1. Introduction to MediaExtractor API
The role of MediaExtractor is to separate audio and video data.
Main API introduction:
- setDataSource(String path): Both local files and network files can be set
- getTrackCount(): Get the number of source file channels
- getTrackFormat(int index): Get the specified (index) channel format
- getSampleTime(): Returns the current timestamp
- readSampleData(ByteBuffer byteBuf, int offset): read the data in the specified channel into the ByteBuffer according to the offset;
- advance(): read the next frame of data
- release(): Release resources after reading
There are mainly several steps to use MediaExtractor:
- Set up the data source
- Get the number of channels, switch to the desired track
- Read the sample data of each frame cyclically
- Release resources after completion
Example of separating MP4 video into audio and video:
private void exactorMedia() {
FileOutputStream videoOutputStream = null;
FileOutputStream audioOutputStream = null;
try {
//分离的视频文件
File videoFile = new File(SDCARD_PATH, "output_video.mp4");
//分离的音频文件
File audioFile = new File(SDCARD_PATH, "output_audios.mp3");
videoOutputStream = new FileOutputStream(videoFile);
audioOutputStream = new FileOutputStream(audioFile);
//源文件
mediaExtractor.setDataSource(SDCARD_PATH + "720p.mp4");
//信道总数
int trackCount = mediaExtractor.getTrackCount();
int audioTrackIndex = -1;
int videoTrackIndex = -1;
for (int i = 0; i < trackCount; i++) {
MediaFormat trackFormat = mediaExtractor.getTrackFormat(i);
String mineType = trackFormat.getString(MediaFormat.KEY_MIME);
//视频信道
if (mineType.startsWith("video/")) {
videoTrackIndex = i;
}
//音频信道
if (mineType.startsWith("audio/")) {
audioTrackIndex = i;
}
}
ByteBuffer byteBuffer = ByteBuffer.allocate(500 * 1024);
//切换到视频信道
mediaExtractor.selectTrack(videoTrackIndex);
while (true) {
int readSampleCount = mediaExtractor.readSampleData(byteBuffer, 0);
if (readSampleCount < 0) {
Log.d("dimen", "视频分离完成 ");
break;
}
//保存视频信道信息
byte[] buffer = new byte[readSampleCount];
byteBuffer.get(buffer);
videoOutputStream.write(buffer);
byteBuffer.clear();
mediaExtractor.advance();
}
//切换到音频信道
mediaExtractor.selectTrack(audioTrackIndex);
while (true) {
int readSampleCount = mediaExtractor.readSampleData(byteBuffer, 0);
if (readSampleCount < 0) {
Log.d("dimen", "音频分离完成 ");
break;
}
//保存音频信息
byte[] buffer = new byte[readSampleCount];
byteBuffer.get(buffer);
audioOutputStream.write(buffer);
byteBuffer.clear();
mediaExtractor.advance();
}
} catch (IOException e) {
e.printStackTrace();
} finally {
mediaExtractor.release();
try {
videoOutputStream.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
}2. Introduction to MediaMuxer API
The role of MediaMuxer is to generate audio or video files; it can also mix audio and video into one audio and video file.
Related API introduction:
- MediaMuxer(String path, int format): path: the name of the output file format: the format of the output file; currently only supports MP4 format;
- addTrack(MediaFormat format): add channel; we use MediaCodec.getOutpurForma() or Extractor.getTrackFormat(int index) to get MediaFormat; you can also create it yourself;
- start(): start to synthesize files
- writeSampleData(int trackIndex, ByteBuffer byteBuf, MediaCodec.BufferInfo bufferInfo): write the data in ByteBuffer to the file set in the constructor;
- stop(): stop synthesizing files
- release(): release resources
Steps to use MediaMuxer:
- Set the target file path and audio and video format
- Add tracks to be synthesized, including audio tracks and video tracks
- Start synthesis, write sample data for each frame cyclically
- Release after completion
Examples of pure video separation:
private void SeparateVideo() {
int videoIndex = -1;
try {
mediaExtractor.setDataSource(SDCARD_PATH + "720p.mp4");
int trackCount = mediaExtractor.getTrackCount();
for (int i = 0; i < trackCount; i++) {
MediaFormat trackFormat = mediaExtractor.getTrackFormat(i);
String mimeType = trackFormat.getString(MediaFormat.KEY_MIME);
// 取出视频的信号
if (mimeType.startsWith("video/")) {
videoIndex = i;
}
}
//切换道视频信号的信道
mediaExtractor.selectTrack(videoIndex);
MediaFormat trackFormat = mediaExtractor.getTrackFormat(videoIndex);
mediaMuxer = new MediaMuxer(SDCARD_PATH + "/output_video2.mp4", MediaMuxer.OutputFormat.MUXER_OUTPUT_MPEG_4);
//追踪此信道
int trackIndex = mediaMuxer.addTrack(trackFormat);
ByteBuffer byteBuffer = ByteBuffer.allocate(1024 * 500);
MediaCodec.BufferInfo bufferInfo = new MediaCodec.BufferInfo();
mediaMuxer.start();
long videoSampleTime;
//获取每帧的之间的时间
{
mediaExtractor.readSampleData(byteBuffer, 0);
//skip first I frame
if (mediaExtractor.getSampleFlags() == MediaExtractor.SAMPLE_FLAG_SYNC)
mediaExtractor.advance();
mediaExtractor.readSampleData(byteBuffer, 0);
long firstVideoPTS = mediaExtractor.getSampleTime();
mediaExtractor.advance();
mediaExtractor.readSampleData(byteBuffer, 0);
long SecondVideoPTS = mediaExtractor.getSampleTime();
videoSampleTime = Math.abs(SecondVideoPTS - firstVideoPTS);
Log.d("dimen", "videoSampleTime is " + videoSampleTime);
}
//重新切换此信道，不然上面跳过了3帧,造成前面的帧数模糊
mediaExtractor.unselectTrack(videoIndex);
mediaExtractor.selectTrack(videoIndex);
while (true) {
//读取帧之间的数据
int readSampleSize = mediaExtractor.readSampleData(byteBuffer, 0);
if (readSampleSize < 0) {
break;
}
mediaExtractor.advance();
bufferInfo.size = readSampleSize;
bufferInfo.offset = 0;
bufferInfo.flags = mediaExtractor.getSampleFlags();
bufferInfo.presentationTimeUs += videoSampleTime;
//写入帧的数据
mediaMuxer.writeSampleData(trackIndex, byteBuffer, bufferInfo);
}
//release
mediaMuxer.stop();
mediaExtractor.release();
mediaMuxer.release();
Log.e("dimen", "finish");
} catch (IOException e) {
e.printStackTrace();
}
}Example of separating pure audio:
private void SeparateAudio() {
int audioIndex = -1;
try {
mediaExtractor.setDataSource(SDCARD_PATH + "720p.mp4");
int trackCount = mediaExtractor.getTrackCount();
for (int i = 0; i < trackCount; i++) {
MediaFormat trackFormat = mediaExtractor.getTrackFormat(i);
if (trackFormat.getString(MediaFormat.KEY_MIME).startsWith("audio/")) {
audioIndex = i;
}
}
mediaExtractor.selectTrack(audioIndex);
MediaFormat trackFormat = mediaExtractor.getTrackFormat(audioIndex);
mediaMuxer = new MediaMuxer(SDCARD_PATH + "/output_audios2.mp3", MediaMuxer.OutputFormat.MUXER_OUTPUT_MPEG_4);
int writeAudioIndex = mediaMuxer.addTrack(trackFormat);
mediaMuxer.start();
ByteBuffer byteBuffer = ByteBuffer.allocate(500 * 1024);
MediaCodec.BufferInfo bufferInfo = new MediaCodec.BufferInfo();
long stampTime = 0;
//获取帧之间的间隔时间
{
mediaExtractor.readSampleData(byteBuffer, 0);
if (mediaExtractor.getSampleFlags() == MediaExtractor.SAMPLE_FLAG_SYNC) {
mediaExtractor.advance();
}
mediaExtractor.readSampleData(byteBuffer, 0);
long secondTime = mediaExtractor.getSampleTime();
mediaExtractor.advance();
mediaExtractor.readSampleData(byteBuffer, 0);
long thirdTime = mediaExtractor.getSampleTime();
stampTime = Math.abs(thirdTime - secondTime);
Log.e("dimen", stampTime + "");
}
mediaExtractor.unselectTrack(audioIndex);
mediaExtractor.selectTrack(audioIndex);
while (true) {
int readSampleSize = mediaExtractor.readSampleData(byteBuffer, 0);
if (readSampleSize < 0) {
break;
}
mediaExtractor.advance();
bufferInfo.size = readSampleSize;
bufferInfo.flags = mediaExtractor.getSampleFlags();
bufferInfo.offset = 0;
bufferInfo.presentationTimeUs += stampTime;
mediaMuxer.writeSampleData(writeAudioIndex, byteBuffer, bufferInfo);
}
mediaMuxer.stop();
mediaMuxer.release();
mediaExtractor.release();
Log.e("dimen", "finish");
} catch (IOException e) {
e.printStackTrace();
}
}Examples of pure audio and pure video synthesis:
private void SynthesisAudioVideo() {
try {
MediaExtractor videoExtractor = new MediaExtractor();
videoExtractor.setDataSource(SDCARD_PATH + "output_video2.mp4");
MediaFormat videoFormat = null;
int videoTrackIndex = -1;
int videoTrackCount = videoExtractor.getTrackCount();
for (int i = 0; i < videoTrackCount; i++) {
videoFormat = videoExtractor.getTrackFormat(i);
String mimeType = videoFormat.getString(MediaFormat.KEY_MIME);
if (mimeType.startsWith("video/")) {
videoTrackIndex = i;
break;
}
}
MediaExtractor audioExtractor = new MediaExtractor();
audioExtractor.setDataSource(SDCARD_PATH + "output_audios2.mp3");
MediaFormat audioFormat = null;
int audioTrackIndex = -1;
int audioTrackCount = audioExtractor.getTrackCount();
for (int i = 0; i < audioTrackCount; i++) {
audioFormat = audioExtractor.getTrackFormat(i);
String mimeType = audioFormat.getString(MediaFormat.KEY_MIME);
if (mimeType.startsWith("audio/")) {
audioTrackIndex = i;
break;
}
}
videoExtractor.selectTrack(videoTrackIndex);
audioExtractor.selectTrack(audioTrackIndex);
MediaCodec.BufferInfo videoBufferInfo = new MediaCodec.BufferInfo();
MediaCodec.BufferInfo audioBufferInfo = new MediaCodec.BufferInfo();
MediaMuxer mediaMuxer = new MediaMuxer(SDCARD_PATH + "/output.mp4", MediaMuxer.OutputFormat.MUXER_OUTPUT_MPEG_4);
int writeVideoTrackIndex = mediaMuxer.addTrack(videoFormat);
int writeAudioTrackIndex = mediaMuxer.addTrack(audioFormat);
mediaMuxer.start();
ByteBuffer byteBuffer = ByteBuffer.allocate(500 * 1024);
long sampleTime = 0;
{
videoExtractor.readSampleData(byteBuffer, 0);
if (videoExtractor.getSampleFlags() == MediaExtractor.SAMPLE_FLAG_SYNC) {
videoExtractor.advance();
}
videoExtractor.readSampleData(byteBuffer, 0);
long secondTime = videoExtractor.getSampleTime();
videoExtractor.advance();
long thirdTime = videoExtractor.getSampleTime();
sampleTime = Math.abs(thirdTime - secondTime);
}
videoExtractor.unselectTrack(videoTrackIndex);
videoExtractor.selectTrack(videoTrackIndex);
while (true) {
int readVideoSampleSize = videoExtractor.readSampleData(byteBuffer, 0);
if (readVideoSampleSize < 0) {
break;
}
videoBufferInfo.size = readVideoSampleSize;
videoBufferInfo.presentationTimeUs += sampleTime;
videoBufferInfo.offset = 0;
videoBufferInfo.flags = videoExtractor.getSampleFlags();
mediaMuxer.writeSampleData(writeVideoTrackIndex, byteBuffer, videoBufferInfo);
videoExtractor.advance();
}
while (true) {
int readAudioSampleSize = audioExtractor.readSampleData(byteBuffer, 0);
if (readAudioSampleSize < 0) {
break;
}
audioBufferInfo.size = readAudioSampleSize;
audioBufferInfo.presentationTimeUs += sampleTime;
audioBufferInfo.offset = 0;
audioBufferInfo.flags = videoExtractor.getSampleFlags();
mediaMuxer.writeSampleData(writeAudioTrackIndex, byteBuffer, audioBufferInfo);
audioExtractor.advance();
}
mediaMuxer.stop();
mediaMuxer.release();
videoExtractor.release();
audioExtractor.release();
} catch (IOException e) {
e.printStackTrace();
}
}Project address: https://github.com/ChloeDimen/AudioAndVideo