byte array to short array and back again in java

Question

I'm having some issues taking audio data stored in a byte array, converting it to a big-endian short array, encoding it, then changing it back into a byte array. Here is what I have. The original audio data is stored in audioBytes2. I am using the same format for decode with a minus on the cos function instead. Unfortunately, changing the byte and short data types is non-negotiable.

    short[] audioData = null;
    int nlengthInSamples = audioBytes2.length / 2;
    audioData = new short[nlengthInSamples];

    for (int i = 0; i < nlengthInSamples; i++) {
       short MSB = (short) audioBytes2[2*i+1];
       short LSB = (short) audioBytes2[2*i];
       audioData[i] = (short) (MSB << 8 | (255 & LSB));
    }

    int i = 0;
    while (i < audioData.length) {
        audioData[i] = (short)(audioData[i] + (short)5*Math.cos(2*Math.PI*i/(((Number)EncodeBox.getValue()).intValue())));
        i++;
    }

    short x = 0;
    i = 0;
    while (i < audioData.length) {
        x = audioData[i];
        audioBytes2[2*i+1] = (byte)(x >>> 0);
        audioBytes2[2*i] = (byte)(x >>> 8);
        i++;
    }

I have done everything that I can think of to make this work, but the closest I've come is getting it to work every other encode/decode and I have no idea why. Thanks for any help.

is it big-endian or little-endian? I think you need java.nio.ByteBuffer to handle this conversion. — LiuYan 刘研
– LiuYan 刘研, Commented Apr 11, 2011 at 18:29
Possible duplicate of how to convert short array to byte array — patryk.beza
– patryk.beza, Commented May 11, 2016 at 23:05

Peter Lawrey · Accepted Answer · 2011-04-11 20:22:51Z

105

I also suggest you try ByteBuffer.

byte[] bytes = {};
short[] shorts = new short[bytes.length/2];
// to turn bytes to shorts as either big endian or little endian. 
ByteBuffer.wrap(bytes).order(ByteOrder.LITTLE_ENDIAN).asShortBuffer().get(shorts);

// to turn shorts back to bytes.
byte[] bytes2 = new byte[shortsA.length * 2];
ByteBuffer.wrap(bytes2).order(ByteOrder.LITTLE_ENDIAN).asShortBuffer().put(shortsA);

edited Apr 11, 2011 at 20:22

answered Apr 11, 2011 at 18:49

Peter Lawrey

535k83 gold badges770 silver badges1.2k bronze badges

Sign up to request clarification or add additional context in comments.

10 Comments

Aaron Over a year ago

short[] audioData = ByteBuffer.wrap(audioBytes2).order(ByteOrder.BIG_ENDIAN).asShortBuffer().array(); Throws an UnsupportedOperationException.

kdgregory Over a year ago

@Aaron - yes, but what throws that exception? (hint: a ShortBuffer acts as a view on an underlying ByteBuffer, and its get() method should do exactly what you want).

Peter Lawrey Over a year ago

@kdgregory, It wasn't until you suggested the fix. I forgot array() only works if the underlying store is an short[] or similar primitive array to match the XxxxxBuffer.

Aaron Over a year ago

Is this only converting the bytes directly to shorts or is it combining two bytes into a short like I need it to?

Peter Lawrey Over a year ago

As you can see it create half as many shorts as bytes and twice as many bytes are shorts. If it didn't do the conversion you needed the ByteOrder would be pointless. as just casting byte to short and back again doesn't require a ByteOrder. If you have doubts, I suggest you try it and see if it suits your needed.

|

Scott Izu · Accepted Answer · 2013-08-08 06:30:04Z

13

public short bytesToShort(byte[] bytes) {
     return ByteBuffer.wrap(bytes).order(ByteOrder.LITTLE_ENDIAN).getShort();
}
public byte[] shortToBytes(short value) {
    return ByteBuffer.allocate(2).order(ByteOrder.LITTLE_ENDIAN).putShort(value).array();
}

answered Aug 8, 2013 at 6:30

Scott Izu

2,31925 silver badges14 bronze badges

1 Comment

Nikolay Shmyrev Over a year ago

It does not convert short array to byte array.

Edwin Dalorzo · Accepted Answer · 2011-04-11 18:48:11Z

6

How about some ByteBuffers?

byte[] payload = new byte[]{0x7F,0x1B,0x10,0x11};
ByteBuffer bb = ByteBuffer.wrap(payload).order(ByteOrder.BIG_ENDIAN);
ShortBuffer sb = bb.asShortBuffer();
while(sb.hasRemaining()){
  System.out.println(sb.get());
}

answered Apr 11, 2011 at 18:48

Edwin Dalorzo

78.9k25 gold badges151 silver badges211 bronze badges

Comments

Radiodef · Accepted Answer · 2018-06-22 03:36:02Z

6

byte[2] bytes;

int r = bytes[1] & 0xFF;
r = (r << 8) | (bytes[0] & 0xFF);

short s = (short)r;

edited Jun 22, 2018 at 3:36

Radiodef

38k14 gold badges95 silver badges127 bronze badges

answered Jun 27, 2015 at 10:59

Jagadeesh

2495 silver badges9 bronze badges

Comments

Matt DiMeo · Accepted Answer · 2011-04-11 18:30:05Z

2

Your code is doing little-endian shorts, not big. You've the indexing for MSB and LSB swapped.

Since you are using big-endian shorts, you could be using a DataInputStream wrapped around a ByteArrayInputStream (and DataOutputStream/ByteArrayOutputStream) on the other end, rather than doing your own decoding.

If you're getting every other decode working, I'd guess you've got an odd number of bytes, or an off-by-one error elsewhere which is causing your mistake to get fixed on every other pass.

Finally, I'd step through the array with i+=2 and use MSB= arr[i] and LSB=arr[i+1] rather than multiplying by 2, but that's just me.

answered Apr 11, 2011 at 18:30

Matt DiMeo

1,1869 silver badges12 bronze badges

1 Comment

Aaron Over a year ago

I'm actually using something similar to that after the reconversion with an audioInputStream.

user900699 · Accepted Answer · 2025-06-08 07:59:43Z

0

If you are using the Guava Lib, it supports methods such as Shorts.fromBytes(), and for integers Ints.fromBytes() that does this kind of operation for you.

answered Jun 8 at 7:59

user900699

Comments

jtahlborn · Accepted Answer · 2011-04-11 18:34:23Z

-1

It looks like you are swapping the byte order between reading the bytes in and writing them back out (unsure if this is intentional or not).

answered Apr 11, 2011 at 18:34

jtahlborn

53.8k5 gold badges80 silver badges122 bronze badges

Collectives™ on Stack Overflow

byte array to short array and back again in java

7 Answers 7

10 Comments

1 Comment

Comments

Comments

1 Comment

Comments

Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

7 Answers 7

10 Comments

1 Comment

Comments

Comments

1 Comment

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related