您可以使用MediaRecorder直接将流录制到AAC，但似乎没有办法将现有的PCM / WAV文件编码为AAC。编码到AAC的能力本身存在于Android中，我想使用它。是否有办法使用预先存在的音频文件？
答案 0 :(得分：3)
看看这个美丽的（并且完美地工作）示例： Mp4ParserSample
查看类的最后部分（行335-442），convert Runnable对象就完成了工作！您必须根据需要调整代码，调整输入和输出文件路径以及转换参数（采样率，比特率等）。
public static final String AUDIO_RECORDING_FILE_NAME = "audio_Capturing-190814-034638.422.wav"; // Input PCM file
public static final String COMPRESSED_AUDIO_FILE_NAME = "convertedmp4.m4a"; // Output MP4/M4A file
public static final String COMPRESSED_AUDIO_FILE_MIME_TYPE = "audio/mp4a-latm";
public static final int COMPRESSED_AUDIO_FILE_BIT_RATE = 64000; // 64kbps
public static final int SAMPLING_RATE = 48000;
public static final int BUFFER_SIZE = 48000;
public static final int CODEC_TIMEOUT_IN_MS = 5000;
String LOGTAG = "CONVERT AUDIO";
Runnable convert = new Runnable() {
@TargetApi(Build.VERSION_CODES.JELLY_BEAN_MR2)
@Override
public void run() {
android.os.Process.setThreadPriority(android.os.Process.THREAD_PRIORITY_BACKGROUND);
try {
String filePath = Environment.getExternalStorageDirectory().getPath() + "/" + AUDIO_RECORDING_FILE_NAME;
File inputFile = new File(filePath);
FileInputStream fis = new FileInputStream(inputFile);
File outputFile = new File(Environment.getExternalStorageDirectory().getAbsolutePath() + "/" + COMPRESSED_AUDIO_FILE_NAME);
if (outputFile.exists()) outputFile.delete();
MediaMuxer mux = new MediaMuxer(outputFile.getAbsolutePath(), MediaMuxer.OutputFormat.MUXER_OUTPUT_MPEG_4);
MediaFormat outputFormat = MediaFormat.createAudioFormat(COMPRESSED_AUDIO_FILE_MIME_TYPE,SAMPLING_RATE, 1);
outputFormat.setInteger(MediaFormat.KEY_AAC_PROFILE, MediaCodecInfo.CodecProfileLevel.AACObjectLC);
outputFormat.setInteger(MediaFormat.KEY_BIT_RATE, COMPRESSED_AUDIO_FILE_BIT_RATE);
outputFormat.setInteger(MediaFormat.KEY_MAX_INPUT_SIZE, 16384);
MediaCodec codec = MediaCodec.createEncoderByType(COMPRESSED_AUDIO_FILE_MIME_TYPE);
codec.configure(outputFormat, null, null, MediaCodec.CONFIGURE_FLAG_ENCODE);
codec.start();
ByteBuffer[] codecInputBuffers = codec.getInputBuffers(); // Note: Array of buffers
ByteBuffer[] codecOutputBuffers = codec.getOutputBuffers();
MediaCodec.BufferInfo outBuffInfo = new MediaCodec.BufferInfo();
byte[] tempBuffer = new byte[BUFFER_SIZE];
boolean hasMoreData = true;
double presentationTimeUs = 0;
int audioTrackIdx = 0;
int totalBytesRead = 0;
int percentComplete = 0;
do {
int inputBufIndex = 0;
while (inputBufIndex != -1 && hasMoreData) {
inputBufIndex = codec.dequeueInputBuffer(CODEC_TIMEOUT_IN_MS);
if (inputBufIndex >= 0) {
ByteBuffer dstBuf = codecInputBuffers[inputBufIndex];
dstBuf.clear();
int bytesRead = fis.read(tempBuffer, 0, dstBuf.limit());
Log.e("bytesRead","Readed "+bytesRead);
if (bytesRead == -1) { // -1 implies EOS
hasMoreData = false;
codec.queueInputBuffer(inputBufIndex, 0, 0, (long) presentationTimeUs, MediaCodec.BUFFER_FLAG_END_OF_STREAM);
} else {
totalBytesRead += bytesRead;
dstBuf.put(tempBuffer, 0, bytesRead);
codec.queueInputBuffer(inputBufIndex, 0, bytesRead, (long) presentationTimeUs, 0);
presentationTimeUs = 1000000l * (totalBytesRead / 2) / SAMPLING_RATE;
}
}
}
// Drain audio
int outputBufIndex = 0;
while (outputBufIndex != MediaCodec.INFO_TRY_AGAIN_LATER) {
outputBufIndex = codec.dequeueOutputBuffer(outBuffInfo, CODEC_TIMEOUT_IN_MS);
if (outputBufIndex >= 0) {
ByteBuffer encodedData = codecOutputBuffers[outputBufIndex];
encodedData.position(outBuffInfo.offset);
encodedData.limit(outBuffInfo.offset + outBuffInfo.size);
if ((outBuffInfo.flags & MediaCodec.BUFFER_FLAG_CODEC_CONFIG) != 0 && outBuffInfo.size != 0) {
codec.releaseOutputBuffer(outputBufIndex, false);
}else{
mux.writeSampleData(audioTrackIdx, codecOutputBuffers[outputBufIndex], outBuffInfo);
codec.releaseOutputBuffer(outputBufIndex, false);
}
} else if (outputBufIndex == MediaCodec.INFO_OUTPUT_FORMAT_CHANGED) {
outputFormat = codec.getOutputFormat();
Log.v(LOGTAG, "Output format changed - " + outputFormat);
audioTrackIdx = mux.addTrack(outputFormat);
mux.start();
} else if (outputBufIndex == MediaCodec.INFO_OUTPUT_BUFFERS_CHANGED) {
Log.e(LOGTAG, "Output buffers changed during encode!");
} else if (outputBufIndex == MediaCodec.INFO_TRY_AGAIN_LATER) {
// NO OP
} else {
Log.e(LOGTAG, "Unknown return code from dequeueOutputBuffer - " + outputBufIndex);
}
}
percentComplete = (int) Math.round(((float) totalBytesRead / (float) inputFile.length()) * 100.0);
Log.v(LOGTAG, "Conversion % - " + percentComplete);
} while (outBuffInfo.flags != MediaCodec.BUFFER_FLAG_END_OF_STREAM);
fis.close();
mux.stop();
mux.release();
Log.v(LOGTAG, "Compression done ...");
} catch (FileNotFoundException e) {
Log.e(LOGTAG, "File not found!", e);
} catch (IOException e) {
Log.e(LOGTAG, "IO exception!", e);
}
//mStop = false;
// Notify UI thread...
}
};
答案 1 :(得分：1)
您可以轻松使用本机代码，并在框架中使用IOMX C ++接口来解码器。但这对构建敏感，不适用于其他手机和Android风格。
另一个选择是移植一个像ffmpeg这样的开源aac编码器，并在jni上写一个应用程序。至少使用具有相同架构的手机（arm-9，cortex a8 ..）。
JB有一个MediaCodec只是为了满足您的愿望。但问题是JB的设备的安装基础会更长一段时间。
http://developer.android.com/about/versions/android-4.1.html#Multimedia
答案 2 :(得分：0)