JLayer Mono Mp3 to PCM decoding

Question

I am currently working on mp3 decoding with javalayer 1.1.

So I want to receive the raw PCM data from my 44100 Hz, 16bit, Mp3s. It is perfectly working fine with ste

Answer 1

Hm... My answer comes a bit late.. Sorry for that.

I completly solved the issue.

JLayer did some weird stuff. If the input mp3 is Stereo, the values in the pcmbuffer are encoded like this: leftchannel, rightchannel, leftchannel, ... This is how it should be. But if the input mp3 is Mono the I get the same amount of samples in the pcmbuffer. But its not like: monochannel, 0, monochannel, 0 The whole data is in the first half of the pcmbuffer and the second half is all 0. So you just need to cut off the second half.

Answer 2

I got it working, converting to byte[], using this code:

ByteArrayOutputStream outStream = new ByteArrayOutputStream(1024);
int divider = 1;
if (SAMPLE_RATE < 44100) divider *= 2;
if (CHANNELS == 1) divider *= 2;

[...]

short[] pcmBuffer = buffer.getBuffer();    
for (int i=0; i<pcm.length/divider; i++) {
    outStream.write(pcm[i] & 0xff);
    outStream.write((pcm[i] >> 8 ) & 0xff);
}

The key was the divider parameter, that is 1 in stereo-44, 2 in mono-44 and 4 in mono-22. Didn't try yet other combinations.