for (p = 0; p < numPlanes; p++) {
    uint8_t *buf = frame->data[p];
    uint8_t *src = somesrcbuffer[p];

    for (i = 0; i < height; i++) {
        memcpy(buf, src, width);
        buf += frame->linesize[p];
        src += mystrides[p];
    }
}