cavs.c

linux下的MPEG1

        h->pic_type = FF_I_TYPE;
        if(get_bits1(&s->gb))
            get_bits(&s->gb,16);//time_code
    }
    /* release last B frame */
    if(h->picture.data[0])
        s->avctx->release_buffer(s->avctx, (AVFrame *)&h->picture);

    s->avctx->get_buffer(s->avctx, (AVFrame *)&h->picture);
    init_pic(h);
    h->picture.poc = get_bits(&s->gb,8)*2;

    /* get temporal distances and MV scaling factors */
    if(h->pic_type != FF_B_TYPE) {
        h->dist[0] = (h->picture.poc - h->DPB[0].poc  + 512) % 512;
    } else {
        h->dist[0] = (h->DPB[0].poc  - h->picture.poc + 512) % 512;
    }
    h->dist[1] = (h->picture.poc - h->DPB[1].poc  + 512) % 512;
    h->scale_den[0] = h->dist[0] ? 512/h->dist[0] : 0;
    h->scale_den[1] = h->dist[1] ? 512/h->dist[1] : 0;
    if(h->pic_type == FF_B_TYPE) {
        h->sym_factor = h->dist[0]*h->scale_den[1];
    } else {
        h->direct_den[0] = h->dist[0] ? 16384/h->dist[0] : 0;
        h->direct_den[1] = h->dist[1] ? 16384/h->dist[1] : 0;
    }

    if(s->low_delay)
        get_ue_golomb(&s->gb); //bbv_check_times
    h->progressive             = get_bits1(&s->gb);
    if(h->progressive)
        h->pic_structure = 1;
    else if(!(h->pic_structure = get_bits1(&s->gb) && (h->stc == PIC_PB_START_CODE)) )
        get_bits1(&s->gb);     //advanced_pred_mode_disable
    skip_bits1(&s->gb);        //top_field_first
    skip_bits1(&s->gb);        //repeat_first_field
    h->qp_fixed                = get_bits1(&s->gb);
    h->qp                      = get_bits(&s->gb,6);
    if(h->pic_type == FF_I_TYPE) {
        if(!h->progressive && !h->pic_structure)
            skip_bits1(&s->gb);//what is this?
        skip_bits(&s->gb,4);   //reserved bits
    } else {
        if(!(h->pic_type == FF_B_TYPE && h->pic_structure == 1))
            h->ref_flag        = get_bits1(&s->gb);
        skip_bits(&s->gb,4);   //reserved bits
        h->skip_mode_flag      = get_bits1(&s->gb);
    }
    h->loop_filter_disable     = get_bits1(&s->gb);
    if(!h->loop_filter_disable && get_bits1(&s->gb)) {
        h->alpha_offset        = get_se_golomb(&s->gb);
        h->beta_offset         = get_se_golomb(&s->gb);
    } else {
        h->alpha_offset = h->beta_offset  = 0;
    }
    check_for_slice(h);
    if(h->pic_type == FF_I_TYPE) {
        do {
            decode_mb_i(h, 0);
        } while(next_mb(h));
    } else if(h->pic_type == FF_P_TYPE) {
        do {
            if(h->skip_mode_flag) {
                skip_count = get_ue_golomb(&s->gb);
                while(skip_count--) {
                    decode_mb_p(h,P_SKIP);
                    if(!next_mb(h))
                        goto done;
                }
                mb_type = get_ue_golomb(&s->gb) + P_16X16;
            } else
                mb_type = get_ue_golomb(&s->gb) + P_SKIP;
            if(mb_type > P_8X8) {
                decode_mb_i(h, mb_type - P_8X8 - 1);
            } else
                decode_mb_p(h,mb_type);
        } while(next_mb(h));
    } else { /* FF_B_TYPE */
        do {
            if(h->skip_mode_flag) {
                skip_count = get_ue_golomb(&s->gb);
                while(skip_count--) {
                    decode_mb_b(h,B_SKIP);
                    if(!next_mb(h))
                        goto done;
                }
                mb_type = get_ue_golomb(&s->gb) + B_DIRECT;
            } else
                mb_type = get_ue_golomb(&s->gb) + B_SKIP;
            if(mb_type > B_8X8) {
                decode_mb_i(h, mb_type - B_8X8 - 1);
            } else
                decode_mb_b(h,mb_type);
        } while(next_mb(h));
    }
 done:
    if(h->pic_type != FF_B_TYPE) {
        if(h->DPB[1].data[0])
            s->avctx->release_buffer(s->avctx, (AVFrame *)&h->DPB[1]);
        memcpy(&h->DPB[1], &h->DPB[0], sizeof(Picture));
        memcpy(&h->DPB[0], &h->picture, sizeof(Picture));
        memset(&h->picture,0,sizeof(Picture));
    }
    return 0;
}

/*****************************************************************************
 *
 * headers and interface
 *
 ****************************************************************************/

/**
 * some predictions require data from the top-neighbouring macroblock.
 * this data has to be stored for one complete row of macroblocks
 * and this storage space is allocated here
 */
static void init_top_lines(AVSContext *h) {
    /* alloc top line of predictors */
    h->top_qp       = av_malloc( h->mb_width);
    h->top_mv[0]    = av_malloc((h->mb_width*2+1)*sizeof(vector_t));
    h->top_mv[1]    = av_malloc((h->mb_width*2+1)*sizeof(vector_t));
    h->top_pred_Y   = av_malloc( h->mb_width*2*sizeof(*h->top_pred_Y));
    h->top_border_y = av_malloc((h->mb_width+1)*16);
    h->top_border_u = av_malloc((h->mb_width)*10);
    h->top_border_v = av_malloc((h->mb_width)*10);

    /* alloc space for co-located MVs and types */
    h->col_mv       = av_malloc( h->mb_width*h->mb_height*4*sizeof(vector_t));
    h->col_type_base = av_malloc(h->mb_width*h->mb_height);
    h->block        = av_mallocz(64*sizeof(DCTELEM));
}

static int decode_seq_header(AVSContext *h) {
    MpegEncContext *s = &h->s;
    extern const AVRational ff_frame_rate_tab[];
    int frame_rate_code;

    h->profile =         get_bits(&s->gb,8);
    h->level =           get_bits(&s->gb,8);
    skip_bits1(&s->gb); //progressive sequence
    s->width =           get_bits(&s->gb,14);
    s->height =          get_bits(&s->gb,14);
    skip_bits(&s->gb,2); //chroma format
    skip_bits(&s->gb,3); //sample_precision
    h->aspect_ratio =    get_bits(&s->gb,4);
    frame_rate_code =    get_bits(&s->gb,4);
    skip_bits(&s->gb,18);//bit_rate_lower
    skip_bits1(&s->gb);  //marker_bit
    skip_bits(&s->gb,12);//bit_rate_upper
    s->low_delay =       get_bits1(&s->gb);
    h->mb_width  = (s->width  + 15) >> 4;
    h->mb_height = (s->height + 15) >> 4;
    h->s.avctx->time_base.den = ff_frame_rate_tab[frame_rate_code].num;
    h->s.avctx->time_base.num = ff_frame_rate_tab[frame_rate_code].den;
    h->s.avctx->width  = s->width;
    h->s.avctx->height = s->height;
    if(!h->top_qp)
        init_top_lines(h);
    return 0;
}

static void cavs_flush(AVCodecContext * avctx) {
    AVSContext *h = avctx->priv_data;
    h->got_keyframe = 0;
}

static int cavs_decode_frame(AVCodecContext * avctx,void *data, int *data_size,
                             uint8_t * buf, int buf_size) {
    AVSContext *h = avctx->priv_data;
    MpegEncContext *s = &h->s;
    int input_size;
    const uint8_t *buf_end;
    const uint8_t *buf_ptr;
    AVFrame *picture = data;
    uint32_t stc;

    s->avctx = avctx;

    if (buf_size == 0) {
        if(!s->low_delay && h->DPB[0].data[0]) {
            *data_size = sizeof(AVPicture);
            *picture = *(AVFrame *) &h->DPB[0];
        }
        return 0;
    }

    buf_ptr = buf;
    buf_end = buf + buf_size;
    for(;;) {
        buf_ptr = ff_find_start_code(buf_ptr,buf_end, &stc);
        if(stc & 0xFFFFFE00)
            return FFMAX(0, buf_ptr - buf - s->parse_context.last_index);
        input_size = (buf_end - buf_ptr)*8;
        switch(stc) {
        case SEQ_START_CODE:
            init_get_bits(&s->gb, buf_ptr, input_size);
            decode_seq_header(h);
            break;
        case PIC_I_START_CODE:
            if(!h->got_keyframe) {
                if(h->DPB[0].data[0])
                    avctx->release_buffer(avctx, (AVFrame *)&h->DPB[0]);
                if(h->DPB[1].data[0])
                    avctx->release_buffer(avctx, (AVFrame *)&h->DPB[1]);
                h->got_keyframe = 1;
            }
        case PIC_PB_START_CODE:
            *data_size = 0;
            if(!h->got_keyframe)
                break;
            init_get_bits(&s->gb, buf_ptr, input_size);
            h->stc = stc;
            if(decode_pic(h))
                break;
            *data_size = sizeof(AVPicture);
            if(h->pic_type != FF_B_TYPE) {
                if(h->DPB[1].data[0]) {
                    *picture = *(AVFrame *) &h->DPB[1];
                } else {
                    *data_size = 0;
                }
            } else
                *picture = *(AVFrame *) &h->picture;
            break;
        case EXT_START_CODE:
            //mpeg_decode_extension(avctx,buf_ptr, input_size);
            break;
        case USER_START_CODE:
            //mpeg_decode_user_data(avctx,buf_ptr, input_size);
            break;
        default:
            if (stc >= SLICE_MIN_START_CODE &&
                stc <= SLICE_MAX_START_CODE) {
                init_get_bits(&s->gb, buf_ptr, input_size);
                decode_slice_header(h, &s->gb);
            }
            break;
        }
    }
}

static int cavs_decode_init(AVCodecContext * avctx) {
    AVSContext *h = avctx->priv_data;
    MpegEncContext * const s = &h->s;

    MPV_decode_defaults(s);
    s->avctx = avctx;

    avctx->pix_fmt= PIX_FMT_YUV420P;

    h->luma_scan[0] = 0;
    h->luma_scan[1] = 8;
    h->intra_pred_l[      INTRA_L_VERT] = intra_pred_vert;
    h->intra_pred_l[     INTRA_L_HORIZ] = intra_pred_horiz;
    h->intra_pred_l[        INTRA_L_LP] = intra_pred_lp;
    h->intra_pred_l[ INTRA_L_DOWN_LEFT] = intra_pred_down_left;
    h->intra_pred_l[INTRA_L_DOWN_RIGHT] = intra_pred_down_right;
    h->intra_pred_l[   INTRA_L_LP_LEFT] = intra_pred_lp_left;
    h->intra_pred_l[    INTRA_L_LP_TOP] = intra_pred_lp_top;
    h->intra_pred_l[    INTRA_L_DC_128] = intra_pred_dc_128;
    h->intra_pred_c[        INTRA_C_LP] = intra_pred_lp;
    h->intra_pred_c[     INTRA_C_HORIZ] = intra_pred_horiz;
    h->intra_pred_c[      INTRA_C_VERT] = intra_pred_vert;
    h->intra_pred_c[     INTRA_C_PLANE] = intra_pred_plane;
    h->intra_pred_c[   INTRA_C_LP_LEFT] = intra_pred_lp_left;
    h->intra_pred_c[    INTRA_C_LP_TOP] = intra_pred_lp_top;
    h->intra_pred_c[    INTRA_C_DC_128] = intra_pred_dc_128;
    h->mv[ 7] = un_mv;
    h->mv[19] = un_mv;
    return 0;
}

static int cavs_decode_end(AVCodecContext * avctx) {
    AVSContext *h = avctx->priv_data;

    av_free(h->top_qp);
    av_free(h->top_mv[0]);
    av_free(h->top_mv[1]);
    av_free(h->top_pred_Y);
    av_free(h->top_border_y);
    av_free(h->top_border_u);
    av_free(h->top_border_v);
    av_free(h->col_mv);
    av_free(h->col_type_base);
    av_free(h->block);
    return 0;
}

AVCodec cavs_decoder = {
    "cavs",
    CODEC_TYPE_VIDEO,
    CODEC_ID_CAVS,
    sizeof(AVSContext),
    cavs_decode_init,
    NULL,
    cavs_decode_end,
    cavs_decode_frame,
    CODEC_CAP_DR1 | CODEC_CAP_DELAY,
    .flush= cavs_flush,
};
#endif /* CONFIG_CAVS_DECODER */

#ifdef CONFIG_CAVSVIDEO_PARSER
/**
 * finds the end of the current frame in the bitstream.
 * @return the position of the first byte of the next frame, or -1
 */
static int cavs_find_frame_end(ParseContext *pc, const uint8_t *buf,
                               int buf_size) {
    int pic_found, i;
    uint32_t state;

    pic_found= pc->frame_start_found;
    state= pc->state;

    i=0;
    if(!pic_found){
        for(i=0; i<buf_size; i++){
            state= (state<<8) | buf[i];
            if(state == PIC_I_START_CODE || state == PIC_PB_START_CODE){
                i++;
                pic_found=1;
                break;
            }
        }
    }

    if(pic_found){
        /* EOF considered as end of frame */
        if (buf_size == 0)
            return 0;
        for(; i<buf_size; i++){
            state= (state<<8) | buf[i];
            if((state&0xFFFFFF00) == 0x100){
                if(state < SLICE_MIN_START_CODE || state > SLICE_MAX_START_CODE){
                    pc->frame_start_found=0;
                    pc->state=-1;
                    return i-3;
                }
            }
        }
    }
    pc->frame_start_found= pic_found;
    pc->state= state;
    return END_NOT_FOUND;
}

static int cavsvideo_parse(AVCodecParserContext *s,
                           AVCodecContext *avctx,
                           uint8_t **poutbuf, int *poutbuf_size,
                           const uint8_t *buf, int buf_size)
{
    ParseContext *pc = s->priv_data;
    int next;

    if(s->flags & PARSER_FLAG_COMPLETE_FRAMES){
        next= buf_size;
    }else{
        next= cavs_find_frame_end(pc, buf, buf_size);

        if (ff_combine_frame(pc, next, (uint8_t **)&buf, &buf_size) < 0) {
            *poutbuf = NULL;
            *poutbuf_size = 0;
            return buf_size;
        }
    }
    *poutbuf = (uint8_t *)buf;
    *poutbuf_size = buf_size;
    return next;
}

AVCodecParser cavsvideo_parser = {
    { CODEC_ID_CAVS },
    sizeof(ParseContext1),
    NULL,
    cavsvideo_parse,
    ff_parse1_close,
    ff_mpeg4video_split,
};
#endif /* CONFIG_CAVSVIDEO_PARSER */