src/main/java/org/jcodec/codecs/h264/H264Utils.java
public static ByteBuffer joinNALUnits(List<ByteBuffer> nalUnits) {
        int size = 0;
        for (ByteBuffer nal : nalUnits) {
            size += 4 + nal.remaining();
        }
        ByteBuffer allocate = ByteBuffer.allocate(size);
        joinNALUnitsToBuffer(nalUnits, allocate);
        return allocate;
    }
public static ByteBuffer joinNALUnits(List<ByteBuffer> nalUnits) {
        int size = 0;
        for (ByteBuffer nal : nalUnits) {
            size += 4 + nal.remaining();
        }
        ByteBuffer allocate = ByteBuffer.allocate(size);
        joinNALUnitsToBuffer(nalUnits, allocate);
        return allocate;
    }
Joins buffers containing individual NAL units into a single AnnexB
delimited buffer. Each NAL unit will be separated with 00 00 00 01
markers. Allocates a new byte buffer and writes data into it.

@param nalUnits
@param out