mpegvideo.c

一个播放器 使用了evc 大家可以参考下 哦

            free(s->aux_picture_base[i]);
    }
    s->context_initialized = 0;
}


/* draw the edges of width 'w' of an image of size width, height */
static void draw_edges(UINT8 *buf, int wrap, int width, int height, int w)
{
    UINT8 *ptr, *last_line;
    int i;

    last_line = buf + (height - 1) * wrap;
    for(i=0;i<w;i++) {
        /* top and bottom */
        memcpy(buf - (i + 1) * wrap, buf, width);
        memcpy(last_line + (i + 1) * wrap, last_line, width);
    }
    /* left and right */
    ptr = buf;
    for(i=0;i<height;i++) {
        memset(ptr - w, ptr[0], w);
        memset(ptr + width, ptr[width-1], w);
        ptr += wrap;
    }
    /* corners */
    for(i=0;i<w;i++) {
        memset(buf - (i + 1) * wrap - w, buf[0], w); /* top left */
        memset(buf - (i + 1) * wrap + width, buf[width-1], w); /* top right */
        memset(last_line + (i + 1) * wrap - w, last_line[0], w); /* top left */
        memset(last_line + (i + 1) * wrap + width, last_line[width-1], w); /* top right */
    }
}


/* generic function for encode/decode called before a frame is coded/decoded */
void MPV_frame_start(MpegEncContext *s)
{
    int i;
    UINT8 *tmp;

    if (s->pict_type == B_TYPE) {
        for(i=0;i<3;i++) {
            s->current_picture[i] = s->aux_picture[i];
        }
    } else {
        for(i=0;i<3;i++) {
            /* swap next and last */
            tmp = s->last_picture[i];
            s->last_picture[i] = s->next_picture[i];
            s->next_picture[i] = tmp;
            s->current_picture[i] = tmp;
        }
    }
}

/* generic function for encode/decode called after a frame has been coded/decoded */
void MPV_frame_end(MpegEncContext *s)
{
    /* draw edge for correct motion prediction if outside */
    if (s->pict_type != B_TYPE) {
        draw_edges(s->current_picture[0], s->linesize, s->width, s->height, EDGE_WIDTH);
        draw_edges(s->current_picture[1], s->linesize/2, s->width/2, s->height/2, EDGE_WIDTH/2);
        draw_edges(s->current_picture[2], s->linesize/2, s->width/2, s->height/2, EDGE_WIDTH/2);
    }
}


static int clip(int a, int amin, int amax)
{
    if (a < amin)
        return amin;
    else if (a > amax)
        return amax;
    else
        return a;
}


/* apply one mpeg motion vector to the three components */
static  void mpeg_motion(MpegEncContext *s,
                               UINT8 *dest_y, UINT8 *dest_cb, UINT8 *dest_cr,
                               int dest_offset,
                               UINT8 **ref_picture, int src_offset,
                               int field_based, op_pixels_func *pix_op,
                               int motion_x, int motion_y, int h)
{
    UINT8 *ptr;
    int dxy, offset, mx, my, src_x, src_y, height, linesize;
    
    dxy = ((motion_y & 1) << 1) | (motion_x & 1);
    src_x = s->mb_x * 16 + (motion_x >> 1);
    src_y = s->mb_y * (16 >> field_based) + (motion_y >> 1);
                
    /* WARNING: do no forget half pels */
    height = s->height >> field_based;
    src_x = clip(src_x, -16, s->width);
    if (src_x == s->width)
        dxy &= ~1;
    src_y = clip(src_y, -16, height);
    if (src_y == height)
        dxy &= ~2;
    linesize = s->linesize << field_based;
    ptr = ref_picture[0] + (src_y * linesize) + (src_x) + src_offset;
    dest_y += dest_offset;
    pix_op[dxy](dest_y, ptr, linesize, h);
    pix_op[dxy](dest_y + 8, ptr + 8, linesize, h);

    if (s->out_format == FMT_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;
    }
    
    src_x = s->mb_x * 8 + mx;
    src_y = s->mb_y * (8 >> field_based) + my;
    src_x = clip(src_x, -8, s->width >> 1);
    if (src_x == (s->width >> 1))
        dxy &= ~1;
    src_y = clip(src_y, -8, height >> 1);
    if (src_y == (height >> 1))
        dxy &= ~2;

    offset = (src_y * (linesize >> 1)) + src_x + (src_offset >> 1);
    ptr = ref_picture[1] + offset;
    pix_op[dxy](dest_cb + (dest_offset >> 1), ptr, linesize >> 1, h >> 1);
    ptr = ref_picture[2] + offset;
    pix_op[dxy](dest_cr + (dest_offset >> 1), ptr, linesize >> 1, h >> 1);
}

static  void MPV_motion(MpegEncContext *s, 
                              UINT8 *dest_y, UINT8 *dest_cb, UINT8 *dest_cr,
                              int dir, UINT8 **ref_picture, 
                              op_pixels_func *pix_op)
{
    int dxy, offset, mx, my, src_x, src_y, motion_x, motion_y;
    int mb_x, mb_y, i;
    UINT8 *ptr, *dest;

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

    switch(s->mv_type) {
    case MV_TYPE_16X16:
        mpeg_motion(s, dest_y, dest_cb, dest_cr, 0,
                    ref_picture, 0,
                    0, pix_op,
                    s->mv[dir][0][0], s->mv[dir][0][1], 16);
        break;
    case MV_TYPE_8X8:
        for(i=0;i<4;i++) {
            motion_x = s->mv[dir][i][0];
            motion_y = s->mv[dir][i][1];

            dxy = ((motion_y & 1) << 1) | (motion_x & 1);
            src_x = mb_x * 16 + (motion_x >> 1) + (i & 1) * 8;
            src_y = mb_y * 16 + (motion_y >> 1) + ((i >> 1) & 1) * 8;
                    
            /* WARNING: do no forget half pels */
            src_x = clip(src_x, -16, s->width);
            if (src_x == s->width)
                dxy &= ~1;
            src_y = clip(src_y, -16, s->height);
            if (src_y == s->height)
                dxy &= ~2;
                    
            ptr = ref_picture[0] + (src_y * s->linesize) + (src_x);
            dest = dest_y + ((i & 1) * 8) + (i >> 1) * 8 * s->linesize;
            pix_op[dxy](dest, ptr, s->linesize, 8);
        }
        /* In case of 8X8, we construct a single chroma motion vector
           with a special rounding */
        mx = 0;
        my = 0;
        for(i=0;i<4;i++) {
            mx += s->mv[dir][i][0];
            my += s->mv[dir][i][1];
        }
        if (mx >= 0)
            mx = (h263_chroma_roundtab[mx & 0xf] + ((mx >> 3) & ~1));
        else {
            mx = -mx;
            mx = -(h263_chroma_roundtab[mx & 0xf] + ((mx >> 3) & ~1));
        }
        if (my >= 0)
            my = (h263_chroma_roundtab[my & 0xf] + ((my >> 3) & ~1));
        else {
            my = -my;
            my = -(h263_chroma_roundtab[my & 0xf] + ((my >> 3) & ~1));
        }
        dxy = ((my & 1) << 1) | (mx & 1);
        mx >>= 1;
        my >>= 1;

        src_x = mb_x * 8 + mx;
        src_y = mb_y * 8 + my;
        src_x = clip(src_x, -8, s->width/2);
        if (src_x == s->width/2)
            dxy &= ~1;
        src_y = clip(src_y, -8, s->height/2);
        if (src_y == s->height/2)
            dxy &= ~2;
        
        offset = (src_y * (s->linesize >> 1)) + src_x;
        ptr = ref_picture[1] + offset;
        pix_op[dxy](dest_cb, ptr, s->linesize >> 1, 8);
        ptr = ref_picture[2] + offset;
        pix_op[dxy](dest_cr, ptr, s->linesize >> 1, 8);
        break;
    case MV_TYPE_FIELD:
        if (s->picture_structure == PICT_FRAME) {
            /* top field */
            mpeg_motion(s, dest_y, dest_cb, dest_cr, 0,
                        ref_picture, s->field_select[dir][0] ? s->linesize : 0,
                        1, pix_op,
                        s->mv[dir][0][0], s->mv[dir][0][1], 8);
            /* bottom field */
            mpeg_motion(s, dest_y, dest_cb, dest_cr, s->linesize,
                        ref_picture, s->field_select[dir][1] ? s->linesize : 0,
                        1, pix_op,
                        s->mv[dir][1][0], s->mv[dir][1][1], 8);
        } else {
            

        }
        break;
    }
}


static void  put_dct(MpegEncContext *s, 
                           DCTELEM *block, int i, UINT8 *dest, int line_size)
{
    dct_unquantize(s, block, i, s->qscale);
	idct_special (block, dest, line_size, 0);
}

/* add block[] to dest[] */
static void  add_dct(MpegEncContext *s, 
                           DCTELEM *block, int i, UINT8 *dest, int line_size)
{
    if (s->block_last_index[i] >= 0) {
		dct_unquantize(s, block, i, s->qscale);
		idct_special (block, dest, line_size, 1);
    }
}

/* generic function called after a macroblock has been parsed by the
   decoder or after it has been encoded by the encoder.

   Important variables used:
   s->mb_intra : true if intra macroblock
   s->mv_dir   : motion vector direction
   s->mv_type  : motion vector type
   s->mv       : motion vector
   s->interlaced_dct : true if interlaced dct used (mpeg2)
 */
void MPV_decode_mb(MpegEncContext *s, DCTELEM block[6][64])
{
    int mb_x, mb_y, motion_x, motion_y;
    int dct_linesize, dct_offset;
    op_pixels_func *op_pix;

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

    /* update DC predictors for P macroblocks */
    if (!s->mb_intra) {
        if (s->h263_pred) {
            int wrap, x, y, v;
            wrap = 2 * s->mb_width + 2;
            v = 1024;
            x = 2 * mb_x + 1;
            y = 2 * mb_y + 1;
            s->dc_val[0][(x) + (y) * wrap] = v;
            s->dc_val[0][(x + 1) + (y) * wrap] = v;
            s->dc_val[0][(x) + (y + 1) * wrap] = v;
            s->dc_val[0][(x + 1) + (y + 1) * wrap] = v;
            /* ac pred */
            memset(s->ac_val[0][(x) + (y) * wrap], 0, 16 * sizeof(INT16));
            memset(s->ac_val[0][(x + 1) + (y) * wrap], 0, 16 * sizeof(INT16));
            memset(s->ac_val[0][(x) + (y + 1) * wrap], 0, 16 * sizeof(INT16));
            memset(s->ac_val[0][(x + 1) + (y + 1) * wrap], 0, 16 * sizeof(INT16));
            if (s->h263_msmpeg4) {
                s->coded_block[(x) + (y) * wrap] = 0;
                s->coded_block[(x + 1) + (y) * wrap] = 0;
                s->coded_block[(x) + (y + 1) * wrap] = 0;
                s->coded_block[(x + 1) + (y + 1) * wrap] = 0;
            }
            /* chroma */
            wrap = s->mb_width + 2;
            x = mb_x + 1;
            y = mb_y + 1;
            s->dc_val[1][(x) + (y) * wrap] = v;
            s->dc_val[2][(x) + (y) * wrap] = v;
            /* ac pred */
            memset(s->ac_val[1][(x) + (y) * wrap], 0, 16 * sizeof(INT16));
            memset(s->ac_val[2][(x) + (y) * wrap], 0, 16 * sizeof(INT16));
        } else {
            s->last_dc[0] = 128 << s->intra_dc_precision;
            s->last_dc[1] = 128 << s->intra_dc_precision;
            s->last_dc[2] = 128 << s->intra_dc_precision;
        }
    }
    
    /* 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;
        if (s->mb_intra) {
            motion_x = 0;
            motion_y = 0;
            goto motion_init;
        } else if (s->mv_type == MV_TYPE_16X16) {
            motion_x = s->mv[0][0][0];
            motion_y = s->mv[0][0][1];
        motion_init:
            /* no update if 8X8 because it has been done during parsing */
            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;
        }
    }
    
    if (!s->intra_only) {
        UINT8 *dest_y, *dest_cb, *dest_cr;

        dest_y = s->current_picture[0] + (mb_y * 16 * s->linesize) + mb_x * 16;
        dest_cb = s->current_picture[1] + (mb_y * 8 * (s->linesize >> 1)) + mb_x * 8;
        dest_cr = s->current_picture[2] + (mb_y * 8 * (s->linesize >> 1)) + mb_x * 8;

        if (s->interlaced_dct) {
            dct_linesize = s->linesize * 2;
            dct_offset = s->linesize;
        } else {
            dct_linesize = s->linesize;
            dct_offset = s->linesize * 8;
        }

        if (!s->mb_intra) {
            /* motion handling */
            if (!s->no_rounding) 
                op_pix = put_pixels_tab;
            else
                op_pix = put_no_rnd_pixels_tab;

            if (s->mv_dir & MV_DIR_FORWARD) {
                MPV_motion(s, dest_y, dest_cb, dest_cr, 0, s->last_picture, op_pix);
                if (!s->no_rounding) 
                    op_pix = avg_pixels_tab;
                else
                    op_pix = avg_no_rnd_pixels_tab;
            }
            if (s->mv_dir & MV_DIR_BACKWARD) {
                MPV_motion(s, dest_y, dest_cb, dest_cr, 1, s->next_picture, op_pix);
            }

            /* add dct residue */
            add_dct(s, block[0], 0, dest_y, dct_linesize);
            add_dct(s, block[1], 1, dest_y + 8, dct_linesize);
            add_dct(s, block[2], 2, dest_y + dct_offset, dct_linesize);
            add_dct(s, block[3], 3, dest_y + dct_offset + 8, dct_linesize);

            add_dct(s, block[4], 4, dest_cb, dct_linesize >> 1);
            add_dct(s, block[5], 5, dest_cr, dct_linesize >> 1);
        } else {
            /* dct only in intra block */
            put_dct(s, block[0], 0, dest_y, dct_linesize);
            put_dct(s, block[1], 1, dest_y + 8, dct_linesize);
            put_dct(s, block[2], 2, dest_y + dct_offset, dct_linesize);
            put_dct(s, block[3], 3, dest_y + dct_offset + 8, dct_linesize);

            put_dct(s, block[4], 4, dest_cb, dct_linesize >> 1);
            put_dct(s, block[5], 5, dest_cr, dct_linesize >> 1);
        }
    }
}



static void dct_unquantize(MpegEncContext *s, 
                           DCTELEM *block, int n, int qscale)
{
    int i, level;
    const UINT16 *quant_matrix;

    if (s->mb_intra) {
        if (n < 4) 
            block[0] = block[0] * s->y_dc_scale;
        else
            block[0] = block[0] * s->c_dc_scale;
        if (s->out_format == FMT_H263) {
            i = 1;
            goto unquant_even;
        }
        /* XXX: only mpeg1 */
        quant_matrix = s->intra_matrix;
        for(i=1;i<64;i++) {
            level = block[i];
            if (level) {
                if (level < 0) {
                    level = -level;
                    level = (int)(level * qscale * quant_matrix[i]) >> 3;
                    level = (level - 1) | 1;
                    level = -level;
                } else {
                    level = (int)(level * qscale * quant_matrix[i]) >> 3;
                    level = (level - 1) | 1;
                }
                block[i] = level;
            }
        }
    } else {
        i = 0;
    unquant_even:
        quant_matrix = s->non_intra_matrix;
        for(;i<64;i++) {
            level = block[i];
            if (level) {
                if (level < 0) {
                    level = -level;
                    level = (((level << 1) + 1) * qscale *
                             ((int) (quant_matrix[i]))) >> 4;
                    level = (level - 1) | 1;
                    level = -level;
                } else {
                    level = (((level << 1) + 1) * qscale *
                             ((int) (quant_matrix[i]))) >> 4;
                    level = (level - 1) | 1;
                }
                block[i] = level;
            }
        }
    }
}
                         

/* rate control */

/* an I frame is I_FRAME_SIZE_RATIO bigger than a P frame */
#define I_FRAME_SIZE_RATIO 3.0
#define QSCALE_K           20

static void rate_control_init(MpegEncContext *s)
{
    s->wanted_bits = 0;

    if (s->intra_only) {
        s->I_frame_bits = ((INT64)s->bit_rate * FRAME_RATE_BASE) / s->frame_rate;
        s->P_frame_bits = s->I_frame_bits;
    } else {
        s->P_frame_bits = (int) ((float)(s->gop_size * s->bit_rate) / 
                                 (float)((float)s->frame_rate / FRAME_RATE_BASE * (I_FRAME_SIZE_RATIO + s->gop_size - 1)));
        s->I_frame_bits = (int)(s->P_frame_bits * I_FRAME_SIZE_RATIO);
    }
    
}


/*
 * This heuristic is rather poor, but at least we do not have to
 * change the qscale at every macroblock.
 */
static int rate_estimate_qscale(MpegEncContext *s)
{
    long total_bits = s->total_bits;
    float q;
    int qscale, diff, qmin;

    if (s->pict_type == I_TYPE) {
        s->wanted_bits += s->I_frame_bits;
    } else {
        s->wanted_bits += s->P_frame_bits;
    }
    diff = s->wanted_bits - total_bits;
    q = 31.0 - (float)diff / (QSCALE_K * s->mb_height * s->mb_width);
    /* adjust for I frame */
    if (s->pict_type == I_TYPE && !s->intra_only) {
        q /= I_FRAME_SIZE_RATIO;
    }

    /* using a too small Q scale leeds to problems in mpeg1 and h263
       because AC coefficients are clamped to 255 or 127 */
    qmin = 3;
    if (q < qmin)
        q = qmin;
    else if (q > 31)
        q = 31;
    qscale = (int)(q + 0.5);
    return qscale;
}