src/main/java/org/jcodec/codecs/h264/H264Utils.java
public static void joinNALUnitsToBuffer(List<ByteBuffer> nalUnits, ByteBuffer out) {
        for (ByteBuffer nal : nalUnits) {
            out.putInt(1);
            out.put(nal.duplicate());
        }
    }
public static void joinNALUnitsToBuffer(List<ByteBuffer> nalUnits, ByteBuffer out) {
        for (ByteBuffer nal : nalUnits) {
            out.putInt(1);
            out.put(nal.duplicate());
        }
    }
Joins buffers containing individual NAL units into a single AnnexB
delimited buffer. Each NAL unit will be separated with 00 00 00 01
markers.

@param nalUnits
@param out