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• javacv and moviepy comparison for video generation

  15 septembre 2024, par Vikram

  I am trying to generate video using images, where image have some overlays text and png icons. I am using javacv library for this.
Final output video seems pixelated, i don't understand what is it since i do not have video processing domain knowledge, i am beginner to this.
I know that video bitrate and choice of video encoder are important factor which contributes to video quality and there are many more factors too.

  


  I am providing you two output for comparison, one of them is generated using javacv and another one is from moviepy library

  


  Please watch it in full screen since the problem i am talking about only gets highlighted in full screen, you will see the pixel dancing in javacv generated video, but python output seems stable

  


  https://imgur.com/a/aowNnKg - javacv generated

  


  https://imgur.com/a/eiLXrbk - Moviepy generated

  


  I am using same encoder in both of the implementation

  


  Encoder - libx264
bitrate - 
   800 Kbps for javacv 
   500 Kbps for moviepy

frame rate - 24fps for both of them

output video size -> 
    7MB (javacv)
    5MB (Moviepy)




  


  generated output size from javacv is bigger then moviepy generated video.

  


  here is my java configuration for FFmpegFrameRecorder

  


          FFmpegFrameRecorder recorder = new FFmpegFrameRecorder(this.outputPath, 
                                           this.screensizeX, this.screensizeY);
        if(this.videoCodecName!=null && "libx264".equals(this.videoCodecName)) {
            recorder.setVideoCodec(avcodec.AV_CODEC_ID_H264);
        }
        recorder.setFormat("mp4"); 
        recorder.setPixelFormat(avutil.AV_PIX_FMT_YUV420);
        recorder.setVideoBitrate(800000);
        recorder.setImageWidth(this.screensizeX);
        recorder.setFrameRate(24);



  


  and here is python configuration for writing video file

  


  Full_final_clip.write_videofile(
                            f"{video_folder_path}/{FILE_ID}_INTERMEDIATE.mp4",
                            codec="libx264",
                            audio_codec="aac",
                            temp_audiofile=f"{FILE_ID}_INTER_temp-audio.m4a",
                            remove_temp=True,
                            fps=24,
                        )



  


  as you can see i am not specifying bitrate in python, but i checked that bitrate of final output is around 500 kbps, which is lower then what i specified in java, yet java generated video quality seems poor.

  


  I have tried setting crf value also , but it seems it does not have any impact when used.

  


  increasing bitrate improve quality somewhat but at the cost of file size, still generated output seems pixelated.

  


  Can someone please highlight what might be the issue, and how python is generating better quality video, when both of the libraries use ffmpeg at the backend.

  


  Edit 1 : also, I am adding code which is being used to make zoom animation for continuous frames, As somewhere i read that this might be the cause for pixel jitter, please see and let me know if there is any improvement we can do to remove pixel jittering

  


  private Mat applyZoomEffect(Mat frame, int currentFrame, long effectFrames, int width, int height, String mode, String position, double speed) {
        long totalFrames = effectFrames;
        double i = currentFrame;
        if ("out".equals(mode)) {
            i = totalFrames - i;
        }
        double zoom = 1 + (i * ((0.1 * speed) / totalFrames));

        double originalCenterX = width/2.0;
        double originalCenterY = height/2.0;
   

        // Resize image
        //opencv_imgproc.resize(frame, resizedMat, new Size(newWidth, newHeight));

        // Determine crop region based on position
        double x = 0, y = 0;
        switch (position.toLowerCase()) {
            case "center":
                // Adjusting for center zoom
                 x = originalCenterX - originalCenterX * zoom;
                 y = originalCenterY - originalCenterY * zoom;
                 
                 x= (width-(width*zoom))/2.0;
                 y= (height-(height*zoom))/2.0;
                break;
        }

        double[][] rowData = {{zoom, 0, x},{0,zoom,y}};

        double[] flatData = flattenArray(rowData);

        // Create a DoublePointer from the flattened array
        DoublePointer doublePointer = new DoublePointer(flatData);

        // Create a Mat object with two rows and three columns
        Mat mat = new Mat(2, 3, org.bytedeco.opencv.global.opencv_core.CV_64F); // CV_64F is for double type

        // Put the data into the Mat object
        mat.data().put(doublePointer);
        Mat transformedFrame = new Mat();
        opencv_imgproc.warpAffine(frame, transformedFrame, mat, new Size(frame.cols(), frame.rows()),opencv_imgproc.INTER_LANCZOS4,0,new Scalar(0,0,0,0));
        return transformedFrame;
    }


  


• YUV Raw frames to video stream

  30 septembre 2014, par Ahmed Nassar

  Im trying to stream raw YUV frames in an array generated in a C++ program to video using FFPEG. Can anyone point me to the right direction ?

• How to draw a waveform from an RTSP audio using ffmpeg and Python

  9 mars 2023, par S Andrew

  I have a Hikvision camera. Using ffmpeg, I can extract the audio from it and save it in wav file using below code :

  


  import os
os.system("ffmpeg -i rtsp://admin:password@192.168.0.27:554/Streaming/Channels/101/ -q:a 0 -map a -t 10 file.wav")


  


  It creates file.wav file and when played I can hear the audio recorded from camera. Now I am planning to draw the waveform of these audio's. For this I have below code :

  


  os.system("ffmpeg -i rtsp://admin:password@192.168.0.27:554/Streaming/Channels/101/ -filter_complex showwavespic -frames:v 1 output.png")


  


  and below is the output I get after pressing q

  


  [q] command received. Exiting.

Finishing stream 0:0 without any data written to it.
Output #0, image2, to 'output.png':
  Metadata:
    title           : Media Presentation
    encoder         : Lavf59.26.100
  Stream #0:0: Video: png, rgba, 600x240 [SAR 1:1 DAR 5:2], q=2-31, 200 kb/s, 1 fps, 1 tbn
    Metadata:
      encoder         : Lavc59.36.100 png
frame=    0 fps=0.0 q=0.0 Lsize=N/A time=00:00:00.00 bitrate=N/A speed=   0x    
video:0kB audio:0kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: unknown
Output file is empty, nothing was encoded (check -ss / -t / -frames parameters if used)


  


  and there is no file generated. I tried the above code with and mp3 file and it generated the output.png with waveform. How can I resolve the issue ?