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• avformat/mov : Add support for exporting Video Extension Usage info

  30 mai 2024, par Derek Buitenhuis

  avformat/mov : Add support for exporting Video Extension Usage info
  This box is provided by files created by the Apple Vision Pro, as well
  
  as the iPhone 15+ when capture for Vision Pro is enabled.
  The boxes are a mix of things documented by Apple in some PDFs, their
  
  API docs, and reverse engineering. Ideally we will have a real spec
  
  one day.
  Links :
  
    * https://developer.apple.com/av-foundation/Stereo-Video-ISOBMFF-Extensions.pdf
  
    * https://developer.apple.com/documentation/videotoolbox/kvtcompressionpropertykey_horizontaldisparityadjustment
  
    * https://developer.apple.com/documentation/videotoolbox/kvtcompressionpropertykey_stereocamerabaseline
  
    * https://developer.apple.com/documentation/videotoolbox/kvtcompressionpropertykey_heroeye
  Signed-off-by : Derek Buitenhuis <derek.buitenhuis@gmail.com>
  

  • [DH] libavformat/mov.c

• How can I fix choppy ffmpeg RTP streaming over wifi ?

  19 décembre 2015, par awidgery

  I have a Raspberry Pi, with a USB mic and a WiFi dongle dongle connected.

  I’m trying to stream audio only from the Pi, with the intention of receiving the stream over wifi to a custom iOS mobile app using VLCKit. I’m using ffmpeg on the Pi as I need a reasonably low (<2s) latency for this project, and using Icecast/Darkice gave around 15s latency.

  The code executed on the Pi is :

  ffmpeg -f alsa -i plughw:1,0 -acodec libmp3lame -ab 128k -ac 1 -ar 44100  -f rtp rtp://234.5.5.5:1234

  On the Pi end I have a device playing (Christmas !) music constantly into the USB mic for testing purposes. The Pi is only connected by WiFi - not ethernet.

  For testing receiving the stream, I’m using VLC (on a Macbook/iPhone).

  When the Mac is connected through Ethernet, the stream works fine, as you can see here :

  https://goo.gl/photos/HZgNh7z4HgaqHBaP7

  However, when the Mac is connected via WiFi, the stream is choppy, as you can see here :

  https://goo.gl/photos/qjAVH6djqS9Jbvmh6

  You can also see a ping trace from the Mac to the Pi, and the VLC stats. As you can see there doesn’t seem to be a correlation between either of these and the choppiness.

  I’ve tried the VLC iOS app and the choppiness is the same as the Mac on WiFi.

  How can I decrease/remove this chop, even if doing so increases latency a bit ?

• 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.