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• Pass double pointer parameter through P/Invoke when it is NULL

  1er août 2015, par BartMao

  I try to call FFMPEG method via P/Invoke

   int avformat_find_stream_info(AVFormatContext *ic, AVDictionary **options);

  So my P/Invoke method defined like this :

  [DllImport("avformat-55", EntryPoint = "avformat_find_stream_info", CallingConvention = CallingConvention.Cdecl)]
  
      public extern static int AVFormatFindStreamInfo(IntPtr ic, ref IntPtr options);

  and I need pass an IntPtr.Zero for the options, so I call this way :

  var p = IntPtr.Zero;
  
  rst = AVFormatFindStreamInfo(context, ref p);

  and an AccessViolation exception throws.

  But when I remove the ref from the signature, and directly pass an IntPtr.Zero to it, it actually works.
  I think the signature with ref keyword is the right way, but I don’t know why the exception throws.

• How to pass command line arguments to FFMpeg in iOS

  23 septembre 2014, par Arif Nadeem

  This is a beginner question, since I am new to iOS(I started it today), so please pardon my ignorance and lack of iOS knowledge.

  After building and successfully using FFMpeg for Android I wanted to do the same for iOS.
  So I built FFMpeg successfully for iOS by following this link, but after all that pain I am confused as how to use FFMpeg in iOS, I mean how can I pass command line arguments to libffmpeg.a file ?

  I am assuming that there must be a way to run the .a file as an executable and then pass command line arguments and hope for FFMpeg to do the magic, I did the same in Android and it worked beautifully.

  I am also aware that I can use ffmpeg.c class and use its main method, but the question remains ; how do I pass those command line arguments ?

  Is there something I am supposed to be aware of here, is the thing what I am doing now correct or am I falling short on my approach ?

  I wanted to mix two audio files, so the command for doing that would be ffmpeg -i firstSound.wav -i secondSound.wav -filter_complex amix=inputs=2:duration=longest finalOutput.wav, how do I do the same in iOS ?

  Can someone please shed some light on this ?

• Two-pass (or multipass) encoding with FFmpeg libraries

  13 mars 2014, par taansari

  I want to do two pass encoding using FFmpeg libraries. Sample codes provided as documentation show encoding/decoding, muxing/demuxing etc., but the encoding process is single pass. I want to do/experiment with two-pass encoding. Is there some example/sample provided elsewhere ?

  Thanks in advance !