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Mix byte array android

I would like to mix audio byte array, but I didn't succeed to sum the array.(note i already added some silent bytes of 0 as padding before).
I have an ArrayList of byte[] which contains:
the first byte[] is header (44 bytes).
Following byte[] are raw data byte array to be mixed
Here is my code:
ArrayList<byte[]> ListAudio = new ArrayList<byte[]>();
byte[] header= WriteHeader(); //wav header 44 bytes
ListAudio.add(header);
for (byte[] b : audioTreatment.ListDataByte) {
ListAudio.add(b);
}
//calculate total length of audio
int length = 0;
for (byte[] array : ListAudio) {
length += array.length;
}
final int len = length;
final byte[] mixBytes = new byte[len];
for (byte[] array : ListAudio) {
for (int i = 44; i < len; ++i) {
mixBytes[i] += array[i];
// mixBytes[i]=(byte) ((bytes1[i]+bytes2[i]) / 2);
}
}
I found somewhere that the method to mix digital byte array is :
mixBytes[i]=(byte) ((bytes1[i]+bytes2[i]) / 2);
I don't arrive to include the calcul above, to sum the byte array.
How can i sum the bytes array from my ArrayList ?

you have to declare your sources to merge them
byte[] source1 = ListAudio.get(0); //first from list
byte[] source2 = ListAudio.get(1); //second from list
int length = Math.min(source1.length, source2.length);//length of new array
length = length - 44; //skipping 44 byte
byte[] dest = new byte[length];
for(int index = 0; index < length; index ++){
byte b1 = source1[index+44];
byte b2 = source2[index+44];
dest[index] = (byte) ((b1+b2) / 2);
}
That would merge the first two byte[] from your list.
If you want to merge other sources you can change them by selecting other byte[] from your List.
HINT
The length of the destination is declared as Math.min(a,b) but you can fill missing bytes with zeros if you want...
if you want to merge all arrays, you have to adjust your merge operation
mixing two bytes: mixBytes[i]=(byte) ((bytes1[i]+bytes2[i]) / 2);
mixing three bytes: mixBytes[i]=(byte) ((bytes1[i]+bytes2[i]+bytes3[i]) / 3);
mixing N bytes: mixBytes[i]=(byte) ((bytes1[i]+bytes2[i]+bytes3[i]+...+bytesN[i]) / N);
ok, for your code snipped it would be:
int length = ...;//length of result, either min or max as mentioned above, see HINT
byte[] mixBytes = new byte[length];
int amountAudio = ListAudio.size(); //amount of tracks in your list aka 'N'
int sum;
for(int index = 0; index < length; index++){
sum = 0;
for(byte[] source: ListAudio){
//adding all byte into one big integer
sum = sum + source[index]; //NOTE: watch for indexOutOfBoundsException
}
//afterward divide the big int through amount of Audio tracks in your list
mixBytes[index] = (byte)(sum / amountAudio);
}

Using get() and put() to access pixel values in OpenCV for Java

I am a beginner in using OpenCV for JAVA. I want to access individual pixel values of an image matrix. Since, JAVA jar for OpenCV doesn't offer nice functions like C++, I ran into some trouble. After lot of searching, I found out two different methods to do that though they are not explained properly (not even in documentation). We can do that either using get() and put() functions or by converting the mat data into a primitive java type such as arrays. I tried both but getting different output results! Please help explaining what am I doing wrong. Am I using them wrong or some other silly problem. I am still a newbie so please forgive if its a stupid question. :)
CASE 1: Using get() function
Mat A = Highgui.imread(image_addr); \\"image_addr" is the address of the image
Mat C = A.clone();
Size sizeA = A.size();
for (int i = 0; i < sizeA.height; i++)
for (int j = 0; j < sizeA.width; j++) {
double[] data = A.get(i, j);
data[0] = data[0] / 2;
data[1] = data[1] / 2;
data[2] = data[2] / 2;
C.put(i, j, data);
}
CASE 2: Using Array
Mat A = Highgui.imread(image_addr); \\"image_addr" is the address of the image
Mat C = A.clone();
int size = (int) (A.total() * A.channels());
byte[] temp = new byte[size];
A.get(0, 0, temp);
for (int i = 0; i < size; i++)
temp[i] = (byte) (temp[i] / 2);
C.put(0, 0, temp);
Now according to my understanding they both should do the same thing. They both access the individual pixel values (all 3 channels) and making it half. I am getting no error after running. But, the output image I am getting is different in these two cases. Can someone please explain what is the issue? May be I don't understand exactly how get() function works? Is it because of the byte() casting? Please help.
Thanks!

It was happening because of byte() casting. I changed the data type of mat image in second case to *CV_64FC3* so that I can use double[] instead of byte[] and it solved the problem.
Mat A = Highgui.imread(image_addr); //"image_addr" is the address of the image
Mat C = A.clone();
A.convertTo(A, CvType.CV_64FC3); // New line added.
int size = (int) (A.total() * A.channels());
double[] temp = new double[size]; // use double[] instead of byte[]
A.get(0, 0, temp);
for (int i = 0; i < size; i++)
temp[i] = (temp[i] / 2); // no more casting required.
C.put(0, 0, temp);
FYI, I also did some time measurement and using second method is way faster than first method.

Found a simple and working solution after a lot of searching-
Mat img = Highgui.imread("Input.jpg"); //Reads image from the file system and puts into matrix
int rows = img.rows(); //Calculates number of rows
int cols = img.cols(); //Calculates number of columns
int ch = img.channels(); //Calculates number of channels (Grayscale: 1, RGB: 3, etc.)
for (int i=0; i<rows; i++)
{
for (int j=0; j<cols; j++)
{
double[] data = img.get(i, j); //Stores element in an array
for (int k = 0; k < ch; k++) //Runs for the available number of channels
{
data[k] = data[k] * 2; //Pixel modification done here
}
img.put(i, j, data); //Puts element back into matrix
}
}
Highgui.imwrite("Output.jpg", img); //Writes image back to the file system using values of the modified matrix
Note: An important point that has not been mentioned anywhere online is that the method put does not write pixels onto Input.jpg. It merely updates the values of the matrix img. Therefore, the above code does not alter anything in the input image. For producing a visible output, the matrix img needs to be written onto a file i.e., Output.jpg in this case. Also, using img.get(i, j) seems to be a better way of handling the matrix elements rather than using the accepted solution above as this helps in visualizing and working with the image matrix in a better way and does not require a large contiguous memory allocation.

Arraylist in a Arraylist

How is it possible to store data (bytes) input like this:
input data (bytes) : 01 23 45 and 67 89 10
At the end Arraylist row : [[01,23,45],[67,89,10]]
// declaration
List<List<Byte>> row = new ArrayList<List<Byte>>();
List<Byte> myBytes = new ArrayList<Byte>();
int j=0;
// code before this defines the arraylengt to cut the buffer in pieces of 3 bytes
// and clears the Mybytes arraylist to be able to fill the buffer with new values
if(arrayLength > 0)
{
myBytes.add(value); // fill first arraylist (buffer) with byte value (for example: 01)
if(arrayLength == 1) // when buffer myBytes is full (with values 01 23 45) write value to position j in the new arraylist
{
row.add(j,new ArrayList<Byte>());
row.set(j,myBytes);
j +=j;
}
arrayLength -= 1; // for cutting the buffer in pieces of 3 bytes
}
Thank you for helping me !!

Just use an Arraylist with an Array of Bytes new ArrayList<Byte[]>();. It's a good way to produce a [n][3]-Matrix.

I'd suggest just using a matrix of size [n][3]. You can make sure that it stays as a byte by adding ifs, and must make it an int matrix that way it can have as many rows as you want.

I found the answer, use a arraylist to buffer the values convert to byte array and place them in a other arraylist. Thanks guys !
Note: Make shure u use myBytes.clear();
Here is my code:
if(bool == true)
{
myBytes.add(value); // buffer
if(arrayLength == 1)
{
byte[] data = new byte[myBytes.size()];
for (int i = 0; i < data.length; i++)
{
data[i] = (byte) myBytes.get(i);
}
row.add(data);
}
arrayLength -= 1;
}

Converting array with samples into byte array

I have two-dimensional array of integers. First index indicates the number of channels. The second one indicates the number of sample in the channel. How can I save this array into the audio file? I know, I have to convert it to byte array, but I have no idea how to do that.
// edit
More info. I already have a class for drawing a waveform. It is here:
http://javafaq.nu/java-example-code-716.html
now I want to cut part of this wave and save it to the new file. So I have to cut part of int[][] samplesContainer, convert it to byte array (I don't know how) and then save it to file with the same format as audioInputStream.
// edit
OK. So the biggest problem is to write inverted function to this one:
protected int[][] getSampleArray(byte[] eightBitByteArray) {
int[][] toReturn = new int[getNumberOfChannels()][eightBitByteArray.length / (2 * getNumberOfChannels())];
int index = 0;
//loop through the byte[]
for (int t = 0; t < eightBitByteArray.length;) {
//for each iteration, loop through the channels
for (int a = 0; a < getNumberOfChannels(); a++) {
//do the byte to sample conversion
//see AmplitudeEditor for more info
int low = (int) eightBitByteArray[t];
t++;
int high = (int) eightBitByteArray[t];
t++;
int sample = (high << 8) + (low & 0x00ff);
if (sample < sampleMin) {
sampleMin = sample;
} else if (sample > sampleMax) {
sampleMax = sample;
}
//set the value.
toReturn[a][index] = sample;
}
index++;
}
return toReturn;
}
I don't understand why there is second incrementation of t, after high. I also have no idea how can i get high and low from sample.

The code you posted reads a sample stream, byte by byte, into the samples array. The code assumes that, in the stream, every two 8-bit bytes form a 16-bit sample, and that there is one sample for each of the NumOfChannels channels.
So, given an array of samples like the one returned by that code,
int[][] samples;
and a byte array for streaming,
byte[] stream;
you might build the converse stream of bytes this way
for (int i=0; i<NumOfSamples; i++) {
for (int j=0; j<NumOfChannels; j++) {
int sample=samples[i][j];
byte low = (byte) (sample & 0xff) ;
byte high = (byte) ((sample & 0xff00 ) >> 8);
stream[((i*NumOfChannels)+j)*2] = low;
stream[(((i*NumOfChannels)+j)*2)+1] = high;
}
}

Fast reading of little endian integers from file

I need to read a binary file consisting of 4 byte integers (little endian) into a 2D array for my Android application. My current solution is the following:
DataInputStream inp = null;
try {
inp = new DataInputStream(new BufferedInputStream(new FileInputStream(procData), 32768));
}
catch (FileNotFoundException e) {
Log.e(TAG, "File not found");
}
int[][] test_data = new int[SIZE_X][SIZE_Y];
byte[] buffer = new byte[4];
ByteBuffer byteBuffer = ByteBuffer.allocate(4);
for (int i=0; i < SIZE_Y; i++) {
for (int j=0; j < SIZE_X; j++) {
inp.read(buffer);
byteBuffer = ByteBuffer.wrap(buffer);
test_data[j][SIZE_Y - i - 1] = byteBuffer.order(ByteOrder.LITTLE_ENDIAN).getInt();
}
}
This is pretty slow for a 2k*2k array, it takes about 25 seconds. I can see in the DDMS that the garbage collector is working overtime, so that is probably one reason for the slowness.
There has to be a more efficient way of using the ByteBuffer to read that file into the array, but I'm not seeing it at the moment. Any idea on how to speed this up?

Why not read into a 4-byte buffer and then rearrange the bytes manually? It will look like this:
for (int i=0; i < SIZE_Y; i++) {
for (int j=0; j < SIZE_X; j++) {
inp.read(buffer);
int nextInt = (buffer[0] & 0xFF) | (buffer[1] & 0xFF) << 8 | (buffer[2] & 0xFF) << 16 | (buffer[3] & 0xFF) << 24;
test_data[j][SIZE_Y - i - 1] = nextInt;
}
}
Of course, it is assumed that read reads all four bytes, but you should check for the situation when it's not. This way you won't create any objects during reading (so no strain on the garbage collector), you don't call anything, you just use bitwise operations.

If you are on a platform that supports memory-mapped files, consider the MappedByteBuffer and friends from java.nio
FileChannel channel = new RandomAccessFile(procData, "r").getChannel();
MappedByteBuffer map = channel.map(FileChannel.MapMode.READ_ONLY, 0, 4 * SIZE_X * SIZE_Y);
map.order(ByteOrder.LITTLE_ENDIAN);
IntBuffer buffer = map.asIntBuffer();
int[][] test_data = new int[SIZE_X][SIZE_Y];
for (int i=0; i < SIZE_Y; i++) {
for (int j=0; j < SIZE_X; j++) {
test_data[j][SIZE_Y - i - 1] = buffer.get();
}
}
If you need cross-platform support or your platform lacks memory-mapped buffers, you may still want to avoid performing the conversions yourself using an IntBuffer. Consider dropping the BufferedInputStream, allocating a larger ByteBuffer yourself and obtaining a little-endian IntBuffer view on the data. Then in a loop reset the buffer positions to 0, use DataInputStream.readFully to read the large regions at once into the ByteBuffer, and pull int values out of the IntBuffer.

First of all, your 'inp.read(buffer)' is unsafe, as read contract does not guarantee that it will read all 4 bytes.
That aside, for quick transformation use the algorithm from DataInputStream.readInt
I've adapted for you case of byte array of 4 bytes:
int little2big(byte[ ] b) {
return (b[3]&0xff)<<24)+((b[2]&0xff)<<16)+((b[1]&0xff)<<8)+(b[0]&0xff);
}

I don't think it is necessary to reinvent the wheel and perform the byte reordering for endianness again. This is error prone and there is a reason a class like ByteBuffer exists.
Your code can be optimized in the sense that it wastes objects. When a byte[] is wrapped by a ByteBuffer the buffer adds a view, but the original array remains the same. It does not matter wheather the original array is modified/read from directly or the ByteBuffer instance is used.
Therefore, you only need to initialize one instance of ByteBuffer and also have to set the ByteOrder once.
To start again, just use rewind() to set the counter again to the beginning of the buffer.
I have taken your code and modified it as desribed. Be aware that it does not check for errors if there are not enough bytes in the input left. I would suggest to use inp.readFully, as this will throw EOFException if not enough bytes to fill the buffer are found.
int[][] test_data = new int[SIZE_X][SIZE_Y];
ByteBuffer byteBuffer = ByteBuffer.wrap(new byte[4]).order(ByteOrder.LITTLE_ENDIAN);
for (int i=0; i < SIZE_Y; i++) {
for (int j=0; j < SIZE_X; j++) {
inp.read(byteBuffer.array());
byteBuffer.rewind();
test_data[j][SIZE_Y - i - 1] = byteBuffer.getInt();
}
}