当一起使用AudioTrack和MediaSync时，我遇到了一个严重的内存泄漏问题。在我看来，问题在于AudioTrack不会释放某些本机资源。结果，该应用只能运行几次，此后，由于不再有可用的曲目，因此无法创建AudioTrack。
下面是一个导致内存泄漏的简短示例。完整项目可以在GitHub上here下载。 APK文件可以下载here。
final MediaSync mediaSync = new MediaSync();
mediaSync.setSurface(mSurface);
final Surface inputSurface = mediaSync.createInputSurface(); // There is no the memory leak if I don't create this input surface.
final AudioTrack audioTrack = new AudioTrack.Builder()
.setAudioAttributes(new AudioAttributes.Builder()
.setUsage(AudioAttributes.USAGE_MEDIA)
.setContentType(AudioAttributes.CONTENT_TYPE_MOVIE)
.build())
.setAudioFormat(new AudioFormat.Builder()
.setEncoding(AudioFormat.ENCODING_PCM_16BIT)
.setSampleRate(48000)
.setChannelMask(12)
.build())
.build();
mediaSync.setAudioTrack(audioTrack); // There is no the memory leak if I don't set AudioTrack.
mediaSync.release();
inputSurface.release();
audioTrack.release();
我通过以下方式重现该问题：
Logcat：
2019-03-15 09:19:57.313 239-15387/? E/AudioFlinger: no more track names available
2019-03-15 09:19:57.313 239-15387/? E/AudioFlinger: createTrack_l() initCheck failed -12; no control block?
2019-03-15 09:19:57.313 3413-3413/com.audiotrackmemoryleak E/AudioTrack: AudioFlinger could not create track, status: -12
2019-03-15 09:19:57.313 3413-3413/com.audiotrackmemoryleak E/AudioTrack-JNI: Error -12 initializing AudioTrack
2019-03-15 09:19:57.313 3413-3413/com.audiotrackmemoryleak E/android.media.AudioTrack: Error code -20 when initializing AudioTrack.
2019-03-15 09:19:57.315 3413-3413/com.audiotrackmemoryleak D/AndroidRuntime: Shutting down VM
2019-03-15 09:19:57.316 3413-3413/com.audiotrackmemoryleak E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.audiotrackmemoryleak, PID: 3413
java.lang.UnsupportedOperationException: Cannot create AudioTrack
at android.media.AudioTrack$Builder.build(AudioTrack.java:776)
at com.audiotrackmemoryleak.MainActivity.createMediaSync(MainActivity.java:68)
at com.audiotrackmemoryleak.MainActivity.access$100(MainActivity.java:18)
at com.audiotrackmemoryleak.MainActivity$1.surfaceCreated(MainActivity.java:32)
at android.view.SurfaceView.updateWindow(SurfaceView.java:618)
at ...
命令adb shell dumpsys media.audio_flinger演示了该问题：
...
Clients:
pid: 3413
Notification Clients:
pid: 239
pid: 841
pid: 3413
pid: 28651
Global session refs:
session pid count
3193 3413 1
3201 3413 1
3209 3413 1
3217 3413 1
3225 3413 1
3233 3413 1
3241 3413 1
3249 3413 1
3257 3413 1
3265 3413 1
3273 3413 1
3281 3413 1
3289 3413 1
3297 3413 1
...
14 Tracks of which 0 are active
Name Active Client Type Fmt Chn mask Session fCount S F SRate L dB R dB Server Main buf Aux Buf Flags UndFrmCnt
7 no 3413 3 00000001 00000003 3249 1924 I 0 48000 0 0 00000000 0xa77fe000 0x0 0x000 0
5 no 3413 3 00000001 00000003 3233 1924 I 0 48000 0 0 00000000 0xa77fe000 0x0 0x000 0
12 no 3413 3 00000001 00000003 3289 1924 I 0 48000 0 0 00000000 0xa77fe000 0x0 0x000 0
3 no 3413 3 00000001 00000003 3217 1924 I 0 48000 0 0 00000000 0xa77fe000 0x0 0x000 0
8 no 3413 3 00000001 00000003 3257 1924 I 0 48000 0 0 00000000 0xa77fe000 0x0 0x000 0
9 no 3413 3 00000001 00000003 3265 1924 I 0 48000 0 0 00000000 0xa77fe000 0x0 0x000 0
4 no 3413 3 00000001 00000003 3225 1924 I 0 48000 0 0 00000000 0xa77fe000 0x0 0x000 0
1 no 3413 3 00000001 00000003 3201 1924 I 0 48000 0 0 00000000 0xa77fe000 0x0 0x000 0
11 no 3413 3 00000001 00000003 3281 1924 I 0 48000 0 0 00000000 0xa77fe000 0x0 0x000 0
0 no 3413 3 00000001 00000003 3193 1924 I 0 48000 0 0 00000000 0xa77fe000 0x0 0x000 0
6 no 3413 3 00000001 00000003 3241 1924 I 0 48000 0 0 00000000 0xa77fe000 0x0 0x000 0
13 no 3413 3 00000001 00000003 3297 1924 I 0 48000 0 0 00000000 0xa77fe000 0x0 0x000 0
2 no 3413 3 00000001 00000003 3209 1924 I 0 48000 0 0 00000000 0xa77fe000 0x0 0x000 0
10 no 3413 3 00000001 00000003 3273 1924 I 0 48000 0 0 00000000 0xa77fe000 0x0 0x000 0
0 Effect Chains
...
我想知道这里是否有人可以解释发生了什么？如何正确释放AudioTrack？
答案 0 :(得分：4)
我不确定这是否是SDK错误，但与AudioAttributes.FLAG_DEEP_BUFFER有关。通过构建器构造AudioTrack时，默认情况下会设置此标志。查看您的情况here：shouldEnablePowerSaving()的检查返回true，并且切换情况导致PERFORMANCE_MODE_POWER_SAVING启用FLAG_DEEP_BUFFER。
要解决此问题，您应该禁用此标志，例如，将.setFlags(AudioAttributes.FLAG_LOW_LATENCY)调用添加到AudioAttributes，但是它需要至少24 SDK。否则，您可以完全放弃使用AudioTrack.Builder，并且像这样构造轨道：
int audioSampleRate = 48000;
int channelConfig = AudioFormat.CHANNEL_OUT_STEREO;
int bufSize = AudioTrack.getMinBufferSize(audioSampleRate, channelConfig, AudioFormat.ENCODING_PCM_16BIT);
AudioTrack audioTrack = new AudioTrack(AudioManager.STREAM_MUSIC, audioSampleRate,
channelConfig, AudioFormat.ENCODING_PCM_16BIT, bufSize, AudioTrack.MODE_STREAM);
或者您可以检查the code of shouldEnablePowerSaving() check并使其不通过其他任何方式。
更新：
因此，上述解决方案只是将漏洞转移到另一个音频线程。我进行了进一步调查，发现surfaceCreated()将同一个Surface对象放在我的android 8设备上。实际上，this is the correct behaviour since android 7。我认为它以某种方式破坏了mediaSync表面逻辑：如果您删除对mediaSync.createInputSurface()的调用并在释放它之前添加mediaSync.setSurface(null)调用，则泄漏将消失。
我不知道如何解决此问题，因为Surface被系统重用，并且无法知道何时将其实际销毁。我建议切换到TextureView，它具有相似但更清晰的API，并且不会在活动暂停时破坏表面。您需要从createMediaSync()中删除onResume()调用，并像这样使用它：
setContentView(R.layout.activity_main);
final TextureView textureView = findViewById(R.id.texture_view);
textureView.setSurfaceTextureListener(new TextureView.SurfaceTextureListener() {
@Override
public void onSurfaceTextureAvailable(SurfaceTexture surface, int width, int height) {
mSurface = new Surface(surface);
createMediaSync();
}
@Override
public void onSurfaceTextureSizeChanged(SurfaceTexture surface, int width, int height) {
}
@Override
public boolean onSurfaceTextureDestroyed(SurfaceTexture surface) {
//release resources here
return true;
}
@Override
public void onSurfaceTextureUpdated(SurfaceTexture surface) {
}
});
祝你好运！