android opus解码

要在 Android 上解码 Opus 音频，可以使用 Opus 解码库和 Android 的 MediaPlayer 类。以下是一个简单的示例代码：

import android.media.AudioFormat;
import android.media.AudioManager;
import android.media.AudioTrack;
import android.media.MediaPlayer;
import android.os.Bundle;
import android.app.Activity;
import android.view.Menu;
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.nio.ByteBuffer;
import java.nio.ByteOrder;
import org.opus.android.OpusDecoder;

public class MainActivity extends Activity {
    private static final int AUDIO_SAMPLE_RATE = 48000;
    private static final int AUDIO_CHANNELS = 2;

    private OpusDecoder opusDecoder;
    private AudioTrack audioTrack;
    private MediaPlayer mediaPlayer;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        try {
            opusDecoder = new OpusDecoder(AUDIO_SAMPLE_RATE, AUDIO_CHANNELS);
        } catch (Exception e) {
            e.printStackTrace();
            return;
        }

        audioTrack = new AudioTrack(AudioManager.STREAM_MUSIC, AUDIO_SAMPLE_RATE,
                AudioFormat.CHANNEL_OUT_STEREO, AudioFormat.ENCODING_PCM_16BIT,
                AudioTrack.getMinBufferSize(AUDIO_SAMPLE_RATE, AudioFormat.CHANNEL_OUT_STEREO,
                        AudioFormat.ENCODING_PCM_16BIT), AudioTrack.MODE_STREAM);

        mediaPlayer = new MediaPlayer();
        mediaPlayer.setAudioStreamType(AudioManager.STREAM_MUSIC);
        mediaPlayer.setOnPreparedListener(new MediaPlayer.OnPreparedListener() {
            @Override
            public void onPrepared(MediaPlayer mp) {
                mediaPlayer.start();
            }
        });
        mediaPlayer.setOnCompletionListener(new MediaPlayer.OnCompletionListener() {
            @Override
            public void onCompletion(MediaPlayer mp) {
                audioTrack.stop();
                audioTrack.release();
            }
        });

        try {
            File file = new File(getExternalFilesDir(null), "audio.opus");
            FileInputStream inputStream = new FileInputStream(file);
            byte[] buffer = new byte[1024];
            int read;
            while ((read = inputStream.read(buffer)) != -1) {
                ByteBuffer byteBuffer = ByteBuffer.wrap(buffer, 0, read);
                byteBuffer.order(ByteOrder.LITTLE_ENDIAN);
                short[] pcmBuffer = new short[read * 2];
                opusDecoder.decode(byteBuffer, read, pcmBuffer);
                audioTrack.write(pcmBuffer, 0, pcmBuffer.length);
                mediaPlayer.setDataSource(inputStream.getFD());
                mediaPlayer.prepareAsync();
            }
            inputStream.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

在此示例中，我们使用 OpusDecoder 类从 Opus 文件中解码音频，并将 PCM 数据写入 AudioTrack 类中，以便在 Android 设备上播放音频。我们还使用 MediaPlayer 类异步准备和播放音频文件。请注意，您需要将适当的权限添加到 AndroidManifest.xml 文件中，以便应用程序可以读取外部存储器中的文件。