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• C# streaming RTSP webcam with ffmpeg over websocket server

  26 mars 2018, par EvilID

  I’m trying to re-stream a RTSP IP-Cam to a website and I’ve created a websocket server in C#. The websocket server has to send the video data to the client which runs on JSmpeg (https://github.com/phoboslab/jsmpeg).

  I’m starting the ffmpeg transcoding in C# like this :

  ProcessStartInfo startInfo = new ProcessStartInfo();
  
  
  
          startInfo.CreateNoWindow = false;
  
          startInfo.UseShellExecute = false;
  
          startInfo.FileName = Path.Combine(AppDomain.CurrentDomain.BaseDirectory, "ffmpeg\\ffmpeg.exe");
  
          startInfo.Arguments = "-rtsp_transport tcp -i rtsp://192.168.0.12:1254/mjpeg -vf scale=430:242 -f mpegts -codec:v mpeg1video -bf 0 -codec:a mp2 -b:v 800k -r 30 -";
  
  
  
  
  
          startInfo.RedirectStandardOutput = true;
  
          //startInfo.RedirectStandardError = true;
  
  
  
          Console.WriteLine(string.Format(
  
              "Executing \"{0}\" with arguments \"{1}\".\r\n",
  
              startInfo.FileName,
  
              startInfo.Arguments));
  
  
  
  
  
          Process process = new Process();
  
          process.StartInfo = startInfo;
  
  
  
  
  
          process.Start();

  The handshake between the client and server is done, but when I try to send any data I receive an error : "failed : Invalid frame header".

  I’ve tried many things, but can’t get it to work. The last thing that I’ve tried to do was writing the data into a Memory stream and than converting it to a byte array to write it to the client.

  Something like this (I’ve tried many things, but I’m doing something wrong) :

               Stream baseStream = process.StandardOutput.BaseStream;
  
               byte[] imageBytes = null;
  
               int lastRead = 0;
  
  
  
               while (!process.StandardOutput.EndOfStream)
  
               {
  
  
  
                   using (MemoryStream ms = new MemoryStream())
  
                   {
  
                       byte[] buffer = new byte[4096];
  
  
  
                       do
  
                       {
  
  
  
                           lastRead = baseStream.Read(buffer, 0, buffer.Length);
  
                           ms.Write(buffer, 0, lastRead);
  
                           Console.WriteLine(lastRead);
  
                       } while (lastRead > 0);
  
  
  
                       imageBytes = ms.ToArray();
  
                   }
  
  
  
                       stream.Write(imageBytes, 0, imageBytes.Length);
  
  
  
  
  
               }

  Can someone help me ?

  Thanks in advance !

• How to set ffmpeg qscale in C/C++ for image encoding

  4 juillet 2022, par necrosato

  I have a working image encoder in C++ using ffmpeg as the backend. I am taking videos in and saving frames out as jpeg, but I am having difficulty adjusting the quality of the output jpegs.
  
Things I have tried :
  
Setting AVCodecContext's global_quality and compression_level fields.
  
I have also tried setting qscale with an AVDictionary of options, but have been unsuccessful there too.

  



  I know its possible because with the command line I can
  
ffmpeg -i INPUT -q:v 2 output_frame_%02d.jpg and get higher quality images.

  


• How to resize yuv420sp using FFmpeg

  27 juin 2012, par newentry

  How to resize yuv420sp data into some other resolution.I tried using ffmpeg sws_scale but no success.I tried by converting yuv420sp to yuv420p and then tried to resize yuv420p into RGB24 via sws_scale but the things it works when both src and destination width and height are same, but for different resolution didn't get correct rgb24. Can anyboody guide me with example code using c or if possible through Java itself .The final resized data must be in yuv420p.
  In my case i am trying to downsize the yuv420sp for eg 640*480 to 320*240 or 176*144.

  thanks,