xuggle学习-视频解码

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//新建容器，以供容纳流
    IContainer container = IContainer.make();
    
    //开始读流
    if (container.open(filename, IContainer.Type.READ, null) < 0)
        throw new IllegalArgumentException("could not open file: " + filename);
    
    //获取流数
    int numStreams = container.getNumStreams();
    
    int videoStreamId = -1;
    IStreamCoder videoCoder = null;
    //从流中识别视频流
    for (int i = 0; i < numStreams; i++)
    {
        IStream stream = container.getStream(i);
        IStreamCoder coder = stream.getStreamCoder();
        
        if (coder.getCodecType() == ICodec.Type.CODEC_TYPE_VIDEO)
        {
            videoStreamId = i;
            videoCoder = coder;
            break;
        }
    }
    
    if (videoStreamId == -1)
        throw new RuntimeException("could not find video stream in container: " + filename);
    
    //读取视频流
    if (videoCoder.open() < 0)
        throw new RuntimeException("could not open video decoder for container: " + filename);
    
    IVideoResampler resampler = null;
    //重新编码图片格式
    if (videoCoder.getPixelType() != IPixelFormat.Type.BGR24)
    {
        resampler =
            IVideoResampler.make(videoCoder.getWidth(),
                videoCoder.getHeight(),
                IPixelFormat.Type.BGR24,
                videoCoder.getWidth(),
                videoCoder.getHeight(),
                videoCoder.getPixelType());
        if (resampler == null)
            throw new RuntimeException("could not create color space " + "resampler for: " + filename);
    }
    
//    循环读取
    IPacket packet = IPacket.make();
    long firstTimestampInStream = Global.NO_PTS;
    long systemClockStartTime = 0;
    while (container.readNextPacket(packet) >= 0)
    {
        if (packet.getStreamIndex() == videoStreamId)//识别视频流
        {
            //图片编码
            IVideoPicture picture =
                IVideoPicture.make(videoCoder.getPixelType(), videoCoder.getWidth(), videoCoder.getHeight());
            
            int offset = 0;
            
            while (offset < packet.getSize())
            {
                int bytesDecoded = videoCoder.decodeVideo(picture, packet, offset);
                if (bytesDecoded < 0)
                    throw new RuntimeException("got error decoding video in: " + filename);
                offset += bytesDecoded;
                
                //图片帧已读取完，保存图片
                if (picture.isComplete())
                {
                    IVideoPicture newPic = picture;
                    if (resampler != null)
                    {
                        newPic =
                            IVideoPicture.make(resampler.getOutputPixelFormat(),
                                picture.getWidth(),
                                picture.getHeight());
                        if (resampler.resample(newPic, picture) < 0)
                            throw new RuntimeException("could not resample video from: " + filename);
                    }
                    if (newPic.getPixelType() != IPixelFormat.Type.BGR24)
                        throw new RuntimeException("could not decode video" + " as BGR 24 bit data in: " + filename);
                    BufferedImage javaImage = Utils.videoPictureToImage(newPic);
                    
                    //保存图片到本地
                    processFrame(picture, image);
                } 
               }
            }
        }
    }

/**
 * 根据固定间隔采集图片
 */
private static void processFrame(IVideoPicture picture, BufferedImage image) {
    try {
        
        //mLastPtsWrite记录最近一次图片采集时间
        //NANO_SECONDS_BETWEEN_FRAMES，纳秒时间间隔
        if(mLastPtsWrite == Global.NO_PTS)
            mLastPtsWrite = picture.getPts() - NANO_SECONDS_BETWEEN_FRAMES;
        
        //每隔NANO_SECONDS_BETWEEN_FRAMES采集
        if(picture.getPts() - mLastPtsWrite >= NANO_SECONDS_BETWEEN_FRAMES) {
            
            File file = new File("c:/1/" + i + ".jpg");
            i++;
            
            ImageIO.write(image, "jpg", file);
            
            double seconds = ((double)picture.getPts()) / Global.DEFAULT_PTS_PER_SECOND;
            System.out.printf("at elapsed time of %6.3f seconds wrote: %s\n", seconds, file);
            
            mLastPtsWrite += NANO_SECONDS_BETWEEN_FRAMES;
        }
    } catch (Exception e) {
        e.printStackTrace();
    }
}