mpegvideo.c

杜比AC-3编码解码器（参考程序）

        mb_incr -= 33;
    }
    put_bits(&s->pb, mbAddrIncrTable[mb_incr][1], 
             mbAddrIncrTable[mb_incr][0]);
    
    /* empty macroblock */
    put_bits(&s->pb, 3, 1); /* motion only */
    
    /* zero motion x & y */
    put_bits(&s->pb, 1, 1); 
    put_bits(&s->pb, 1, 1); 
}

static int dct_quantize(MpegEncContext *s, DCTELEM *block, int n, int qscale);
static void encode_block(MpegEncContext *s, 
                         DCTELEM *block, 
                         int component);
static void dct_unquantize(MpegEncContext *s, DCTELEM *block, int n, int qscale);
static void mpeg1_encode_mb(MpegEncContext *s, int mb_x, int mb_y,
                            DCTELEM block[6][64],
                            int motion_x, int motion_y);

static void encode_picture(MpegEncContext *s, int picture_number)
{
    int mb_x, mb_y;
    UINT8 *ptr;
    DCTELEM block[6][64];
    int i, motion_x, motion_y;

    s->picture_number = picture_number;
#if 1
    s->qscale = rate_estimate_qscale(s);
#else
    s->qscale = 10;
#endif
    /* precompute matrix */
    if (s->out_format == FMT_MJPEG) {
        /* for mjpeg, we do include qscale in the matrix */
        s->init_intra_matrix[0] = default_intra_matrix[0];
        for(i=1;i<64;i++)
            s->init_intra_matrix[i] = (default_intra_matrix[i] * s->qscale) >> 3;
        convert_matrix(s->intra_matrix, s->init_intra_matrix, 8);
    } else {
        convert_matrix(s->intra_matrix, default_intra_matrix, s->qscale);
        convert_matrix(s->non_intra_matrix, default_non_intra_matrix, s->qscale);
    }

    switch(s->out_format) {
    case FMT_MJPEG:
        mjpeg_picture_header(s);
        break;
    case FMT_H263:
        if (s->h263_pred) 
            mpeg4_encode_picture_header(s, picture_number);
        else if (s->h263_rv10) 
            rv10_encode_picture_header(s, picture_number);
        else
            h263_picture_header(s, picture_number);
        break;
    case FMT_MPEG1:
        /* mpeg1 picture header */
        put_header(s, PICTURE_START_CODE);
        /* temporal reference */
        put_bits(&s->pb, 10, (s->fake_picture_number - 
                              s->gop_picture_number) & 0x3ff); 
        
        put_bits(&s->pb, 3, s->pict_type);
        put_bits(&s->pb, 16, 0xffff); /* non constant bit rate */
        
        if (s->pict_type == P_TYPE) {
            put_bits(&s->pb, 1, 0); /* half pel coordinates */
            put_bits(&s->pb, 3, s->f_code); /* forward_f_code */
        }
        
        put_bits(&s->pb, 1, 0); /* extra bit picture */
        
        /* only one slice */
        put_header(s, SLICE_MIN_START_CODE);
        put_bits(&s->pb, 5, s->qscale); /* quantizer scale */
        put_bits(&s->pb, 1, 0); /* slice extra information */
        break;
    }
        
    /* init last dc values */
    /* note: quant matrix value (8) is implied here */
    s->last_dc[0] = 128;
    s->last_dc[1] = 128;
    s->last_dc[2] = 128;
    s->mb_incr = 1;
    s->last_motion_x = 0;
    s->last_motion_y = 0;

    for(mb_y=0; mb_y < s->mb_height; mb_y++) {
        for(mb_x=0; mb_x < s->mb_width; mb_x++) {

            s->mb_x = mb_x;
            s->mb_y = mb_y;

            /* compute motion vector and macro block type (intra or non intra) */
            motion_x = 0;
            motion_y = 0;
            if (s->pict_type == P_TYPE) {
                s->mb_intra = estimate_motion(s, mb_x, mb_y,
                                              &motion_x,
                                              &motion_y);
            } else {
                s->mb_intra = 1;
            }

            /* get the pixels */
            ptr = s->new_picture[0] + (mb_y * 16 * s->width) + mb_x * 16;
            get_pixels(block[0], ptr, s->width);
            get_pixels(block[1], ptr + 8, s->width);
            get_pixels(block[2], ptr + 8 * s->width, s->width);
            get_pixels(block[3], ptr + 8 * s->width + 8, s->width);
            ptr = s->new_picture[1] + (mb_y * 8 * (s->width >> 1)) + mb_x * 8;
            get_pixels(block[4],ptr, s->width >> 1);

            ptr = s->new_picture[2] + (mb_y * 8 * (s->width >> 1)) + mb_x * 8;
            get_pixels(block[5],ptr, s->width >> 1);

            /* subtract previous frame if non intra */
            if (!s->mb_intra) {
                int dxy, offset, mx, my;

                dxy = ((motion_y & 1) << 1) | (motion_x & 1);
                ptr = s->last_picture[0] + 
                    ((mb_y * 16 + (motion_y >> 1)) * s->width) + 
                    (mb_x * 16 + (motion_x >> 1));

                sub_pixels_2(block[0], ptr, s->width, dxy);
                sub_pixels_2(block[1], ptr + 8, s->width, dxy);
                sub_pixels_2(block[2], ptr + s->width * 8, s->width, dxy);
                sub_pixels_2(block[3], ptr + 8 + s->width * 8, s->width ,dxy);

                if (s->out_format == FMT_H263) {
                    /* special rounding for h263 */
                    dxy = 0;
                    if ((motion_x & 3) != 0)
                        dxy |= 1;
                    if ((motion_y & 3) != 0)
                        dxy |= 2;
                    mx = motion_x >> 2;
                    my = motion_y >> 2;
                } else {
                    mx = motion_x / 2;
                    my = motion_y / 2;
                    dxy = ((my & 1) << 1) | (mx & 1);
                    mx >>= 1;
                    my >>= 1;
                }
                offset = ((mb_y * 8 + my) * (s->width >> 1)) + (mb_x * 8 + mx);
                ptr = s->last_picture[1] + offset;
                sub_pixels_2(block[4], ptr, s->width >> 1, dxy);
                ptr = s->last_picture[2] + offset;
                sub_pixels_2(block[5], ptr, s->width >> 1, dxy);
            }

            /* DCT & quantize */
            if (s->h263_pred) {
                h263_dc_scale(s);
            } else {
                /* default quantization values */
                s->y_dc_scale = 8;
                s->c_dc_scale = 8;
            }

            for(i=0;i<6;i++) {
                int last_index;
                last_index = dct_quantize(s, block[i], i, s->qscale);
                s->block_last_index[i] = last_index;
            }

            /* huffman encode */
            switch(s->out_format) {
            case FMT_MPEG1:
                mpeg1_encode_mb(s, mb_x, mb_y, block, motion_x, motion_y);
                break;
            case FMT_H263:
                h263_encode_mb(s, block, motion_x, motion_y);
                break;
            case FMT_MJPEG:
                mjpeg_encode_mb(s, block);
                break;
            }

            /* update DC predictors for P macroblocks */
            if (!s->mb_intra) {
                if (s->h263_pred) {
                    int wrap, x, y;
                    wrap = 2 * s->mb_width + 2;
                    x = 2 * mb_x + 1;
                    y = 2 * mb_y + 1;
                    s->dc_val[0][(x) + (y) * wrap] = 1024;
                    s->dc_val[0][(x + 1) + (y) * wrap] = 1024;
                    s->dc_val[0][(x) + (y + 1) * wrap] = 1024;
                    s->dc_val[0][(x + 1) + (y + 1) * wrap] = 1024;
                    wrap = s->mb_width + 2;
                    x = mb_x + 1;
                    y = mb_y + 1;
                    s->dc_val[1][(x) + (y) * wrap] = 1024;
                    s->dc_val[2][(x) + (y) * wrap] = 1024;
                } else {
                    s->last_dc[0] = 128;
                    s->last_dc[1] = 128;
                    s->last_dc[2] = 128;
                }
            }

            /* update motion predictor */
            if (s->out_format == FMT_H263) {
                int x, y, wrap;
                
                x = 2 * mb_x + 1;
                y = 2 * mb_y + 1;
                wrap = 2 * s->mb_width + 2;
                s->motion_val[(x) + (y) * wrap][0] = motion_x;
                s->motion_val[(x) + (y) * wrap][1] = motion_y;
                s->motion_val[(x + 1) + (y) * wrap][0] = motion_x;
                s->motion_val[(x + 1) + (y) * wrap][1] = motion_y;
                s->motion_val[(x) + (y + 1) * wrap][0] = motion_x;
                s->motion_val[(x) + (y + 1) * wrap][1] = motion_y;
                s->motion_val[(x + 1) + (y + 1) * wrap][0] = motion_x;
                s->motion_val[(x + 1) + (y + 1) * wrap][1] = motion_y;
            } else {
                s->last_motion_x = motion_x;
                s->last_motion_y = motion_y;
            }
            
            /* decompress blocks so that we keep the state of the decoder */
            if (!s->intra_only) {
                for(i=0;i<6;i++) {
                    if (s->block_last_index[i] >= 0) {
                        dct_unquantize(s, block[i], i, s->qscale);
                        j_rev_dct (block[i]);
                    }
                }

                if (!s->mb_intra) {
                    int dxy, offset, mx, my;
                    dxy = ((motion_y & 1) << 1) | (motion_x & 1);
                    ptr = s->last_picture[0] + 
                        ((mb_y * 16 + (motion_y >> 1)) * s->width) + 
                        (mb_x * 16 + (motion_x >> 1));
                    
                    add_pixels_2(block[0], ptr, s->width, dxy);
                    add_pixels_2(block[1], ptr + 8, s->width, dxy);
                    add_pixels_2(block[2], ptr + s->width * 8, s->width, dxy);
                    add_pixels_2(block[3], ptr + 8 + s->width * 8, s->width, dxy);

                    if (s->out_format == FMT_H263) {
                        /* special rounding for h263 */
                        dxy = 0;
                        if ((motion_x & 3) != 0)
                            dxy |= 1;
                        if ((motion_y & 3) != 0)
                            dxy |= 2;
                        mx = motion_x >> 2;
                        my = motion_y >> 2;
                    } else {
                        mx = motion_x / 2;
                        my = motion_y / 2;
                        dxy = ((my & 1) << 1) | (mx & 1);
                        mx >>= 1;
                        my >>= 1;
                    }
                    offset = ((mb_y * 8 + my) * (s->width >> 1)) + (mb_x * 8 + mx);
                    ptr = s->last_picture[1] + offset;
                    add_pixels_2(block[4], ptr, s->width >> 1, dxy);
                    ptr = s->last_picture[2] + offset;
                    add_pixels_2(block[5], ptr, s->width >> 1, dxy);
                }

                /* write the pixels */
                ptr = s->current_picture[0] + (mb_y * 16 * s->width) + mb_x * 16;
                put_pixels(block[0], ptr, s->width);
                put_pixels(block[1], ptr + 8, s->width);
                put_pixels(block[2], ptr + 8 * s->width, s->width);
                put_pixels(block[3], ptr + 8 * s->width + 8, s->width);
                ptr = s->current_picture[1] + (mb_y * 8 * (s->width >> 1)) + mb_x * 8;
                put_pixels(block[4],ptr, s->width >> 1);
                
                ptr = s->current_picture[2] + (mb_y * 8 * (s->width >> 1)) + mb_x * 8;
                put_pixels(block[5],ptr, s->width >> 1);
            }
        }
    }
}

static void mpeg1_encode_motion(MpegEncContext *s, int val)
{
    int code, bit_size, l, m, bits, range;

    if (val == 0) {
        /* zero vector */
        code = 0;
        put_bits(&s->pb,
                 mbMotionVectorTable[code + 16][1], 
                 mbMotionVectorTable[code + 16][0]); 
    } else {
        bit_size = s->f_code - 1;
        range = 1 << bit_size;
        /* modulo encoding */
        l = 16 * range;
        m = 2 * l;
        if (val < -l) {
            val += m;
        } else if (val >= l) {
            val -= m;
        }

        if (val >= 0) {
            val--;
            code = (val >> bit_size) + 1;
            bits = val & (range - 1);
        } else {
            val = -val;
            val--;
            code = (val >> bit_size) + 1;
            bits = val & (range - 1);
            code = -code;
        }
        put_bits(&s->pb,
                 mbMotionVectorTable[code + 16][1], 
                 mbMotionVectorTable[code + 16][0]); 
        if (bit_size > 0) {
            put_bits(&s->pb, bit_size, bits);
        }
    }
}

static void mpeg1_encode_mb(MpegEncContext *s, int mb_x, int mb_y,
                            DCTELEM block[6][64],
                            int motion_x, int motion_y)
{
    int mb_incr, i, cbp;

    /* compute cbp */
    cbp = 0;
    for(i=0;i<6;i++) {
        if (s->block_last_index[i] >= 0)
            cbp |= 1 << (5 - i);
    }

    /* skip macroblock, except if first or last macroblock of a slice */
    if ((cbp | motion_x | motion_y) == 0 &&
        (!((mb_x | mb_y) == 0 ||
           (mb_x == s->mb_width - 1 && mb_y == s->mb_height - 1)))) {
        s->mb_incr++;
    } else {
        /* output mb incr */
        mb_incr = s->mb_incr;

        while (mb_incr > 33) {
            put_bits(&s->pb, 11, 0x008);
            mb_incr -= 33;
        }
        put_bits(&s->pb, mbAddrIncrTable[mb_incr][1], 
                 mbAddrIncrTable[mb_incr][0]);
        
        if (s->pict_type == I_TYPE) {
            put_bits(&s->pb, 1, 1); /* macroblock_type : macroblock_quant = 0 */
        } else {
            if (s->mb_intra) {
                put_bits(&s->pb, 5, 0x03);
            } else {
                if (cbp != 0) {