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• Real time compression/encoding using ffmpeg in objective c

  20 février 2014, par halfwaythru

  I have a small application written in Objective-c that looks for the video devices on the machine and allows the user to record video. I need to be able to compress this video stream in real time. I do not want to save the whole video, I want to compress it as much as possible and only write out the compressed version.

  I also don't want to use the AVFoundation's build in compression methods and need to use a third party library like ffmpeg.

  So far, I have been able to record the video and get individual frames using 'AVCaptureVideoDataOutputSampleBufferDelegate' in this method :

  - (void)captureOutput:(AVCaptureOutput *)captureOutput
  
     didOutputSampleBuffer:(CMSampleBufferRef)sampleBuffer
  
     fromConnection:(AVCaptureConnection *)connection

  So I have a stream of images basically, and I want to throw them into ffmpeg (which is all set up on my machine). Do I need to call a terminal command to do this ? And if I do, how do I use the image stack as my input to the ffmpeg command, instead of the video. Also, how do I combine all the little videos in the end ?

  Any help is appreciated. Thanks !

• avfoundation : Fix compilation for OSes other than macOS and iOS

  25 mars, par Martin Storsjö

  avfoundation : Fix compilation for OSes other than macOS and iOS
  E.g. tvOS doesn't have devicesWithMediaType.
  In principle, we could probably disable building the whole
  
  input device on such OSes, but that would either require
  
  testing explicitly for the OS type in configure (which we don't
  
  do anywhere so far), or test for individual objective C methods.
  This approach allows the code to compile, but no input devices
  
  will be found at runtime.
  Signed-off-by : Martin Storsjö <martin@martin.st>
  

  • [DH] libavdevice/avfoundation.m

• How to concatenate multiple videos with ffmpeg while preserving each file's duration [closed]

  24 janvier 2024, par GaoJin

  I have several video clips. Let's say 10 clips.
I want to concatenate them all to one video.
The duration of video clips varies and when I get property with ffprobe it says.
11.37s, 10.7s, 6.67s, 12s, 9s ...
But after I concatenated them all, the duration of result video is a little longer than the sum of individual videos.

  


  And what bothers me is the moment when one video transitions to the next.
Sometimes the transition moment comes about 1 sec than it must be at(The moment get by calculation)

  


  I converted all video clips to constant 30 fps and h264.

  


  ffmpeg -y -i "D:\\output\\temp_clip0.mp4" -i "D:\\output\\temp_clip1.mp4" -i "D:\\output\\temp_clip2.mp4" -i "D:\\output\\temp_clip3.mp4" -i "D:\\output\\temp_clip4.mp4" -i "D:\\output\\temp_clip5.mp4" -i "D:\\output\\temp_clip6.mp4" -i "D:\\output\\temp_clip7.mp4" -i "D:\\output\\temp_clip8.mp4" -i "D:\\output\\temp_clip9.mp4" -i "D:\\output\\temp_clip10.mp4" -i "D:\\output\\temp_clip11.mp4" -i "D:\\output\\temp_clip12.mp4" -i "D:\\output\\temp_clip13.mp4" -i "D:\\output\\temp_clip14.mp4" -i "D:\\output\\temp_clip15.mp4" -filter_complex [0:v][1:v][2:v][3:v][4:v][5:v][6:v][7:v][8:v][9:v][10:v][11:v][12:v][13:v][14:v][15:v]concat=n=16:v=1[outv] -map [outv] concated.mp4