mpeg12enc.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

                if (s->chroma_y_shift) {
                    put_bits(&s->pb, ff_mpeg12_mbPatTable[cbp][1], ff_mpeg12_mbPatTable[cbp][0]);
                } else {
                    put_bits(&s->pb, ff_mpeg12_mbPatTable[cbp>>2][1], ff_mpeg12_mbPatTable[cbp>>2][0]);
                    put_bits(&s->pb, 2, cbp & 3);
                }
            }
        }
        for(i=0;i<mb_block_count;i++) {
            if (cbp & (1 << (mb_block_count - 1 - i))) {
                mpeg1_encode_block(s, block[i], i);
            }
        }
        s->mb_skip_run = 0;
        if(s->mb_intra)
            s->i_tex_bits+= get_bits_diff(s);
        else
            s->p_tex_bits+= get_bits_diff(s);
    }
}

void mpeg1_encode_mb(MpegEncContext *s, DCTELEM block[6][64], int motion_x, int motion_y)
{
    if (s->chroma_format == CHROMA_420) mpeg1_encode_mb_internal(s, block, motion_x, motion_y, 6);
    else                                mpeg1_encode_mb_internal(s, block, motion_x, motion_y, 8);
}

// RAL: Parameter added: f_or_b_code
static void mpeg1_encode_motion(MpegEncContext *s, int val, int f_or_b_code)
{
    int code, bit_size, l, bits, range, sign;

    if (val == 0) {
        /* zero vector */
        code = 0;
        put_bits(&s->pb,
                 ff_mpeg12_mbMotionVectorTable[0][1],
                 ff_mpeg12_mbMotionVectorTable[0][0]);
    } else {
        bit_size = f_or_b_code - 1;
        range = 1 << bit_size;
        /* modulo encoding */
        l= INT_BIT - 5 - bit_size;
        val= (val<<l)>>l;

        if (val >= 0) {
            val--;
            code = (val >> bit_size) + 1;
            bits = val & (range - 1);
            sign = 0;
        } else {
            val = -val;
            val--;
            code = (val >> bit_size) + 1;
            bits = val & (range - 1);
            sign = 1;
        }

        assert(code > 0 && code <= 16);

        put_bits(&s->pb,
                 ff_mpeg12_mbMotionVectorTable[code][1],
                 ff_mpeg12_mbMotionVectorTable[code][0]);

        put_bits(&s->pb, 1, sign);
        if (bit_size > 0) {
            put_bits(&s->pb, bit_size, bits);
        }
    }
}

void ff_mpeg1_encode_init(MpegEncContext *s)
{
    static int done=0;

    ff_mpeg12_common_init(s);

    if(!done){
        int f_code;
        int mv;
        int i;

        done=1;
        init_rl(&ff_rl_mpeg1, ff_mpeg12_static_rl_table_store[0]);
        init_rl(&ff_rl_mpeg2, ff_mpeg12_static_rl_table_store[1]);

        for(i=0; i<64; i++)
        {
                mpeg1_max_level[0][i]= ff_rl_mpeg1.max_level[0][i];
                mpeg1_index_run[0][i]= ff_rl_mpeg1.index_run[0][i];
        }

        init_uni_ac_vlc(&ff_rl_mpeg1, uni_mpeg1_ac_vlc_len);
        if(s->intra_vlc_format)
            init_uni_ac_vlc(&ff_rl_mpeg2, uni_mpeg2_ac_vlc_len);

        /* build unified dc encoding tables */
        for(i=-255; i<256; i++)
        {
                int adiff, index;
                int bits, code;
                int diff=i;

                adiff = FFABS(diff);
                if(diff<0) diff--;
                index = av_log2(2*adiff);

                bits= ff_mpeg12_vlc_dc_lum_bits[index] + index;
                code= (ff_mpeg12_vlc_dc_lum_code[index]<<index) + (diff & ((1 << index) - 1));
                mpeg1_lum_dc_uni[i+255]= bits + (code<<8);

                bits= ff_mpeg12_vlc_dc_chroma_bits[index] + index;
                code= (ff_mpeg12_vlc_dc_chroma_code[index]<<index) + (diff & ((1 << index) - 1));
                mpeg1_chr_dc_uni[i+255]= bits + (code<<8);
        }

        for(f_code=1; f_code<=MAX_FCODE; f_code++){
            for(mv=-MAX_MV; mv<=MAX_MV; mv++){
                int len;

                if(mv==0) len= ff_mpeg12_mbMotionVectorTable[0][1];
                else{
                    int val, bit_size, range, code;

                    bit_size = f_code - 1;
                    range = 1 << bit_size;

                    val=mv;
                    if (val < 0)
                        val = -val;
                    val--;
                    code = (val >> bit_size) + 1;
                    if(code<17){
                        len= ff_mpeg12_mbMotionVectorTable[code][1] + 1 + bit_size;
                    }else{
                        len= ff_mpeg12_mbMotionVectorTable[16][1] + 2 + bit_size;
                    }
                }

                mv_penalty[f_code][mv+MAX_MV]= len;
            }
        }


        for(f_code=MAX_FCODE; f_code>0; f_code--){
            for(mv=-(8<<f_code); mv<(8<<f_code); mv++){
                fcode_tab[mv+MAX_MV]= f_code;
            }
        }
    }
    s->me.mv_penalty= mv_penalty;
    s->fcode_tab= fcode_tab;
    if(s->codec_id == CODEC_ID_MPEG1VIDEO){
        s->min_qcoeff=-255;
        s->max_qcoeff= 255;
    }else{
        s->min_qcoeff=-2047;
        s->max_qcoeff= 2047;
    }
    if (s->intra_vlc_format) {
        s->intra_ac_vlc_length=
        s->intra_ac_vlc_last_length= uni_mpeg2_ac_vlc_len;
    } else {
        s->intra_ac_vlc_length=
        s->intra_ac_vlc_last_length= uni_mpeg1_ac_vlc_len;
    }
    s->inter_ac_vlc_length=
    s->inter_ac_vlc_last_length= uni_mpeg1_ac_vlc_len;
}

static inline void encode_dc(MpegEncContext *s, int diff, int component)
{
  if(((unsigned) (diff+255)) >= 511){
        int index;

        if(diff<0){
            index= av_log2_16bit(-2*diff);
            diff--;
        }else{
            index= av_log2_16bit(2*diff);
        }
        if (component == 0) {
            put_bits(
                &s->pb,
                ff_mpeg12_vlc_dc_lum_bits[index] + index,
                (ff_mpeg12_vlc_dc_lum_code[index]<<index) + (diff & ((1 << index) - 1)));
        }else{
            put_bits(
                &s->pb,
                ff_mpeg12_vlc_dc_chroma_bits[index] + index,
                (ff_mpeg12_vlc_dc_chroma_code[index]<<index) + (diff & ((1 << index) - 1)));
        }
  }else{
    if (component == 0) {
        put_bits(
            &s->pb,
            mpeg1_lum_dc_uni[diff+255]&0xFF,
            mpeg1_lum_dc_uni[diff+255]>>8);
    } else {
        put_bits(
            &s->pb,
            mpeg1_chr_dc_uni[diff+255]&0xFF,
            mpeg1_chr_dc_uni[diff+255]>>8);
    }
  }
}

static void mpeg1_encode_block(MpegEncContext *s,
                               DCTELEM *block,
                               int n)
{
    int alevel, level, last_non_zero, dc, diff, i, j, run, last_index, sign;
    int code, component;
    const uint16_t (*table_vlc)[2] = ff_rl_mpeg1.table_vlc;

    last_index = s->block_last_index[n];

    /* DC coef */
    if (s->mb_intra) {
        component = (n <= 3 ? 0 : (n&1) + 1);
        dc = block[0]; /* overflow is impossible */
        diff = dc - s->last_dc[component];
        encode_dc(s, diff, component);
        s->last_dc[component] = dc;
        i = 1;
        if (s->intra_vlc_format)
            table_vlc = ff_rl_mpeg2.table_vlc;
    } else {
        /* encode the first coefficient : needs to be done here because
           it is handled slightly differently */
        level = block[0];
        if (abs(level) == 1) {
                code = ((uint32_t)level >> 31); /* the sign bit */
                put_bits(&s->pb, 2, code | 0x02);
                i = 1;
        } else {
            i = 0;
            last_non_zero = -1;
            goto next_coef;
        }
    }

    /* now quantify & encode AC coefs */
    last_non_zero = i - 1;

    for(;i<=last_index;i++) {
        j = s->intra_scantable.permutated[i];
        level = block[j];
    next_coef:
#if 0
        if (level != 0)
            dprintf(s->avctx, "level[%d]=%d\n", i, level);
#endif
        /* encode using VLC */
        if (level != 0) {
            run = i - last_non_zero - 1;

            alevel= level;
            MASK_ABS(sign, alevel)
            sign&=1;

            if (alevel <= mpeg1_max_level[0][run]){
                code= mpeg1_index_run[0][run] + alevel - 1;
                /* store the vlc & sign at once */
                put_bits(&s->pb, table_vlc[code][1]+1, (table_vlc[code][0]<<1) + sign);
            } else {
                /* escape seems to be pretty rare <5% so I do not optimize it */
                put_bits(&s->pb, table_vlc[111][1], table_vlc[111][0]);
                /* escape: only clip in this case */
                put_bits(&s->pb, 6, run);
                if(s->codec_id == CODEC_ID_MPEG1VIDEO){
                    if (alevel < 128) {
                        put_bits(&s->pb, 8, level & 0xff);
                    } else {
                        if (level < 0) {
                            put_bits(&s->pb, 16, 0x8001 + level + 255);
                        } else {
                            put_bits(&s->pb, 16, level & 0xffff);
                        }
                    }
                }else{
                    put_bits(&s->pb, 12, level & 0xfff);
                }
            }
            last_non_zero = i;
        }
    }
    /* end of block */
    put_bits(&s->pb, table_vlc[112][1], table_vlc[112][0]);
}

AVCodec mpeg1video_encoder = {
    "mpeg1video",
    CODEC_TYPE_VIDEO,
    CODEC_ID_MPEG1VIDEO,
    sizeof(MpegEncContext),
    encode_init,
    MPV_encode_picture,
    MPV_encode_end,
    .supported_framerates= ff_frame_rate_tab+1,
    .pix_fmts= (enum PixelFormat[]){PIX_FMT_YUV420P, -1},
    .capabilities= CODEC_CAP_DELAY,
};

AVCodec mpeg2video_encoder = {
    "mpeg2video",
    CODEC_TYPE_VIDEO,
    CODEC_ID_MPEG2VIDEO,
    sizeof(MpegEncContext),
    encode_init,
    MPV_encode_picture,
    MPV_encode_end,
    .supported_framerates= ff_frame_rate_tab+1,
    .pix_fmts= (enum PixelFormat[]){PIX_FMT_YUV420P, PIX_FMT_YUV422P, -1},
    .capabilities= CODEC_CAP_DELAY,
};