调用方法

	var url = "https://xxxx.mp3"DownloadAndConvertTask(context.cacheDir.path).execute(url)

代码实现

class DownloadAndConvertTask constructor(cacheDirPath: String): AsyncTask<String?, Void?, Void?>() {//缓存路径var cacheDir = File(cacheDirPath)override fun doInBackground(vararg params: String?): Void? {if (params.isNotEmpty()) {val audioUrl = params[0]if (audioUrl != null) {val path = downloadAudioFile(audioUrl)val pcmPath = decodeAudioToPcm(path)if(!pcmPath.isNullOrBlank()){// TODO ... 这里拿到pcm文件路径}}}return null}/*** 下載音频文件到本地* @param audioUrl 要下载的音频链接* @return 下载到本地的文件路径*/private fun downloadAudioFile(audioUrl: String): String{Log.d("downloadAndConvert", "audioUrl = "+audioUrl)var urlConnection: HttpURLConnection?var outputStream: FileOutputStream?// Open a connection to the audio file URLval url = URL(audioUrl)urlConnection = url.openConnection() as HttpURLConnectionurlConnection.connect()// Create a temporary file to store the downloaded audio dataval tempFile: File = File.createTempFile("temp_audio", null, cacheDir)outputStream = FileOutputStream(tempFile)// Write the downloaded audio data to the temporary fileval buffer = ByteArray(1024)var bytesRead: Intwhile (urlConnection.inputStream.read(buffer).also { bytesRead = it } != -1) {outputStream.write(buffer, 0, bytesRead)}outputStream.close()urlConnection.inputStream.close()urlConnection.disconnect()return tempFile.absolutePath}/*** 音頻文件解码为pcm格式* @param inputAudioFile 要转码的音频文件路径* @return pcm文件路径*/private fun decodeAudioToPcm(inputAudioFile: String): String? {Log.d(TAG, "decodeAudioToPcm start inputAudioFile = $inputAudioFile")if(inputAudioFile.isEmpty()){return null}if(inputAudioFile.endsWith(".pcm")){return inputAudioFile}val timeStart = System.currentTimeMillis()val mediaExtractor = MediaExtractor()var mediaCodec: MediaCodec? = nullvar outputStream: FileOutputStream? = nullval tempPcmFile: File = File.createTempFile("temp_audio_pcm", ".pcm", cacheDir)try {// 设置数据源为输入音频文件mediaExtractor.setDataSource(inputAudioFile)// 选择第一个默认轨道（多个音轨时，请注意选择音轨）mediaExtractor.selectTrack(0)// 获取音频轨道的格式val inputFormat = mediaExtractor.getTrackFormat(0)Log.d(TAG, "decodeAudioToPcm MediaFormat.KEY_MIME = "+inputFormat.getString(MediaFormat.KEY_MIME))// 创建用于解码的 MediaCodecmediaCodec = MediaCodec.createDecoderByType(inputFormat.getString(MediaFormat.KEY_MIME)!!)mediaCodec.configure(inputFormat, null, null, 0)mediaCodec.start()// 开始解码并写入到 PCM 文件val codecInputBuffers = mediaCodec.inputBuffersval codecOutputBuffers = mediaCodec.outputBuffersval bufferInfo = MediaCodec.BufferInfo()// 输出 PCM 文件的路径val pcmOutputFile = File(tempPcmFile.absolutePath)outputStream = FileOutputStream(pcmOutputFile)var isDone = falsewhile (!isDone) {// 获取可用的输入缓冲区val inputBufferIndex = mediaCodec.dequeueInputBuffer(10000)if (inputBufferIndex >= 0) {// 获取输入缓冲区val inputBuffer = codecInputBuffers[inputBufferIndex]// 读取音频数据到输入缓冲区val sampleSize = mediaExtractor.readSampleData(inputBuffer, 0)if (sampleSize < 0) {// 如果没有更多数据，发送 EOS（End of Stream）标志mediaCodec.queueInputBuffer(inputBufferIndex, 0, 0, 0, MediaCodec.BUFFER_FLAG_END_OF_STREAM)isDone = true} else {// 将数据放入输入缓冲区，并前进到下一帧mediaCodec.queueInputBuffer(inputBufferIndex, 0, sampleSize, mediaExtractor.sampleTime, 0 )mediaExtractor.advance()}}// 获取解码后的输出数据val outputBufferIndex = mediaCodec.dequeueOutputBuffer(bufferInfo, 10000)if (outputBufferIndex >= 0) {// 获取输出缓冲区val outputBuffer = codecOutputBuffers[outputBufferIndex]// 将 PCM 数据从输出缓冲区中读取到字节数组中val chunk = ByteArray(bufferInfo.size)outputBuffer.get(chunk)outputBuffer.clear()// 将 PCM 数据写入到输出文件outputStream.write(chunk, 0, chunk.size)// 释放输出缓冲区mediaCodec.releaseOutputBuffer(outputBufferIndex, false)}}} catch (e: IOException) {Log.e(TAG, "Error decoding audio to PCM: " + e.message)return null} finally {try {// 关闭资源if (mediaCodec != null) {mediaCodec.stop()mediaCodec.release()}mediaExtractor.release()outputStream?.close()} catch (e: IOException) {e.printStackTrace()}}Log.d(TAG, "decodeAudioToPcm end outputPcmFile = "+tempPcmFile.absolutePath)Log.d(TAG, "decodeAudioToPcm end outputPcmFile.length = "+tempPcmFile.length())Log.d(TAG, "decodeAudioToPcm time consuming (ms) = "+(System.currentTimeMillis()-timeStart))return tempPcmFile.absolutePath}}