static void to_meta_with_crop(AVCodecContext *avctx, AVFrame *p, int *dest)
{
    int blockx, blocky, x, y;
    int luma = 0;
    int height = FFMIN(avctx->height, C64YRES);
    int width  = FFMIN(avctx->width , C64XRES);
    uint8_t *src = p->data[0];

    for (blocky = 0; blocky < C64YRES; blocky += 8) {
        for (blockx = 0; blockx < C64XRES; blockx += 8) {
            for (y = blocky; y < blocky + 8 && y < C64YRES; y++) {
                for (x = blockx; x < blockx + 8 && x < C64XRES; x += 2) {
                    if(x < width && y < height) {
                        /* build average over 2 pixels */
                        luma = (src[(x + 0 + y * p->linesize[0])] +
                                src[(x + 1 + y * p->linesize[0])]) / 2;
                        /* write blocks as linear data now so they are suitable for elbg */
                        dest[0] = luma;
                    }
                    dest++;
                }
            }
        }
    }
}