Android的AudioRecord问题吗？ [英] Android AudioRecord questions?

问题描述

我一直在瞎搞了Android API的AudioRecord特征，发现了一些奇怪的行为吧。

I have been messing around with the AudioRecord feature of the Android API and found some strange behaviors with it.

背景信息： 我的手机是HTC不可思议 我使用的Eclipse插件为Android开发的模拟器。 目标平台或操作系统是2.2 ......既然是我的手机使用。

Background info: My phone is a HTC Incredible I am using the Eclipse plugin for Android development with the emulator. Targeted platform or OS is 2.2... Since it is what my phone uses.

有些code：

bufferSize = AudioRecord.getMinBufferSize(FREQUENCY, AudioFormat.CHANNEL_CONFIGURATION_MONO, AudioFormat.ENCODING_PCM_16BIT);
audioRecord = new AudioRecord(MediaRecorder.AudioSource.MIC, FREQUENCY, AudioFormat.CHANNEL_CONFIGURATION_MONO, AudioFormat.ENCODING_PCM_16BIT, bufferSize);

这是在code我用它来设置AudioRecord API使用。现在，模拟器也喜欢频率设置为8000为它工作。回来与缓冲区大小640对于手机我用44100的一个问题在这里似乎得到的PCM数据的波动似乎是8位有符号的浪潮。我得到的值从-127到128。我认为值 AudioFormat.ENCODING_PCM_16BIT 会产生不同的东西。

This is the code I use to setup the AudioRecord API with. Now, for the emulator it likes FREQUENCY to be set to 8000 for it to work. Comes back with a buffer size 640. For the phone I use 44100. One issue here is it seems the resulting PCM data for the wave seems to be an eight bit signed wave. I get values from -127 to 128. I thought the value AudioFormat.ENCODING_PCM_16BIT would produce something different.

我处理一个线程音频，

public void run() {
  while(isRecording) {
    audioRecord.startRecording();
    byte[] data = new byte[bufferSize];
    audioRecord.read(data, 0, bufferSize);
    listener.setData(data);
    handleData(data);
  }
  audioRecord.release();
}

我有办法以图形方式显示于使用 SurfaceView 相应的波的实时性。似乎有一个很大的噪音从MIC到来。我得到这个噪声仿真器和手机为好。我是否需要通过某种过滤器（S）的运行数据？我想用这个数据来计算一些有趣的FFT和东西只是为了玩的浪潮。但我需要降低噪音不知何故。

I have a way to graphically display to corresponding wave in real time using a SurfaceView. There seems to be a lot of noise coming from the MIC. I get this noise from the emulator and the phone as well. Do I need to run the data through some sort of filter(s)? I would like to use this data to calculate some fun FFT and stuff just to play around with the wave. But I need to reduce the noise somehow.

有没有其他人的经验这一点。有没有人有办法解决吗？

Has anyone else experience this as well. Does anyone have a solution?

我AP preciated你的时间和响应， 谢谢， DK

I appreciated your time and responses, thanks, dk

推荐答案

当您阅读从AudioFormat.ENCODING_PCM_16BIT字节流，它可以使你俩上下每个样品的2个连续的字节字节。这会显得极其嘈杂的，如果你只是把每个字节是一个样本（而不是一半样本，它实际上是），再加上签售会是错误的第一个字节（它在小尾数顺序）。

When you read bytes from a "AudioFormat.ENCODING_PCM_16BIT" stream, it actually gives you both the upper and lower bytes of each sample as 2 sequential bytes. This will seem extremely noisy if you just take each byte to be a sample (instead of the half sample it actually is), plus the signing will be wrong for the first byte (it's in little endian order).

要得到有意义的数据输出流，通过短裤读，如：

To get meaningful data out of the stream, read via shorts, e.g.

public void run() {
  while(isRecording) {
    audioRecord.startRecording();
    short[] data = new short[bufferSize/2];
    audioRecord.read(data, 0, bufferSize/2);
    listener.setData(data);
    handleData(data);
  }
  audioRecord.release();
}

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