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• AccessViolationException occurred in AForge.Video.FFMPEG.dll

  11 mai 2017, par Prakash M

  I have a camera class, in this class I used a timer and in its tick event I am saving video using AForge.Net’s VideoFileWriter in C++/Cli (x86, .net framework : v4.6).
  This is not supposed to happen, as this is managed code. But even if I wrap in try catch block, program crashes because of AccessViolationException. I have verified that Image is not null. Something to do with VideoFileWriter. This happens anytime between app start to 30 minutes of running.

  An unhandled exception of type ’System.AccessViolationException’
  occurred in AForge.Video.FFMPEG.dll
  Additional information : Attempted to read or write protected memory.
  This is often an indication that other memory is corrupt.

  In Visual Studio’s output I see

  Exception thrown at 0x0C4D689F (swscale-2.dll) in test.exe : 0xC0000005 : Access violation writing location 0x09F83D80.
  Exception thrown : ’System.AccessViolationException’ in
  AForge.Video.FFMPEG.dll

  code :

   private: System::Void Video_Recorder_Tick(System::Object^  sender, System::Timers::ElapsedEventArgs^  e)
  
    {
  
        Bitmap^ save = ConvertMatToBitmap(image); //function to convert opencv's Mat to .net's Bitmap        
  
        if(writer!= nullptr)
  
         writer->WriteVideoFrame(save);
  
         delete save;
  
     }
  
  
  
    VideoFileWriter ^writer = gcnew VideoFileWriter();
  
  
  
    private: Void load_VideoWriter()
  
    {
  
      writer->Open("C:/video.avi", 640, 480, 10, VideoCodec::Default);        
  
    }

  Visual Studio showed few values for writer

  BitRate 400000
  Codec Default
  FrameRate 10
  Height 480
  IsOpen true
  Width 640
  

  Let me know if anybody needs more info.
  call stack didn’t help much

  

  To my surprise no one on internet is having this issue !
  Code seems straight forward, what could possibly be the issue ?

• Xuggler encoding and muxing

  18 décembre 2012, par HeineyBehinds

  I'm trying to use Xuggler (which I believe uses ffmpeg under the hood) to do the following :

  • Accept a raw MPJPEG video bitstream (from a small TTL serial camera) and encode/transcode it to h.264 ; and
  • Accept a raw audio bitsream (from a microphone) and encode it to AAC ; then
  • Mux the two (audio and video) bitsreams together into a MPEG-TS container

  I've watched/read some of their excellent tutorials, and so far here's what I've got :

  // I'll worry about implementing this functionality later, but
  
  // involves querying native device drivers.
  
  byte[] nextMjpeg = getNextMjpegFromSerialPort();
  
  
  
  // I'll also worry about implementing this functionality as well;
  
  // I'm simply providing these for thoroughness.
  
  BufferedImage mjpeg = MjpegFactory.newMjpeg(nextMjpeg);
  
  
  
  // Specify a h.264 video stream (how?)
  
  String h264Stream = "???";
  
  
  
  IMediaWriter writer = ToolFactory.makeWriter(h264Stream);
  
  writer.addVideoStream(0, 0, ICodec.ID.CODEC_ID_H264);
  
  writer.encodeVideo(0, mjpeg);

  For one, I think I'm close here, but it's still not correct ; and I've only gotten this far by reading the video code examples (not the audio - I can't find any good audio examples).

  Literally, I'll be getting byte-level access to the raw video and audio feeds coming into my Xuggler implementation. But for the life of me I can't figure out how to get them into an h.264/AAC/MPEG-TS format. Thanks in advance for any help here.

• FFMpegWriter not using the bitrate specified ? Animation is very blurry

  18 mai 2022, par cebo

  I am using matplotlib's FunAnimation as well as FFMpegWriter to try to write a simulation animation to a file. I'd like to save a high quality version of it, but when I increase the bitrate value of the writer, the actual bitrate of the .mp4 it creates seems to increase in discrete steps up to a fairly low value after which it doesn't increase any more whatsoever.

  


  My code is roughly :

  


  dpi = 96&#xA;fig = plt.figure(figsize=(width/dpi, height/dpi), dpi=dpi)&#xA;anim = FuncAnimation(fig, myAnimation, frames=100, interval=1, blit=True)&#xA;writer = animation.FFMpegWriter(fps=10, bitrate=<some number="number">)&#xA;anim.save(&#x27;MyAnimation.mp4&#x27;, writer=writer)&#xA;</some>

  


  The animation is only 200x200px so I feel like it shouldn't be a problem to have a high quality video, but I can't seem to get a high enough bitrate. For the following bitrates specified in my code, the actual bitrate shown in the files properties are :

  


  BR In Code   => Actual BR (kbps)
-1 / None    => 13
100          => 58
1000         => 76
10000        => 76


  


  The bitrate doesn't seem to track very well at all, and won't go above 76kbps at all. The video is still badly blurry at this bitrate.

  


  What do I need to do to increase the bitrate or else the quality of the video file ?

  


  Alternatively, is there a better video format/writer to use for this purpose ? Specifically one that is broadly supported so I could embed it in a website or upload it to YouTube or something like that.

  


  Edit :

  


  To be more specific about the issue, neighboring pixels are being blended together, resulting in a blurry look. The following imgur album shows several examples with different settings :

  


  https://imgur.com/a/cxQnV4x

  


  These include the view in the figure window from plt.show(), default bitrate, a "high" bitrate, and something else I just tried which was to increase the dpi. While the results are much nicer it also nearly doubled the execution time so I'd like to avoid it.

  


  It seems silly to have to upscale what is effectively "pixel art" in order for it to look good, but I guess this is an artifact of the signal processing approach mpeg uses, which is why I suspect a different file format might be the best solution for small framed animations like this. If I wanted to do a 1920*1080 animation the blurring would probably be less of an issue.