Javacv: Using FFmpegFrameFilter to rotate and set padding results in black and white image with green/purple blurs

[RJonkersTC]

The goal I have is to broadcast to a RTMP server and that is going perfect in landscape mode. When I record in portrait mode, the resolution remains the same as in landscape (1280x720) and to prevent the video from becoming stretched out, I use the FFmpegFrameFilter to make changes to the video. I rotate the image, scale it and set padding to 'simulate' black bars like this:

filter = new FFmpegFrameFilter("transpose=2, scale=480:720, pad=1280:720:400:0:color=black", imageWidth, imageHeight);

The size of the new video looks about right, but the video is in black and white instead of color and there are green/purple blurs on the left/right edges of the video.

I have set the pixel format to AV_PIX_FMT_NV21, but that does not resolve the issue. If I delete the "pad=1280:720:400:0:color=black" part, the video does remain in color, but the image is all stretched out.

Once the orientation changes:

@Override
    public void onConfigurationChanged(Configuration newConfig) {
        super.onConfigurationChanged(newConfig);

        if(recorder != null) {
            if(newConfig.orientation == Configuration.ORIENTATION_PORTRAIT) {
                filter = new FFmpegFrameFilter("transpose=2, scale=-1:720", imageWidth, imageHeight);
                filter.setPixelFormat(avutil.AV_PIX_FMT_NV21); // default camera format on Android
                try {
                    filter.start();
                } catch (FrameFilter.Exception e) {
                    e.printStackTrace();
                }
            }

            else {
                filter = null;
            }
        }
    }

OnPreviewFrame:

@Override
        public void onPreviewFrame(byte[] data, Camera camera) {
            if (audioRecord == null || audioRecord.getRecordingState() != AudioRecord.RECORDSTATE_RECORDING) {
                startTime = System.currentTimeMillis();
                return;
            }
            if (RECORD_LENGTH > 0) {
                int i = imagesIndex++ % images.length;
                yuvImage = images[i];
                timestamps[i] = 1000 * (System.currentTimeMillis() - startTime);
            }
            /* get video data */
            if (yuvImage != null && recording) {
                ((ByteBuffer)yuvImage.image[0].position(0)).put(data);

                if (RECORD_LENGTH <= 0) try {
                    Log.v(LOG_TAG,"Writing Frame");
                    long t = 1000 * (System.currentTimeMillis() - startTime);
                    if (t > recorder.getTimestamp()) {
                        recorder.setTimestamp(t);
                    }

                    if(filter != null) {
                        try {
                            filter.push(yuvImage);
                            Frame frame;
                            while ((frame = filter.pull()) != null) {
                                recorder.record(frame);
                            }
                        } catch (FrameFilter.Exception e) {
                            e.printStackTrace();
                        }
                    }

                    else {
                        recorder.record(yuvImage);
                    }
                } catch (FFmpegFrameRecorder.Exception e) {
                    Log.v(LOG_TAG,e.getMessage());
                    e.printStackTrace();
                }
            }
        }
    }

Do you have any suggestions?

[saudet]

Is this an issue with FFmpegFrameFilter? Or is it a question about FFmpeg filters?

[RJonkersTC]

This is not a question about FFmpeg filters, but a question about FFmpegFrameFilter. I just tried a similar command with regular FFmpeg and it worked fine, so looks like it's an issue with FFmpegFrameFilter.

[saudet]

I know some filters don't support all pixel formats very well, so you might want to try and use a different one. It's possible to do conversion within the graph with the format filter:
https://ffmpeg.org/ffmpeg-filters.html#format-1
https://github.com/bytedeco/javacv/issues/232#issuecomment-162601656

[saudet]

Have you been able to find the right combination of filters to get this working?

[RJonkersTC]

Hi,

No I've been unable to get it working. In the end I've decided to use Kickflip for my project.

Thanks for your help though!

[orenk86]

I'm also experiencing the same issue. I've been trying all sorts of combinations of filters and formats, so far no luck.
Did anybody find a decent solution for this?

[saudet]

Try to put "format=rgba" and/or "format=bgr24" filters at various stages in the graph...

[orenk86]

Hey thanks @saudet , turns out the problem was in the "pad" filter (perhaps it's a support issue with the pixel formats like you suggested)...
I've ended up using the "crop" filter instead, which works very nicely. Here's my full portrait mode filter so far:

String transpose = cameraId == Camera.CameraInfo.CAMERA_FACING_FRONT ? "2" : "1";
String scale = "-1:ih";
String crop = "iw:ih:(ow-iw)/2:0";
filter = new FFmpegFrameFilter("transpose=" + transpose + ", scale=" + scale + ", crop=" + crop, imageWidth, imageHeight);
filter.setPixelFormat(avutil.AV_PIX_FMT_NV21);