用java实现UDP接收rtp的音频流，并解析rtp音频流将PCMA/PCMU格式音频数据并转换成PCM格式，如何比特率不是16要调整16比特，并给出调用案例和详细的注释

实现UDP接收rtp的音频流，可以使用Java的DatagramSocket类来进行网络数据包的接收，解析rtp音频流可以参考RFC3550中的相关规范。将PCMA/PCMU格式音频数据转换成PCM格式，可以使用Java的AudioFormat类和AudioInputStream类来进行音频格式的转换。具体实现的代码如下：

import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetAddress;
import java.util.Arrays;

import javax.sound.sampled.AudioFormat;
import javax.sound.sampled.AudioInputStream;
import javax.sound.sampled.AudioSystem;
import javax.sound.sampled.DataLine;
import javax.sound.sampled.TargetDataLine;

public class RTPAudioReceiver {
    private static final int RTP_HEADER_SIZE = 12;
    private static final int UDP_PACKET_SIZE = 1500;
    private static final int AUDIO_SAMPLE_RATE = 8000;
    private static final int AUDIO_SAMPLE_SIZE_IN_BITS = 16;
    private static final int AUDIO_CHANNELS = 1;
    private static final boolean AUDIO_SIGNED = true;
    private static final boolean AUDIO_BIG_ENDIAN = true;

    private DatagramSocket socket;
    private InetAddress remoteAddress;
    private int remotePort;
    private AudioFormat audioFormat;
    private DataLine.Info dataLineInfo;
    private TargetDataLine targetDataLine;

    public RTPAudioReceiver(String remoteIP, int remotePort) throws IOException {
        this.remoteAddress = InetAddress.getByName(remoteIP);
        this.remotePort = remotePort;
        this.socket = new DatagramSocket();
        this.audioFormat = new AudioFormat(
                AUDIO_SAMPLE_RATE, AUDIO_SAMPLE_SIZE_IN_BITS,
                AUDIO_CHANNELS, AUDIO_SIGNED, AUDIO_BIG_ENDIAN);
        this.dataLineInfo = new DataLine.Info(TargetDataLine.class, audioFormat);
        this.targetDataLine = (TargetDataLine) AudioSystem.getLine(dataLineInfo);
    }

    public void start() throws Exception {
        targetDataLine.open(audioFormat);
        targetDataLine.start();
        byte[] buffer = new byte[UDP_PACKET_SIZE];
        while (true) {
            DatagramPacket packet = new DatagramPacket(buffer, buffer.length, remoteAddress, remotePort);
            socket.receive(packet);
            byte[] rtpPacket = Arrays.copyOf(packet.getData(), packet.getLength());
            byte[] pcmData = decodeRTP(rtpPacket);
            if (pcmData != null) {
                playAudio(pcmData);
            }
        }
    }

    private byte[] decodeRTP(byte[] rtpPacket) {
        int payloadType = (rtpPacket[1] & 0xFF) & 0x7F;
        if (payloadType != 0) {
            // 不支持的payload type
            return null;
        }
        int sequenceNumber = ((rtpPacket[2] & 0xFF) << 8) | (rtpPacket[3] & 0xFF);
        int timestamp = ((rtpPacket[4] & 0xFF) << 24) | ((rtpPacket[5] & 0xFF) << 16) | ((rtpPacket[6] & 0xFF) << 8) | (rtpPacket[7] & 0xFF);
        int ssrc = ((rtpPacket[8] & 0xFF) << 24) | ((rtpPacket[9] & 0xFF) << 16) | ((rtpPacket[10] & 0xFF) << 8) | (rtpPacket[11] & 0xFF);
        byte[] payload = Arrays.copyOfRange(rtpPacket, RTP_HEADER_SIZE, rtpPacket.length);
        if (payload.length == 0) {
            return null;
        }
        byte[] pcmData = decodePayload(payload);
        return pcmData;
    }

    private byte[] decodePayload(byte[] payload) {
        int numSamples = payload.length;
        byte[] pcmData = new byte[numSamples * 2];
        for (int i = 0; i < numSamples; i++) {
            int pcmValue = ((int) payload[i]) << 8;
            pcmData[i * 2] = (byte) (pcmValue & 0xFF);
            pcmData[i * 2 + 1] = (byte) ((pcmValue >> 8) & 0xFF);
        }
        return pcmData;
    }

    private void playAudio(byte[] pcmData) {
        AudioInputStream audioInputStream = new AudioInputStream(
                new ByteArrayInputStream(pcmData), audioFormat, pcmData.length / audioFormat.getFrameSize());
        ByteArrayOutputStream baos = new ByteArrayOutputStream();
        try {
            AudioSystem.write(audioInputStream, AudioFileFormat.Type.WAVE, baos);
        } catch (IOException e) {
            e.printStackTrace();
        }
        byte[] audioBytes = baos.toByteArray();
        try {
            baos.close();
            audioInputStream.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
        targetDataLine.write(audioBytes, 0, audioBytes.length);
    }

    public static void main(String[] args) throws Exception {
        RTPAudioReceiver receiver = new RTPAudioReceiver("127.0.0.1", 12345);
        receiver.start();
    }
}

调用示例：

RTPAudioReceiver receiver = new RTPAudioReceiver("127.0.0.1", 12345);
receiver.start();

其中，参数"127.0.0.1"表示远程IP地址，参数12345表示远程端口号。