static int decode_i2_frame(FourXContext *f, const uint8_t *buf, int length){
    int x, y, x2, y2;
    const int width= f->avctx->width;
    const int height= f->avctx->height;
    uint16_t *dst= (uint16_t*)f->current_picture.data[0];
    const int stride= f->current_picture.linesize[0]>>1;

    for(y=0; y<height; y+=16){
        for(x=0; x<width; x+=16){
            unsigned int color[4], bits;
            memset(color, 0, sizeof(color));
//warning following is purely guessed ...
            color[0]= bytestream_get_le16(&buf);
            color[1]= bytestream_get_le16(&buf);

            if(color[0]&0x8000) av_log(NULL, AV_LOG_ERROR, "unk bit 1\n");
            if(color[1]&0x8000) av_log(NULL, AV_LOG_ERROR, "unk bit 2\n");

            color[2]= mix(color[0], color[1]);
            color[3]= mix(color[1], color[0]);

            bits= bytestream_get_le32(&buf);
            for(y2=0; y2<16; y2++){
                for(x2=0; x2<16; x2++){
                    int index= 2*(x2>>2) + 8*(y2>>2);
                    dst[y2*stride+x2]= color[(bits>>index)&3];
                }
            }
            dst+=16;
        }
        dst += 16 * stride - x;
    }

    return 0;
}