vc1.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

/*
 * VC-1 and WMV3 decoder
 * Copyright (c) 2006-2007 Konstantin Shishkov
 * Partly based on vc9.c (c) 2005 Anonymous, Alex Beregszaszi, Michael Niedermayer
 *
 * 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 vc1.c
 * VC-1 and WMV3 decoder
 *
 */
#include "dsputil.h"
#include "avcodec.h"
#include "mpegvideo.h"
#include "vc1.h"
#include "vc1data.h"
#include "vc1acdata.h"
#include "msmpeg4data.h"
#include "unary.h"

#undef NDEBUG
#include <assert.h>

#define MB_INTRA_VLC_BITS 9
#define DC_VLC_BITS 9
#define AC_VLC_BITS 9
static const uint16_t table_mb_intra[64][2];


static inline int decode210(GetBitContext *gb){
    if (get_bits1(gb))
        return 0;
    else
        return 2 - get_bits1(gb);
}

/**
 * Init VC-1 specific tables and VC1Context members
 * @param v The VC1Context to initialize
 * @return Status
 */
static int vc1_init_common(VC1Context *v)
{
    static int done = 0;
    int i = 0;

    v->hrd_rate = v->hrd_buffer = NULL;

    /* VLC tables */
    if(!done)
    {
        done = 1;
        init_vlc(&ff_vc1_bfraction_vlc, VC1_BFRACTION_VLC_BITS, 23,
                 ff_vc1_bfraction_bits, 1, 1,
                 ff_vc1_bfraction_codes, 1, 1, 1);
        init_vlc(&ff_vc1_norm2_vlc, VC1_NORM2_VLC_BITS, 4,
                 ff_vc1_norm2_bits, 1, 1,
                 ff_vc1_norm2_codes, 1, 1, 1);
        init_vlc(&ff_vc1_norm6_vlc, VC1_NORM6_VLC_BITS, 64,
                 ff_vc1_norm6_bits, 1, 1,
                 ff_vc1_norm6_codes, 2, 2, 1);
        init_vlc(&ff_vc1_imode_vlc, VC1_IMODE_VLC_BITS, 7,
                 ff_vc1_imode_bits, 1, 1,
                 ff_vc1_imode_codes, 1, 1, 1);
        for (i=0; i<3; i++)
        {
            init_vlc(&ff_vc1_ttmb_vlc[i], VC1_TTMB_VLC_BITS, 16,
                     ff_vc1_ttmb_bits[i], 1, 1,
                     ff_vc1_ttmb_codes[i], 2, 2, 1);
            init_vlc(&ff_vc1_ttblk_vlc[i], VC1_TTBLK_VLC_BITS, 8,
                     ff_vc1_ttblk_bits[i], 1, 1,
                     ff_vc1_ttblk_codes[i], 1, 1, 1);
            init_vlc(&ff_vc1_subblkpat_vlc[i], VC1_SUBBLKPAT_VLC_BITS, 15,
                     ff_vc1_subblkpat_bits[i], 1, 1,
                     ff_vc1_subblkpat_codes[i], 1, 1, 1);
        }
        for(i=0; i<4; i++)
        {
            init_vlc(&ff_vc1_4mv_block_pattern_vlc[i], VC1_4MV_BLOCK_PATTERN_VLC_BITS, 16,
                     ff_vc1_4mv_block_pattern_bits[i], 1, 1,
                     ff_vc1_4mv_block_pattern_codes[i], 1, 1, 1);
            init_vlc(&ff_vc1_cbpcy_p_vlc[i], VC1_CBPCY_P_VLC_BITS, 64,
                     ff_vc1_cbpcy_p_bits[i], 1, 1,
                     ff_vc1_cbpcy_p_codes[i], 2, 2, 1);
            init_vlc(&ff_vc1_mv_diff_vlc[i], VC1_MV_DIFF_VLC_BITS, 73,
                     ff_vc1_mv_diff_bits[i], 1, 1,
                     ff_vc1_mv_diff_codes[i], 2, 2, 1);
        }
        for(i=0; i<8; i++)
            init_vlc(&ff_vc1_ac_coeff_table[i], AC_VLC_BITS, vc1_ac_sizes[i],
                     &vc1_ac_tables[i][0][1], 8, 4,
                     &vc1_ac_tables[i][0][0], 8, 4, 1);
        init_vlc(&ff_msmp4_mb_i_vlc, MB_INTRA_VLC_BITS, 64,
                 &ff_msmp4_mb_i_table[0][1], 4, 2,
                 &ff_msmp4_mb_i_table[0][0], 4, 2, 1);
    }

    /* Other defaults */
    v->pq = -1;
    v->mvrange = 0; /* 7.1.1.18, p80 */

    return 0;
}

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

/** @addtogroup bitplane
 * Imode types
 * @{
 */
enum Imode {
    IMODE_RAW,
    IMODE_NORM2,
    IMODE_DIFF2,
    IMODE_NORM6,
    IMODE_DIFF6,
    IMODE_ROWSKIP,
    IMODE_COLSKIP
};
/** @} */ //imode defines

/** 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_bits1(gb)) //rowskip
            memset(plane, 0, width);
        else
            for (x=0; x<width; x++)
                plane[x] = get_bits1(gb);
        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
 * @todo 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_bits1(gb)) //colskip
            for (y=0; y<height; y++)
                plane[y*stride] = 0;
        else
            for (y=0; y<height; y++)
                plane[y*stride] = get_bits1(gb);
        plane ++;
    }
}

/** Decode a bitplane's bits
 * @param bp Bitplane where to store the decode bits
 * @param v VC-1 context for bit reading and logging
 * @return Status
 * @todo FIXME: Optimize
 */
static int bitplane_decoding(uint8_t* data, int *raw_flag, VC1Context *v)
{
    GetBitContext *gb = &v->s.gb;

    int imode, x, y, code, offset;
    uint8_t invert, *planep = data;
    int width, height, stride;

    width = v->s.mb_width;
    height = v->s.mb_height;
    stride = v->s.mb_stride;
    invert = get_bits1(gb);
    imode = get_vlc2(gb, ff_vc1_imode_vlc.table, VC1_IMODE_VLC_BITS, 1);

    *raw_flag = 0;
    switch (imode)
    {
    case IMODE_RAW:
        //Data is actually read in the MB layer (same for all tests == "raw")
        *raw_flag = 1; //invert ignored
        return invert;
    case IMODE_DIFF2:
    case IMODE_NORM2:
        if ((height * width) & 1)
        {
            *planep++ = get_bits1(gb);
            offset = 1;
        }
        else offset = 0;
        // decode bitplane as one long line
        for (y = offset; y < height * width; y += 2) {
            code = get_vlc2(gb, ff_vc1_norm2_vlc.table, VC1_NORM2_VLC_BITS, 1);
            *planep++ = code & 1;
            offset++;
            if(offset == width) {
                offset = 0;
                planep += stride - width;
            }
            *planep++ = code >> 1;
            offset++;
            if(offset == width) {
                offset = 0;
                planep += stride - width;
            }
        }
        break;
    case IMODE_DIFF6:
    case IMODE_NORM6:
        if(!(height % 3) && (width % 3)) { // use 2x3 decoding
            for(y = 0; y < height; y+= 3) {
                for(x = width & 1; x < width; x += 2) {
                    code = get_vlc2(gb, ff_vc1_norm6_vlc.table, VC1_NORM6_VLC_BITS, 2);
                    if(code < 0){
                        av_log(v->s.avctx, AV_LOG_DEBUG, "invalid NORM-6 VLC\n");
                        return -1;
                    }
                    planep[x + 0] = (code >> 0) & 1;
                    planep[x + 1] = (code >> 1) & 1;
                    planep[x + 0 + stride] = (code >> 2) & 1;
                    planep[x + 1 + stride] = (code >> 3) & 1;
                    planep[x + 0 + stride * 2] = (code >> 4) & 1;
                    planep[x + 1 + stride * 2] = (code >> 5) & 1;
                }
                planep += stride * 3;
            }
            if(width & 1) decode_colskip(data, 1, height, stride, &v->s.gb);
        } else { // 3x2
            planep += (height & 1) * stride;
            for(y = height & 1; y < height; y += 2) {
                for(x = width % 3; x < width; x += 3) {
                    code = get_vlc2(gb, ff_vc1_norm6_vlc.table, VC1_NORM6_VLC_BITS, 2);
                    if(code < 0){
                        av_log(v->s.avctx, AV_LOG_DEBUG, "invalid NORM-6 VLC\n");
                        return -1;
                    }
                    planep[x + 0] = (code >> 0) & 1;
                    planep[x + 1] = (code >> 1) & 1;
                    planep[x + 2] = (code >> 2) & 1;
                    planep[x + 0 + stride] = (code >> 3) & 1;
                    planep[x + 1 + stride] = (code >> 4) & 1;
                    planep[x + 2 + stride] = (code >> 5) & 1;
                }
                planep += stride * 2;
            }
            x = width % 3;
            if(x) decode_colskip(data  ,             x, height    , stride, &v->s.gb);
            if(height & 1) decode_rowskip(data+x, width - x, 1, stride, &v->s.gb);
        }
        break;
    case IMODE_ROWSKIP:
        decode_rowskip(data, width, height, stride, &v->s.gb);
        break;
    case IMODE_COLSKIP:
        decode_colskip(data, width, height, stride, &v->s.gb);
        break;
    default: break;
    }

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

/** @} */ //Bitplane group

/***********************************************************************/
/** VOP Dquant decoding
 * @param v VC-1 Context
 */
static int vop_dquant_decoding(VC1Context *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_bits1(gb);
        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_bits1(gb);
                if(!v->dqbilevel)
                    v->halfpq = 0;
            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;