vc9.c

ffmpeg源码分析

    if (v->profile < PROFILE_ADVANCED)
#endif
    {
        v->finterpflag = get_bits(gb, 1); //common
        v->res_rtm_flag = get_bits(gb, 1); //reserved
        if (!v->res_rtm_flag)
        {
            av_log(avctx, AV_LOG_ERROR,
                   "0 for reserved RES_RTM_FLAG is forbidden\n");
            //return -1;
        }
#if TRACE
        av_log(avctx, AV_LOG_INFO,
               "Profile %i:\nfrmrtq_postproc=%i, bitrtq_postproc=%i\n"
               "LoopFilter=%i, MultiRes=%i, FastUVMV=%i, Extended MV=%i\n"
               "Rangered=%i, VSTransform=%i, Overlap=%i, SyncMarker=%i\n"
               "DQuant=%i, Quantizer mode=%i, Max B frames=%i\n",
               v->profile, v->frmrtq_postproc, v->bitrtq_postproc,
               v->s.loop_filter, v->multires, v->fastuvmc, v->extended_mv,
               v->rangered, v->vstransform, v->overlap, v->s.resync_marker,
               v->dquant, v->quantizer_mode, avctx->max_b_frames
               );
        return 0;
#endif
    }
#if HAS_ADVANCED_PROFILE
    else return decode_advanced_sequence_header(avctx, gb);
#endif
}


#if HAS_ADVANCED_PROFILE
/** Entry point decoding (Advanced Profile)
 * @param avctx Codec context
 * @param gb GetBit context initialized from avctx->extra_data
 * @return Status
 */
static int advanced_entry_point_process(AVCodecContext *avctx, GetBitContext *gb)
{
    VC9Context *v = avctx->priv_data;
    int i;
    if (v->profile != PROFILE_ADVANCED)
    {
        av_log(avctx, AV_LOG_ERROR,
               "Entry point are only defined in Advanced Profile!\n");
        return -1; //Only for advanced profile!
    }
    if (v->hrd_param_flag)
    {
        //Update buffer fullness
        av_log(avctx, AV_LOG_DEBUG, "Buffer fullness update\n");
        assert(v->hrd_num_leaky_buckets > 0);
        for (i=0; i<v->hrd_num_leaky_buckets; i++)
            v->hrd_fullness[i] = get_bits(gb, 8);
    }
    if ((v->range_mapy_flag = get_bits(gb, 1)))
    {
        //RANGE_MAPY
        av_log(avctx, AV_LOG_DEBUG, "RANGE_MAPY\n");
        v->range_mapy = get_bits(gb, 3);
    }
    if ((v->range_mapuv_flag = get_bits(gb, 1)))
    {
        //RANGE_MAPUV
        av_log(avctx, AV_LOG_DEBUG, "RANGE_MAPUV\n");
        v->range_mapuv = get_bits(gb, 3);
    }
    if (v->panscanflag)
    {
        //NUMPANSCANWIN
        v->numpanscanwin = get_bits(gb, 3);
        av_log(avctx, AV_LOG_DEBUG, "NUMPANSCANWIN: %u\n", v->numpanscanwin);
    }
    return 0;
}
#endif

/***********************************************************************/
/**
 * @defgroup bitplane VC9 Bitplane decoding
 * @see 8.7, p56
 * @{
 */

/** @addtogroup bitplane
 * Imode types
 * @{
 */
#define IMODE_RAW     0
#define IMODE_NORM2   1
#define IMODE_DIFF2   2
#define IMODE_NORM6   3
#define IMODE_DIFF6   4
#define IMODE_ROWSKIP 5
#define IMODE_COLSKIP 6
/** @} */ //imode defines

/** Allocate the buffer from a bitplane, given its dimensions
 * @param bp Bitplane which buffer is to allocate
 * @param[in] width Width of the buffer
 * @param[in] height Height of the buffer
 * @return Status
 * @todo TODO: Take into account stride
 * @todo TODO: Allow use of external buffers ?
 */
static int alloc_bitplane(BitPlane *bp, int width, int height)
{
    if (!bp || bp->width<0 || bp->height<0) return -1;
    bp->data = (uint8_t*)av_malloc(width*height);
    if (!bp->data) return -1;
    bp->width = bp->stride = width;
    bp->height = height;
    return 0;
}

/** Free the bitplane's buffer
 * @param bp Bitplane which buffer is to free
 */
static void free_bitplane(BitPlane *bp)
{
    bp->width = bp->stride = bp->height = 0;
    if (bp->data) av_freep(&bp->data);
}

/** Decode rows by checking if they are skipped
 * @param plane Buffer to store decoded bits
 * @param[in] width Width of this buffer
 * @param[in] height Height of this buffer
 * @param[in] stride of this buffer
 */
static void decode_rowskip(uint8_t* plane, int width, int height, int stride, GetBitContext *gb){
    int x, y;

    for (y=0; y<height; y++){
        if (!get_bits(gb, 1)) //rowskip
            memset(plane, 0, width);
        else
            for (x=0; x<width; x++)
                plane[x] = get_bits(gb, 1);
        plane += stride;
    }
}

/** Decode columns by checking if they are skipped
 * @param plane Buffer to store decoded bits
 * @param[in] width Width of this buffer
 * @param[in] height Height of this buffer
 * @param[in] stride of this buffer
 * @fixme FIXME: Optimize
 */
static void decode_colskip(uint8_t* plane, int width, int height, int stride, GetBitContext *gb){
    int x, y;

    for (x=0; x<width; x++){
        if (!get_bits(gb, 1)) //colskip
            for (y=0; y<height; y++)
                plane[y*stride] = 0;
        else
            for (y=0; y<height; y++)
                plane[y*stride] = get_bits(gb, 1);
        plane ++;
    }
}

/** Decode a bitplane's bits
 * @param bp Bitplane where to store the decode bits
 * @param v VC9 context for bit reading and logging
 * @return Status
 * @fixme FIXME: Optimize
 * @todo TODO: Decide if a struct is needed
 */
static int bitplane_decoding(BitPlane *bp, VC9Context *v)
{
    GetBitContext *gb = &v->s.gb;

    int imode, x, y, code, use_vertical_tile, tile_w, tile_h, offset;
    uint8_t invert, *planep = bp->data;

    invert = get_bits(gb, 1);
    imode = get_vlc2(gb, vc9_imode_vlc.table, VC9_IMODE_VLC_BITS, 2);

    bp->is_raw = 0;
    switch (imode)
    {
    case IMODE_RAW:
        //Data is actually read in the MB layer (same for all tests == "raw")
        bp->is_raw = 1; //invert ignored
        return invert;
    case IMODE_DIFF2:
    case IMODE_NORM2:
        if ((bp->height*bp->width) & 1)
        {
            *(++planep) = get_bits(gb, 1);
            offset = x = 1;
        }
        else offset = x = 0;

        for (y=0; y<bp->height; y++)
        {
            for(; x<bp->width; x+=2)
            {
                code = get_vlc2(gb, vc9_norm2_vlc.table, VC9_NORM2_VLC_BITS, 2);
                *(++planep) = code&1; //lsb => left
                *(++planep) = (code>>1)&1; //msb => right
            }
            planep += bp->stride-bp->width;
            if ((bp->width-offset)&1) //Odd number previously processed
            {
                code = get_vlc2(gb, vc9_norm2_vlc.table, VC9_NORM2_VLC_BITS, 2);
                *planep = code&1;
                planep += bp->stride-bp->width;
                *planep = (code>>1)&1; //msb => right
                offset = x = 1;
            }
            else
            {
                offset = x = 0;
                planep += bp->stride-bp->width;
            }
        }
        break;
    case IMODE_DIFF6:
    case IMODE_NORM6:
        use_vertical_tile=  bp->height%3==0 &&  bp->width%3!=0;
        tile_w= use_vertical_tile ? 2 : 3;
        tile_h= use_vertical_tile ? 3 : 2;

        for(y=  bp->height%tile_h; y< bp->height; y+=tile_h){
            for(x=  bp->width%tile_w; x< bp->width; x+=tile_w){
                code = get_vlc2(gb, vc9_norm6_vlc.table, VC9_NORM6_VLC_BITS, 2);
                if(code<0){
                    av_log(v->s.avctx, AV_LOG_DEBUG, "invalid NORM-6 VLC\n");
                    return -1;
                }
                //FIXME following is a pure guess and probably wrong
                //FIXME A bitplane (0 | !0), so could the shifts be avoided ?
                planep[x     + 0*bp->stride]= (code>>0)&1;
                planep[x + 1 + 0*bp->stride]= (code>>1)&1;
                //FIXME Does branch prediction help here?
                if(use_vertical_tile){
                    planep[x + 0 + 1*bp->stride]= (code>>2)&1;
                    planep[x + 1 + 1*bp->stride]= (code>>3)&1;
                    planep[x + 0 + 2*bp->stride]= (code>>4)&1;
                    planep[x + 1 + 2*bp->stride]= (code>>5)&1;
                }else{
                    planep[x + 2 + 0*bp->stride]= (code>>2)&1;
                    planep[x + 0 + 1*bp->stride]= (code>>3)&1;
                    planep[x + 1 + 1*bp->stride]= (code>>4)&1;
                    planep[x + 2 + 1*bp->stride]= (code>>5)&1;
                }
            }
        }

        x=  bp->width % tile_w;
        decode_colskip(bp->data  ,             x, bp->height         , bp->stride, &v->s.gb);
        decode_rowskip(bp->data+x, bp->width - x, bp->height % tile_h, bp->stride, &v->s.gb);

        break;
    case IMODE_ROWSKIP:
        decode_rowskip(bp->data, bp->width, bp->height, bp->stride, &v->s.gb);
        break;
    case IMODE_COLSKIP:
        decode_colskip(bp->data, bp->width, bp->height, bp->stride, &v->s.gb);
        break;
    default: break;
    }

    /* Applying diff operator */
    if (imode == IMODE_DIFF2 || imode == IMODE_DIFF6)
    {
        planep = bp->data;
        planep[0] ^= invert;
        for (x=1; x<bp->width; x++)
            planep[x] ^= planep[x-1];
        for (y=1; y<bp->height; y++)
        {
            planep += bp->stride;
            planep[0] ^= planep[-bp->stride];
            for (x=1; x<bp->width; x++)
            {
                if (planep[x-1] != planep[x-bp->stride]) planep[x] ^= invert;
                else                                     planep[x] ^= planep[x-1];
            }
        }
    }
    else if (invert)
    {
        planep = bp->data;
        for (x=0; x<bp->width*bp->height; x++) planep[x] = !planep[x]; //FIXME stride
    }
    return (imode<<1) + invert;
}
/** @} */ //Bitplane group

/***********************************************************************/
/** VOP Dquant decoding
 * @param v VC9 Context
 */
static int vop_dquant_decoding(VC9Context *v)
{
    GetBitContext *gb = &v->s.gb;
    int pqdiff;

    //variable size
    if (v->dquant == 2)
    {
        pqdiff = get_bits(gb, 3);
        if (pqdiff == 7) v->altpq = get_bits(gb, 5);
        else v->altpq = v->pq + pqdiff + 1;
    }
    else
    {
        v->dquantfrm = get_bits(gb, 1);
        if ( v->dquantfrm )
        {
            v->dqprofile = get_bits(gb, 2);
            switch (v->dqprofile)
            {
            case DQPROFILE_SINGLE_EDGE:
            case DQPROFILE_DOUBLE_EDGES:
                v->dqsbedge = get_bits(gb, 2);
                break;
            case DQPROFILE_ALL_MBS:
                v->dqbilevel = get_bits(gb, 1);
            default: break; //Forbidden ?
            }
            if (!v->dqbilevel || v->dqprofile != DQPROFILE_ALL_MBS)
            {
                pqdiff = get_bits(gb, 3);
                if (pqdiff == 7) v->altpq = get_bits(gb, 5);
                else v->altpq = v->pq + pqdiff + 1;
            }
        }
    }
    return 0;
}

/***********************************************************************/
/**
 * @defgroup all_frame_hdr All VC9 profiles frame header
 * @brief Part of the frame header decoding from all profiles
 * @warning Only pro/epilog differs between Simple/Main and Advanced => check caller
 * @{
 */
/** B and BI frame header decoding, primary part
 * @see Tables 11+12, p62-65
 * @param v VC9 context
 * @return Status
 * @warning Also handles BI frames
 */
static int decode_b_picture_primary_header(VC9Context *v)
{
    GetBitContext *gb = &v->s.gb;
    int pqindex;

    /* Prolog common to all frametypes should be done in caller */
    if (v->profile == PROFILE_SIMPLE)
    {
        av_log(v->s.avctx, AV_LOG_ERROR, "Found a B frame while in Simple Profile!\n");
        return FRAME_SKIPPED;
    }
    v->bfraction = vc9_bfraction_lut[get_vlc2(gb, vc9_bfraction_vlc.table,
                                              VC9_BFRACTION_VLC_BITS, 2)];
    if (v->bfraction < -1)
    {
        av_log(v->s.avctx, AV_LOG_ERROR, "Invalid BFRaction\n");
        return FRAME_SKIPPED;
    }
    else if (!v->bfraction)
    {
        /* We actually have a BI frame */
        v->s.pict_type = BI_TYPE;
        v->buffer_fullness = get_bits(gb, 7);
    }

    /* Read the quantization stuff */
    pqindex = get_bits(gb, 5);
    if (v->quantizer_mode == QUANT_FRAME_IMPLICIT)
        v->pq = pquant_table[0][pqindex];
    else
    {
        v->pq = pquant_table[v->quantizer_mode-1][pqindex];
    }
    if (pqindex < 9) v->halfpq = get_bits(gb, 1);
    if (v->quantizer_mode == QUANT_FRAME_EXPLICIT)
        v->pquantizer = get_bits(gb, 1);
#if HAS_ADVANCED_PROFILE
    if (v->profile == PROFILE_ADVANCED)
    {
        if (v->postprocflag) v->postproc = get_bits(gb, 2);
        if (v->extended_mv == 1 && v->s.pict_type != BI_TYPE)
            v->mvrange = get_prefix(gb, 0, 3);
    }
#endif
    else
    {
        if (v->extended_mv == 1)
            v->mvrange = get_prefix(gb, 0, 3);
    }
    /* Read the MV mode */
    if (v->s.pict_type != BI_TYPE)
    {
        v->mv_mode = get_bits(gb, 1);
        if (v->pq < 13)
        {
            if (!v->mv_mode)
            {
                v->mv_mode = get_bits(gb, 2);
                if (v->mv_mode)
                av_log(v->s.avctx, AV_LOG_ERROR,
                       "mv_mode for lowquant B frame was %i\n", v->mv_mode);
            }
        }