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• Getting accurate time from FFMPeg with Objective C (Audio Queue Services)

  2 avril 2012, par Winston

  My iPhone app plays an audio file using FFMPeg.

  I'm getting the elapsed time (to show to user) from the playing audio (in minutes and seconds after converting from microseconds, given by FFMPeg) like so :

  AudioTimeStamp currentTimeStamp;
  
  AudioQueueGetCurrentTime (audioQueue, NULL, &currentTimeStamp, NULL);
  
  
  
  getFFMPEGtime = currentTimeStamp.mSampleTime/self.basicAudioDescription.mSampleRate;
  
  
  
  self.currentAudioTime = [NSString stringWithFormat: @"%02d:%02d",
  
                              (int) getFFMPEGtime / (int)60000000,
  
                              (int) ((getFFMPEGtime % 60000000)/1000000)];

  Everything works fine, but when I scrub back or forward to play another portion of the song, the elapsed time will go back to zero, no matter the current position. The timer will always zero out.

  I know I'm suposed to do some math to keep track of the old time and the new time, maybe constructing another clock or so, perhaps implementing another callback function, etc... I'm not sure what way I should go.

  My questions are :

  1) What's the best approach to keep track of the elapsed time when going back/forward in a song, avoiding the clock to always going back to zero ?

  2) Should I look deeply into FFMPeg functions or should I stick with Objective-C and Cocoa Touch for solving this problem ?

  Please, I need some advices/ideas from experienced programmers. I'm stuck. Thanks beforehand !

• iOS Libavcodec - Trim and convert a video

  14 juillet 2015, par AnujAroshA

  In my iOS project, I am trying to take an .mp4 video file, cut out a small clip in the middle of the file, and convert the output to .mov file. I am using libavcodec to do this.

  I built the FFmpeg libraries for iOS using this script and added to my project.

  The code I am using to trim and convert the video file is this.

  The issues with final output of the file are :

  1. When I copy the output from the iPhone to my mac, the video meta data for duration and video dimensions are blank. If I do the same for the original, I get the video length and dimensions correctly. I must not be creating the video meta data on the new video correctly.

  2. The frame rate on the outputted video appears to be wrong. I expect to see e.g. 250 frames over 10 seconds (25fps), but instead I see 250 frames over 4 seconds, then only the last frame for the remaining 6 seconds.

  3. The code should seek to 100s in the video before starting trimming. Instead, the code appears to crop the video starting at the beginning.

• how to encode mp4 from movie content for wowza streaming ?

  15 juillet 2014, par lng0415

  i want to encode to mp4(h.264 codec) from avi,mpg..... for wowza streaming.

  encode mp4 using ffmpeg, jave.

  encode is success, but wowza streaming is not work on android and iphone OS.
  (it’s play successfully on my PC)

  please help me.

  thank you.

  ps. i’m sorry. i’m poor at english.

  [using jave]

  File source = new File("D://temp/20140704_163504.mp4");
  
  File target = new File("D://temp/jave.mp4");
  
  
  
  AudioAttributes audio = new AudioAttributes();
  
  audio.setCodec("libmp3lame");
  
  audio.setBitRate(new Integer(64000));
  
  audio.setChannels(new Integer(1));
  
  audio.setSamplingRate(new Integer(22050));
  
  
  
  VideoAttributes video = new VideoAttributes();
  
  video.setCodec("h263");
  
  video.setBitRate(new Integer(320000));
  
  video.setFrameRate(new Integer(15));
  
  video.setSize(new VideoSize(400, 300));
  
  
  
  EncodingAttributes attrs = new EncodingAttributes();
  
  attrs.setFormat("mp4");
  
  attrs.setAudioAttributes(audio);
  
  attrs.setVideoAttributes(video);
  
  Encoder encoder = new Encoder();
  
  encoder.encode(source, target, attrs);