Question

I'm trying to draw a spectral representation of some recorded audio. Using the AudioRecord class, i get an array of bytes with amplitude values i guess.

Now the problem is that i don't know how to represent the time axis.

Any ideas??

Recording code:

 public void startRecording(View v) {
    mIsRecording = true;
    mRecorder.startRecording();


    new Thread(new Runnable() {
        @Override
        public void run() {

                while (mIsRecording) {
                    int readSize = mRecorder.read(mBuffer, 0, mBuffer.length);

                }

        }
    }).start();
}

Recorder init:

private void initRecorder() {
    int bufferSize = AudioRecord.getMinBufferSize(SAMPLE_RATE, AudioFormat.CHANNEL_IN_MONO,
            AudioFormat.ENCODING_PCM_16BIT);
    mBuffer = new short[bufferSize];
    mRecorder = new AudioRecord(MediaRecorder.AudioSource.MIC, SAMPLE_RATE, AudioFormat.CHANNEL_IN_MONO,
            AudioFormat.ENCODING_PCM_16BIT, bufferSize);
}

Thanks in advance.

Answer 1

首先，当你谈论频谱时，你指的是音频信号的频率成分，这与振幅非常不同。

无论如何，如果要绘制幅度随时间的变化， x轴将是 y轴幅度的时间。这里的关键值是采样率，它定义了您每秒记录的采样数;您需要决定在屏幕上绘制平均振幅值的时间（与采样率相关），然后......只需绘制它。我建议你从更简单的事情开始，比如Samsung official docs中的以下示例：

AudioRecord recorder; // our recorder, must be initialized first
short[] buffer; // buffer where we will put captured samples
DataOutputStream output; // output stream to target file
boolean isRecording; // indicates if sound is currently being captured
ProgressBar pb; // our progress bar recieved from layout
while (isRecording) {
  double sum = 0;
  int readSize = recorder.read(buffer, 0, buffer.length);
  for (int i = 0; i < readSize; i++) {
      output.writeShort(buffer [i]);
      sum += buffer [i] * buffer [i];
  }
  if (readSize > 0) {
      final double amplitude = sum / readSize;
      pb.setProgress((int) Math.sqrt(amplitude));
  }
}

此示例显示实时幅度值（使用ProgressBar）;您可以调整此示例并按时间顺序绘制幅度值（例如，在Canvas中绘制连续的垂直线）

Draw Amplitudes by time Audio Android

1 个答案: