AudioRecord - 无效的音频缓冲区大小

Question

当使用AudioFormat.ENCODING_PCM_8BIT作为AudioFormat时，我遇到以下问题。当使用AudioFormat.ENCODING_PCM_16BIT这些工作正常。

bufferSize = AudioRecord.getMinBufferSize(sampleRate, AudioFormat.CHANNEL_IN_MONO, AudioFormat.ENCODING_PCM_8BIT); 
audio = new AudioRecord(MediaRecorder.AudioSource.CAMCORDER, sampleRate, AudioFormat.CHANNEL_IN_MONO, AudioFormat.ENCODING_PCM_8BIT, bufferSize); 

的logcat：

03-26 10:03:49.643: E/AndroidRuntime(19949): FATAL EXCEPTION: main 
03-26 10:03:49.643: E/AndroidRuntime(19949): java.lang.IllegalArgumentException: Invalid audio buffer size. 
03-26 10:03:49.643: E/AndroidRuntime(19949): at android.media.AudioRecord.audioBuffSizeCheck(AudioRecord.java:340) 
03-26 10:03:49.643: E/AndroidRuntime(19949): at android.media.AudioRecord.<init>(AudioRecord.java:237) 
03-26 10:03:49.643: E/AndroidRuntime(19949): at com.kris.test.SoundMeter.runForCamMic(SoundMeter.java:57) 
03-26 10:03:49.643: E/AndroidRuntime(19949): at com.kris.test.VolumeCalc.run(VolumeCalc.java:89) 
03-26 10:03:49.643: E/AndroidRuntime(19949): at com.kris.test.StateChecker.micCalibration(StateChecker.java:159) 
03-26 10:03:49.643: E/AndroidRuntime(19949): at com.kris.test.Settings$3.onClick(Settings.java:354) 
03-26 10:03:49.643: E/AndroidRuntime(19949): at com.android.internal.app.AlertController$ButtonHandler.handleMessage(AlertController.java:167) 
03-26 10:03:49.643: E/AndroidRuntime(19949): at android.os.Handler.dispatchMessage(Handler.java:99) 
03-26 10:03:49.643: E/AndroidRuntime(19949): at android.os.Looper.loop(Looper.java:137) 
03-26 10:03:49.643: E/AndroidRuntime(19949): at android.app.ActivityThread.main(ActivityThread.java:4921) 
03-26 10:03:49.643: E/AndroidRuntime(19949): at java.lang.reflect.Method.invokeNative(Native Method) 
03-26 10:03:49.643: E/AndroidRuntime(19949): at java.lang.reflect.Method.invoke(Method.java:511) 
03-26 10:03:49.643: E/AndroidRuntime(19949): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1027) 
03-26 10:03:49.643: E/AndroidRuntime(19949): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:794) 
03-26 10:03:49.643: E/AndroidRuntime(19949): at dalvik.system.NativeStart.main(Native Method) 

Answer 1

AudioRecord.getMinBufferSize不支持PCM_8BIT（见AudioRecord source code)，并且将返回ERROR_BAD_VALUE（-2），如果你传递一个PCM_8BIT格式它

一个解决办法。要切换到使用PCM_16BIT编码另一种可能性（我没有验证它是否有效）是根据要求最小缓冲区大小并在构造AudioRecord实例时将返回的大小除以2。