我需要将PCM文件转换为AAC或MP4文件。到目前为止，我使用的是MediaCodec和MediaMuxer，但MediaMuxer是由Android 4.3支持的。是否有不使用MediaMuxer的方法来进行转换?
我的代码是:
MediaMuxer mux = null;
try {
File inputFile = new File(filePath + ".pcm");
FileInputStream fis = new FileInputStream(inputFile);
mux = new MediaMuxer(filePath + ".mp4", 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);
MediaCodec codec = MediaCodec.createEncoderByType(COMPRESSED_AUDIO_FILE_MIME_TYPE);
codec.configure(outputFormat, null, null, MediaCodec.CONFIGURE_FLAG_ENCODE);
codec.start();
ByteBuffer[] codecInputBuffers = codec.getInputBuffers();
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;
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());
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("AUDIO", "Output format changed - " + outputFormat);
audioTrackIdx = mux.addTrack(outputFormat);
mux.start();
} else if (outputBufIndex == MediaCodec.INFO_OUTPUT_BUFFERS_CHANGED) {
Log.e("AUDIO", "Output buffers changed during encode!");
} else if (outputBufIndex != MediaCodec.INFO_TRY_AGAIN_LATER){
Log.e("AUDIO", "Unknown return code from dequeueOutputBuffer - " + outputBufIndex);
}
}
percentComplete = (int) Math.round(((float) totalBytesRead / (float) inputFile.length()) * 100.0);
Log.v("AUDIO", "Conversion % - " + percentComplete);
} while (outBuffInfo.flags != MediaCodec.BUFFER_FLAG_END_OF_STREAM);
fis.close();
mux.stop();
mux.release();
正如你已经指出的，对于这类工作，没有与旧版本的Android兼容的公共系统API。
无论如何，您可以使用本机编码器(如FFMPEG)来追求自定义解决方案。timsu/android-aac-encAndroid AAC编码器项目
Android Stagefright VO AAC编码器的提取。
这个项目为底层的JNI编码器
提供了一个简单的Java API，它应该已经准备好使用了，因为本机库已经为通用的ARM架构编译了(请注意，我还没有测试过它)。整个库只有500kb，所以它不会让你的APK变胖那么多。为了快速测试，在项目中导入以下部分:
- 本机AAC编码的Java绑定
- 预编译的AAC编码器。so库
- 使用示例(语音编码)
您应该能够轻松地将示例调整为您的代码。