Android音视频分离和合成
mp4音频是由视频和音频组成，Android 提供了 MediaExtractor 和 MediaMuxer 以及MediaFormat类，用来把音频或视频单独抽取出来，然后合成新的视频。下面分别介绍视频的分解和合成，效果如下：
一、视频的分解
1、设置数据源获取音轨数据
MediaExtractor extractor = new MediaExtractor();
try {
//设置数据源
extractor.setDataSource(file.getAbsolutePath());
} catch (IOException e) {
e.printStackTrace();
}
//获取轨道数量
trackCount = extractor.getTrackCount();2、遍历音轨数量，得到想要的轨道
//查找需要的视频轨道与音频轨道index
for (int i = 0; i < trackCount; i++) {
//遍历所以轨道
MediaFormat itemMediaFormat = extractor.getTrackFormat(i);
String itemMime = itemMediaFormat.getString(MediaFormat.KEY_MIME);
if (itemMime.startsWith("video")) {
//获取视频轨道位置
videoTrackIndex = i;
videoMediaFormat = itemMediaFormat;
continue;
}
if (itemMime.startsWith("audio")) {
//获取音频轨道位置
audioTrackIndex = i;
audioMediaFormat = itemMediaFormat;
continue;
}
}3、创建输出音视频文件夹
File videoFile = new File(videoPath);
File audioFile = new File(audioPath);
if (videoFile.exists()) {
videoFile.delete();
}
if (audioFile.exists()) {
audioFile.delete();
}4、写入数据释放资源
/**
*
* @param extractor 源数据
* @param format 需要分离的音视频或者视频
* @param path 视频或者音频输出路径
* @param index 轨道下标
* @throws IOException
*/
private void muxerAudio(MediaExtractor extractor, MediaFormat format, String path, int index) throws IOException {
MediaFormat trackFormat = extractor.getTrackFormat(index);
MediaMuxer mediaMuxer = new MediaMuxer(path, MediaMuxer.OutputFormat.MUXER_OUTPUT_MPEG_4);
int trackIndex = mediaMuxer.addTrack(trackFormat);
extractor.selectTrack(index);
mediaMuxer.start();
int maxVideoBufferCount = format.getInteger(MediaFormat.KEY_MAX_INPUT_SIZE);
ByteBuffer byteBuffer = ByteBuffer.allocate(maxVideoBufferCount);
MediaCodec.BufferInfo bufferInfo = new MediaCodec.BufferInfo();
//时长：这里需要区分音频或者视频，两个是根据不同的计算方法，否则会导致分离的音频或者视频时长不一致或者崩溃
long videoSampleTime = 0;
try {
videoSampleTime = getSampleTime(trackFormat);
} catch (Exception e) {
videoSampleTime = getSampleTime(extractor, byteBuffer);
}
while (true) {
int readSampleDataSize = extractor.readSampleData(byteBuffer, 0);
if (readSampleDataSize < 0) {
break;
}
bufferInfo.size = readSampleDataSize;
bufferInfo.offset = 0;
bufferInfo.flags = extractor.getSampleFlags();
bufferInfo.presentationTimeUs += videoSampleTime;
mediaMuxer.writeSampleData(trackIndex, byteBuffer, bufferInfo);
//该方法放在前面会导致首帧录屏
extractor.advance();
}
//释放音轨
extractor.unselectTrack(index);
mediaMuxer.stop();
//内部也会执行stop，所以可以不用执行stop
mediaMuxer.release();
}附上两种时间的计算方法：
/**
* 通过帧率来计算：适用于视频
*/
private long getSampleTime(MediaFormat mediaFormat) {
//每秒多少帧
int frameRate = mediaFormat.getInteger(MediaFormat.KEY_FRAME_RATE);
//得出平均每一帧间隔多少微妙
return 1000 * 1000 / frameRate;
}
/**
* 通过设置PTS的办法：适用于音频，该方法使得视频播放变慢
*/
private long getSampleTime(MediaExtractor audioExtractor, ByteBuffer buffer) {
long videoSampleTime;
audioExtractor.readSampleData(buffer, 0);
//skip first I frame
if (audioExtractor.getSampleFlags() == MediaExtractor.SAMPLE_FLAG_SYNC)
audioExtractor.advance();
audioExtractor.readSampleData(buffer, 0);
long firstVideoPTS = audioExtractor.getSampleTime();
audioExtractor.advance();
audioExtractor.readSampleData(buffer, 0);
long SecondVideoPTS = audioExtractor.getSampleTime();
videoSampleTime = Math.abs(SecondVideoPTS - firstVideoPTS);
return videoSampleTime;
}二、视频的合成
视频和合成和上面比较类似，是分别设置数据源到MediaExtractor，然后获取对应的轨道数据，最后同步写入。
/**
* @param videoPath 源视频路径
* @param audioPath 源音频路径
* @param outPath 输出路径
*/
private void startComposeTrack(String videoPath, String audioPath,String outPath) {
try {
MediaExtractor videoExtractor = new MediaExtractor();
videoExtractor.setDataSource(videoPath);
MediaExtractor audioExtractor = new MediaExtractor();
audioExtractor.setDataSource(audioPath);
MediaMuxer muxer = new MediaMuxer(outPath, MediaMuxer.OutputFormat.MUXER_OUTPUT_MPEG_4);
videoExtractor.selectTrack(0);
MediaFormat videoFormat = videoExtractor.getTrackFormat(0);
int videoTrack = muxer.addTrack(videoFormat);
audioExtractor.selectTrack(0);
MediaFormat audioFormat = audioExtractor.getTrackFormat(0);
int audioTrack = muxer.addTrack(audioFormat);
boolean sawEOS = false;
int frameCount = 0;
int offset = 100;
int sampleSize = 256 * 1024;
ByteBuffer videoBuf = ByteBuffer.allocate(sampleSize);
ByteBuffer audioBuf = ByteBuffer.allocate(sampleSize);
MediaCodec.BufferInfo videoBufferInfo = new MediaCodec.BufferInfo();
MediaCodec.BufferInfo audioBufferInfo = new MediaCodec.BufferInfo();
videoExtractor.seekTo(0, MediaExtractor.SEEK_TO_CLOSEST_SYNC);
audioExtractor.seekTo(0, MediaExtractor.SEEK_TO_CLOSEST_SYNC);
muxer.start();
while (!sawEOS) {
videoBufferInfo.offset = offset;
videoBufferInfo.size = videoExtractor.readSampleData(videoBuf, offset);
if (videoBufferInfo.size < 0 || audioBufferInfo.size < 0) {
sawEOS = true;
videoBufferInfo.size = 0;
} else {
videoBufferInfo.presentationTimeUs = videoExtractor.getSampleTime();
//noinspection WrongConstant
videoBufferInfo.flags = videoExtractor.getSampleFlags();
muxer.writeSampleData(videoTrack, videoBuf, videoBufferInfo);
videoExtractor.advance();
frameCount++;
}
}
boolean sawEOS2 = false;
int frameCount2 = 0;
while (!sawEOS2) {
frameCount2++;
audioBufferInfo.offset = offset;
audioBufferInfo.size = audioExtractor.readSampleData(audioBuf, offset);
if (videoBufferInfo.size < 0 || audioBufferInfo.size < 0) {
sawEOS2 = true;
audioBufferInfo.size = 0;
} else {
audioBufferInfo.presentationTimeUs = audioExtractor.getSampleTime();
audioBufferInfo.flags = audioExtractor.getSampleFlags();
muxer.writeSampleData(audioTrack, audioBuf, audioBufferInfo);
audioExtractor.advance();
}
}
muxer.stop();
muxer.release();
audioExtractor.release();
} catch (IOException e) {
e.printStackTrace();
} catch (Exception e) {
e.printStackTrace();
}
}这里比较耗时，需要在子线程进行。