dv.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

/*
 * DV decoder
 * Copyright (c) 2002 Fabrice Bellard.
 * Copyright (c) 2004 Roman Shaposhnik.
 *
 * DV encoder
 * Copyright (c) 2003 Roman Shaposhnik.
 *
 * 50 Mbps (DVCPRO50) support
 * Copyright (c) 2006 Daniel Maas <[e-mail]>
 *
 * Many thanks to Dan Dennedy <[e-mail]> for providing wealth
 * of DV technical info.
 *
 * 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 dv.c
 * DV codec.
 */
#define ALT_BITSTREAM_READER
#include "avcodec.h"
#include "dsputil.h"
#include "mpegvideo.h"
#include "simple_idct.h"
#include "dvdata.h"

//#undef NDEBUG
//#include <assert.h>

typedef struct DVVideoContext {
    const DVprofile* sys;
    AVFrame picture;
    AVCodecContext *avctx;
    uint8_t *buf;

    uint8_t dv_zigzag[2][64];
    uint8_t dv_idct_shift[2][2][22][64];

    void (*get_pixels)(DCTELEM *block, const uint8_t *pixels, int line_size);
    void (*fdct[2])(DCTELEM *block);
    void (*idct_put[2])(uint8_t *dest, int line_size, DCTELEM *block);
} DVVideoContext;

/* MultiThreading - dv_anchor applies to entire DV codec, not just the avcontext */
/* one element is needed for each video segment in a DV frame */
/* at most there are 2 DIF channels * 12 DIF sequences * 27 video segments (PAL 50Mbps) */
#define DV_ANCHOR_SIZE (2*12*27)

static void* dv_anchor[DV_ANCHOR_SIZE];

#define TEX_VLC_BITS 9

#ifdef DV_CODEC_TINY_TARGET
#define DV_VLC_MAP_RUN_SIZE 15
#define DV_VLC_MAP_LEV_SIZE 23
#else
#define DV_VLC_MAP_RUN_SIZE  64
#define DV_VLC_MAP_LEV_SIZE 512 //FIXME sign was removed so this should be /2 but needs check
#endif

/* XXX: also include quantization */
static RL_VLC_ELEM dv_rl_vlc[1184];
/* VLC encoding lookup table */
static struct dv_vlc_pair {
   uint32_t vlc;
   uint8_t  size;
} dv_vlc_map[DV_VLC_MAP_RUN_SIZE][DV_VLC_MAP_LEV_SIZE];

static void dv_build_unquantize_tables(DVVideoContext *s, uint8_t* perm)
{
    int i, q, j;

    /* NOTE: max left shift is 6 */
    for(q = 0; q < 22; q++) {
        /* 88DCT */
        for(i = 1; i < 64; i++) {
            /* 88 table */
            j = perm[i];
            s->dv_idct_shift[0][0][q][j] =
                dv_quant_shifts[q][dv_88_areas[i]] + 1;
            s->dv_idct_shift[1][0][q][j] = s->dv_idct_shift[0][0][q][j] + 1;
        }

        /* 248DCT */
        for(i = 1; i < 64; i++) {
            /* 248 table */
            s->dv_idct_shift[0][1][q][i] =
                dv_quant_shifts[q][dv_248_areas[i]] + 1;
            s->dv_idct_shift[1][1][q][i] = s->dv_idct_shift[0][1][q][i] + 1;
        }
    }
}

static int dvvideo_init(AVCodecContext *avctx)
{
    DVVideoContext *s = avctx->priv_data;
    DSPContext dsp;
    static int done=0;
    int i, j;

    if (!done) {
        VLC dv_vlc;
        uint16_t new_dv_vlc_bits[NB_DV_VLC*2];
        uint8_t new_dv_vlc_len[NB_DV_VLC*2];
        uint8_t new_dv_vlc_run[NB_DV_VLC*2];
        int16_t new_dv_vlc_level[NB_DV_VLC*2];

        done = 1;

        /* dv_anchor lets each thread know its Id */
        for (i=0; i<DV_ANCHOR_SIZE; i++)
            dv_anchor[i] = (void*)(size_t)i;

        /* it's faster to include sign bit in a generic VLC parsing scheme */
        for (i=0, j=0; i<NB_DV_VLC; i++, j++) {
            new_dv_vlc_bits[j] = dv_vlc_bits[i];
            new_dv_vlc_len[j] = dv_vlc_len[i];
            new_dv_vlc_run[j] = dv_vlc_run[i];
            new_dv_vlc_level[j] = dv_vlc_level[i];

            if (dv_vlc_level[i]) {
                new_dv_vlc_bits[j] <<= 1;
                new_dv_vlc_len[j]++;

                j++;
                new_dv_vlc_bits[j] = (dv_vlc_bits[i] << 1) | 1;
                new_dv_vlc_len[j] = dv_vlc_len[i] + 1;
                new_dv_vlc_run[j] = dv_vlc_run[i];
                new_dv_vlc_level[j] = -dv_vlc_level[i];
            }
        }

        /* NOTE: as a trick, we use the fact the no codes are unused
           to accelerate the parsing of partial codes */
        init_vlc(&dv_vlc, TEX_VLC_BITS, j,
                 new_dv_vlc_len, 1, 1, new_dv_vlc_bits, 2, 2, 0);
        assert(dv_vlc.table_size == 1184);

        for(i = 0; i < dv_vlc.table_size; i++){
            int code= dv_vlc.table[i][0];
            int len = dv_vlc.table[i][1];
            int level, run;

            if(len<0){ //more bits needed
                run= 0;
                level= code;
            } else {
                run=   new_dv_vlc_run[code] + 1;
                level= new_dv_vlc_level[code];
            }
            dv_rl_vlc[i].len = len;
            dv_rl_vlc[i].level = level;
            dv_rl_vlc[i].run = run;
        }
        free_vlc(&dv_vlc);

        for (i = 0; i < NB_DV_VLC - 1; i++) {
           if (dv_vlc_run[i] >= DV_VLC_MAP_RUN_SIZE)
               continue;
#ifdef DV_CODEC_TINY_TARGET
           if (dv_vlc_level[i] >= DV_VLC_MAP_LEV_SIZE)
               continue;
#endif

           if (dv_vlc_map[dv_vlc_run[i]][dv_vlc_level[i]].size != 0)
               continue;

           dv_vlc_map[dv_vlc_run[i]][dv_vlc_level[i]].vlc = dv_vlc_bits[i] <<
                                                            (!!dv_vlc_level[i]);
           dv_vlc_map[dv_vlc_run[i]][dv_vlc_level[i]].size = dv_vlc_len[i] +
                                                             (!!dv_vlc_level[i]);
        }
        for (i = 0; i < DV_VLC_MAP_RUN_SIZE; i++) {
#ifdef DV_CODEC_TINY_TARGET
           for (j = 1; j < DV_VLC_MAP_LEV_SIZE; j++) {
              if (dv_vlc_map[i][j].size == 0) {
                  dv_vlc_map[i][j].vlc = dv_vlc_map[0][j].vlc |
                            (dv_vlc_map[i-1][0].vlc << (dv_vlc_map[0][j].size));
                  dv_vlc_map[i][j].size = dv_vlc_map[i-1][0].size +
                                          dv_vlc_map[0][j].size;
              }
           }
#else
           for (j = 1; j < DV_VLC_MAP_LEV_SIZE/2; j++) {
              if (dv_vlc_map[i][j].size == 0) {
                  dv_vlc_map[i][j].vlc = dv_vlc_map[0][j].vlc |
                            (dv_vlc_map[i-1][0].vlc << (dv_vlc_map[0][j].size));
                  dv_vlc_map[i][j].size = dv_vlc_map[i-1][0].size +
                                          dv_vlc_map[0][j].size;
              }
              dv_vlc_map[i][((uint16_t)(-j))&0x1ff].vlc =
                                            dv_vlc_map[i][j].vlc | 1;
              dv_vlc_map[i][((uint16_t)(-j))&0x1ff].size =
                                            dv_vlc_map[i][j].size;
           }
#endif
        }
    }

    /* Generic DSP setup */
    dsputil_init(&dsp, avctx);
    s->get_pixels = dsp.get_pixels;

    /* 88DCT setup */
    s->fdct[0] = dsp.fdct;
    s->idct_put[0] = dsp.idct_put;
    for (i=0; i<64; i++)
       s->dv_zigzag[0][i] = dsp.idct_permutation[ff_zigzag_direct[i]];

    /* 248DCT setup */
    s->fdct[1] = dsp.fdct248;
    s->idct_put[1] = simple_idct248_put;  // FIXME: need to add it to DSP
    if(avctx->lowres){
        for (i=0; i<64; i++){
            int j= ff_zigzag248_direct[i];
            s->dv_zigzag[1][i] = dsp.idct_permutation[(j&7) + (j&8)*4 + (j&48)/2];
        }
    }else
        memcpy(s->dv_zigzag[1], ff_zigzag248_direct, 64);

    /* XXX: do it only for constant case */
    dv_build_unquantize_tables(s, dsp.idct_permutation);

    avctx->coded_frame = &s->picture;
    s->avctx= avctx;

    return 0;
}

// #define VLC_DEBUG
// #define printf(...) av_log(NULL, AV_LOG_ERROR, __VA_ARGS__)

typedef struct BlockInfo {
    const uint8_t *shift_table;
    const uint8_t *scan_table;
    const int *iweight_table;
    uint8_t pos; /* position in block */
    uint8_t dct_mode;
    uint8_t partial_bit_count;
    uint16_t partial_bit_buffer;
    int shift_offset;
} BlockInfo;

/* block size in bits */
static const uint16_t block_sizes[6] = {
    112, 112, 112, 112, 80, 80
};
/* bit budget for AC only in 5 MBs */
static const int vs_total_ac_bits = (100 * 4 + 68*2) * 5;
/* see dv_88_areas and dv_248_areas for details */
static const int mb_area_start[5] = { 1, 6, 21, 43, 64 };

static inline int get_bits_left(GetBitContext *s)
{
    return s->size_in_bits - get_bits_count(s);
}

static inline int get_bits_size(GetBitContext *s)
{
    return s->size_in_bits;
}

static inline int put_bits_left(PutBitContext* s)
{
    return (s->buf_end - s->buf) * 8 - put_bits_count(s);
}

/* decode ac coefs */
static void dv_decode_ac(GetBitContext *gb, BlockInfo *mb, DCTELEM *block)
{
    int last_index = get_bits_size(gb);
    const uint8_t *scan_table = mb->scan_table;
    const uint8_t *shift_table = mb->shift_table;
    const int *iweight_table = mb->iweight_table;
    int pos = mb->pos;
    int partial_bit_count = mb->partial_bit_count;
    int level, pos1, run, vlc_len, index;

    OPEN_READER(re, gb);
    UPDATE_CACHE(re, gb);

    /* if we must parse a partial vlc, we do it here */
    if (partial_bit_count > 0) {
        re_cache = ((unsigned)re_cache >> partial_bit_count) |
                   (mb->partial_bit_buffer << (sizeof(re_cache)*8 - partial_bit_count));
        re_index -= partial_bit_count;
        mb->partial_bit_count = 0;
    }

    /* get the AC coefficients until last_index is reached */
    for(;;) {
#ifdef VLC_DEBUG
        printf("%2d: bits=%04x index=%d\n", pos, SHOW_UBITS(re, gb, 16), re_index);
#endif
        /* our own optimized GET_RL_VLC */
        index = NEG_USR32(re_cache, TEX_VLC_BITS);
        vlc_len = dv_rl_vlc[index].len;
        if (vlc_len < 0) {
            index = NEG_USR32((unsigned)re_cache << TEX_VLC_BITS, -vlc_len) + dv_rl_vlc[index].level;
            vlc_len = TEX_VLC_BITS - vlc_len;
        }
        level = dv_rl_vlc[index].level;
        run = dv_rl_vlc[index].run;

        /* gotta check if we're still within gb boundaries */
        if (re_index + vlc_len > last_index) {
            /* should be < 16 bits otherwise a codeword could have been parsed */
            mb->partial_bit_count = last_index - re_index;
            mb->partial_bit_buffer = NEG_USR32(re_cache, mb->partial_bit_count);
            re_index = last_index;
            break;
        }
        re_index += vlc_len;

#ifdef VLC_DEBUG
        printf("run=%d level=%d\n", run, level);
#endif
        pos += run;
        if (pos >= 64)
            break;

        pos1 = scan_table[pos];
        level <<= shift_table[pos1];

        /* unweigh, round, and shift down */
        level = (level*iweight_table[pos] + (1 << (dv_iweight_bits-1))) >> dv_iweight_bits;

        block[pos1] = level;

        UPDATE_CACHE(re, gb);
    }
    CLOSE_READER(re, gb);
    mb->pos = pos;
}

static inline void bit_copy(PutBitContext *pb, GetBitContext *gb)
{
    int bits_left = get_bits_left(gb);
    while (bits_left >= MIN_CACHE_BITS) {
        put_bits(pb, MIN_CACHE_BITS, get_bits(gb, MIN_CACHE_BITS));
        bits_left -= MIN_CACHE_BITS;
    }
    if (bits_left > 0) {
        put_bits(pb, bits_left, get_bits(gb, bits_left));
    }
}

/* mb_x and mb_y are in units of 8 pixels */
static inline void dv_decode_video_segment(DVVideoContext *s,
                                           uint8_t *buf_ptr1,
                                           const uint16_t *mb_pos_ptr)
{
    int quant, dc, dct_mode, class1, j;
    int mb_index, mb_x, mb_y, v, last_index;
    DCTELEM *block, *block1;
    int c_offset;
    uint8_t *y_ptr;
    void (*idct_put)(uint8_t *dest, int line_size, DCTELEM *block);
    uint8_t *buf_ptr;
    PutBitContext pb, vs_pb;
    GetBitContext gb;
    BlockInfo mb_data[5 * 6], *mb, *mb1;
    DECLARE_ALIGNED_8(DCTELEM, sblock[5*6][64]);
    DECLARE_ALIGNED_8(uint8_t, mb_bit_buffer[80 + 4]); /* allow some slack */
    DECLARE_ALIGNED_8(uint8_t, vs_bit_buffer[5 * 80 + 4]); /* allow some slack */
    const int log2_blocksize= 3-s->avctx->lowres;

    assert((((int)mb_bit_buffer)&7)==0);
    assert((((int)vs_bit_buffer)&7)==0);

    memset(sblock, 0, sizeof(sblock));

    /* pass 1 : read DC and AC coefficients in blocks */
    buf_ptr = buf_ptr1;
    block1 = &sblock[0][0];
    mb1 = mb_data;
    init_put_bits(&vs_pb, vs_bit_buffer, 5 * 80);
    for(mb_index = 0; mb_index < 5; mb_index++, mb1 += 6, block1 += 6 * 64) {
        /* skip header */
        quant = buf_ptr[3] & 0x0f;
        buf_ptr += 4;
        init_put_bits(&pb, mb_bit_buffer, 80);
        mb = mb1;
        block = block1;
        for(j = 0;j < 6; j++) {
            last_index = block_sizes[j];
            init_get_bits(&gb, buf_ptr, last_index);

            /* get the dc */
            dc = get_sbits(&gb, 9);
            dct_mode = get_bits1(&gb);
            mb->dct_mode = dct_mode;
            mb->scan_table = s->dv_zigzag[dct_mode];
            mb->iweight_table = dct_mode ? dv_iweight_248 : dv_iweight_88;
            class1 = get_bits(&gb, 2);
            mb->shift_table = s->dv_idct_shift[class1 == 3][dct_mode]
                [quant + dv_quant_offset[class1]];
            dc = dc << 2;
            /* convert to unsigned because 128 is not added in the
               standard IDCT */
            dc += 1024;
            block[0] = dc;
            buf_ptr += last_index >> 3;
            mb->pos = 0;