FFMpegFrameGrabber.stop() Causes JVM Crash

[MarcWoodyard]

I have a recording object thread that contains a frame recorder and a frame grabber. When it's time to interrupt the thread, calling java this.frameGrabber.stop(); causes the JVM to crash. When I comment it out, the JVM doesn't crash anymore.

 @Override
    public void interrupt() {
        try {
            this.subThread.interrupt();

            if (this.frameRecorder != null)
                this.frameRecorder.stop();

            this.frameGrabber.stop();  // Causes JVM crash
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

Full File:

public class FFMPEGRecorder extends Thread {

    private static DateTimeFormatter fileFormatter = DateTimeFormatter.ofPattern("MM-dd-yyyy hh:mm:ss", Locale.ENGLISH);
    private static DateTimeFormatter directoryFormatter = DateTimeFormatter.ofPattern("MM-dd-yyyy", Locale.ENGLISH);
    private FFmpegFrameGrabber frameGrabber;
    private FFmpegFrameRecorder frameRecorder;
    private CameraScreenshot screenshotThread = new CameraScreenshot();
    private Thread subThread;
    private int id;
    private String cameraName;
    private String streamURL;
    private LocalDateTime start;
    private LocalDateTime end;
    private boolean recordingEnabled;

    public FFMPEGRecorder(int id, String cameraName, String streamURL) {
        this.id = id;
        this.cameraName = cameraName;
        this.streamURL = streamURL;
        this.recordingEnabled = CameraManager.getCamera(id).getRecordingEnabled();
    }

    @Override
    public final void start() {
        try {
            this.frameGrabber = new FFmpegFrameGrabber(this.streamURL);

            System.out.println(this.streamURL);

            this.frameGrabber.setVideoCodec(8);

            if (streamURL.contains("rtsp")) {
                this.frameGrabber.setFormat("rtsp");
                this.frameGrabber.setOption("rtsp_transport", "tcp");
            } else if (streamURL.contains("mjpg"))
                this.frameGrabber.setFormat("mjpeg");
            
            this.frameGrabber.setFrameRate(30);

            this.frameGrabber.start();

            if (this.recordingEnabled)
                this.createNewRecording();

            this.subThread = new Thread(() -> {
                Frame frame;
                while (true) {
                    try {
                        if (this.recordingEnabled && LocalDateTime.now().isAfter(this.end)) {
                            this.frameRecorder.stop();
                            this.createNewRecording();
                        }

                        frame = this.frameGrabber.grab();
                        this.screenshotThread.updateImage(frame);

                        if (this.recordingEnabled && frame != null)
                            this.frameRecorder.record(frame);
                    } catch (Exception e) {
                        e.printStackTrace();
                    }
                }
            });

            this.subThread.start();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    private void createNewRecording() throws FrameRecorder.Exception {
        this.start = LocalDateTime.now();
        this.end = LocalDateTime.now().plusMinutes(2);

        File recordingDir = new File(ProgramSettings.getRecordingDirectory() +
                File.separator +
                this.cameraName +
                File.separator +
                directoryFormatter.format(this.start));

        if (!recordingDir.exists())
            recordingDir.mkdirs();

        String curDir = recordingDir.getAbsoluteFile() +
                File.separator +
                cameraName + " [" + fileFormatter.format(this.start) + "] - [" + fileFormatter.format(this.end) + "].webm";

        this.frameRecorder = new FFmpegFrameRecorder(
                curDir,
                this.frameGrabber.getImageWidth(),
                this.frameGrabber.getImageHeight());

        this.frameRecorder.setVideoCodec(avcodec.AV_CODEC_ID_VP9);
        this.frameRecorder.setFormat("webm");
        this.frameRecorder.setFrameRate(this.frameGrabber.getFrameRate());

        this.frameRecorder.start();
    }

    public BufferedImage getScreenshot() {
        return this.screenshotThread.getCurrentImage();
    }

    @Override
    public void interrupt() {
        try {
            this.subThread.interrupt();

            if (this.frameRecorder != null)
                this.frameRecorder.stop();

            this.frameGrabber.stop();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

}

[saudet]

FFmpegFrameGrabber isn't thread safe. You'll need to synchronize calls.

[MarcWoodyard]

I think I solved it. I changed private FFmpegFrameGrabber frameGrabber; to private FrameGrabber frameGrabber;.

And I changed this.frameGrabber = new FFmpegFrameGrabber(this.streamURL); to this.frameGrabber = new IPCameraFrameGrabber(this.streamURL, 3, 3, TimeUnit.SECONDS);

public class FFMPEGRecorder extends Thread {

    private static DateTimeFormatter fileFormatter = DateTimeFormatter.ofPattern("MM-dd-yyyy hh:mm:ss", Locale.ENGLISH);
    private static DateTimeFormatter directoryFormatter = DateTimeFormatter.ofPattern("MM-dd-yyyy", Locale.ENGLISH);
    private FrameGrabber frameGrabber;
    private FrameRecorder frameRecorder;
    private CameraScreenshot screenshotThread = new CameraScreenshot();
    private Thread subThread;
    private int id;
    private String cameraName;
    private String streamURL;
    private LocalDateTime start;
    private LocalDateTime end;
    private boolean recordingEnabled;

    public FFMPEGRecorder(int id, String cameraName, String streamURL) {
        this.id = id;
        this.cameraName = cameraName;
        this.streamURL = streamURL;
        this.recordingEnabled = CameraManager.getCamera(id).getRecordingEnabled();
    }

    @Override
    public final void start() {
        try {
            this.frameGrabber = new IPCameraFrameGrabber(this.streamURL, 3, 3, TimeUnit.SECONDS);

            this.frameGrabber.setVideoCodec(8);

            if (streamURL.contains("rtsp")) {
                this.frameGrabber.setFormat("rtsp");
                this.frameGrabber.setOption("rtsp_transport", "tcp");
            } else if (streamURL.contains("mjpg"))
                this.frameGrabber.setFormat("mjpeg");

            this.frameGrabber.setFrameRate(30);

            this.frameGrabber.start();

            if (this.recordingEnabled)
                this.createNewRecording();

            this.subThread = new Thread(() -> {
                Frame frame;
                while (true) {
                    try {
                        if (this.recordingEnabled && LocalDateTime.now().isAfter(this.end)) {
                            this.frameRecorder.stop();
                            this.createNewRecording();
                        }

                        frame = this.frameGrabber.grab();

                        if(frame != null) {
                            this.screenshotThread.updateImage(frame);

                            if (this.recordingEnabled)
                                this.frameRecorder.record(frame);
                        }
                    } catch (NullPointerException ignored) {
                    } catch (Exception e) {
                        e.printStackTrace();
                    }
                }
            });

            this.subThread.start();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    private void createNewRecording() throws FrameRecorder.Exception {
        this.start = LocalDateTime.now();
        this.end = LocalDateTime.now().plusMinutes(2);

        File recordingDir = new File(ProgramSettings.getRecordingDirectory() +
                File.separator +
                this.cameraName +
                File.separator +
                directoryFormatter.format(this.start));

        if (!recordingDir.exists())
            recordingDir.mkdirs();

        String curDir = recordingDir.getAbsoluteFile() +
                File.separator +
                cameraName + " [" + fileFormatter.format(this.start) + "] - [" + fileFormatter.format(this.end) + "].webm";

        this.frameRecorder = new FFmpegFrameRecorder(
                curDir,
                this.frameGrabber.getImageWidth(),
                this.frameGrabber.getImageHeight());

        this.frameRecorder.setVideoCodec(avcodec.AV_CODEC_ID_VP9);
        this.frameRecorder.setFormat("webm");
        this.frameRecorder.setFrameRate(this.frameGrabber.getFrameRate());

        this.frameRecorder.start();
    }

    public BufferedImage getScreenshot() {
        return this.screenshotThread.getCurrentImage();
    }

    @Override
    public void interrupt() {
        try {
            this.subThread.interrupt();

            if (this.frameRecorder != null)
                this.frameRecorder.stop();

            this.frameGrabber.close();
            this.frameGrabber.flush();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

}

[saudet]

Good to know that one is thread safe!

/cc @supertick