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• Time running out for proposals for the Open Video Conference

  1er juin 2010, par Basil Gohar — Announcements, conference, open video conference

  We’re a little late on this one, but better late than never ! Time is running out for proposal submissions to the 2010 Open Video Conference. The submission deadline is June 7th, 2010. So, whether you’re a Theora developer, working on … Read more (...)

• Does a packet taken from FFMPEG have absolue time information ?

  12 août 2012, par prosopher

  I'm creating a video player which works with an incomplete video file in which it has some empty(incomplete) sections filled with zeros.

  For example, there's a video file which has section A, B, and C in sequence. A and C are complete and B is incomplete. And A section starts from file offset 0 and includes header information as well.

  Now, I want to know a starting time of section C.

  So I read packets from section A to section C entirely by using FFMPEG and it skipped section B which was what I wanted. But when I took presentation timestamp values from each packet while reading, I found it continuously increasing.

  The problem is I want timestamps from section C to be increased by the amount of section B.

  Even though section B is ignored, I want to know the actual time when I'm supposed to present section C.

  I guess FFMPEG doesn't include absolute time information but calculates time to present a packet based on the last packet's time information which is relative. However, I assume there must be a way to find the absolute time information.

• when audioqueue play lpcm decoded from ffmpeg, the elapsed time of audio queue exceeds the duraion of the media

  15 août 2012, par zhzhy

  When play the lpcm data decoded from ffmpeg with audioqueue, the elapsed time got by AudioQueueGetCurrentTime exceeds the duration of media. But when decode the same media with AVFoundation framework, the elapsed time equals duration of the media, and so when read media by ffmpeg with no decoded, then send the compressed media data to audioqueue, the elapsed time also equals duration of the media. The AudioStreamBasicDescription set as following :

      asbd.mSampleRate = 44100;
  
      asbd.mFormatID = kAudioFormatLinearPCM;
  
      asbd.mFormatFlags = kAudioFormatFlagsCanonical;
  
      asbd.mBytesPerPacket = 4;
  
      asbd.mFramesPerPacket = 1;
  
      asbd.mBytesPerFrame = 4;
  
      asbd.mChannelsPerFrame = 2;
  
      asbd.mBitsPerChannel = 16;
  
      asbd.mReserved = 0;

  When playing with data decoded from AVFoundation, the setting of AudioStreamBasicDescription is the same as above. By my test found that AudioTimeStamp.mSampleTime got by AudioQueueGetCurrentTime is different between ffmpeg and AVFoundation, the value of ffmpeg is greater than AVFoundation. So I want to know how this happen, and how to fix it ?
  Thanks !