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• Using FFmpeg in .net ?

  15 juillet 2016, par daniel

  So I know its a fairly big challenge but I want to write a basic movie player/converter in c# using the FFmpeg library. However, the first obstacle I need to overcome is wrapping the FFmpeg library in c#. I’ve downloaded ffmpeg but couldn’t compile it on Windows, so I downloaded a precompiled version for me. Ok awesome. Then I started looking for C# wrappers.

  I have looked around and have found a few wrappers such as SharpFFmpeg (http://sourceforge.net/projects/sharpffmpeg/) and ffmpeg-sharp (http://code.google.com/p/ffmpeg-sharp/). First of all, I wanted to use ffmpeg-sharp as its LGPL and SharpFFmpeg is GPL. However, it had quite a few compile errors. Turns out it was written for the mono compiler, I tried compiling it with mono but couldn’t figure out how. I then started to manually fix the compiler errors myself, but came across a few scary ones and thought I’d better leave those alone. So I gave up on ffmpeg-sharp.

  Then I looked at SharpFFmpeg and it looks like what I want, all the functions P/Invoked for me. However its GPL ? Both the AVCodec.cs and AVFormat.cs files look like ports of avcodec.c and avformat.c which I reckon I could port myself ? Then not have to worry about licencing.

  But I want to get this right before I go ahead and start coding. Should I :

  1. Write my own C++ library for interacting with ffmpeg, then have my C# program talk to the C++ library in order to play/convert videos etc.

  OR

  2. Port avcodec.h and avformat.h (is that all i need ?) to c# by using a whole lot of DllImports and write it entirely in C# ?

  First of all consider that I’m not great at C++ as I rarely use it but I know enough to get around. The reason I’m thinking #1 might be the better option is that most FFmpeg tutorials are in C++ and I’d also have more control over memory management than if I was to do it in c#.

  What do you think ?
  Also would you happen to have any useful links (perhaps a tutorial) for using FFmpeg ?

• Ffmpeg : How to fix error "Please choose an encoder manually" ?

  9 juillet 2023, par Alex

  I am trying to convert a x265 videofile to a x264 format so it can be played on a television. I am trying the following command

  


  ffmpeg -i input.mkv -f mp4 -vcodec libx264 -preset fast -profile:v main -acodec aac -map 0:0 -map 0:1 -map 0:2 test.mp4


  


  to select videos stream 0:0 for video, stream 0:1 for audio and stream 0:2 for the subtitle. However I get an error

  


  Automatic encoder selection failed Default encoder for format mp4 (codec none) is probably disabled. Please choose an encoder manually.
Error selecting an encoder


  


  How to fix this command ?

  


  P.S. I am not an expert in ffmpeg or videos conversion/formats/encodings/audio formats/subtitle formats.

  


  I found EXACTLY ONE google search result with the exact error phrase HERE. And that is not helping as I do not even understand the first sentence.

  


  Below is the output for the first three streams :

  


  Input #0, matroska,webm, from 'input.mkv':
  Metadata:
    creation_time   : 2021-03-25T09:13:20.000000Z
    ENCODER         : Lavf58.29.100
  Duration: 00:23:57.65, start: 0.000000, bitrate: 2103 kb/s
  Stream #0:0(jpn): Video: hevc (Main 10), yuv420p10le(tv), 1920x1080, SAR 1:1 DAR 16:9, 23.98 fps, 23.98 tbr, 1k tbn (default)
    Metadata:
      title           : [Judas] x265 10b
      ENCODER         : Lavc58.54.100 libx265
      BPS-eng         : 1973938
      DURATION-eng    : 00:23:55.017000000
      NUMBER_OF_FRAMES-eng: 34406
      NUMBER_OF_BYTES-eng: 354079423
      _STATISTICS_WRITING_APP-eng: mkvmerge v48.0.0 ('Fortress Around Your Heart') 64-bit
      _STATISTICS_WRITING_DATE_UTC-eng: 2021-03-25 09:13:20
      _STATISTICS_TAGS-eng: BPS DURATION NUMBER_OF_FRAMES NUMBER_OF_BYTES
  Stream #0:1(jpn): Audio: aac (LC), 44100 Hz, stereo, fltp (default)
    Metadata:
      title           : Japanese
      BPS-eng         : 128000
      DURATION-eng    : 00:23:55.086000000
      NUMBER_OF_FRAMES-eng: 61804
      NUMBER_OF_BYTES-eng: 22961378
      _STATISTICS_WRITING_APP-eng: mkvmerge v48.0.0 ('Fortress Around Your Heart') 64-bit
      _STATISTICS_WRITING_DATE_UTC-eng: 2021-03-25 09:13:20
      _STATISTICS_TAGS-eng: BPS DURATION NUMBER_OF_FRAMES NUMBER_OF_BYTES
  Stream #0:2(eng): Subtitle: ass
    Metadata:
      title           : English
      BPS-eng         : 196
      DURATION-eng    : 00:23:53.580000000
      NUMBER_OF_FRAMES-eng: 478
      NUMBER_OF_BYTES-eng: 35129
      _STATISTICS_WRITING_APP-eng: mkvmerge v48.0.0 ('Fortress Around Your Heart') 64-bit
      _STATISTICS_WRITING_DATE_UTC-eng: 2021-03-25 09:13:20
      _STATISTICS_TAGS-eng: BPS DURATION NUMBER_OF_FRAMES NUMBER_OF_BYTES


  


  I found a related question HERE whose answer I do not fully understand. However, I tried the following command

  


  ffmpeg -i input.mkv -f mp4 -vcodec libx264 -preset fast -profile:v main -acodec aac -map 0:0 -map 0:1 -map 0:2 -c:s mov_text  test.mp4


  


  but got a new error

  


  Error initializing output stream: Error while opening encoder for output stream #0:0 - maybe incorrect parameters such as bit_rate, rate, width or height


  


  I thought I am defining an "encoder" for output stream "#0:0" (which I think is video), namely libx264. So what else to do here ?

  


  I tried -acode copy and also to use -qp 0 in the command line which all did not work.

  


• C# Process in loop reading error output, causes "No async read operation is in progress on the stream" error

  29 mai 2023, par TSLee

  I am trying to read the format of multiple video files using ffmpeg in an asynchronous operation of Process and facing an error, "No async read operation is in progress on the stream". According to https://social.msdn.microsoft.com/Forums/vstudio/en-US/c961f461-7afb-4a92-b0ae-f78c2003b5de/help-an-asynchronous-read-operation-is-already-in-progress-on-the-standardoutput-stream?forum=csharpgeneral, I think I have to use CancelErrorRead(), as BeginErrorReadLine() can't be launched more than once. I also wonder if I use this function in the wrong place, because the read operation has ended in process1.exited() ? But the operation can't proceed to the second index with this error.

  


  How could I use CancelErrorRead()/CancelOutputRead() properly and where should I place them on the code ? I also did an experiment in that I commented these two CancelRead(), and a different error "async read operation has been started on the stream" will appear.

  


              Process process1 = new Process();
            process1.StartInfo.WindowStyle = ProcessWindowStyle.Hidden;
            process1.StartInfo.CreateNoWindow = true;
            process1.StartInfo.UseShellExecute = false;
            process1.StartInfo.FileName = ".\\ffmpeg.exe";
            process1.StartInfo.WorkingDirectory = ".\\";
            process1.EnableRaisingEvents = true;
            process1.StartInfo.RedirectStandardOutput = true; //if this is true, UseShellExecute must be false. true if output should be written to StandardOutput
            process1.StartInfo.RedirectStandardError = true;
            //indicates that the associated Process has written a line that's terminated with a newline
            process1.ErrorDataReceived += new DataReceivedEventHandler(inputHandler);
            process1.Exited += (ending, p) =>
            {
                flag = true;
                process1.CancelOutputRead();
                process1.CancelErrorRead();//
            };
            foreach (String file in inputList)
            {
                if (flag == true)
                {
                    flag = false;
                    process1.StartInfo.Arguments = "-i " + " \"" + file + "\"";
                    Console.WriteLine(process1.StartInfo.Arguments);
                    process1.Start();
                    process1.BeginOutputReadLine();//
                    process1.BeginErrorReadLine();
                    process1.WaitForExit(); //for asynchronous output
                }


            }
        }
        private void inputHandler(object sender, DataReceivedEventArgs l)
        {
             cba.Append(l.Data + "\n");
             videoInput = l.Data;
             //Console.WriteLine(cba);
             //Process p = sender as Process;
             Console.WriteLine(videoInput);

             this.BeginInvoke(new MethodInvoker(() =>
             {

              if (!String.IsNullOrEmpty(videoInput))
              {
                    if (videoInput.Contains("Stream #0:0"))
                    {
                        String subvideoInput1 = 
                        videoInput.Substring(videoInput.IndexOf("Stream #0:0"));
                        String video_inputType = subvideoInput1;
                        textBox1.Text += video_inputType + System.Environment.NewLine;
                        Console.WriteLine(video_inputType);
                     }
                     if (videoInput.Contains("Stream #0:1"))
                     {
                         String subvideoInput2 = 
                         videoInput.Substring(videoInput.IndexOf("Stream #0:1"));
                         Console.WriteLine(subvideoInput2.IndexOf("\n"));
                         Console.WriteLine(subvideoInput2);
                         String audio_inputType = subvideoInput2;
                         textBox1.AppendText(audio_inputType + System.Environment.NewLine);
                         Console.WriteLine(audio_inputType);
                     }
                     if (videoInput.Contains("Duration:"))
                     {
                         String videoinputDuration = 
                         videoInput.Substring(videoInput.IndexOf("Duration:"));
                         String subvideo_inputDuration = videoinputDuration.Substring(9);
                         String inputvideoDuration = 
                     subvideo_inputDuration.Remove(subvideo_inputDuration.IndexOf("."));
                         Console.WriteLine(inputvideoDuration);
                         double totalseconds = 
                         TimeSpan.Parse(inputvideoDuration).TotalSeconds;
                    
                    

                }
            }

        }));


    }