FFmpegFrameRecorder after record video，video size is below origin video？

public static void recordVideo(InputStream inputStream1, String outputFilename) throws CreativeFactoryException {
        try {
            FFmpegFrameGrabber grabber1 = new FFmpegFrameGrabber(inputStream1);
            grabber1.start();

            int w = grabber1.getImageWidth();
            int h = grabber1.getImageHeight();


            FFmpegFrameRecorder recorder = new FFmpegFrameRecorder(outputFilename, w, h, grabber1.getAudioChannels());

            initFrameRecorder(grabber1, recorder);
            recorder.start();

            while (true) {
                Frame frame = grabber1.grabFrame();
                if (frame == null) {
                    break;
                }
                recorder.record(frame);
            }

            grabber1.stop();
            recorder.stop();
        } catch (FrameGrabber.Exception | FrameRecorder.Exception e) {
            throw new CreativeFactoryException("Failed to concat video.", e);
        }
    }


private static void initFrameRecorder(FFmpegFrameGrabber grabber, FFmpegFrameRecorder recorder) {
        recorder.setVideoCodec(grabber.getVideoCodec());
        recorder.setAudioCodec(grabber.getAudioCodec());
        recorder.setFormat("mp4");
        recorder.setFrameRate(grabber.getFrameRate());

        recorder.setAspectRatio(grabber.getAspectRatio());
        recorder.setAudioBitrate(grabber.getAudioBitrate());
        // recorder.setAudioChannels(grabber.getAudioChannels());
        recorder.setVideoBitrate(grabber.getVideoBitrate());

        // 我的笔记本上只有这个值能work，原因不明
        recorder.setSampleFormat(8);
        // recorder.setSampleFormat(grabber.getSampleFormat());
        recorder.setSampleRate(grabber.getSampleRate());
    }

audioBitrate and videoBitrate is downing 1kbps