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• How to transcode a video to custom resolution using Xamarin.MP4Transcoder.Transcoder

  7 juillet 2017, par Prashant

  I need to transcode a video to 640*480 resolution using Xamarin.MP4Transcoder.Transcoder. Currently there are 2 available resolutions 720pFormat and 960x540Format. There is a method called Transcoder For (IMediaFormatStrategy strategy) available in Transcoder class.

  I can create MediaFormat object with MIME Type, Width and Height
  by below mentioned code snippet :

  MediaFormat obj = MediaFormat.CreateVideoFormat("video/mp4", 480, 640);


  but the problem is how can assign it to IMediaFormatStrategy or is there any other way to achieve this.

  Piece of code for Transcoding a video:
  
  
  
  Xamarin.MP4Transcoder.Transcoder.For960x540Format().ConvertAsync(inputFile, outputFile, f =>
                                {
                                  onProgress?.Invoke((int)(f * (double)100), 100);

                                  
                                } );
  
  
  
  inputFile: Video file which needs to be transcoded.
  
  outputFile: Resultant file generated after transcoding.

  For more info you can refer https://github.com/neurospeech/xamarin-android-ffmpeg

  Any help is appreciated. Thanks in advance !!

• How to transcode a video to custom resolution using Xamarin.MP4Transcoder.Transcoder

  12 mai 2017, par Prashant

  I need to transcode a video to 640*480 resolution using Xamarin.MP4Transcoder.Transcoder. Currently there are 2 available resolutions 720pFormat and 960x540Format. There is a method called Transcoder For (IMediaFormatStrategy strategy) available in Transcoder class.

  I can create MediaFormat object with MIME Type, Width and Height
  by below mentioned code snippet :

  MediaFormat obj = MediaFormat.CreateVideoFormat("video/mp4", 480, 640);


  but the problem is how can assign it to IMediaFormatStrategy or is there any other way to achieve this.

  Piece of code for Transcoding a video:
  
  
  
  Xamarin.MP4Transcoder.Transcoder.For960x540Format().ConvertAsync(inputFile, outputFile, f =>
                                {
                                  onProgress?.Invoke((int)(f * (double)100), 100);

                                  
                                } );
  
  
  
  inputFile: Video file which needs to be transcoded.
  
  outputFile: Resultant file generated after transcoding.

  For more info you can refer https://github.com/neurospeech/xamarin-android-ffmpeg

  Any help is appreciated. Thanks in advance !!

• Is there a way to get FFPLAY read from stdin in Matlab using .NET ?

  4 février 2019, par gtab

  I’m trying to read raw h.264 stream from FFMPEG output, process it in Matlab, send it to FFPLAY and display it from there. I use .NET libraries in Matlab, and I am able to read the stream from FFMPEG stdout into Matlab. However, I could not manage to send the processed data to FFPLAY’s stdin. What am I doing wrong ?

  I set up an ffmpeg process to read from its output using System.Diagnostics of .NET in Matlab. Similarly, I set up another process for ffplay. I redirected stdout of ffmpeg and stdin of ffplay. Then, I read lines from ffmpeg and wrote those to ffplay. However, ffplay did not display anything.

  Also, when I try to write to a file from ffmpeg stdout and send ffplay that file, it doesn’t work either. This makes me suspect data drops from ffmpeg stdout, but don’t know how to verify this.

  pFFMPEG = System.Diagnostics.Process();
  
  pFFMPEG.StartInfo = System.Diagnostics.ProcessStartInfo;
  
  pFFMPEG.StartInfo.FileName = 'ffmpeg.exe';
  
  pFFMPEG.StartInfo.Arguments = '-y -nostdin -f dshow -framerate 5 -i video="Logitech Webcam C925e" -vf scale=160:120 -vcodec h264 -an -map 0:v -f nut -';
  
  pFFMPEG.StartInfo.UseShellExecute = false;
  
  pFFMPEG.StartInfo.RedirectStandardOutput = true;
  
  pFFMPEG.StartInfo.RedirectStandardInput = false;
  
  pFFMPEG.StartInfo.RedirectStandardError = false;
  
  pFFMPEG.StartInfo.CreateNoWindow = true;
  
  
  
  pFFPLAY = System.Diagnostics.Process();
  
  pFFPLAY.StartInfo = System.Diagnostics.ProcessStartInfo;
  
  pFFPLAY.StartInfo.FileName = 'ffplay.exe';
  
  pFFPLAY.StartInfo.Arguments = '-i - -autoexit';
  
  pFFPLAY.StartInfo.UseShellExecute = false;
  
  pFFPLAY.StartInfo.RedirectStandardInput = true;
  
  pFFPLAY.StartInfo.RedirectStandardOutput = false;
  
  pFFPLAY.StartInfo.RedirectStandardError = false;
  
  pFFPLAY.StartInfo.CreateNoWindow = false;
  
  
  
  t = zeros(150,1);
  
  ctr = 0;
  
  L = 0;
  
  arr = zeros(10000, 1);
  
  
  
  pFFMPEG.Start();
  
  ffmpegOut = pFFMPEG.StandardOutput;
  
  
  
  temp = ffmpegOut.ReadLine();
  
  temp_arr = uint8(char(temp));
  
  %here, process temp_arr and convert back to char arr temp%
  
  pFFPLAY.Start();
  
  ffplayIn = pFFPLAY.StandardInput;
  
  ffplayIn.WriteLine(temp);
  
  
  
  while ~(isempty(temp)) && ctr < 150 && L < length(arr)
  
      L_end = L+temp.Length;
  
      arr(L+1:L_end) = temp_arr;
  
      temp = ffmpegOut.ReadLine();
  
      L = L_end;
  
      temp_arr = uint8(char(temp));
  
      %here, process temp_arr and convert back to char arr temp %
  
      ffplayIn.WriteLine(temp);
  
      ctr = ctr + 1;
  
  end    

  When I look into the Matlab workspace, I seem to get the output of ffmpeg into Matlab in arr, although I am not sure if there are any drops.
  When I try to send the data to ffplay, nothing happens. I can see ffplay process is running, but no video window shows up.

  Any help is much appreciated.