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• I can't understand how to use ffmpeg in javascript (if it's even possible)

  27 février, par Laimonas Rupeika

  Straight to the problem, I want to use ffmpeg in my javascript project for video editing. So I found cdn : <code class="echappe-js">&lt;script src=&quot;https://cdn.jsdelivr.net/npm/@salomvary/ffmpeg.js-umd@3.1.9001/ffmpeg-mp4.min.js&quot;&gt;&lt;/script&gt; which references to "https://github.com/Kagami/ffmpeg.js", which is ffmpeg port to javascript as I understand ?
I don't get any errors on import, but if I try loading ffmpeg :

  


  // Initialize FFmpeg after the GAPI client is loaded
  const ffmpeg = createFFmpeg({ log: true });

  // // Load the FFmpeg library
  await ffmpeg.load();


  


  I get error : Uncaught (in promise) ReferenceError: createFFmpeg is not defined at initializeGapiClient (index:89:18) and it also messes my whole project. So if possible, how can I use ffmpeg in pure javascript, not Node.js. Should I download ffmpeg library files and then include them in project, I'm totally lost at this.

  


• Inconsistent behavior when placing adjacent video overlays

  24 juillet 2023, par abingham

  This script uses ffmpeg to overlay a red [1] and blue [2] stream atop a yellow [0] stream. The intent is that the red stream will be exactly adjacent to the blue stream ; at frame 1731 the output video should transition immediately from pure red to pure blue :

  


  # These values result in a blank frame where the videos join at around 58s
LENGTH=1800
SPLIT_AT=1731

# These values work just fine.
# LENGTH=1800
# SPLIT_AT=2

ffmpeg \
-f lavfi -r 30 -i "color=c=yellow:s=1920x1080" \
-f lavfi -r 30 -i "color=c=990000:s=1920x1080" \
-f lavfi -r 30 -i "color=c=000099:s=1920x1080" \
-filter_complex \
"[1]concat=n=1[red_concat];"\
"[red_concat]tpad=start=0[red_pad];"\
"[0][red_pad]overlay=enable=between(n\,0\,$SPLIT_AT):eof_action=repeat[red_overlay];"\
"[2]concat=n=1[blue_concat];"\
"[blue_concat]tpad=start=$SPLIT_AT[blue_pad];"\
"[red_overlay][blue_pad]overlay=enable=between(n\,$SPLIT_AT\,$LENGTH):eof_action=repeat[blue_overlay];"\
"[blue_overlay]trim=end_frame=$LENGTH[full];" \
 -map "[full]" video.mp4 -y


  


  However, what I see is that there is a single black frame between the pure red and pure blue. This black seems to be coming from the frames that tpad adds.

  


  What I don't understand is why I'm seeing that black frame. As far as I can tell, my uses of tpad and overlay/enable-between should produce a seamless transition from red to blue. And indeed, if I change the SPLIT_AT value to almost anything else I get exactly that ; the value 1731 is "special" in some way.

  


  Can anyone explain what's going on ? Maybe more importantly, can anyone reproduce this problem ?

  


  My first thought was that I've got some form of fencepost error in how I'm using tpad or enable-between. However, that doesn't explain why the script works for most values but not 1731. This difference in results feels like there's a rounding error somewhere, but since I'm dealing purely in terms of integer frame numbers, I don't see how I could be introducing them.

  


  A few notes :

  


  


  • This is a drastically reduced example from a larger video compositing system. Things like the use of concat may appear unnecessary, but they're representative of what the larger system is doing.

    


  


  • I'm using ffmpeg-6.0 installed via homebrew on an M1 macbook

    


  


  


• avformat/matroskaenc : Support rotations

  6 août 2023, par Andreas Rheinhardt

  avformat/matroskaenc : Support rotations
  Matroska supports orthogonal transformations (both pure rotations
  
  as well as reflections) via its 3D-projection elements, namely
  
  ProjectionPoseYaw (for a horizontal reflection) as well as
  
  ProjectionPoseRoll (for rotations). This commit adds support
  
  for this.
  Support for this in the demuxer has been added in
  
  937bb6bbc1e8654633737e69e403e95a37113058 and
  
  the sample used in the matroska-dovi-write-config8 FATE-test
  
  includes a displaymatrix indicating a rotation which is now
  
  properly written and read, thereby providing coverage for
  
  the relevant code in the muxer as well as the demuxer.
  Signed-off-by : Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
  

  • [DH] libavformat/matroskaenc.c
  • [DH] tests/ref/fate/matroska-dovi-write-config8