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• iFrameExtractor no ffmpeg with build_universal script

  15 août 2016, par AlecGamble

  I’m trying to follow this tutorial on how to extract the frames from an iphone video :

  http://www.codza.com/extracting-frames-from-movies-on-iphone#more-343

  It says to do the following :

  • open Terminal
  • clone the repository : git clone git://github.com/lajos/iFrameExtractor.git
  • go to the ffmpeg folder in the project : cd iFrameExtractor/ffmpeg
  • build the ffmpeg libraries : ./build_universal

  So there’s no ffmpeg folder in iFrameExtractor after cloning the repository so I went to the github page and it says to download the latest version of ffmpeg and move to to the ffmpeg folder (I presume it just means within iFrameExtractor) :

  • Download the latest ffmpeg (0.11.1 tested) :
    git clone git://source.ffmpeg.org/ffmpeg.git

  So I’ve done that but there’s no file or directory when I try to run ./build_universal and I can see that there isn’t.

  Any ideas what I’m doing wrong ?

  Alternatively I was also looking at just installing ffmpeg-ios and trying to extract the frames myself :

  https://github.com/kewlbear/FFmpeg-iOS-build-script

  and I’ve run the script so I’ve got that folder in my xcode project as well but I’m unsure on how to link it properly ?

• How to estimate bandwidth / speed requirements for real-time streaming video ?

  19 juin 2016, par Vivek Seth

  For a project I’m working on, I’m trying to stream video to an iPhone through its headphone jack. My estimated bitrate is about 200kbps (If i’m wrong about this, please ignore that).

  I’d like to squeeze as much performance out of this bitrate as possible and sound is not important for me, only video. My understanding is that to stream a a real-time video I will need to encode it with some codec on-the-fly and send compressed frames to the iPhone for it to decode and render. Based on my research, it seems that H.265 is one of the most space efficient codecs available so i’m considering using that.

  Assuming my basic understanding of live streaming is correct, how would I estimate the FPS I could achieve for a given resolution using the H.265 codec ?

  The best solution I can think of it to take a video file, encode it with H.265 and trim it to 1 minute of length to see how large the file is. The issue I see with this approach is that I think my calculations would include some overhead from the video container format (AVI, MKV, etc) and from the audio channels that I don’t care about.

• Tools to determine video orientation

  6 avril 2014, par JayLev

  I receive videos from different devices and want to encode them using the correct orientation.

  I've seen some of examples of how to determine the orientation of a video from a iPhone.

  With exiftool and mediainfo I can indeed tell if an iPhone video has to be rotated.

  However, for android videos, both portrait and landscape videos have the same rotation and matrix structure as each other.

  Maybe this is just with my phone, I'm trying to find videos taken from newer droid phones.

  My question however is whether there's other tools or a different way to determine the orientation that'll work with all devices.

  EDIT :
  I just checked a video from a Samsung Galaxy S II, and I can get the orientation from exiftool. So it's not a problem with all android phones.
  My android phone is a HTC Desire running on android 2.2.

  And actually (I didn't even notice before) a portrait video will not be correctly oriented even when playing on the phone. So I guess it's not about the tools, the orientation data just doesn't seem to be correct at all.