mpeg12.c

Trolltech公司发布的图形界面操作系统。可在qt-embedded-2.3.7平台上编译为嵌入式图形界面操作系统。

        fprintf(stderr, "slice below image (%d >= %d)\n", start_code, s->mb_height);
        return DECODE_SLICE_ERROR;
    }
    s->last_dc[0] = 1 << (7 + s->intra_dc_precision);
    s->last_dc[1] = s->last_dc[0];
    s->last_dc[2] = s->last_dc[0];
    memset(s->last_mv, 0, sizeof(s->last_mv));
    /* start frame decoding */
    if (s->first_slice) {
        s->first_slice = 0;
        if(MPV_frame_start(s, avctx) < 0)
            return DECODE_SLICE_FATAL_ERROR;
    }

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

    s->qscale = get_qscale(s);
    /* 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)
            return -1; /* error = end of slice, but empty slice is bad or?*/
        if (code >= 33) {
            if (code == 33) {
                s->mb_x += 33;
            }
            /* otherwise, stuffing, nothing to do */
        } else {
            s->mb_x += code;
            break;
        }
    }
    s->mb_y = start_code;
    s->mb_incr= 1;

    for(;;) {
	s->dsp.clear_blocks(s->block[0]);
        
        ret = mpeg_decode_mb(s, s->block);
        dprintf("ret=%d\n", ret);
        if (ret < 0)
            return -1;
    
        MPV_decode_mb(s, s->block);

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

            s->mb_x = 0;
            s->mb_y++;
            PRINT_QP("%s", "\n");
        }
        PRINT_QP("%2d", s->qscale);

        /* skip mb handling */
        if (s->mb_incr == 0) {
            /* read again increment */
            s->mb_incr = 1;
            for(;;) {
                int code = get_vlc2(&s->gb, mbincr_vlc.table, MBINCR_VLC_BITS, 2);
                if (code < 0)
                    goto eos; /* error = end of slice */
                if (code >= 33) {
                    if (code == 33) {
                        s->mb_incr += 33;
                    }
                    /* otherwise, stuffing, nothing to do */
                } else {
                    s->mb_incr += code;
                    break;
                }
            }
        }
        if(s->mb_y >= s->mb_height){
            fprintf(stderr, "slice too long\n");
            return DECODE_SLICE_ERROR;
        }
    }
eos: //end of slice
    
    emms_c();

    /* end of slice reached */
    if (/*s->mb_x == 0 &&*/
        s->mb_y == s->mb_height) {
        /* end of image */
        UINT8 **picture;

        MPV_frame_end(s);

        if (s->pict_type == B_TYPE) {
            picture = s->current_picture;
            avctx->quality = s->qscale;
        } else {
            /* latency of 1 frame for I and P frames */
            /* XXX: use another variable than picture_number */
            if (s->picture_number == 0) {
                picture = NULL;
            } else {
                picture = s->last_picture;
                avctx->quality = s->last_qscale;
            }
            s->last_qscale = s->qscale;
            s->picture_number++;
        }
        if(s->mpeg2)
            avctx->quality>>=1;
        if (picture) {
            pict->data[0] = picture[0];
            pict->data[1] = picture[1];
            pict->data[2] = picture[2];
            pict->linesize[0] = s->linesize;
            pict->linesize[1] = s->uvlinesize;
            pict->linesize[2] = s->uvlinesize;
            return DECODE_SLICE_EOP;
        } else {
            return DECODE_SLICE_OK;
        }
    } else {
        return DECODE_SLICE_OK;
    }
}

static int mpeg1_decode_sequence(AVCodecContext *avctx, 
                                 UINT8 *buf, int buf_size)
{
    Mpeg1Context *s1 = avctx->priv_data;
    MpegEncContext *s = &s1->mpeg_enc_ctx;
    int width, height, i, v, j;

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

    width = get_bits(&s->gb, 12);
    height = get_bits(&s->gb, 12);
    skip_bits(&s->gb, 4);
    s->frame_rate_index = get_bits(&s->gb, 4);
    if (s->frame_rate_index == 0)
        return -1;
    s->bit_rate = get_bits(&s->gb, 18) * 400;
    if (get_bits1(&s->gb) == 0) /* marker */
        return -1;
    if (width <= 0 || height <= 0 ||
        (width % 2) != 0 || (height % 2) != 0)
        return -1;
    if (width != s->width ||
        height != s->height) {
        /* start new mpeg1 context decoding */
        s->out_format = FMT_MPEG1;
        if (s1->mpeg_enc_ctx_allocated) {
            MPV_common_end(s);
        }
        s->width = width;
        s->height = height;
        avctx->has_b_frames= s->has_b_frames = 1;
        s->avctx = avctx;
        avctx->width = width;
        avctx->height = height;
        if (s->frame_rate_index >= 9) {
            /* at least give a valid frame rate (some old mpeg1 have this) */
            avctx->frame_rate = 25 * FRAME_RATE_BASE;
        } else {
            avctx->frame_rate = frame_rate_tab[s->frame_rate_index];
        }
        s->frame_rate = avctx->frame_rate;
        avctx->bit_rate = s->bit_rate;
        
        if (MPV_common_init(s) < 0)
            return -1;
        s1->mpeg_enc_ctx_allocated = 1;
    }

    skip_bits(&s->gb, 10); /* vbv_buffer_size */
    skip_bits(&s->gb, 1);

    /* get matrix */
    if (get_bits1(&s->gb)) {
        for(i=0;i<64;i++) {
            v = get_bits(&s->gb, 8);
            j = s->intra_scantable.permutated[i];
            s->intra_matrix[j] = v;
            s->chroma_intra_matrix[j] = v;
        }
#ifdef DEBUG
        dprintf("intra matrix present\n");
        for(i=0;i<64;i++)
            dprintf(" %d", s->intra_matrix[s->intra_scantable.permutated[i]]);
        printf("\n");
#endif
    } else {
        for(i=0;i<64;i++) {
            int j= s->idct_permutation[i];
            v = ff_mpeg1_default_intra_matrix[i];
            s->intra_matrix[j] = v;
            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->intra_scantable.permutated[i];
            s->inter_matrix[j] = v;
            s->chroma_inter_matrix[j] = v;
        }
#ifdef DEBUG
        dprintf("non intra matrix present\n");
        for(i=0;i<64;i++)
            dprintf(" %d", s->inter_matrix[s->intra_scantable.permutated[i]]);
        printf("\n");
#endif
    } else {
        for(i=0;i<64;i++) {
            int j= s->idct_permutation[i];
            v = ff_mpeg1_default_non_intra_matrix[i];
            s->inter_matrix[j] = v;
            s->chroma_inter_matrix[j] = v;
        }
    }

    /* we set mpeg2 parameters so that it emulates mpeg1 */
    s->progressive_sequence = 1;
    s->progressive_frame = 1;
    s->picture_structure = PICT_FRAME;
    s->frame_pred_frame_dct = 1;
    s->mpeg2 = 0;
    avctx->sub_id = 1; /* indicates mpeg1 */
    return 0;
}

/* handle buffering and image synchronisation */
static int mpeg_decode_frame(AVCodecContext *avctx, 
                             void *data, int *data_size,
                             UINT8 *buf, int buf_size)
{
    Mpeg1Context *s = avctx->priv_data;
    UINT8 *buf_end, *buf_ptr, *buf_start;
    int len, start_code_found, ret, code, start_code, input_size;
    AVPicture *picture = data;
    MpegEncContext *s2 = &s->mpeg_enc_ctx;
            
    dprintf("fill_buffer\n");

    *data_size = 0;

    /* special case for last picture */
    if (buf_size == 0) {
        if (s2->picture_number > 0) {
            picture->data[0] = s2->next_picture[0];
            picture->data[1] = s2->next_picture[1];
            picture->data[2] = s2->next_picture[2];
            picture->linesize[0] = s2->linesize;
            picture->linesize[1] = s2->uvlinesize;
            picture->linesize[2] = s2->uvlinesize;
            *data_size = sizeof(AVPicture);
        }
        return 0;
    }

    buf_ptr = buf;
    buf_end = buf + buf_size;

#if 0    
    if (s->repeat_field % 2 == 1) { 
        s->repeat_field++;
        //fprintf(stderr,"\nRepeating last frame: %d -> %d! pict: %d %d", avctx->frame_number-1, avctx->frame_number,
        //        s2->picture_number, s->repeat_field);
        if (avctx->flags & CODEC_FLAG_REPEAT_FIELD) {
            *data_size = sizeof(AVPicture);
            goto the_end;
        }
    }
#endif
    while (buf_ptr < buf_end) {
        buf_start = buf_ptr;
        /* find start next code */
        code = find_start_code(&buf_ptr, buf_end, &s->header_state);
        if (code >= 0) {
            start_code_found = 1;
        } else {
            start_code_found = 0;
        }
        /* copy to buffer */
        len = buf_ptr - buf_start;
        if (len + (s->buf_ptr - s->buffer) > s->buffer_size) {
            /* data too big : flush */
            s->buf_ptr = s->buffer;
            if (start_code_found)
                s->start_code = code;
        } else {
            memcpy(s->buf_ptr, buf_start, len);
            s->buf_ptr += len;
            if(   (!(s2->flags&CODEC_FLAG_TRUNCATED)) && (!start_code_found) 
               && s->buf_ptr+4<s->buffer+s->buffer_size){
                start_code_found= 1;
                code= 0x1FF;
                s->header_state=0xFF;
                s->buf_ptr[0]=0;
                s->buf_ptr[1]=0;
                s->buf_ptr[2]=1;
                s->buf_ptr[3]=0xFF;
                s->buf_ptr+=4;
            }
            if (start_code_found) {
                /* prepare data for next start code */
                input_size = s->buf_ptr - s->buffer;
                start_code = s->start_code;
                s->buf_ptr = s->buffer;
                s->start_code = code;
                switch(start_code) {
                case SEQ_START_CODE:
                    mpeg1_decode_sequence(avctx, s->buffer, 
                                          input_size);
                    break;
                            
                case PICTURE_START_CODE:
                    /* we have a complete image : we try to decompress it */
                    mpeg1_decode_picture(avctx, 
                                         s->buffer, input_size);
                    break;
                case EXT_START_CODE:
                    mpeg_decode_extension(avctx,
                                          s->buffer, input_size);
                    break;
                default:
                    if (start_code >= SLICE_MIN_START_CODE &&
                        start_code <= SLICE_MAX_START_CODE && s2->avctx->hurry_up<5) {
                        ret = mpeg_decode_slice(avctx, picture,
                                                start_code, s->buffer, input_size);
                        if (ret == DECODE_SLICE_EOP) {
                            /* got a picture: exit */
                            /* first check if we must repeat the frame */
                            avctx->repeat_pict = 0;
#if 0
                            if (s2->progressive_frame && s2->repeat_first_field) {
                                //fprintf(stderr,"\nRepeat this frame: %d! pict: %d",avctx->frame_number,s2->picture_number);
                                //s2->repeat_first_field = 0;
                                //s2->progressive_frame = 0;
                                if (++s->repeat_field > 2)
                                    s->repeat_field = 0;
                                avctx->repeat_pict = 1;
                            }
#endif                      
                            if (s2->repeat_first_field) {
                                if (s2->progressive_sequence) {
                                    if (s2->top_field_first)
                                        avctx->repeat_pict = 4;
                                    else
                                        avctx->repeat_pict = 2;
                                } else if (s2->progressive_frame) {
                                    avctx->repeat_pict = 1;
                                }
                            }         
                            *data_size = sizeof(AVPicture);
                            goto the_end;
                        }else if(ret<0){
                            printf("Error while decoding slice\n");
			    if(ret==DECODE_SLICE_FATAL_ERROR) return -1;
                        }
                    }
                    break;
                }
            }
        }
    }
 the_end:
    return buf_ptr - buf;
}

static int mpeg_decode_end(AVCodecContext *avctx)
{
    Mpeg1Context *s = avctx->priv_data;

    if (s->mpeg_enc_ctx_allocated)
        MPV_common_end(&s->mpeg_enc_ctx);
    return 0;
}

AVCodec mpeg_decoder = {
    "mpegvideo",
    CODEC_TYPE_VIDEO,
    CODEC_ID_MPEG1VIDEO,
    sizeof(Mpeg1Context),
    mpeg_decode_init,
    NULL,
    mpeg_decode_end,
    mpeg_decode_frame,
    CODEC_CAP_DRAW_HORIZ_BAND | CODEC_CAP_DR1 | CODEC_CAP_TRUNCATED,
};