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• Interact with ffmpeg from a .NET program - Write Input

  7 mai 2015, par Shimmy

  In reference to this question, as you can see I managed to run and receive data from the program.

  However I didn’t manage to submit data to it, for instance, while converting a file, pressing q immediately stop conversion and stops the program.
  I need my application to support stopping the process as well, and I think this should be done by passing this parameter to the ffmpeg app, since I want it to take care of all uncollected resource or whatever dust it would leave behind if I would just go and use process.Kill()

  Here is what I’ve tried :

  static int lineCount = 0;
  
  static bool flag;
  
  static void process_ErrorDataReceived(object sender, DataReceivedEventArgs e)
  
  {
  
    Console.WriteLine("Error ({1:m:s:fff}: {0})", lineCount++,
  
        DateTime.Now);
  
  
  
    if (e.Data != null && string.Equals(e.Data,"Press [q] to stop, [?] for help")) 
  
      flag = true;
  
  
  
    if (flag)
  
    {
  
      flag = false;
  
      Console.WriteLine("Stopping ({0:m:s:fff})...", DateTime.Now);
  
      process.CancelErrorRead();
  
      process.CancelOutputRead();
  
      process.StandardInput.WriteLine("q");
  
    }   
  
  
  
    Console.WriteLine(e.Data);
  
    Console.WriteLine();
  
  }

  But it doesn’t do anything, seems that once the conversion has been requested, I have no control on it any more, I can only receive output from it. Running it as stand alone does allow me interaction of course.

  What am I missing here, is it a different trick in submitting the output or the code in previous answer is wrong, or I should have chosen a different approach ?

  For your attention, RedirectStandardInput is on.

  NOTE : as you can see in the answer of my previous question, ffmpeg interacts differently, I think the one who knows the answer will be (maybe I’m wrong) someone with experience in ffmpeg.

• Interact with ffmpeg from a .NET program ?

  18 septembre 2011, par Shimmy

  I'm trying to create a .NET wrapper for media-file conversion using ffmepg, here is what I've tried :

  static void Main(string[] args)
  
  {
  
    if (File.Exists("sample.mp3")) File.Delete("sample.mp3");
  
  
  
    string result;
  
  
  
    using (Process p = new Process())
  
    {
  
      p.StartInfo.FileName = "ffmpeg";
  
      p.StartInfo.Arguments = "-i sample.wma sample.mp3";
  
  
  
      p.StartInfo.UseShellExecute = false;
  
      p.StartInfo.RedirectStandardOutput = true;
  
  
  
      p.Start();
  
  
  
      //result is assigned with an empty string!
  
      result = p.StandardOutput.ReadToEnd();
  
  
  
      p.WaitForExit();
  
    }
  
  }

  What actually happens is the content of the ffmpeg program is printed out to the Console app, but the result variable is an empty string. I want to control the conversion progress interactively, so the user doesn't even have to know I'm using ffmpeg, but he still knows the conversion progress' details and what percentage etc. the app is up to.

  Basically I would also be happy with a .NET wrapper for a P/Invoke to conversion function ONLY (I am not interested in a whole external library, unless I can extract the PI function from it).

  Anyone with experience in ffmpeg & .NET ?

  Update
  Please view my further question, how to write input to a running ffmpeg process.

• iPhone ffmpeg dev using libav to decode from AMR to ACC codec

  10 octobre 2011, par VictorT

  It seems to be that, the AMR support of AudioQueue has been disappeared since iOS 4.3 was released. I can't use audio frame received from RSTP server with old way :

  audioFormat.mFormatID = kAudioFormatAMR; 
  
  int err = AudioQueueNewOutput(&audioFormat, MyAudioQueueOutputCallback, self, NULL, kCFRunLoopCommonModes, 0, &audioQueue);

  As a result I received an error in last string.

  Maybe someone know how to decode AMR AVPacket into raw buffer and encode it with AAC or MP3 using LIBAV ?

  I've tried to use

  avcodec_decode_audio3

  It works and I can get raw buffer but when I'm trying to encode it with

  avcodec_encode_audio

  I get 0 as result

  This is my method to encode buffer :

  - (AVPacket) encodeRawFrame:(const short *) in_buffer withSize:(unsigned int) in_buf_byte_size
  
  {
  
      AVPacket res;
  
      AVCodec *codec;
  
      AVCodecContext *c= NULL;
  
      int count, out_size, outbuf_size, frame_byte_size;
  
      uint8_t *outbuf;
  
  
  
      avcodec_init();
  
      avcodec_register_all();
  
  
  
      printf("Audio encoding\n");
  
  
  
      codec = avcodec_find_encoder(CODEC_ID_AAC);
  
      if (!codec) {
  
          fprintf(stderr, "codec not found\n");
  
          return res;
  
      }
  
  
  
      c= avcodec_alloc_context();
  
  
  
      c->bit_rate = 64000;
  
      c->sample_rate = 24000;
  
      c->channels = 2;
  
  
  
      if (avcodec_open(c, codec) < 0) 
  
      {
  
          fprintf(stderr, "could not open codec\n");
  
      }
  
      else
  
      {
  
          frame_byte_size=c->frame_size*2*2;
  
          count = in_buf_byte_size/frame_byte_size;
  
  
  
          fprintf(stderr, "Number of frames: %d\n", count);
  
  
  
          outbuf_size = AVCODEC_MAX_AUDIO_FRAME_SIZE;
  
          outbuf = (uint8_t*) malloc(outbuf_size);
  
  
  
          out_size = avcodec_encode_audio(c, outbuf, outbuf_size, &in_buffer[frame_byte_size*i]);
  
          if(out_size >= 0)
  
          {
  
              res.size = outbuf_size;
  
              res.data = malloc(outbuf_size);                
  
          }
  
  
  
          free(outbuf);
  
      }
  
  
  
  
  
      avcodec_close(c);
  
      av_free(c);
  
      return res;
  
  }

  After encoding "out_size" is always 0 and result buffer is empty.

  Thanks.