Function decode_13

libavcodec/dxa.c:50–189

static const int shift2[6] = { 0, 0, 8, 4, 0, 4 };

static int decode_13(AVCodecContext *avctx, DxaDecContext *c, uint8_t* dst, uint8_t *src, uint8_t *ref)
{
    uint8_t *code, *data, *mv, *msk, *tmp, *tmp2;
    int i, j, k;
    int type, x, y, d, d2;
    int stride = c->pic.linesize[0];
    uint32_t mask;

    code = src  + 12;
    data = code + ((avctx->width * avctx->height) >> 4);
    mv   = data + AV_RB32(src + 0);
    msk  = mv   + AV_RB32(src + 4);

    for(j = 0; j < avctx->height; j += 4){
        for(i = 0; i < avctx->width; i += 4){
            tmp  = dst + i;
            tmp2 = ref + i;
            type = *code++;
            switch(type){
            case 4: // motion compensation
                x = (*mv) >> 4;    if(x & 8) x = 8 - x;
                y = (*mv++) & 0xF; if(y & 8) y = 8 - y;
                tmp2 += x + y*stride;
            case 0: // skip
            case 5: // skip in method 12
                for(y = 0; y < 4; y++){
                    memcpy(tmp, tmp2, 4);
                    tmp  += stride;
                    tmp2 += stride;
                }
                break;
            case 1:  // masked change
            case 10: // masked change with only half of pixels changed
            case 11: // cases 10-15 are for method 12 only
            case 12:
            case 13:
            case 14:
            case 15:
                if(type == 1){
                    mask = AV_RB16(msk);
                    msk += 2;
                }else{
                    type -= 10;
                    mask = ((msk[0] & 0xF0) << shift1[type]) | ((msk[0] & 0xF) << shift2[type]);
                    msk++;
                }
                for(y = 0; y < 4; y++){
                    for(x = 0; x < 4; x++){
                        tmp[x] = (mask & 0x8000) ? *data++ : tmp2[x];
                        mask <<= 1;
                    }
                    tmp  += stride;
                    tmp2 += stride;
                }
                break;
            case 2: // fill block
                for(y = 0; y < 4; y++){
                    memset(tmp, data[0], 4);