src/main/java/org/jcodec/codecs/h264/decode/BlockInterpolator.java
private static void getChroma00(byte[] pic, int picW, int picH, byte[] blk, int blkOff, int blkStride, int x, int y,
            int blkW, int blkH) {
        int off = y * picW + x;
        for (int j = 0; j < blkH; j++) {
            arraycopy(pic, off, blk, blkOff, blkW);
            off += picW;
            blkOff += blkStride;
        }
    }
private static void getChroma00(byte[] pic, int picW, int picH, byte[] blk, int blkOff, int blkStride, int x, int y,
            int blkW, int blkH) {
        int off = y * picW + x;
        for (int j = 0; j < blkH; j++) {
            arraycopy(pic, off, blk, blkOff, blkW);
            off += picW;
            blkOff += blkStride;
        }
    }
Chroma (0,0)