这节谈一下如何在android上实现mp4文件的高效率切割。
业务需求举例:把一段2分钟的mp4文件切割出00:42 至 01:16这段时间的视频,要求足够短的执行时间和尽量少的误差。
分析:mp4Parser只能在关键帧切割,比如,在00:40和00:45分别存在一个可切割关键帧,那么切割视频的头和尾,都应该选择短切割。然后获取到误差的视频短,如果这个误差大于0.5S,用FFmpeg进行一帧一帧编解码切割文件。这样最多会有三段mp4文件,再次将这三段mp4拼接起来就可以了。
下面直接上关键代码,这些代码在PC上新建一个java工程也可以实现。
1.切割文件方法:
/**
需要使用isoviewer-1.0-RC-27包
返回值是目标mp4的开头和结尾时刻
**/
- public static double[] startTrim(File src, File dst, int startMs, int endMs) throws IOException {
- Movie movie = MovieCreator.build(src.getAbsolutePath());
- List<Track> tracks = movie.getTracks();
- movie.setTracks(new LinkedList<Track>());
- double startTime = startMs/1000;
- double endTime = endMs/1000;
- boolean timeCorrected = false;
- // Here we try to find a track that has sync samples. Since we can only start decoding
- // at such a sample we SHOULD make sure that the start of the new fragment is exactly
- // such a frame
- for (Track track : tracks) {
- if (track.getSyncSamples() != null && track.getSyncSamples().length > 0) {
- if (timeCorrected) {
- throw new RuntimeException("The startTime has already been corrected by another track with SyncSample. Not Supported.");
- }
- //true,false表示短截取;false,true表示长截取
- startTime = correctTimeToSyncSample(track, startTime, true);
- endTime = correctTimeToSyncSample(track, endTime, false);
- timeCorrected = true;
- }
- }
- int x = 0;
- for (Track track : tracks) {
- long currentSample = 0;
- double currentTime = 0;
- long startSample = -1;
- long endSample = -1;
- x++;
- for (int i = 0; i < track.getDecodingTimeEntries().size(); i++) {
- TimeToSampleBox.Entry entry = track.getDecodingTimeEntries().get(i);
- for (int j = 0; j < entry.getCount(); j++) {
- // entry.getDelta() is the amount of time the current sample covers.
- if (currentTime <= startTime) {
- // current sample is still before the new starttime
- startSample = currentSample;
- }
- if (currentTime <= endTime) {
- // current sample is after the new start time and still before the new endtime
- endSample = currentSample;
- } else {
- // current sample is after the end of the cropped video
- break;
- }
- currentTime += (double) entry.getDelta() / (double) track.getTrackMetaData().getTimescale();
- currentSample++;
- }
- }
- movie.addTrack(new CroppedTrack(track, startSample, endSample));
- break;
- }
- Container container = new DefaultMp4Builder().build(movie);
- if (!dst.exists()) {
- dst.createNewFile();
- }
- FileOutputStream fos = new FileOutputStream(dst);
- FileChannel fc = fos.getChannel();
- container.writeContainer(fc);
- fc.close();
- fos.close();
- double[] doubleArray = new double[2] ;
- doubleArray[0] = startTime;
- doubleArray[1] = endTime;
- return doubleArray;
- }
2.ffmpeg切割方法,需要jni实现。稍后补充
- public String getMp4ByFFmpeg(double mTimeStart,double mTimeEnd,String videoPath){
- try{
- String mFinalVideoPath = videoPath;
- int audioChannels = 2;
- FFmpegRecorder recorder = new FFmpegRecorder(
- mFinalVideoPath, RecorderConfig.TARGET_VIDEO_WIDTH,
- RecorderConfig.TARGET_VIDEO_HEIGHT, audioChannels);
- RecorderConfig.setRecorderConfig(recorder, RecorderConfig.CONFIG_TYPE_MPEG4_HIGH);
- int totalFrames = 0;
- FFmpegGrabber grabber = FFmpegGrabber.createDefault(mPath);
- grabber.setSquareSize(RecorderConfig.TARGET_VIDEO_WIDTH);
- int degree = VideoFileUtil.getRotate(mPath);
- grabber.setOrientation(degree);
- grabber.start();
- if (mTimeStart > 0) {
- grabber.setTimestamp((long)mTimeStart);
- }
- totalFrames = grabber.getLengthInFrames();
- VideoClip mFinalClip = new VideoClip();
- mFinalClip.mIsFromLocal = true;
- mFinalClip.mHeight = RecorderConfig.TARGET_VIDEO_HEIGHT;
- mFinalClip.mWidth = RecorderConfig.TARGET_VIDEO_WIDTH;
- recorder.setAudioChannels(grabber.getAudioChannels());
- recorder.setSampleRate(grabber.getSampleRate());
- recorder.setAudioCodec(avcodec.AV_CODEC_ID_AAC);
- recorder.setFrameRate(FFmpegRecorder.DEFAULT_FRAME_RATE);
- recorder.setVideoCodec(avcodec.AV_CODEC_ID_MPEG4);
- recorder.start();
- mFinalClip.mOrientation = 0;
- mFinalClip.mFrameRate = (int) recorder.getFrameRate();
- mFinalClip.mSampleRate = recorder.getSampleRate();
- mFinalClip.mAudioBitrate = recorder.getAudioBitrate();
- mFinalClip.mAudioChannels = recorder.getAudioChannels();
- Frame grabbedFrame = new Frame();
- int j = 0;
- boolean videoTimeout = false;
- boolean audioTimeout = false;
- while (grabber.grabFrame(grabbedFrame)) {
- long i = grabber.getTimestamp();
- long k = grabber.getFrameNumber();
- if (videoTimeout && audioTimeout) {
- break;
- }
- if (grabbedFrame.hasVideoFrame()) {
- int progress = 100 * (int) (i - mTimeStart) / mTotalTimeSpan;
- publishProgress(progress);
- }
- if (i > mTimeEnd) {
- if (grabbedFrame.hasAudioFrame()) {
- audioTimeout = true;
- }
- if (grabbedFrame.hasVideoFrame()) {
- videoTimeout = true;
- }
- continue;
- }
- grabbedFrame.setTimeStamp((long)(i - mTimeStart));
- recorder.recordFrameNoException(grabbedFrame);
- SLog.v(TAG, "record image at {}, #{}", i, k);
- j++;
- }
- grabbedFrame.releaseNativeAllocation();
- grabber.stop();
- grabber.release();
- recorder.stop();
- recorder.release();
- mFinalClip.mClipPath = mFinalVideoPath;
- mFinalClip.mDuration = (long) (MP4ParserUtil.getDuration(mFinalVideoPath) * 1000);
- mFinalClip.mTargetMills = mFinalClip.mDuration;
- return mFinalVideoPath;
- } catch (Exception ex) {
- return null;
- }
- }
3.拼接三段视频代码
- public boolean newClipMethod(String dstFile,String srcFile){
- try {
- double[] results = ClipMp4Util.startTrim(new File(dstFile),new File(srcFile),mTimeStart,mTimeEnd);
- if(results == null){
- return false;
- }
- Log.d("","newClipMethod-->results[0]-mTimeStart"+results[0]+" "+mTimeStart/1000);
- Log.d("","newClipMethod-->mTimeEnd-results[1]"+mTimeEnd/1000+" "+results[1]);
- //下面是短截取然后拼接的逻辑
- if(results[0]-mTimeStart/1000>GAP){
- String startMp4 = <span style="font-family: Arial, Helvetica, sans-serif;">getMp4ByFFmpeg(</span><span style="font-family: Arial, Helvetica, sans-serif;">mTimeStart,results[0]*1000,begin);</span>
- }
- if(mTimeEnd/1000-results[1]>GAP){
- String endMp4 = <span style="font-family: Arial, Helvetica, sans-serif;">getMp4ByCode(</span><span style="font-family: Arial, Helvetica, sans-serif;">results[1]*吧1000,mTimeEnd,end);</span>
- }
- String[] videos = new String[3];
- videos[0] = begin;
- videos[1] = dst;
- videos[2] = end;
- appendVideo(videos);
- } catch (Exception e) {
- //如果不是同一格式的视频,这里合成会报错,直接返回中间视频.所以长视频选取长误差的方式,前后都多截取一段
- Log.d("","new Method exception-->"+e);
- e.printStackTrace();
- }
- return true;
- }
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