Android录音并且输出为Mp4文件的方法教程

fun prepare(file: File?, outputFormat: Int = MediaMuxer.OutputFormat.MUXER_OUTPUT_MPEG_4, audioSource: Int = MediaRecorder.AudioSource.MIC, sampleRateInHz: Int = 44100, channelConfig: Int = AudioFormat.CHANNEL_IN_STEREO, audioFormat: Int = AudioFormat.ENCODING_PCM_16BIT, bufferSizeInBytes: Int = AudioRecord.getMinBufferSize(sampleRateInHz, channelConfig, audioFormat))
{
 //初始化AudioRecord
 prepareAudioRecord(audioSource, sampleRateInHz, channelConfig, audioFormat, bufferSizeInBytes)
 //初始化输出文件
 prepareOutputFile(file)
 //初始化AudioEncoder
 prepareAudioEncoder(sampleRateInHz, outputFormat)
}


private fun prepareAudioRecord(audioSource: Int, sampleRateInHz: Int, channelConfig: Int, audioFormat: Int, bufferSizeInBytes: Int)
{
 minSize = AudioRecord.getMinBufferSize(sampleRateInHz, channelConfig, audioFormat)

 audioRecord = AudioRecord(audioSource, sampleRateInHz, channelConfig, audioFormat, bufferSizeInBytes)
}

private val recordRunnable = Runnable {


 val data = ByteArray(minSize)
 //AudioRecord开始录音
 audioRecord?.startRecording()
 while (isRecording)
 {
  //将音频数据写入ByteArray
  audioRecord?.read(data, 0, data.size)
  audioEncoder.start()
  audioEncoder.drainEncoder(data)
 }
 audioEncoder.release()
 audioRecord?.stop()
 audioRecord?.release()
 audioRecord = null
}

private fun prepareAudioCodec(bitrate: Int, sampleRate: Int)
{
 bufferInfo = MediaCodec.BufferInfo()
 val mediaFormat = MediaFormat()
 mediaFormat.setInteger(MediaFormat.KEY_AAC_PROFILE, MediaCodecInfo.CodecProfileLevel.AACObjectLC)
 mediaFormat.setString(MediaFormat.KEY_MIME, MediaFormat.MIMETYPE_AUDIO_AAC)
 mediaFormat.setInteger(MediaFormat.KEY_BIT_RATE, bitrate)
 mediaFormat.setInteger(MediaFormat.KEY_CHANNEL_COUNT, 2)
 mediaFormat.setInteger(MediaFormat.KEY_SAMPLE_RATE, sampleRate)
 audioCodec = MediaCodec.createEncoderByType(MediaFormat.MIMETYPE_AUDIO_AAC)
 audioCodec.configure(mediaFormat, null, null, MediaCodec.CONFIGURE_FLAG_ENCODE)
}

 fun drainEncoder(data: ByteArray)
{

  val inIndex = audioCodec.dequeueInputBuffer(0)
  if (inIndex > 0)
  {
    val inBuffer = getInBuffer(inIndex)
    inBuffer.clear()
    inBuffer.put(data)
    if (!isEncoding)
    {
      audioCodec.queueInputBuffer(inIndex, 0, 0, System.nanoTime() / 1000, BUFFER_FLAG_END_OF_STREAM)

    } else
    {
      audioCodec.queueInputBuffer(inIndex, 0, data.size, System.nanoTime() / 1000, 0)
    }

  }

  do
  {
    val outIndex = audioCodec.dequeueOutputBuffer(bufferInfo, 0)
    when
    {
      outIndex > 0 ->
      {

        if (bufferInfo.size != 0)
        {
          val outBuffer = getOutBuffer(outIndex)
          outBuffer.position(bufferInfo.offset)
          outBuffer.limit(bufferInfo.offset + bufferInfo.size)
          mediaMuxer.writeSampleData(trackIndex, outBuffer, bufferInfo)
        }
        audioCodec.releaseOutputBuffer(outIndex, false)
      }
      outIndex == MediaCodec.INFO_OUTPUT_FORMAT_CHANGED ->
      {
        trackIndex = mediaMuxer.addTrack(audioCodec.outputFormat)
        mediaMuxer.start()
      }

    }
  } while (outIndex > 0)

  if (bufferInfo.flags and MediaCodec.BUFFER_FLAG_END_OF_STREAM != 0)
  {

    isEncoding = false
  }
}