Android：需要录制麦克风输入

Question

有没有办法在实时播放/预览过程中记录 Android 中的麦克风输入？我尝试使用 AudioRecord 和 AudioTrack 来执行此操作，但问题是我的设备无法播放录制的音频文件。实际上，任何Android播放器应用程序都无法播放录制的音频文件。

另一方面，使用Media.Recorder 进行录音会生成一个录制好的音频文件，可以由任何播放器应用程序播放。但问题是我无法在实时录制麦克风输入时进行预览/回放。

Answer 1

要（几乎）实时录制和播放音频，您可以启动一个单独的线程并使用 AudioRecord 和 AudioTrack。

只是要小心反馈。如果您的设备上的扬声器开得足够大，反馈可能会很快变得非常令人讨厌。

/*
 * Thread to manage live recording/playback of voice input from the device's microphone.
 */
private class Audio extends Thread
{ 
    private boolean stopped = false;

    /**
     * Give the thread high priority so that it's not canceled unexpectedly, and start it
     */
    private Audio()
    { 
        android.os.Process.setThreadPriority(android.os.Process.THREAD_PRIORITY_URGENT_AUDIO);
        start();
    }

    @Override
    public void run()
    { 
        Log.i("Audio", "Running Audio Thread");
        AudioRecord recorder = null;
        AudioTrack track = null;
        short[][]   buffers  = new short[256][160];
        int ix = 0;

        /*
         * Initialize buffer to hold continuously recorded audio data, start recording, and start
         * playback.
         */
        try
        {
            int N = AudioRecord.getMinBufferSize(8000,AudioFormat.CHANNEL_IN_MONO,AudioFormat.ENCODING_PCM_16BIT);
            recorder = new AudioRecord(AudioSource.MIC, 8000, AudioFormat.CHANNEL_IN_MONO, AudioFormat.ENCODING_PCM_16BIT, N*10);
            track = new AudioTrack(AudioManager.STREAM_MUSIC, 8000, 
                    AudioFormat.CHANNEL_OUT_MONO, AudioFormat.ENCODING_PCM_16BIT, N*10, AudioTrack.MODE_STREAM);
            recorder.startRecording();
            track.play();
            /*
             * Loops until something outside of this thread stops it.
             * Reads the data from the recorder and writes it to the audio track for playback.
             */
            while(!stopped)
            { 
                Log.i("Map", "Writing new data to buffer");
                short[] buffer = buffers[ix++ % buffers.length];
                N = recorder.read(buffer,0,buffer.length);
                track.write(buffer, 0, buffer.length);
            }
        }
        catch(Throwable x)
        { 
            Log.w("Audio", "Error reading voice audio", x);
        }
        /*
         * Frees the thread's resources after the loop completes so that it can be run again
         */
        finally
        { 
            recorder.stop();
            recorder.release();
            track.stop();
            track.release();
        }
    }

    /**
     * Called from outside of the thread in order to stop the recording/playback loop
     */
    private void close()
    { 
         stopped = true;
    }

}

编辑

音频并未真正录制到文件中。 AudioRecord 对象将音频编码为 16 位 PCM 数据 并将其放入缓冲区中。然后，AudioTrack 对象从该缓冲区读取数据并通过扬声器播放。 SD 卡上没有您稍后可以访问的文件。

您无法同时从 SD 卡读取和写入文件来实时播放/预览，因此必须使用缓冲区。

Answer 2

需要清单中的以下权限才能正常工作：

<uses-permission android:name="android.permission.RECORD_AUDIO" ></uses-permission>

此外，不需要 2d 缓冲区数组。即使只有一个缓冲区，代码的逻辑也是有效的，如下所示：

short[] buffer = new short[160];
while (!stopped) {
    //Log.i("Map", "Writing new data to buffer");
    int n = recorder.read(buffer, 0, buffer.length);
    track.write(buffer, 0, n);
}