static av_always_inline int check_block(SnowContext *s, int mb_x, int mb_y, int p[3], int intra, const uint8_t *obmc_edged, int *best_rd){
    const int b_stride= s->b_width << s->block_max_depth;
    BlockNode *block= &s->block[mb_x + mb_y * b_stride];
    BlockNode backup= *block;
    unsigned value;
    int rd, index;

    assert(mb_x>=0 && mb_y>=0);
    assert(mb_x<b_stride);

    if(intra){
        block->color[0] = p[0];
        block->color[1] = p[1];
        block->color[2] = p[2];
        block->type |= BLOCK_INTRA;
    }else{
        index= (p[0] + 31*p[1]) & (ME_CACHE_SIZE-1);
        value= s->me_cache_generation + (p[0]>>10) + (p[1]<<6) + (block->ref<<12);
        if(s->me_cache[index] == value)
            return 0;
        s->me_cache[index]= value;

        block->mx= p[0];
        block->my= p[1];
        block->type &= ~BLOCK_INTRA;
    }

    rd= get_block_rd(s, mb_x, mb_y, 0, obmc_edged);

//FIXME chroma
    if(rd < *best_rd){
        *best_rd= rd;
        return 1;
    }else{
        *block= backup;
        return 0;
    }
}