Javacv: How to Crop a Video? (Question)

[guikeller]

Hi there,

I have a video (sample.mov) that contains 30secs of audio + video.
Now, imagine that the 5secs in the beginning and end of the video is just noise.

How can I crop the video starting at 5secs and ending on 25secs?
Generating then a new video file with only 20secs.

Should I use "FFmpegFrameGrabber" to grab the frames and send to a "FFmpegFrameRecorder"?
Is this the right approach? Any code samples would be greatly appreciated, thanks!

Also, thanks for the project. 👍

[saudet]

Yes, that sounds like the right approach. Depending on the original video, you might not need to reencode the frames: https://github.com/bytedeco/javacv/issues/818#issuecomment-349094435

[saudet]

And sample code is available here:
https://github.com/bytedeco/javacv/blob/master/samples/PacketRecorderTest.java

[guikeller]

Thank you very much for your help! 🌟

[guikeller]

Solution below - pretty straightforward:

            // long fiveSecs = 5000000;
            // long twentyFiveSecs = fiveSecs*5;
            // String sourceFile = "/tmp/VIDEO.MOV";
            // String outputFile = "/tmp/CROPPED_VIDEO.MOV";


    public void cropVideo(String sourceFile, String outputFile, long startTime, long endTime){
        try {

            FFmpegFrameGrabber frameGrabber = new FFmpegFrameGrabber(sourceFile);
            frameGrabber.start();

            int width = frameGrabber.getImageWidth();
            int height = frameGrabber.getImageHeight();
            int channels = frameGrabber.getAudioChannels();

            FFmpegFrameRecorder frameRecorder = new FFmpegFrameRecorder(outputFile, width, height, channels);
            frameRecorder.setAudioBitrate(frameGrabber.getAudioBitrate());
            frameRecorder.setVideoBitrate(frameGrabber.getVideoBitrate());
            frameRecorder.setVideoQuality(0); // MAX Quality!

            while (true) {
                Frame frame = frameGrabber.grab();
                if (frame != null){
                    Long timestamp = frameGrabber.getTimestamp();
                    if (timestamp < startTime) {
                        continue;
                    }
                    frameRecorder.record(frame);
                    if (timestamp > endTime) {
                        break;
                    }
                } else {
                    break;
                }
            }

            frameRecorder.stop();
            frameGrabber.stop();
        } catch (Exception ex) {
            throw new IllegalArgumentException("cropVideo :: could not crop video: "+sourceFile+" / "+outputFile+" / "+startTime+" / "+endTime, ex);
        }
    }

[guikeller]

Hey @saudet

Quick question, how do I copy all metadata from "sourceFile" onto "outputFile" ?
Thank you very much for your help so far, really appreciate it 😄

Cheers 👍

[saudet]

Great! As for the metadata, I guess we would have to enhance FFmpegFrameGrabber and FFmpegFrameRecorder a bit for this. Could you send a pull request? :)

[guikeller]

Thanks for the quick answer; as soon as I get some things out of the way I will try to contribute with a PR by adding this feature; cheers!

[saudet]

I've given access to the Map fields in the commit above. We can now do something like recorder.setMetadata(grabber.getMetadata()) and it should work!

[guikeller]

That's great news!

Thanks for doing that, looking forward to the next release! 👍

[saudet]

Please try the SNAPSHOT artifacts!

[guikeller]

Will do! If you don't hear back from me anymore is because all is going well.. 😆