Javacv: Change the resolution when pushing with FFmpegFrameRecorder

[cndota123]

How do I configure the relevant configuration of FFmpegFrameRecorder to change the video resolution when implementing video stream output, just like the -s or -vf scale command in FFmpeg.

[saudet]

All images get resized to the width and height values given in the constructor.

[cndota123]

I think I used this method, but it didn't solve the corresponding problem.
This is my code

   public Stream pull() throws CommonException {
        grabber = new FFmpegFrameGrabber(sourceUrl);
        grabber.setOption("rtsp_transport", "tcp");
        try {
            grabber.start();
        } catch (FrameGrabber.Exception e) {
            logger.error(sourceUrl + " pull fail");
            e.printStackTrace();
            throw new CommonException("2001", Result.getMessage("2001"));
        }
        return this;
    }

    public Stream push() throws CommonException {
        recorder = new FFmpegFrameRecorder(outputUrl, width, height, audioRecord);
        recorder.setFormat("flv");
        recorder.setVideoCodec(avcodec.AV_CODEC_ID_H264);
        recorder.setAudioCodecName("acc");
        avformat.AVFormatContext avFormatContext = grabber.getFormatContext();
        recorder.setAudioChannels(audioRecord);
        recorder.setSampleRate(44100);
        recorder.setVideoBitrate(videoBitrate);

        recorder.setVideoOption("tune", "zerolatency");
        recorder.setFrameRate(25);
        recorder.setGopSize(25 * 2);
        //recorder.setOption("vf scale", "480:320");
        try {
            recorder.start(avFormatContext);
        } catch (FrameRecorder.Exception e) {
            logger.error(outputUrl + " push fail");
            e.printStackTrace();
            throw new CommonException("2002", Result.getMessage("2002"));
        }
        return this;
    }
    public void start() throws CommonException {
        int errIndex = 0;
        for (int noFrameIndex = 0; noFrameIndex < 5 || errIndex > 1 || interrupted == 1; ) {
            isRun = true;
            avcodec.AVPacket avPacket;
            try {
                avPacket = grabber.grabPacket();
                if (avPacket == null || (avPacket.size() <= 0) || (avPacket.data() == null)) {
                    noFrameIndex++;
                    continue;
                }
                errIndex += recorder.recordPacket(avPacket) ? 0 : 1;
                av_free_packet(avPacket);

            } catch (FrameGrabber.Exception e) {
                e.printStackTrace();
                errIndex++;
            } catch (FrameRecorder.Exception e) {
                e.printStackTrace();
                errIndex++;
            }
        }
        if (interrupted == 0) {
            restart();
        } else {
            stop();
        }
    }

I use it like this.pull().push().start(),the source video resolution is 640x480,the creation statement of FFmpegFrameRecorder is new FFmpegFrameRecorder(outputUrl, 480, 272, 1),But the resolution of the output stream is still 640x480

[saudet]

You're not calling record() anywhere.
You'll need to call record() somewhere.

[cndota123]

I modified the code for the start method.

    public void start() {
        long startTime = 0;
        Frame frame;
        try {
            while ((frame = grabber.grab()) != null) {
                if (startTime == 0)
                    startTime = System.currentTimeMillis();
                long time = System.currentTimeMillis() - startTime;
                recorder.setTimestamp(1000 * time);
                recorder.record(frame);
            }
        } catch (FrameGrabber.Exception e) {
            e.printStackTrace();
        } catch (FrameRecorder.Exception e) {
            e.printStackTrace();
        }
    }

But it didn't work and produced an exception,this is output information of ffmpeg

Input #0, rtsp, from 'rtsp://user:[email protected]:1554/h264/ch1/sub/av_stream':
  Metadata:
    title           : Media Presentation
  Duration: N/A, start: 0.240000, bitrate: N/A
    Stream #0:0: Video: h264 (Main), yuvj420p(pc, bt709, progressive), 640x480 [SAR 1:1 DAR 4:3], 25 fps, 25 tbr, 90k tbn, 50 tbc
[flv @ 0x7ff07c148900] Using AVStream.codec to pass codec parameters to muxers is deprecated, use AVStream.codecpar instead.
Output #0, flv, to 'rtmp://127.0.0.1:9100/live/a2334ccd-e030-41e5-8957-91761a636b1e':
  Metadata:
    encoder         : Lavf58.20.100
    Stream #0:0: Video: h264 (Main) ([7][0][0][0] / 0x0007), yuvj420p(pc, bt709, progressive), 640x480 [SAR 1:1 DAR 4:3], q=2-31, 25 fps, 1k tbn, 25 tbc
    Stream #0:1: Audio: aac (LC) ([10][0][0][0] / 0x000A), 44100 Hz, mono, fltp, 64 kb/s
[swscaler @ 0x7ff07c31b900] deprecated pixel format used, make sure you did set range correctly
[swscaler @ 0x7ff07c4e4100] deprecated pixel format used, make sure you did set range correctly
Exception in thread "Thread-9" java.lang.NullPointerException
    at org.bytedeco.javacv.FFmpegFrameRecorder.recordImage(FFmpegFrameRecorder.java:931)
    at org.bytedeco.javacv.FFmpegFrameRecorder.record(FFmpegFrameRecorder.java:876)
    at org.bytedeco.javacv.FFmpegFrameRecorder.record(FFmpegFrameRecorder.java:869)

[saudet]

Passing null frames to FFmpegFrameRecorder isn't going to work. Make sure that doesn't happen.

[cndota123]

Exceptions in this line of code in the recordImage method.

avutil.av_image_fill_arrays(new PointerPointer(this.tmp_picture), this.tmp_picture.linesize(), data, pixelFormat, width, height, 1);

this.tmp_picture is null,but I didn't see any instantiation about it during the debugging process.

[saudet]

It happens on start(). You should be getting another exception before that if you didn't call start(), but anyway, just call start(), it will work.

[cndota123]

You are right. I used the start(AVFormatContext ifmt_ctx) method. After changing to the start() method, he worked normally. Thank you very much for your answer. It helped me a lot.