Android(java方法）上实现mp4的分割和拼接 （二）

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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