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• Ffmpeg only receives a piece of information from the pipe

  4 juillet 2017, par Maxim Fedorov

  First of all - my english is not very good, i`m sorry for that.

  I use ffmpeg from c# to convert images to video. To interact with ffmpeg, I use pipes.

  public async Task ExecuteCommand(
  
          string arguments,
  
          Action<namedpipeserverstream> sendDataUsingPipe)
  
      {
  
          var inStream = new NamedPipeServerStream(
  
              "from_ffmpeg",
  
              PipeDirection.In,
  
              1,
  
              PipeTransmissionMode.Byte,
  
              PipeOptions.Asynchronous,
  
              PipeBufferSize,
  
              PipeBufferSize);
  
  
  
          var outStream = new NamedPipeServerStream(
  
              "to_ffmpeg",
  
              PipeDirection.Out,
  
              1,
  
              PipeTransmissionMode.Byte,
  
              PipeOptions.Asynchronous,
  
              PipeBufferSize,
  
              PipeBufferSize);
  
  
  
          var waitInConnectionTask = inStream.WaitForConnectionAsync();
  
          var waitOutConnectionTask = outStream.WaitForConnectionAsync();
  
  
  
          byte[] byteData;
  
  
  
          using (inStream)
  
          using (outStream)
  
          using (var inStreamReader = new StreamReader(inStream))
  
          using (var process = new Process())
  
          {
  
              process.StartInfo = new ProcessStartInfo
  
              {
  
                  RedirectStandardOutput = true,
  
                  RedirectStandardError = true,
  
                  RedirectStandardInput = true,
  
                  FileName = PathToFfmpeg,
  
                  Arguments = arguments,
  
                  UseShellExecute = false,
  
                  CreateNoWindow = true
  
              };
  
  
  
              process.Start();
  
  
  
              await waitOutConnectionTask;
  
  
  
              sendDataUsingPipe.Invoke(outStream);
  
  
  
              outStream.Disconnect();
  
              outStream.Close();
  
  
  
              await waitInConnectionTask;
  
  
  
              var logTask = Task.Run(() => process.StandardError.ReadToEnd());
  
              var dataBuf = ReadAll(inStream);
  
  
  
              var shouldBeEmpty = inStreamReader.ReadToEnd();
  
              if (!string.IsNullOrEmpty(shouldBeEmpty))
  
                  throw new Exception();
  
  
  
              var processExitTask = Task.Run(() => process.WaitForExit());
  
              await Task.WhenAny(logTask, processExitTask);
  
              var log = logTask.Result;
  
  
  
              byteData = dataBuf;
  
  
  
              process.Close();
  
              inStream.Disconnect();
  
              inStream.Close();
  
          }
  
  
  
          return byteData;
  
      }
  
  </namedpipeserverstream>

  Action "sendDataUsingPipe" looks like

  Action<namedpipeserverstream> sendDataUsingPipe = stream =>
  
          {
  
              foreach (var imageBytes in data)
  
              {
  
                  using (var image = Image.FromStream(new MemoryStream(imageBytes)))
  
                  {
  
                      image.Save(stream, ImageFormat.Jpeg);
  
                  }
  
              }
  
          };
  
  </namedpipeserverstream>

  When I send 10/20/30 images (regardless of the size) ffmpeg processes everything.
  When I needed to transfer 600/700 / .. images, then in the ffmpeg log I see that it only received 189-192, and in the video there are also only 189-192 images.
  There are no errors in the logs or exceptions in the code.

  What could be the reason for this behavior ?

• FFMPEG API : How to clear real-time buffer ?

  29 novembre 2018, par user67

  Here’s the c++ code that I’m using to access my webcam.

  int Camera::Init(char* file_name,
  
                  char* device_name,
  
                  char* format,
  
                  char* resolution,
  
                  char* frame_rate,
  
                  char* pixel_format)
  
  {
  
      av_log(NULL, AV_LOG_INFO, "---INIT STARTED\n");
  
      avdevice_register_all();
  
      av_register_all();
  
  
  
      AVDictionary* properties_collection = NULL;
  
      av_dict_set(&properties_collection, "f", format, NULL);
  
      av_dict_set(&properties_collection, "video_size", resolution, NULL);
  
      av_dict_set(&properties_collection, "framerate", frame_rate, NULL);
  
      av_dict_set(&properties_collection, "pix_fmt", pixel_format, NULL);
  
      AVInputFormat *input_format = av_find_input_format("dshow");
  
      char command_line[256];
  
      sprintf(command_line, "video=%s", device_name);
  
      AVFormatContext *input_context = avformat_alloc_context();
  
      //input_context->flags |= AVFMT_FLAG_NOBUFFER;      //DOESN'T HELP
  
      //input_context->max_picture_buffer = 0;            //ERR
  
  
  
      int err_code = 0;
  
      err_code = avformat_open_input(&input_context,
  
                                      command_line,
  
                                      input_format,
  
                                      &properties_collection);
  
      int i = 0;
  
      while (i++ < 30)
  
      {
  
          Sleep(1000);
  
          //avformat_flush(input_context); //DOESN'T HELP
  
          //av_free(input_context); //ERR
  
      }
  
      system("pause");
  
      return 0;
  
  }

  Right after "avformat_open_input()" it starts reading frames to some internal buffer without me even calling "av_read_frame()".
  After about 10 seconds it start’s giving me error messages :

  [dshow @ 0014ed40] real-time buffer [VirtualBox Webcam - FULL HD 1080P Webcam] [video input] 
  
  too full or near too full (62% of size: 3041280 [rtbufsize parameter])! 
  
  frame dropped!
  
  ...
  
  ...
  
  ...
  
  [dshow @ 0014ed40] real-time buffer [VirtualBox Webcam - FULL HD 1080P Webcam] [video input] 
  
  too full or near too full (100% of size: 3041280 [rtbufsize parameter])! 
  
  frame dropped!

  How to clear this buffer or avoid using it ?

  Thanks in advance.

  P.S.Please pardon my english.

  P.P.S.Have a good day.

• ffmpeg : two videos side-by-side with audio1 lang=ger & audio2 lang=eng

  19 janvier 2023, par miridigital

  I have two videos from two GoPro cameras. Both videos are rendered via ffmpeg side-by-side into a single video (left and right) and the audio is currently combined/mixed into two channels (stereo). I can hear both camera audio channels at the same time.

  


  Two channels stereo :

  


  ffmpeg -i video1.mp4 -i video2.mp4 -filter_complex "[0:v][1:v]hstack=inputs=2[v]; [0:a][1:a]amerge[a]" -map "[v]" -map "[a]" -ac 2 side-by-side.mp4


  


  audio from both videos mixed into a single file with 2 channels - mediainfo

  


  Now I want to switch between the two audio channels (cam1 or cam2) while I'm playing the side-by-side video.

  


  My first try : With four channels (without -ac 2 parameter) :

  


  ffmpeg -i video1.mp4 -i video2.mp4 -filter_complex "[0:v][1:v]hstack=inputs=2[v]; [0:a][1:a]amerge[a]" -map "[v]" -map "[a]" side-by-side.mp4


  


  audio from both videos mixed into a single file with 4 channels - mediainfo

  


  But the most video players can't easily select the channels 1+2 or 3+4 while playing.

  


  So I tried two languages :

  


  ffmpeg -i video1.mp4 -i video2.mp4 -filter_complex "[0:v][1:v]hstack=inputs=2[v]; [0:a][1:a]amerge[a]" -map "[v]" -map "[a]" -metadata:s:a:0 language=ger -metadata:s:a:1 language=eng side-by-side.mp4


  


  audio from both videos mixed into a single file with 4 channels with languages - mediainfo

  


  But that's wrong. I can only see german with 4 channels. How can I put channels 1+2 into german and channels 3+4 into english ? Afterwards I should be able to use the multi language feature from most video players to switch the audio between cameras.

  


  Thank you,
  
Miriam