snow.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

    for(level=decomposition_count-1; level>=0; level--){
        while(cs[level].y <= FFMIN((y>>level)+support, height>>level)){
            switch(type){
            case DWT_97: spatial_compose97i_dy(cs+level, buffer, width>>level, height>>level, stride<<level);
                    break;
            case DWT_53: spatial_compose53i_dy(cs+level, buffer, width>>level, height>>level, stride<<level);
                    break;
            }
        }
    }
}

static void ff_spatial_idwt_buffered_slice(DSPContext *dsp, dwt_compose_t *cs, slice_buffer * slice_buf, int width, int height, int stride_line, int type, int decomposition_count, int y){
    const int support = type==1 ? 3 : 5;
    int level;
    if(type==2) return;

    for(level=decomposition_count-1; level>=0; level--){
        while(cs[level].y <= FFMIN((y>>level)+support, height>>level)){
            switch(type){
            case DWT_97: spatial_compose97i_dy_buffered(dsp, cs+level, slice_buf, width>>level, height>>level, stride_line<<level);
                    break;
            case DWT_53: spatial_compose53i_dy_buffered(cs+level, slice_buf, width>>level, height>>level, stride_line<<level);
                    break;
            }
        }
    }
}

static void ff_spatial_idwt(IDWTELEM *buffer, int width, int height, int stride, int type, int decomposition_count){
        dwt_compose_t cs[MAX_DECOMPOSITIONS];
        int y;
        ff_spatial_idwt_init(cs, buffer, width, height, stride, type, decomposition_count);
        for(y=0; y<height; y+=4)
            ff_spatial_idwt_slice(cs, buffer, width, height, stride, type, decomposition_count, y);
}

static int encode_subband_c0run(SnowContext *s, SubBand *b, IDWTELEM *src, IDWTELEM *parent, int stride, int orientation){
    const int w= b->width;
    const int h= b->height;
    int x, y;

    if(1){
        int run=0;
        int runs[w*h];
        int run_index=0;
        int max_index;

        for(y=0; y<h; y++){
            for(x=0; x<w; x++){
                int v, p=0;
                int /*ll=0, */l=0, lt=0, t=0, rt=0;
                v= src[x + y*stride];

                if(y){
                    t= src[x + (y-1)*stride];
                    if(x){
                        lt= src[x - 1 + (y-1)*stride];
                    }
                    if(x + 1 < w){
                        rt= src[x + 1 + (y-1)*stride];
                    }
                }
                if(x){
                    l= src[x - 1 + y*stride];
                    /*if(x > 1){
                        if(orientation==1) ll= src[y + (x-2)*stride];
                        else               ll= src[x - 2 + y*stride];
                    }*/
                }
                if(parent){
                    int px= x>>1;
                    int py= y>>1;
                    if(px<b->parent->width && py<b->parent->height)
                        p= parent[px + py*2*stride];
                }
                if(!(/*ll|*/l|lt|t|rt|p)){
                    if(v){
                        runs[run_index++]= run;
                        run=0;
                    }else{
                        run++;
                    }
                }
            }
        }
        max_index= run_index;
        runs[run_index++]= run;
        run_index=0;
        run= runs[run_index++];

        put_symbol2(&s->c, b->state[30], max_index, 0);
        if(run_index <= max_index)
            put_symbol2(&s->c, b->state[1], run, 3);

        for(y=0; y<h; y++){
            if(s->c.bytestream_end - s->c.bytestream < w*40){
                av_log(s->avctx, AV_LOG_ERROR, "encoded frame too large\n");
                return -1;
            }
            for(x=0; x<w; x++){
                int v, p=0;
                int /*ll=0, */l=0, lt=0, t=0, rt=0;
                v= src[x + y*stride];

                if(y){
                    t= src[x + (y-1)*stride];
                    if(x){
                        lt= src[x - 1 + (y-1)*stride];
                    }
                    if(x + 1 < w){
                        rt= src[x + 1 + (y-1)*stride];
                    }
                }
                if(x){
                    l= src[x - 1 + y*stride];
                    /*if(x > 1){
                        if(orientation==1) ll= src[y + (x-2)*stride];
                        else               ll= src[x - 2 + y*stride];
                    }*/
                }
                if(parent){
                    int px= x>>1;
                    int py= y>>1;
                    if(px<b->parent->width && py<b->parent->height)
                        p= parent[px + py*2*stride];
                }
                if(/*ll|*/l|lt|t|rt|p){
                    int context= av_log2(/*FFABS(ll) + */3*FFABS(l) + FFABS(lt) + 2*FFABS(t) + FFABS(rt) + FFABS(p));

                    put_rac(&s->c, &b->state[0][context], !!v);
                }else{
                    if(!run){
                        run= runs[run_index++];

                        if(run_index <= max_index)
                            put_symbol2(&s->c, b->state[1], run, 3);
                        assert(v);
                    }else{
                        run--;
                        assert(!v);
                    }
                }
                if(v){
                    int context= av_log2(/*FFABS(ll) + */3*FFABS(l) + FFABS(lt) + 2*FFABS(t) + FFABS(rt) + FFABS(p));
                    int l2= 2*FFABS(l) + (l<0);
                    int t2= 2*FFABS(t) + (t<0);

                    put_symbol2(&s->c, b->state[context + 2], FFABS(v)-1, context-4);
                    put_rac(&s->c, &b->state[0][16 + 1 + 3 + quant3bA[l2&0xFF] + 3*quant3bA[t2&0xFF]], v<0);
                }
            }
        }
    }
    return 0;
}

static int encode_subband(SnowContext *s, SubBand *b, IDWTELEM *src, IDWTELEM *parent, int stride, int orientation){
//    encode_subband_qtree(s, b, src, parent, stride, orientation);
//    encode_subband_z0run(s, b, src, parent, stride, orientation);
    return encode_subband_c0run(s, b, src, parent, stride, orientation);
//    encode_subband_dzr(s, b, src, parent, stride, orientation);
}

static inline void unpack_coeffs(SnowContext *s, SubBand *b, SubBand * parent, int orientation){
    const int w= b->width;
    const int h= b->height;
    int x,y;

    if(1){
        int run, runs;
        x_and_coeff *xc= b->x_coeff;
        x_and_coeff *prev_xc= NULL;
        x_and_coeff *prev2_xc= xc;
        x_and_coeff *parent_xc= parent ? parent->x_coeff : NULL;
        x_and_coeff *prev_parent_xc= parent_xc;

        runs= get_symbol2(&s->c, b->state[30], 0);
        if(runs-- > 0) run= get_symbol2(&s->c, b->state[1], 3);
        else           run= INT_MAX;

        for(y=0; y<h; y++){
            int v=0;
            int lt=0, t=0, rt=0;

            if(y && prev_xc->x == 0){
                rt= prev_xc->coeff;
            }
            for(x=0; x<w; x++){
                int p=0;
                const int l= v;

                lt= t; t= rt;

                if(y){
                    if(prev_xc->x <= x)
                        prev_xc++;
                    if(prev_xc->x == x + 1)
                        rt= prev_xc->coeff;
                    else
                        rt=0;
                }
                if(parent_xc){
                    if(x>>1 > parent_xc->x){
                        parent_xc++;
                    }
                    if(x>>1 == parent_xc->x){
                        p= parent_xc->coeff;
                    }
                }
                if(/*ll|*/l|lt|t|rt|p){
                    int context= av_log2(/*FFABS(ll) + */3*(l>>1) + (lt>>1) + (t&~1) + (rt>>1) + (p>>1));

                    v=get_rac(&s->c, &b->state[0][context]);
                    if(v){
                        v= 2*(get_symbol2(&s->c, b->state[context + 2], context-4) + 1);
                        v+=get_rac(&s->c, &b->state[0][16 + 1 + 3 + quant3bA[l&0xFF] + 3*quant3bA[t&0xFF]]);

                        xc->x=x;
                        (xc++)->coeff= v;
                    }
                }else{
                    if(!run){
                        if(runs-- > 0) run= get_symbol2(&s->c, b->state[1], 3);
                        else           run= INT_MAX;
                        v= 2*(get_symbol2(&s->c, b->state[0 + 2], 0-4) + 1);
                        v+=get_rac(&s->c, &b->state[0][16 + 1 + 3]);

                        xc->x=x;
                        (xc++)->coeff= v;
                    }else{
                        int max_run;
                        run--;
                        v=0;

                        if(y) max_run= FFMIN(run, prev_xc->x - x - 2);
                        else  max_run= FFMIN(run, w-x-1);
                        if(parent_xc)
                            max_run= FFMIN(max_run, 2*parent_xc->x - x - 1);
                        x+= max_run;
                        run-= max_run;
                    }
                }
            }
            (xc++)->x= w+1; //end marker
            prev_xc= prev2_xc;
            prev2_xc= xc;

            if(parent_xc){
                if(y&1){
                    while(parent_xc->x != parent->width+1)
                        parent_xc++;
                    parent_xc++;
                    prev_parent_xc= parent_xc;
                }else{
                    parent_xc= prev_parent_xc;
                }
            }
        }

        (xc++)->x= w+1; //end marker
    }
}

static inline void decode_subband_slice_buffered(SnowContext *s, SubBand *b, slice_buffer * sb, int start_y, int h, int save_state[1]){
    const int w= b->width;
    int y;
    const int qlog= av_clip(s->qlog + b->qlog, 0, QROOT*16);
    int qmul= qexp[qlog&(QROOT-1)]<<(qlog>>QSHIFT);
    int qadd= (s->qbias*qmul)>>QBIAS_SHIFT;
    int new_index = 0;

    START_TIMER

    if(b->ibuf == s->spatial_idwt_buffer || s->qlog == LOSSLESS_QLOG){
        qadd= 0;
        qmul= 1<<QEXPSHIFT;
    }

    /* If we are on the second or later slice, restore our index. */
    if (start_y != 0)
        new_index = save_state[0];


    for(y=start_y; y<h; y++){
        int x = 0;
        int v;
        IDWTELEM * line = slice_buffer_get_line(sb, y * b->stride_line + b->buf_y_offset) + b->buf_x_offset;
        memset(line, 0, b->width*sizeof(IDWTELEM));
        v = b->x_coeff[new_index].coeff;
        x = b->x_coeff[new_index++].x;
        while(x < w)
        {
            register int t= ( (v>>1)*qmul + qadd)>>QEXPSHIFT;
            register int u= -(v&1);
            line[x] = (t^u) - u;

            v = b->x_coeff[new_index].coeff;
            x = b->x_coeff[new_index++].x;
        }
    }
    if(w > 200 && start_y != 0/*level+1 == s->spatial_decomposition_count*/){
        STOP_TIMER("decode_subband")
    }

    /* Save our variables for the next slice. */
    save_state[0] = new_index;

    return;
}

static void reset_contexts(SnowContext *s){ //FIXME better initial contexts
    int plane_index, level, orientation;

    for(plane_index=0; plane_index<3; plane_index++){
        for(level=0; level<MAX_DECOMPOSITIONS; level++){
            for(orientation=level ? 1:0; orientation<4; orientation++){
                memset(s->plane[plane_index].band[level][orientation].state, MID_STATE, sizeof(s->plane[plane_index].band[level][orientation].state));
            }
        }
    }
    memset(s->header_state, MID_STATE, sizeof(s->header_state));
    memset(s->block_state, MID_STATE, sizeof(s->block_state));
}

static int alloc_blocks(SnowContext *s){
    int w= -((-s->avctx->width )>>LOG2_MB_SIZE);
    int h= -((-s->avctx->height)>>LOG2_MB_SIZE);

    s->b_width = w;
    s->b_height= h;

    s->block= av_mallocz(w * h * sizeof(BlockNode) << (s->b