1.文章介绍
写这篇文章的目的主要是分享这段时间自己对MediaCodec的学习和理解，也顺便把在实际调试中踩的坑记录下，给关注该技术的同学一些参考。
2.实现目标
在Android设备上把本地视频或者网络视频解码后重新编码为H264(video/avc)/AAC(audio/mp4a-latm)，最后合成可播放的音视频文件。
3.技术核心
关注该技术的同学，一般都能从网络上搜到如Android设备上从Camera获取YUV实现硬解，从麦克风采集PCM实现音频播放等文章，这样的文章很多很多了。
而本文章的技术点是：通过MediaExtractor从一个音视频文件中解复用出video es和audio es，然后通过MediaCodec硬解码分别输出YUV和PCM，再通过MediaCodec合成video es和audio es，最后通过MediaMuxer合成音视频文件，这样的尝试应该可以让各位同学更好的学习和了解MediaCodec。
以下是构想的实际应用场景图：
通过配置编码器参数，可以使编码后的音视频更小，这样从一定程度上就可以减少带宽使用。
4.干货
如果你已经看到这里，说明你也同样关注该文章所提及到的技术，以下技术内容如果有错误的地方，请留言，我会同步更新。
1.先给出一段代码定义，避免踩坑
/** How long to wait for the next buffer to become available. */
private static final int TIMEOUT_USEC = 10000;
/** parameters for the video encoder */
private static final String OUTPUT_VIDEO_MIME_TYPE = "video/avc"; // H.264 Advanced Video Coding
private static final int OUTPUT_VIDEO_BIT_RATE = 512 * 1024; // 512 kbps maybe better
private static final int OUTPUT_VIDEO_FRAME_RATE = 25; // 25fps
private static final int OUTPUT_VIDEO_IFRAME_INTERVAL = 10; // 10 seconds between I-frames
private static final int OUTPUT_VIDEO_COLOR_FORMAT = MediaCodecInfo.CodecCapabilities.COLOR_FormatYUV420SemiPlanar;
/** parameters for the audio encoder */
private static final String OUTPUT_AUDIO_MIME_TYPE = "audio/mp4a-latm"; // Advanced Audio Coding
private static final int OUTPUT_AUDIO_BIT_RATE = 64 * 1024; // 64 kbps
private static final int OUTPUT_AUDIO_AAC_PROFILE = MediaCodecInfo.CodecProfileLevel.AACObjectLC; // better then AACObjectHE?
/** parameters for the audio encoder config from input stream */
private int OUTPUT_AUDIO_CHANNEL_COUNT = 1; // Must match the input stream.can not config
private int OUTPUT_AUDIO_SAMPLE_RATE_HZ = 48000; // Must match the input stream.can not config
/** Whether to copy the video from the test video. */
private boolean mCopyVideo = false;
/** Whether to copy the audio from the test audio. */
private boolean mCopyAudio = false;
/** Width of the output frames. */
private int mWidth = -1;
/** Height of the output frames. */
private int mHeight = -1;
/** The raw resource used as the input file. */
private String mBaseFileRoot;
/** The raw resource used as the input file. */
private String mBaseFile;
/** The destination file for the encoded output. */
private String mOutputFile;
private boolean interrupted = false;
首先视频编码的COLOR_FORMAT是需要特别注意的，可以通过以下代码测试Android设备支持的format：
private void showSupportedColorFormat(MediaCodecInfo.CodecCapabilities caps) {
for (int c : caps.colorFormats) {
if (VERBOSE)
Log.d(TAG, "supported color format: " + c);
}
}
一般来说COLOR_FormatYUV420SemiPlanar这个值在4.4版本上比较通用，在5.0版本及以上MediaCodec的实现有了变化，而COLOR_FormatYUV420Flexible通用性更好；
调试时在某个Android设备上使用COLOR_FormatYUV420PackedPlanar来解码、编码，颜色就出现了问题，黄色全变成了蓝色，整个色调偏冷等。
对于音频编码，需要注意以下几个问题：
1.OUTPUT_AUDIO_AAC_PROFILE，这个参数使用AACObjectLC会比AACObjectHE的兼容性会更好，我在调试时，使用AACObjectHE，某些编码格式的音频es无法编码。
2.OUTPUT_AUDIO_CHANNEL_COUNT，音频的声道数最好和源音频的声道数保持一致，否则编码时音频es的时间戳可能是乱序的
3.OUTPUT_AUDIO_SAMPLE_RATE_HZ，音频的波特率最好和源音频的波特率保持一致，否则编码时音频es的时间戳可能是乱序的
2.配置
在进行实际解码编码工作前，需要配置好解复用器，解码器和编码器以及混合器。
private void extractDecodeEncodeMux() throws Exception {
// Exception that may be thrown during release.
Exception exception = null;
MediaExtractor videoExtractor = null;
MediaExtractor audioExtractor = null;
OutputSurface outputSurface = null;
MediaCodec videoDecoder = null;
MediaCodec audioDecoder = null;
MediaCodec videoEncoder = null;
MediaCodec audioEncoder = null;
MediaMuxer muxer = null;
InputSurface inputSurface = null;
try {
if (mCopyVideo) {
videoExtractor = createExtractor();
int videoInputTrack = getAndSelectVideoTrackIndex(videoExtractor);
Log.d(TAG, " video track in test video " + videoInputTrack);
MediaFormat inputFormat = videoExtractor
.getTrackFormat(videoInputTrack);
if (VERBOSE)
Log.d(TAG, "video base input format: " + inputFormat);
// make sure decode buffer size equals encode buffer size
inputFormat.setInteger(MediaFormat.KEY_COLOR_FORMAT,
OUTPUT_VIDEO_COLOR_FORMAT);
if (mWidth != -1) {
inputFormat.setInteger(MediaFormat.KEY_WIDTH, mWidth);
} else {
mWidth = inputFormat.getInteger(MediaFormat.KEY_WIDTH);
}
if (mHeight != -1) {
inputFormat.setInteger(MediaFormat.KEY_HEIGHT, mHeight);
} else {
mHeight = inputFormat.getInteger(MediaFormat.KEY_HEIGHT);
}
if (VERBOSE)Log.d(TAG, "video match input format: " + inputFormat);
MediaCodecInfo videoCodecInfo = selectCodec(OUTPUT_VIDEO_MIME_TYPE);
if (videoCodecInfo == null) {
Log.e(TAG, "Unable to find an appropriate codec for "
+ OUTPUT_VIDEO_MIME_TYPE);
return;
}
if (VERBOSE)
Log.d(TAG, "video found codec: " + videoCodecInfo.getName());
MediaFormat outputVideoFormat = MediaFormat.createVideoFormat(
OUTPUT_VIDEO_MIME_TYPE, mWidth, mHeight);
outputVideoFormat.setInteger(MediaFormat.KEY_COLOR_FORMAT,
OUTPUT_VIDEO_COLOR_FORMAT);
outputVideoFormat.setInteger(MediaFormat.KEY_BIT_RATE,
OUTPUT_VIDEO_BIT_RATE);
outputVideoFormat.setInteger(MediaFormat.KEY_FRAME_RATE,
OUTPUT_VIDEO_FRAME_RATE);
outputVideoFormat.setInteger(MediaFormat.KEY_I_FRAME_INTERVAL,
OUTPUT_VIDEO_IFRAME_INTERVAL);
if (VERBOSE)Log.d(TAG, "video encode format: " + outputVideoFormat);
videoEncoder = createVideoEncoder(videoCodecInfo,
outputVideoFormat, null);
videoDecoder = createVideoDecoder(inputFormat, null);
}
if (mCopyAudio) {
audioExtractor = createExtractor();
int audioInputTrack = getAndSelectAudioTrackIndex(audioExtractor);
Log.d(TAG, " audio track in test audio " + audioInputTrack);
MediaFormat inputFormat = audioExtractor
.getTrackFormat(audioInputTrack);
if (VERBOSE)
Log.d(TAG, "audio base input format: " + inputFormat);
// inputFormat.setInteger(MediaFormat.KEY_AAC_PROFILE,OUTPUT_AUDIO_AAC_PROFILE);
OUTPUT_AUDIO_SAMPLE_RATE_HZ = inputFormat.getInteger(
MediaFormat.KEY_SAMPLE_RATE,
OUTPUT_AUDIO_SAMPLE_RATE_HZ);
OUTPUT_AUDIO_CHANNEL_COUNT = inputFormat.getInteger(
MediaFormat.KEY_CHANNEL_COUNT,
OUTPUT_AUDIO_CHANNEL_COUNT);
if (VERBOSE)Log.d(TAG, "audio match input format: " + inputFormat);
MediaCodecInfo audioCodecInfo = selectCodec(OUTPUT_AUDIO_MIME_TYPE);
if (audioCodecInfo == null) {
Log.e(TAG, "Unable to find an appropriate codec for "
+ OUTPUT_AUDIO_MIME_TYPE);
return;
}
if (VERBOSE)
Log.d(TAG, "audio found codec: " + audioCodecInfo.getName());
MediaFormat outputAudioFormat = MediaFormat.createAudioFormat(
OUTPUT_AUDIO_MIME_TYPE, OUTPUT_AUDIO_SAMPLE_RATE_HZ,
OUTPUT_AUDIO_CHANNEL_COUNT);
outputAudioFormat.setInteger(MediaFormat.KEY_MAX_INPUT_SIZE,
100 * 1024);
outputAudioFormat.setInteger(MediaFormat.KEY_BIT_RATE,
OUTPUT_AUDIO_BIT_RATE);
outputAudioFormat.setInteger(MediaFormat.KEY_AAC_PROFILE,
OUTPUT_AUDIO_AAC_PROFILE);
if (VERBOSE)
Log.d(TAG, "audio encode format: " + outputAudioFormat);
// Create a MediaCodec for the desired codec, then configure it
// as an encoder with our desired properties.
audioEncoder = createAudioEncoder(audioCodecInfo,
outputAudioFormat);
// Create a MediaCodec for the decoder, based on the extractor's
// format.
audioDecoder = createAudioDecoder(inputFormat);
}
setOutputFile();
// Creates a muxer but do not start or add tracks just yet.
muxer = createMuxer();
doExtractDecodeEncodeMux(videoExtractor, audioExtractor,
videoDecoder, videoEncoder, audioDecoder, audioEncoder,
muxer, inputSurface, outputSurface);
if (mCallback != null) {
mCallback.onCallBack(CodecCallBack.STATUS_SUCCESS);
}
}finally {
if (VERBOSE)
Log.d(TAG, "releasing extractor, decoder, encoder, and muxer");
try {
if (videoExtractor != null) {
videoExtractor.release();
}
} catch (Exception e) {
Log.e(TAG, "error while releasing videoExtractor", e);
// if (exception == null) {
// exception = e;
// }
}
try {
if (audioExtractor != null) {
audioExtractor.release();
}
} catch (Exception e) {
Log.e(TAG, "error while releasing audioExtractor", e);
// if (exception == null) {
// exception = e;
// }
}
try {
if (videoDecoder != null) {
videoDecoder.stop();
videoDecoder.release();
}
} catch (Exception e) {
Log.e(TAG, "error while releasing videoDecoder", e);
// if (exception == null) {
// exception = e;
// }
}
try {
if (outputSurface != null) {
outputSurface.release();
}
} catch (Exception e) {
Log.e(TAG, "error while releasing outputSurface", e);
// if (exception == null) {
// exception = e;
// }
}
try {
if (videoEncoder != null) {
videoEncoder.stop();
videoEncoder.release();
}
} catch (Exception e) {
Log.e(TAG, "error while releasing videoEncoder", e);
// if (exception == null) {
// exception = e;
// }
}
try {
if (audioDecoder != null) {
audioDecoder.stop();
audioDecoder.release();
}
} catch (Exception e) {
Log.e(TAG, "error while releasing audioDecoder", e);
// if (exception == null) {
// exception = e;
// }
}
try {
if (audioEncoder != null) {
audioEncoder.stop();
audioEncoder.release();
}
} catch (Exception e) {
Log.e(TAG, "error while releasing audioEncoder", e);
// if (exception == null) {
// exception = e;
// }
}
try {
if (muxer != null) {
muxer.stop();
muxer.release();
}
} catch (Exception e) {
Log.e(TAG, "error while releasing muxer", e);
// if (exception == null) {
// exception = e;
// }
}
try {
if (inputSurface != null) {
inputSurface.release();
}
} catch (Exception e) {
Log.e(TAG, "error while releasing inputSurface", e);
// if (exception == null) {
// exception = e;
// }
}
}
if (exception != null) {
throw exception;
}
}
上面一段代码很多，但是结构应该很清晰
1.分别创建videoExtractor和audioExtractor来对输入流解复用，得到video es和audio es:
/**
* Creates an extractor that reads its frames from {@link #mSourceResId}.
*/
private MediaExtractor createExtractor() throws IOException {
// net source
MediaExtractor extractor = new MediaExtractor();
if (mBaseFile.contains(":")) {
extractor.setDataSource(mBaseFile);
} else {
File mFile = new File(mBaseFile);
extractor.setDataSource(mFile.toString());
}
return extractor;
}
private int getAndSelectVideoTrackIndex(MediaExtractor extractor) {
for (int index = 0; index < extractor.getTrackCount(); ++index) {
if (VERBOSE) {
Log.d(TAG, "format for track " + index + " is "
+ getMimeTypeFor(extractor.getTrackFormat(index)));
}
if (isVideoFormat(extractor.getTrackFormat(index))) {
extractor.selectTrack(index);
return index;
}
}
return -1;
}
private int getAndSelectAudioTrackIndex(MediaExtractor extractor) {
for (int index = 0; index < extractor.getTrackCount(); ++index) {
if (VERBOSE) {
Log.d(TAG, "format for track " + index + " is "
+ getMimeTypeFor(extractor.getTrackFormat(index)));
}
if (isAudioFormat(extractor.getTrackFormat(index))) {
extractor.selectTrack(index);
return index;
}
}
return -1;
}
2.通过Extractor获取源es流的信息，如果是视频流则创建及配置对应的视频解码器和视频编码器，如果是音频则创建及配置对应的音频解码器和音频编码器
/**
* Returns the first codec capable of encoding the specified MIME type, or
* null if no match was found.
*/
private static MediaCodecInfo selectCodec(String mimeType) {
int numCodecs = MediaCodecList.getCodecCount();
for (int i = 0; i < numCodecs; i++) {
MediaCodecInfo codecInfo = MediaCodecList.getCodecInfoAt(i);
if (!codecInfo.isEncoder()) {
continue;
}
String[] types = codecInfo.getSupportedTypes();
for (int j = 0; j < types.length; j++) {
if (types[j].equalsIgnoreCase(mimeType)) {
return codecInfo;
}
}
}
return null;
}
/**
* Creates a decoder for the given format, which outputs to the given
* surface.
*
* @param inputFormat
* the format of the stream to decode
* @param surface
* into which to decode the frames
*/
private MediaCodec createVideoDecoder(MediaFormat inputFormat,
Surface surface) {
MediaCodec decoder = MediaCodec
.createDecoderByType(getMimeTypeFor(inputFormat));
decoder.configure(inputFormat, surface, null, 0);
decoder.start();
return decoder;
}
/**
* Creates an encoder for the given format using the specified codec, taking
* input from a surface.
*
*
* The surface to use as input is stored in the given reference.
*
* @param codecInfo
* of the codec to use
* @param format
* of the stream to be produced
* @param surfaceReference
* to store the surface to use as input
*/
private MediaCodec createVideoEncoder(MediaCodecInfo codecInfo,
MediaFormat format, AtomicReference surfaceReference) {
MediaCodec encoder = MediaCodec.createByCodecName(codecInfo.getName());
encoder.configure(format, null, null, MediaCodec.CONFIGURE_FLAG_ENCODE);
// Must be called before start() is.
if (surfaceReference != null) {
surfaceReference.set(encoder.createInputSurface());
}
encoder.start();
return encoder;
}
/**
* Creates a decoder for the given format.
*
* @param inputFormat
* the format of the stream to decode
*/
private MediaCodec createAudioDecoder(MediaFormat inputFormat) {
MediaCodec decoder = MediaCodec
.createDecoderByType(getMimeTypeFor(inputFormat));
decoder.configure(inputFormat, null, null, 0);
decoder.start();
return decoder;
}
/**
* Creates an encoder for the given format using the specified codec.
*
* @param codecInfo
* of the codec to use
* @param format
* of the stream to be produced
*/
private MediaCodec createAudioEncoder(MediaCodecInfo codecInfo,
MediaFormat format) {
MediaCodec encoder = MediaCodec.createByCodecName(codecInfo.getName());
encoder.configure(format, null, null, MediaCodec.CONFIGURE_FLAG_ENCODE);
encoder.start();
return encoder;
}
3.创建一个Muxer，把音视频es混合成文件
/**
* Creates a muxer to write the encoded frames. The muxer is not started as
* it needs to be started only after all streams have been added.
*/
private MediaMuxer createMuxer() throws IOException {
return new MediaMuxer(mOutputFile, MediaMuxer.OutputFormat.MUXER_OUTPUT_MPEG_4);
}
3.解复用、解码，编码，混合
到这一步终于要开始实际工作了：
/**
* Does the actual work for extracting, decoding, encoding and muxing.
*/
private void doExtractDecodeEncodeMux(MediaExtractor videoExtractor,
MediaExtractor audioExtractor, MediaCodec videoDecoder,
MediaCodec videoEncoder, MediaCodec audioDecoder,
MediaCodec audioEncoder, MediaMuxer muxer,
InputSurface inputSurface, OutputSurface outputSurface) {
ByteBuffer[] videoDecoderInputBuffers = null;
ByteBuffer[] videoDecoderOutputBuffers = null;
ByteBuffer[] videoEncoderInputBuffers = null;
ByteBuffer[] videoEncoderOutputBuffers = null;
MediaCodec.BufferInfo videoDecoderOutputBufferInfo = null;
MediaCodec.BufferInfo videoEncoderOutputBufferInfo = null;
if (mCopyVideo) {
videoDecoderInputBuffers = videoDecoder.getInputBuffers();
videoDecoderOutputBuffers = videoDecoder.getOutputBuffers();
videoEncoderInputBuffers = videoEncoder.getInputBuffers();
videoEncoderOutputBuffers = videoEncoder.getOutputBuffers();
videoDecoderOutputBufferInfo = new MediaCodec.BufferInfo();
videoEncoderOutputBufferInfo = new MediaCodec.BufferInfo();
}
ByteBuffer[] audioDecoderInputBuffers = null;
ByteBuffer[] audioDecoderOutputBuffers = null;
ByteBuffer[] audioEncoderInputBuffers = null;
ByteBuffer[] audioEncoderOutputBuffers = null;
MediaCodec.BufferInfo audioDecoderOutputBufferInfo = null;
MediaCodec.BufferInfo audioEncoderOutputBufferInfo = null;
if (mCopyAudio) {
audioDecoderInputBuffers = audioDecoder.getInputBuffers();
audioDecoderOutputBuffers = audioDecoder.getOutputBuffers();
audioEncoderInputBuffers = audioEncoder.getInputBuffers();
audioEncoderOutputBuffers = audioEncoder.getOutputBuffers();
audioDecoderOutputBufferInfo = new MediaCodec.BufferInfo();
audioEncoderOutputBufferInfo = new MediaCodec.BufferInfo();
}
// We will get these from the decoders when notified of a format change.
MediaFormat decoderOutputVideoFormat = null;
MediaFormat decoderOutputAudioFormat = null;
// We will get these from the encoders when notified of a format change.
MediaFormat encoderOutputVideoFormat = null;
MediaFormat encoderOutputAudioFormat = null;
// We will determine these once we have the output format.
int outputVideoTrack = -1;
int outputAudioTrack = -1;
// Whether things are done on the video side.
boolean videoExtractorDone = false;
boolean videoDecoderDone = false;
boolean videoEncoderDone = false;
// Whether things are done on the audio side.
boolean audioExtractorDone = false;
boolean audioDecoderDone = false;
boolean audioEncoderDone = false;
// The video decoder output buffer to process, -1 if none.
int pendingVideoDecoderOutputBufferIndex = -1;
// The audio decoder output buffer to process, -1 if none.
int pendingAudioDecoderOutputBufferIndex = -1;
boolean muxing = false;
int videoExtractedFrameCount = 0;
int videoDecodedFrameCount = 0;
int videoEncodedFrameCount = 0;
int audioExtractedFrameCount = 0;
int audioDecodedFrameCount = 0;
int audioEncodedFrameCount = 0;
boolean mVideoConfig = false;
boolean mainVideoFrame = false;
long mLastVideoSampleTime = 0;
long mVideoSampleTime = 0;
boolean mAudioConfig = false;
boolean mainAudioFrame = false;
long mLastAudioSampleTime = 0;
long mAudioSampleTime = 0;
while (!interrupted&& ((mCopyVideo && !videoEncoderDone) || (mCopyAudio && !audioEncoderDone))) {
//###########################Video###################################
// Extract video from file and feed to decoder.
// Do not extract video if we have determined the output format but
// we are not yet ready to mux the frames.
while (mCopyVideo && !videoExtractorDone
&& (encoderOutputVideoFormat == null || muxing)) {
int decoderInputBufferIndex = videoDecoder
.dequeueInputBuffer(TIMEOUT_USEC);
if (decoderInputBufferIndex <= MediaCodec.INFO_TRY_AGAIN_LATER) {
if (VERBOSE)
Log.d(TAG, "no video decoder input buffer: "
+ decoderInputBufferIndex);
break;
}
if (VERBOSE) {
Log.d(TAG,
"video decoder dequeueInputBuffer: returned input buffer: "
+ decoderInputBufferIndex);
}
ByteBuffer decoderInputBuffer = videoDecoderInputBuffers[decoderInputBufferIndex];
int size = videoExtractor.readSampleData(decoderInputBuffer, 0);
if (videoExtractor.getSampleFlags() == MediaExtractor.SAMPLE_FLAG_SYNC) {
Log.d(TAG, " video decoder SAMPLE_FLAG_SYNC ");
}
long presentationTime = videoExtractor.getSampleTime();
if (VERBOSE) {
Log.d(TAG, "video extractor: returned buffer of size "
+ size);
Log.d(TAG, "video extractor: returned buffer for time "
+ presentationTime);
}
if (size > 0) {
videoDecoder.queueInputBuffer(decoderInputBufferIndex, 0,
size, presentationTime,
videoExtractor.getSampleFlags());
}
videoExtractorDone = !videoExtractor.advance();
if (videoExtractorDone) {
if (VERBOSE)
Log.d(TAG, "video extractor: EOS");
videoDecoder.queueInputBuffer(decoderInputBufferIndex, 0,
0, 0, MediaCodec.BUFFER_FLAG_END_OF_STREAM);
}
videoExtractedFrameCount++;
// We extracted a frame, let's try something else next.
break;
}
//###########################Audio###################################
// Extract audio from file and feed to decoder.
// Do not extract audio if we have determined the output format but
// we are not yet ready to mux the frames.
while (mCopyAudio && !audioExtractorDone
&& (encoderOutputAudioFormat == null || muxing)) {
int decoderInputBufferIndex = audioDecoder.dequeueInputBuffer(TIMEOUT_USEC);
if (decoderInputBufferIndex <= MediaCodec.INFO_TRY_AGAIN_LATER) {
if (VERBOSE)Log.d(TAG, "no audio decoder input buffer: "+decoderInputBufferIndex);
break;
}
if (VERBOSE) {
Log.d(TAG, "audio decoder dequeueInputBuffer: returned input buffer: "
+ decoderInputBufferIndex);
}
ByteBuffer decoderInputBuffer = audioDecoderInputBuffers[decoderInputBufferIndex];
int size = audioExtractor.readSampleData(decoderInputBuffer, 0);
long presentationTime = audioExtractor.getSampleTime();
if (VERBOSE) {
Log.d(TAG, "audio extractor: returned buffer of size "
+ size);
Log.d(TAG, "audio extractor: returned buffer for time "
+ presentationTime);
}
if (size > 0) {
audioDecoder.queueInputBuffer(decoderInputBufferIndex, 0,
size, presentationTime,
audioExtractor.getSampleFlags());
}
audioExtractorDone = !audioExtractor.advance();
if (audioExtractorDone) {
if (VERBOSE)Log.d(TAG, "audio extractor: EOS");
audioDecoder.queueInputBuffer(decoderInputBufferIndex, 0,
0, 0, MediaCodec.BUFFER_FLAG_END_OF_STREAM);
}
audioExtractedFrameCount++;
// We extracted a frame, let's try something else next.
break;
}
// Poll output frames from the video decoder and feed the encoder.
while (mCopyVideo && !videoDecoderDone
&& pendingVideoDecoderOutputBufferIndex == -1
&& (encoderOutputVideoFormat == null || muxing)) {
int decoderOutputBufferIndex = videoDecoder.dequeueOutputBuffer(videoDecoderOutputBufferInfo,
TIMEOUT_USEC);
if (decoderOutputBufferIndex == MediaCodec.INFO_TRY_AGAIN_LATER) {
if (VERBOSE)Log.d(TAG, "no video decoder output buffer");
break;
}else if (decoderOutputBufferIndex == MediaCodec.INFO_OUTPUT_FORMAT_CHANGED) {
//do what for this?
decoderOutputVideoFormat = videoDecoder.getOutputFormat();
if (VERBOSE) {
Log.d(TAG, "video decoder: output format changed: " + decoderOutputVideoFormat);
}
break;
}else if (decoderOutputBufferIndex == MediaCodec.INFO_OUTPUT_BUFFERS_CHANGED) {
if (VERBOSE)Log.d(TAG, "video decoder: output buffers changed");
videoDecoderOutputBuffers = videoDecoder.getOutputBuffers();
break;
}
if (VERBOSE) {
Log.d(TAG, "video decoder: returned output buffer: "
+ decoderOutputBufferIndex);
Log.d(TAG, "video decoder: returned buffer of size "
+ videoDecoderOutputBufferInfo.size);
}
if ((videoDecoderOutputBufferInfo.flags & MediaCodec.BUFFER_FLAG_CODEC_CONFIG) != 0) {
if (VERBOSE)Log.d(TAG, "video decoder: codec config buffer");
videoDecoder.releaseOutputBuffer(decoderOutputBufferIndex,false);
break;
}
if (VERBOSE) {
Log.d(TAG, "video decoder: returned buffer for time "
+ videoDecoderOutputBufferInfo.presentationTimeUs);
}
pendingVideoDecoderOutputBufferIndex = decoderOutputBufferIndex;
videoDecodedFrameCount++;
// We extracted a pending frame, let's try something else next.
break;
}
// Feed the pending decoded audio buffer to the video encoder.
while (mCopyVideo && pendingVideoDecoderOutputBufferIndex != -1) {
if (VERBOSE) {
Log.d(TAG,"video decoder: attempting to process pending buffer: "
+ pendingVideoDecoderOutputBufferIndex);
}
int encoderInputBufferIndex = videoEncoder.dequeueInputBuffer(TIMEOUT_USEC);
if (encoderInputBufferIndex <= MediaCodec.INFO_TRY_AGAIN_LATER) {
if (VERBOSE)Log.d(TAG, "no video encoder input buffer: "
+encoderInputBufferIndex);
break;
}
if (VERBOSE) {
Log.d(TAG, "video encoder: returned input buffer: "
+ encoderInputBufferIndex);
}
ByteBuffer encoderInputBuffer = videoEncoderInputBuffers[encoderInputBufferIndex];
int size = videoDecoderOutputBufferInfo.size;
long presentationTime = videoDecoderOutputBufferInfo.presentationTimeUs;
if (VERBOSE) {
Log.d(TAG, "video decoder: processing pending buffer: "
+ pendingVideoDecoderOutputBufferIndex);
Log.d(TAG, "video decoder: pending buffer of size " + size);
Log.d(TAG, "video decoder: pending buffer for time "
+ presentationTime);
}
if (size >= 0) {
try {
ByteBuffer decoderOutputBuffer = videoDecoderOutputBuffers[pendingVideoDecoderOutputBufferIndex]
.duplicate();
decoderOutputBuffer
.position(videoDecoderOutputBufferInfo.offset);
decoderOutputBuffer
.limit(videoDecoderOutputBufferInfo.offset + size);
encoderInputBuffer.position(0);
encoderInputBuffer.put(decoderOutputBuffer);
//size not enable
videoEncoder.queueInputBuffer(encoderInputBufferIndex, 0,
size, presentationTime,
videoDecoderOutputBufferInfo.flags);
} catch (Exception e) {
// TODO: handle exception
e.printStackTrace();
}
}
videoDecoder.releaseOutputBuffer(
pendingVideoDecoderOutputBufferIndex, false);
pendingVideoDecoderOutputBufferIndex = -1;
if ((videoDecoderOutputBufferInfo.flags & MediaCodec.BUFFER_FLAG_END_OF_STREAM) != 0) {
if (VERBOSE)Log.d(TAG, "video decoder: EOS");
videoDecoderDone = true;
}
// We enqueued a pending frame, let's try something else next.
break;
}
// Poll frames from the video encoder and send them to the muxer.
while (mCopyVideo && !videoEncoderDone
&& (encoderOutputVideoFormat == null || muxing)) {
// can not get avilabel outputBuffers?
int encoderOutputBufferIndex = videoEncoder.dequeueOutputBuffer(videoEncoderOutputBufferInfo,
TIMEOUT_USEC);
if (encoderOutputBufferIndex == MediaCodec.INFO_TRY_AGAIN_LATER) {
if (VERBOSE)Log.d(TAG, "no video encoder output buffer");
break;
}else if (encoderOutputBufferIndex == MediaCodec.INFO_OUTPUT_FORMAT_CHANGED) {
if (VERBOSE)Log.d(TAG, "video encoder: output format changed");
if (outputVideoTrack >= 0) {
// fail("video encoder changed its output format again?");
Log.d(TAG,"video encoder changed its output format again?");
}
encoderOutputVideoFormat = videoEncoder.getOutputFormat();
break;
}else if (encoderOutputBufferIndex == MediaCodec.INFO_OUTPUT_BUFFERS_CHANGED) {
if (VERBOSE)Log.d(TAG, "video encoder: output buffers changed");
videoEncoderOutputBuffers = videoEncoder.getOutputBuffers();
break;
}
// assertTrue("should have added track before processing output", muxing);
if (VERBOSE) {
Log.d(TAG, "video encoder: returned output buffer: "
+ encoderOutputBufferIndex);
Log.d(TAG, "video encoder: returned buffer of size "
+ videoEncoderOutputBufferInfo.size);
}
ByteBuffer encoderOutputBuffer = videoEncoderOutputBuffers[encoderOutputBufferIndex];
if ((videoEncoderOutputBufferInfo.flags & MediaCodec.BUFFER_FLAG_CODEC_CONFIG) != 0) {
if (VERBOSE)Log.d(TAG, "video encoder: codec config buffer");
// Simply ignore codec config buffers.
mVideoConfig = true;
videoEncoder.releaseOutputBuffer(encoderOutputBufferIndex,false);
break;
}
if (VERBOSE) {
Log.d(TAG, "video encoder: returned buffer for time "
+ videoEncoderOutputBufferInfo.presentationTimeUs);
}
if(mVideoConfig){
if(!mainVideoFrame){
mLastVideoSampleTime = videoEncoderOutputBufferInfo.presentationTimeUs;
mainVideoFrame = true;
}else{
if(mVideoSampleTime == 0){
mVideoSampleTime = videoEncoderOutputBufferInfo.presentationTimeUs - mLastVideoSampleTime;
}
}
}
videoEncoderOutputBufferInfo.presentationTimeUs = mLastVideoSampleTime + mVideoSampleTime;
if (videoEncoderOutputBufferInfo.size != 0) {
muxer.writeSampleData(outputVideoTrack,
encoderOutputBuffer, videoEncoderOutputBufferInfo);
mLastVideoSampleTime = videoEncoderOutputBufferInfo.presentationTimeUs;
}
if ((videoEncoderOutputBufferInfo.flags & MediaCodec.BUFFER_FLAG_END_OF_STREAM) != 0) {
if (VERBOSE)Log.d(TAG, "video encoder: EOS");
videoEncoderDone = true;
}
videoEncoder.releaseOutputBuffer(encoderOutputBufferIndex,
false);
videoEncodedFrameCount++;
// We enqueued an encoded frame, let's try something else next.
break;
}
// Poll output frames from the audio decoder.
// Do not poll if we already have a pending buffer to feed to the
// encoder.
while (mCopyAudio && !audioDecoderDone
&& pendingAudioDecoderOutputBufferIndex == -1
&& (encoderOutputAudioFormat == null || muxing)) {
int decoderOutputBufferIndex = audioDecoder
.dequeueOutputBuffer(audioDecoderOutputBufferInfo,TIMEOUT_USEC);
if (decoderOutputBufferIndex == MediaCodec.INFO_TRY_AGAIN_LATER) {
if (VERBOSE)Log.d(TAG, "no audio decoder output buffer");
break;
}else if (decoderOutputBufferIndex == MediaCodec.INFO_OUTPUT_FORMAT_CHANGED) {
decoderOutputAudioFormat = audioDecoder.getOutputFormat();
if (VERBOSE) {
Log.d(TAG, "audio decoder: output format changed: " + decoderOutputAudioFormat);
}
break;
}else if (decoderOutputBufferIndex == MediaCodec.INFO_OUTPUT_BUFFERS_CHANGED) {
if (VERBOSE)Log.d(TAG, "audio decoder: output buffers changed");
audioDecoderOutputBuffers = audioDecoder.getOutputBuffers();
break;
}
if (VERBOSE) {
Log.d(TAG, "audio decoder: returned output buffer: "
+ decoderOutputBufferIndex);
Log.d(TAG, "audio decoder: returned buffer of size "
+ audioDecoderOutputBufferInfo.size);
Log.d(TAG, "audio decoder: returned buffer for time "
+ audioDecoderOutputBufferInfo.presentationTimeUs);
}
if ((audioDecoderOutputBufferInfo.flags & MediaCodec.BUFFER_FLAG_CODEC_CONFIG) != 0) {
if (VERBOSE)Log.d(TAG, "audio decoder: codec config buffer");
audioDecoder.releaseOutputBuffer(decoderOutputBufferIndex,false);
break;
}
if (VERBOSE) {
Log.d(TAG, "audio decoder: output buffer is now pending: "
+ decoderOutputBufferIndex);
}
pendingAudioDecoderOutputBufferIndex = decoderOutputBufferIndex;
audioDecodedFrameCount++;
// We extracted a pending frame, let's try something else next.
break;
}
// Feed the pending decoded audio buffer to the audio encoder.
while (mCopyAudio && pendingAudioDecoderOutputBufferIndex != -1) {
if (VERBOSE) {
Log.d(TAG,"audio decoder: attempting to process pending buffer: "+ pendingAudioDecoderOutputBufferIndex);
}
int encoderInputBufferIndex = audioEncoder.dequeueInputBuffer(TIMEOUT_USEC);
if (encoderInputBufferIndex <= MediaCodec.INFO_TRY_AGAIN_LATER) {
if (VERBOSE)Log.d(TAG, "no audio encoder input buffer: "+encoderInputBufferIndex);
break;
}
if (VERBOSE) {
Log.d(TAG, "audio encoder: returned input buffer: "+ encoderInputBufferIndex);
}
ByteBuffer encoderInputBuffer = audioEncoderInputBuffers[encoderInputBufferIndex];
int size = audioDecoderOutputBufferInfo.size;
long presentationTime = audioDecoderOutputBufferInfo.presentationTimeUs;
if (VERBOSE) {
Log.d(TAG, "audio decoder: processing pending buffer: "+ pendingAudioDecoderOutputBufferIndex);
Log.d(TAG, "audio decoder: pending buffer of size " + size);
Log.d(TAG, "audio decoder: pending buffer for time "+ presentationTime);
}
if (size >= 0) {
try {
ByteBuffer decoderOutputBuffer = audioDecoderOutputBuffers[pendingAudioDecoderOutputBufferIndex]
.duplicate();
decoderOutputBuffer
.position(audioDecoderOutputBufferInfo.offset);
decoderOutputBuffer
.limit(audioDecoderOutputBufferInfo.offset + size);
encoderInputBuffer.position(0);
encoderInputBuffer.put(decoderOutputBuffer);
audioEncoder.queueInputBuffer(encoderInputBufferIndex, 0,
audioDecoderOutputBufferInfo.offset + size, presentationTime,
audioDecoderOutputBufferInfo.flags);
} catch (Exception e) {
// TODO: handle exception
e.printStackTrace();
}
}
audioDecoder.releaseOutputBuffer(pendingAudioDecoderOutputBufferIndex, false);
pendingAudioDecoderOutputBufferIndex = -1;
if ((audioDecoderOutputBufferInfo.flags & MediaCodec.BUFFER_FLAG_END_OF_STREAM) != 0) {
if (VERBOSE)Log.d(TAG, "audio decoder: EOS");
audioDecoderDone = true;
}
// We enqueued a pending frame, let's try something else next.
break;
}
// Poll frames from the audio encoder and send them to the muxer.
while (mCopyAudio && !audioEncoderDone
&& (encoderOutputAudioFormat == null || muxing)) {
int encoderOutputBufferIndex = audioEncoder
.dequeueOutputBuffer(audioEncoderOutputBufferInfo,TIMEOUT_USEC);
if (encoderOutputBufferIndex == MediaCodec.INFO_TRY_AGAIN_LATER) {
if (VERBOSE)Log.d(TAG, "no audio encoder output buffer");
break;
}else if (encoderOutputBufferIndex == MediaCodec.INFO_OUTPUT_FORMAT_CHANGED) {
if (VERBOSE)Log.d(TAG, "audio encoder: output format changed");
if (outputAudioTrack >= 0) {
// fail("audio encoder changed its output format again?");
Log.d(TAG,"audio encoder changed its output format again?");
}
encoderOutputAudioFormat = audioEncoder.getOutputFormat();
break;
}else if (encoderOutputBufferIndex == MediaCodec.INFO_OUTPUT_BUFFERS_CHANGED) {
if (VERBOSE)Log.d(TAG, "audio encoder: output buffers changed");
audioEncoderOutputBuffers = audioEncoder.getOutputBuffers();
break;
}
// assertTrue("should have added track before processing output",muxing);
if (VERBOSE) {
Log.d(TAG, "audio encoder: returned output buffer: "
+ encoderOutputBufferIndex);
Log.d(TAG, "audio encoder: returned buffer of size "
+ audioEncoderOutputBufferInfo.size);
}
ByteBuffer encoderOutputBuffer = audioEncoderOutputBuffers[encoderOutputBufferIndex];
if ((audioEncoderOutputBufferInfo.flags & MediaCodec.BUFFER_FLAG_CODEC_CONFIG) != 0) {
if (VERBOSE)Log.d(TAG, "audio encoder: codec config buffer");
// Simply ignore codec config buffers.
mAudioConfig = true;
audioEncoder.releaseOutputBuffer(encoderOutputBufferIndex,false);
break;
}
if (VERBOSE) {
Log.d(TAG, " audio encoder: returned buffer for time "
+ audioEncoderOutputBufferInfo.presentationTimeUs);
}
if(mAudioConfig){
if(!mainAudioFrame){
mLastAudioSampleTime = audioEncoderOutputBufferInfo.presentationTimeUs;
mainAudioFrame = true;
}else{
if(mAudioSampleTime == 0){
mAudioSampleTime = audioEncoderOutputBufferInfo.presentationTimeUs - mLastAudioSampleTime;
}
}
}
audioEncoderOutputBufferInfo.presentationTimeUs = mLastAudioSampleTime + mAudioSampleTime;
if (audioEncoderOutputBufferInfo.size != 0) {
muxer.writeSampleData(outputAudioTrack,
encoderOutputBuffer, audioEncoderOutputBufferInfo);
mLastAudioSampleTime = audioEncoderOutputBufferInfo.presentationTimeUs;
}
if ((audioEncoderOutputBufferInfo.flags & MediaCodec.BUFFER_FLAG_END_OF_STREAM) != 0) {
if (VERBOSE)Log.d(TAG, "audio encoder: EOS");
audioEncoderDone = true;
}
audioEncoder.releaseOutputBuffer(encoderOutputBufferIndex,false);
audioEncodedFrameCount++;
// We enqueued an encoded frame, let's try something else next.
break;
}
if (!muxing && (!mCopyAudio || encoderOutputAudioFormat != null)
&& (!mCopyVideo || encoderOutputVideoFormat != null)) {
if (mCopyVideo) {
Log.d(TAG, "muxer: adding video track.");
outputVideoTrack = muxer.addTrack(encoderOutputVideoFormat);
}
if (mCopyAudio) {
Log.d(TAG, "muxer: adding audio track.");
outputAudioTrack = muxer.addTrack(encoderOutputAudioFormat);
}
Log.d(TAG, "muxer: starting");
muxer.start();
muxing = true;
}
}
Log.d(TAG, "exit looper");
}
分析上面的代码流程：
1.等待decode中的inputbuffer准备好
2.通过Extractor把es数据读取到decode-inputbuffer中
3.等待decode解码，解码成功后可分别获取yuv(视频)，pcm(音频)的数据decode-outputbuffer
4.等待encode中的inputbuffer准备好
5.把解码后的yuv、pcm填充到encode的encode-inputbuffer中
6.等待encode编码，编码成功后可获取es数据encode-outputbuffer
7.通过Muxer把encode-outputbuffer数据重新合成文件或码流
有过开发经验的人会发现，两次使用Extractor去解音视频是冗余的，另外流程1-流程7中不是严格等待会有乱序风险。是的，开发时确实有这样的问题，已经修改并优化，事情多，更新会有点慢。
5.结束语
本篇文章全面的分析实现了重编码的流程，Java的实现方式上显得笨拙了些，作为参考还是多少有些价值。C++的版本已经调试的差不多了，性能上比Java高了些，但最近事情多，本文就先草草结束，有时间会更新本文并补充流程图，感谢持续关注！