeg1Context*)s;

    /* start frame decoding */
    if(s->first_field || s->picture_structure==PICT_FRAME){
        if(MPV_frame_start(s, avctx) < 0)
            return -1;

        ff_er_frame_start(s);

        /* first check if we must repeat the frame */
        s->current_picture_ptr->repeat_pict = 0;
        if (s->repeat_first_field) {
            if (s->progressive_sequence) {
                if (s->top_field_first)
                    s->current_picture_ptr->repeat_pict = 4;
                else
                    s->current_picture_ptr->repeat_pict = 2;
            } else if (s->progressive_frame) {
                s->current_picture_ptr->repeat_pict = 1;
            }
        }

        *s->current_picture_ptr->pan_scan= s1->pan_scan;
    }else{ //second field
            int i;

            if(!s->current_picture_ptr){
                av_log(s->avctx, AV_LOG_ERROR, "first field missing\n");
                return -1;
            }

            for(i=0; i<4; i++){
                s->current_picture.data[i] = s->current_picture_ptr->data[i];
                if(s->picture_structure == PICT_BOTTOM_FIELD){
                    s->current_picture.data[i] += s->current_picture_ptr->linesize[i];
                }
            }
    }
#ifdef HAVE_XVMC
// MPV_frame_start will call this function too,
// but we need to call it on every field
    if(s->avctx->xvmc_acceleration)
         XVMC_field_start(s,avctx);
#endif

    return 0;
}

#define DECODE_SLICE_ERROR -1
#define DECODE_SLICE_OK 0

/**
 * decodes a slice. MpegEncContext.mb_y must be set to the MB row from the startcode
 * @return DECODE_SLICE_ERROR if the slice is damaged<br>
 *         DECODE_SLICE_OK if this slice is ok<br>
 */
static int mpeg_decode_slice(Mpeg1Context *s1, int mb_y,
                             const uint8_t **buf, int buf_size)
{
    MpegEncContext *s = &s1->mpeg_enc_ctx;
    AVCodecContext *avctx= s->avctx;
    const int field_pic= s->picture_structure != PICT_FRAME;
    const int lowres= s->avctx->lowres;

    s->resync_mb_x=
    s->resync_mb_y= -1;

    if (mb_y<<field_pic >= s->mb_height){
        av_log(s->avctx, AV_LOG_ERROR, "slice below image (%d >= %d)\n", mb_y, s->mb_height);
        return -1;
    }

    init_get_bits(&s->gb, *buf, buf_size*8);

    ff_mpeg1_clean_buffers(s);
    s->interlaced_dct = 0;

    s->qscale = get_qscale(s);

    if(s->qscale == 0){
        av_log(s->avctx, AV_LOG_ERROR, "qscale == 0\n");
        return -1;
    }

    /* extra slice info */
    while (get_bits1(&s->gb) != 0) {
        skip_bits(&s->gb, 8);
    }

    s->mb_x=0;

    for(;;) {
        int code = get_vlc2(&s->gb, mbincr_vlc.table, MBINCR_VLC_BITS, 2);
        if (code < 0){
            av_log(s->avctx, AV_LOG_ERROR, "first mb_incr damaged\n");
            return -1;
        }
        if (code >= 33) {
            if (code == 33) {
                s->mb_x += 33;
            }
            /* otherwise, stuffing, nothing to do */
        } else {
            s->mb_x += code;
            break;
        }
    }
    if(s->mb_x >= (unsigned)s->mb_width){
        av_log(s->avctx, AV_LOG_ERROR, "initial skip overflow\n");
        return -1;
    }

    s->resync_mb_x= s->mb_x;
    s->resync_mb_y= s->mb_y= mb_y;
    s->mb_skip_run= 0;
    ff_init_block_index(s);

    if (s->mb_y==0 && s->mb_x==0 && (s->first_field || s->picture_structure==PICT_FRAME)) {
        if(s->avctx->debug&FF_DEBUG_PICT_INFO){
             av_log(s->avctx, AV_LOG_DEBUG, "qp:%d fc:%2d%2d%2d%2d %s %s %s %s %s dc:%d pstruct:%d fdct:%d cmv:%d qtype:%d ivlc:%d rff:%d %s\n",
                 s->qscale, s->mpeg_f_code[0][0],s->mpeg_f_code[0][1],s->mpeg_f_code[1][0],s->mpeg_f_code[1][1],
                 s->pict_type == I_TYPE ? "I" : (s->pict_type == P_TYPE ? "P" : (s->pict_type == B_TYPE ? "B" : "S")),
                 s->progressive_sequence ? "ps" :"", s->progressive_frame ? "pf" : "", s->alternate_scan ? "alt" :"", s->top_field_first ? "top" :"",
                 s->intra_dc_precision, s->picture_structure, s->frame_pred_frame_dct, s->concealment_motion_vectors,
                 s->q_scale_type, s->intra_vlc_format, s->repeat_first_field, s->chroma_420_type ? "420" :"");
        }
    }

    for(;;) {
#ifdef HAVE_XVMC
        //one 1 we memcpy blocks in xvmcvideo
        if(s->avctx->xvmc_acceleration > 1)
            XVMC_init_block(s);//set s->block
#endif

        if(mpeg_decode_mb(s, s->block) < 0)
            return -1;

        if(s->current_picture.motion_val[0] && !s->encoding){ //note motion_val is normally NULL unless we want to extract the MVs
            const int wrap = field_pic ? 2*s->b8_stride : s->b8_stride;
            int xy = s->mb_x*2 + s->mb_y*2*wrap;
            int motion_x, motion_y, dir, i;
            if(field_pic && !s->first_field)
                xy += wrap/2;

            for(i=0; i<2; i++){
                for(dir=0; dir<2; dir++){
                    if (s->mb_intra || (dir==1 && s->pict_type != B_TYPE)) {
                        motion_x = motion_y = 0;
                    }else if (s->mv_type == MV_TYPE_16X16 || (s->mv_type == MV_TYPE_FIELD && field_pic)){
                        motion_x = s->mv[dir][0][0];
                        motion_y = s->mv[dir][0][1];
                    } else /*if ((s->mv_type == MV_TYPE_FIELD) || (s->mv_type == MV_TYPE_16X8))*/ {
                        motion_x = s->mv[dir][i][0];
                        motion_y = s->mv[dir][i][1];
                    }

                    s->current_picture.motion_val[dir][xy    ][0] = motion_x;
                    s->current_picture.motion_val[dir][xy    ][1] = motion_y;
                    s->current_picture.motion_val[dir][xy + 1][0] = motion_x;
                    s->current_picture.motion_val[dir][xy + 1][1] = motion_y;
                    s->current_picture.ref_index [dir][xy    ]=
                    s->current_picture.ref_index [dir][xy + 1]= s->field_select[dir][i];
                    assert(s->field_select[dir][i]==0 || s->field_select[dir][i]==1);
                }
                xy += wrap;
            }
        }

        s->dest[0] += 16 >> lowres;
        s->dest[1] +=(16 >> lowres) >> s->chroma_x_shift;
        s->dest[2] +=(16 >> lowres) >> s->chroma_x_shift;

        MPV_decode_mb(s, s->block);

        if (++s->mb_x >= s->mb_width) {
            const int mb_size= 16>>s->avctx->lowres;

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

            s->mb_x = 0;
            s->mb_y++;

            if(s->mb_y<<field_pic >= s->mb_height){
                int left= s->gb.size_in_bits - get_bits_count(&s->gb);
                int is_d10= s->chroma_format==2 && s->pict_type==I_TYPE && avctx->profile==0 && avctx->level==5
                            && s->intra_dc_precision == 2 && s->q_scale_type == 1 && s->alternate_scan == 0
                            && s->progressive_frame == 0 /* vbv_delay == 0xBBB || 0xE10*/;

                if(left < 0 || (left && show_bits(&s->gb, FFMIN(left, 23)) && !is_d10)
                   || (avctx->error_resilience >= FF_ER_AGGRESSIVE && left>8)){
                    av_log(avctx, AV_LOG_ERROR, "end mismatch left=%d %0X\n", left, show_bits(&s->gb, FFMIN(left, 23)));
                    return -1;
                }else
                    goto eos;
            }

            ff_init_block_index(s);
        }

        /* skip mb handling */
        if (s->mb_skip_run == -1) {
            /* read again increment */
            s->mb_skip_run = 0;
            for(;;) {
                int code = get_vlc2(&s->gb, mbincr_vlc.table, MBINCR_VLC_BITS, 2);
                if (code < 0){
                    av_log(s->avctx, AV_LOG_ERROR, "mb incr damaged\n");
                    return -1;
                }
                if (code >= 33) {
                    if (code == 33) {
                        s->mb_skip_run += 33;
                    }else if(code == 35){
                        if(s->mb_skip_run != 0 || show_bits(&s->gb, 15) != 0){
                            av_log(s->avctx, AV_LOG_ERROR, "slice mismatch\n");
                            return -1;
                        }
                        goto eos; /* end of slice */
                    }
                    /* otherwise, stuffing, nothing to do */
                } else {
                    s->mb_skip_run += code;
                    break;
                }
            }
            if(s->mb_skip_run){
                int i;
                if(s->pict_type == I_TYPE){
                    av_log(s->avctx, AV_LOG_ERROR, "skipped MB in I frame at %d %d\n", s->mb_x, s->mb_y);
                    return -1;
                }

                /* skip mb */
                s->mb_intra = 0;
                for(i=0;i<12;i++)
                    s->block_last_index[i] = -1;
                if(s->picture_structure == PICT_FRAME)
                    s->mv_type = MV_TYPE_16X16;
                else
                    s->mv_type = MV_TYPE_FIELD;
                if (s->pict_type == P_TYPE) {
                    /* if P type, zero motion vector is implied */
                    s->mv_dir = MV_DIR_FORWARD;
                    s->mv[0][0][0] = s->mv[0][0][1] = 0;
                    s->last_mv[0][0][0] = s->last_mv[0][0][1] = 0;
                    s->last_mv[0][1][0] = s->last_mv[0][1][1] = 0;
                    s->field_select[0][0]= s->picture_structure - 1;
                } else {
                    /* if B type, reuse previous vectors and directions */
                    s->mv[0][0][0] = s->last_mv[0][0][0];
                    s->mv[0][0][1] = s->last_mv[0][0][1];
                    s->mv[1][0][0] = s->last_mv[1][0][0];
                    s->mv[1][0][1] = s->last_mv[1][0][1];
                }
            }
        }
    }
eos: // end of slice
    *buf += get_bits_count(&s->gb)/8 - 1;
//printf("y %d %d %d %d\n", s->resync_mb_x, s->resync_mb_y, s->mb_x, s->mb_y);
    return 0;
}

static int slice_decode_thread(AVCodecContext *c, void *arg){
    MpegEncContext *s= arg;
    const uint8_t *buf= s->gb.buffer;
    int mb_y= s->start_mb_y;

    s->error_count= 3*(s->end_mb_y - s->start_mb_y)*s->mb_width;

    for(;;){
        uint32_t start_code;
        int ret;

        ret= mpeg_decode_slice((Mpeg1Context*)s, mb_y, &buf, s->gb.buffer_end - buf);
        emms_c();
//av_log(c, AV_LOG_DEBUG, "ret:%d resync:%d/%d mb:%d/%d ts:%d/%d ec:%