How to make alaw_rtp's tonal quality better?

Question

I write my own alaw Encode , Decode and Packetizer. But i have a hard problem is thar the sound is so bad.
The volume is so low and the sound have noise.
How should i do to make it better?
the code :
encode:
package media.codec.audio.alaw;
import com.ibm.media.codec.audio.AudioCodec;
import javax.media.Buffer;
import javax.media.Control;
import javax.media.Format;
import javax.media.ResourceUnavailableException;
import javax.media.format.AudioFormat;
public class JavaEncode extends AudioCodec {
    private Format lastFormat = null;
    private int inputSampleSize;
    private boolean bigEndian = false;
    public JavaEncode() {
        supportedInputFormats = new AudioFormat[]{
                    new AudioFormat(
                    AudioFormat.LINEAR,
                    Format.NOT_SPECIFIED,
                    16,
                    1,
                    Format.NOT_SPECIFIED,
                    Format.NOT_SPECIFIED),
                    new AudioFormat(
                    AudioFormat.LINEAR,
                    Format.NOT_SPECIFIED,
                    8,
                    1,
                    Format.NOT_SPECIFIED,
                    Format.NOT_SPECIFIED)};
        defaultOutputFormats = new AudioFormat[]{
                    new AudioFormat(
                    AudioFormat.ALAW,
                    8000,
                    8,
                    1,
                    Format.NOT_SPECIFIED,
                    Format.NOT_SPECIFIED)};
    @Override
    public String getName() {
        PLUGIN_NAME = "pcm to alaw converter";
        return PLUGIN_NAME;
    @Override
    protected Format[] getMatchingOutputFormats(Format in) {
        AudioFormat inFormat = (AudioFormat) in;
        int sampleRate = (int) (inFormat.getSampleRate());
        supportedOutputFormats = new AudioFormat[]{
                    new AudioFormat(
                    AudioFormat.ALAW,
                    sampleRate,
                    8,
                    1,
                    Format.NOT_SPECIFIED,
                    Format.NOT_SPECIFIED)};
        return supportedOutputFormats;
    @Override
    public void open() throws ResourceUnavailableException {
    @Override
    public void close() {
    private int calculateOutputSize(int inputLength) {
        if (inputSampleSize == 16) {
            inputLength /= 2;
        return inputLength;
    //网络上的A律编码程序...
    private void initConverter(AudioFormat inFormat) {
        lastFormat = inFormat;
        inputSampleSize = inFormat.getSampleSizeInBits();
        bigEndian = inFormat.getEndian() == AudioFormat.BIG_ENDIAN;
    public int process(Buffer inputBuffer, Buffer outputBuffer) {
        if (!checkInputBuffer(inputBuffer)) {
            return BUFFER_PROCESSED_FAILED;
        if (isEOM(inputBuffer)) {
            propagateEOM(outputBuffer);
            return BUFFER_PROCESSED_OK;
        Format newFormat = inputBuffer.getFormat();
        if (lastFormat != newFormat) {
            initConverter((AudioFormat) newFormat);
        int outLength = calculateOutputSize(inputBuffer.getLength());
        byte[] inpData = (byte[]) inputBuffer.getData();
        byte[] outData = validateByteArraySize(outputBuffer, outLength);
        pcm162alaw(inpData, inputBuffer.getOffset(), outData, outputBuffer.getOffset(), outData.length, bigEndian);
        updateOutput(outputBuffer, outputFormat, outLength, outputBuffer.getOffset());
        return BUFFER_PROCESSED_OK;
    private static final byte QUANT_MASK = 0xf; /* Quantization field mask. */
    private static final byte SEG_SHIFT = 4;
    /* Left shift for segment number. */
    private static final short[] seg_end = {
        0xFF, 0x1FF, 0x3FF, 0x7FF, 0xFFF, 0x1FFF, 0x3FFF, 0x7FFF
    private static byte linear2alaw(short pcm_val) /* 2's complement (16-bit range) */ {
        byte mask;
        byte seg = 8;
        byte aval;
        if (pcm_val >= 0) {
            mask = (byte) 0xD5; /* sign (7th) bit = 1 */
        } else {
            mask = 0x55; /* sign bit = 0 */
            pcm_val = (short) (-pcm_val - 8);
        /* Convert the scaled magnitude to segment number. */
        for (int i = 0; i < 8; i++) {
            if (pcm_val <= seg_end) {
seg = (byte) i;
break;
/* Combine the sign, segment, and quantization bits. */
if (seg >= 8) /* out of range, return maximum value. */ {
return (byte) ((0x7F ^ mask) & 0xFF);
} else {
aval = (byte) (seg << SEG_SHIFT);
if (seg < 2) {
aval |= (pcm_val >> 4) & QUANT_MASK;
} else {
aval |= (pcm_val >> (seg + 3)) & QUANT_MASK;
return (byte) ((aval ^ mask) & 0xFF);
private static void pcm162alaw(byte[] inBuffer, int inByteOffset,
byte[] outBuffer, int outByteOffset,
int sampleCount, boolean bigEndian) {
int shortIndex = inByteOffset;
int alawIndex = outByteOffset;
if (bigEndian) { //bigEndian
while (sampleCount > 0) {
outBuffer[alawIndex++] = linear2alaw(bytesToShort16(inBuffer[shortIndex],
inBuffer[shortIndex + 1]));
shortIndex++;
shortIndex++;
sampleCount--;
} else {
while (sampleCount > 0) {
outBuffer[alawIndex++] = linear2alaw(bytesToShort16(inBuffer[shortIndex + 1],
inBuffer[shortIndex]));
shortIndex++;
shortIndex++;
sampleCount--;
private static short bytesToShort16(byte highByte, byte lowByte) {
return (short) ((highByte << 8) | (lowByte & 0xFF));
//&#22686;&#21152;&#22238;&#22768;&#25233;&#21046;
@Override
public java.lang.Object[] getControls() {
if (controls == null) {
controls = new Control[1];
controls[0] = new com.sun.media.controls.SilenceSuppressionAdapter(this, false, false);
return (Object[]) controls;

Answer 1

the command of use alaw_rtp:
                audio_format = new AudioFormat("ALAW_RTP", 8000.0, 8, 1);
                switch (payload) {
                    case PayLoad_Ulaw:
                        try {
                            Codec[] codec = new Codec[3];
                            codec[0] = new com.ibm.media.codec.audio.rc.RCModule();
                            codec[1] = new com.ibm.media.codec.audio.ulaw.JavaEncoder();
                            codec[2] = new com.sun.media.codec.audio.ulaw.Packetizer();
                            ((com.sun.media.codec.audio.ulaw.Packetizer) codec[2]).setPacketSize(ptime * 8);
                            (tracks).setCodecChain(codec);
} catch (Exception ex) {
System.err.println("payload error:" + ex);
break;
case PayLoad_Alaw:
try {
Codec[] codec = new Codec[3];
codec[0] = new com.ibm.media.codec.audio.rc.RCModule();
codec[1] = new AlawEncoder();
codec[2] = new AlawPacketizer();
((AlawPacketizer) codec[2]).setPacketSize(ptime * 8);
(tracks[i]).setCodecChain(codec);
} catch (Exception ex) {
System.err.println("payload error:" + ex);
break;
default:
break;
tracks[i].setEnabled(true);
the voice is so bad, have noise.
Some one could tell what's wrong in my code?
Thank you very much for your share!