When playing back decoded Speex data, all I hear is static

Question

I am learning how to use JSpeex for a VoIP application that I will be writing later on for educational purposes. As an attempt to understand how to use JSpeex, I decided to write a simple echo application. Basically, it reads the input from the audio-in line, encodes the data (using Speex), then decodes the data, and writes it to the audio-out line. However, when I run the application, all that I hear is static and no voice whatsoever. I have tried to tinker with the audio format, how I initialize the decoder, and encoder, all of which I have had no luck with. Can anybody perhaps look through the code and try to point out what I am doing wrong? Thanks.

Code:

(Is there a better way to paste code? Because when I paste it, highlight it all, and press the Code button, the indentation gets messed up.)

import java.util.Arrays;

import javax.sound.sampled.AudioFormat;
import javax.sound.sampled.AudioSystem;
import javax.sound.sampled.DataLine;
import javax.sound.sampled.LineUnavailableException;
import javax.sound.sampled.SourceDataLine;
import javax.sound.sampled.TargetDataLine;

import org.xiph.speex.SpeexDecoder;
import org.xiph.speex.SpeexEncoder;

public class SpeexTest {

    public static void main(String[] args) throws Exception {
    int sample_rate = 8000;
    int sample_size = 16;
    int channels = 1;
    AudioFormat format = new AudioFormat(sample_rate, sample_size,
        channels, true, true);
    TargetDataLine line_in;
    DataLine.Info info_in = new DataLine.Info(TargetDataLine.class, format);
    try {
        line_in = (TargetDataLine) AudioSystem.getLine(info_in);
        line_in.open(format);
    } catch (LineUnavailableException ex) {
        ex.printStackTrace();
        return;
    }
    DataLine.Info info_out = new DataLine.Info(SourceDataLine.class, format);
    SourceDataLine line_out;
    try {
        line_out = (SourceDataLine) AudioSystem.getLine(info_out);
        line_out.open(format);
    } catch (LineUnavailableException ex) {
        ex.printStackTrace();
        return;
    }
    SpeexEncoder encoder = new SpeexEncoder();
    SpeexDecoder decoder = new SpeexDecoder();
    encoder.init(1, 1, sample_rate, channels);
    decoder.init(1, sample_rate, channels, false);
    int raw_block_size = encoder.getFrameSize() * channels
        * (sample_size / 8);
    byte[] buffer = new byte[raw_block_size * 2];
    line_in.start();
    line_out.start();
    while (true) {
        int read = line_in.read(buffer, 0, raw_block_size);
        if (!encoder.processData(buffer, 0, raw_block_size)) {
        System.err.println("Could not encode data!");
        break;
        }
        int encoded = encoder.getProcessedData(buffer, 0);
        System.out.println(encoded
            + " bytes resulted as a result of encoding " + read
            + " raw bytes.");
        byte[] encoded_data = new byte[encoded];
        System.arraycopy(buffer, 0, encoded_data, 0, encoded);
        decoder.processData(encoded_data, 0, encoded);
        byte[] decoded_data = new byte[decoder.getProcessedDataByteSize()];
        int decoded = decoder.getProcessedData(decoded_data, 0);
        System.out.println(decoded
            + " bytes resulted as a result of decoding " + encoded
            + " encoded bytes.");
        line_out.write(decoded_data, 0, decoded);
    }
    }
}

And here is some output (the same always repeats):

15 bytes resulted as a result of encoding 640 raw bytes.
640 bytes resulted as a result of decoding 15 encoded bytes.

Answer 1

The JSpeex input/output is little-endian. Either swap the bytes before encoding/after decoding, or open the DataLines with

AudioFormat format = new AudioFormat(sample_rate, sample_size,
            channels, true, false);