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• Is there a way to cut first 1 second of video from .webm without keyframe present using Ffmpeg ?

  14 avril 2020, par Patrick_42

  Recently I had a task to process several thousand videos, both .mp4 and .webm. The goal was to cut 1 second off from the front of the video. As a constraint, I wanted to avoid re-encoding the videos, as the number of jobs would take far too much time. The .mp4 files went smoothly, each job taking only a few seconds.

  



  However, when trying to accomplish the same thing for the .webm files, I've hit a block. This is command I am running :

  



  ffmpeg -i downloaded_raw_vids/{{vid_hash}}.webm -ss 00:00:01 -map 0 -c copy trimmed_videos/{video_url}.webm


  



  What seems to happen is that no cut or edit happens whatsoever on the .webm files. Now if I change the timestamp to something like

  



  ffmpeg -i downloaded_raw_vids/{{vid_hash}}.webm -ss 00:00:15 -map 0 -c copy trimmed_videos/{video_url}.webm


  



  I end up with a file that has roughly the first 10 seconds cut out, but not the 15 seconds specified.

  



  My understanding is that .webm files can only be cut on keyframes, and the keyframes are too sparse to actually cut around the 1 second mark as desired originally. It does seem like the first keyframe is present around the 10 second mark, which is why the 15 second argument cuts at that point.

  



  Ultimately I am wondering if there is a way to accomplish the 1 second cut, without having to re-encode every .webm file I am working with.

  


• Filter useless white frames at the beginning and duplicated frames at the end of captured video

  21 septembre 2020, par gumkins

  I'm capturing HTML animation with use of Puppeteer and MediaRecorder API.

  


  Before starting the capturing I'm waiting for networkidle event (I tried networkidle0-2 but result is identical)

  


  await page.goto(url, { waitUntil: 'networkidle0' })


  


  For some reason, the animation starts to play 2-3 seconds after the capturing starts, and thus, white frames are captures.
Similar, at the end of the video there are identical frames because capturing duration is a bit longer than animation plays.

  


  Thus I want to detect and cut off those repeating white frames at the beginning and repeating non-white frames at the end of the video (mp4/webm).

  


  I tried some solutions, like described here, for instance

  


  ffmpeg -i input.mp4 -vf mpdecimate,setpts=N/FRAME_RATE/TB out.mp4


  


  It does remove duplicates, but the problem is that it cuts off dups in the middle as well.

  


  Thus, if I have a 15 sec animation,it removes all dups at the beginning, all dups at the end and all dups in the middle, and what is left after it is just a several identical frames which are pack into less than 1 sec video.

  


• aarch64 : Detect I8MM on Windows via SVE-I8MM

  17 septembre 2024, par Martin Storsjö

  aarch64 : Detect I8MM on Windows via SVE-I8MM
  There's no direct processor feature constant for I8MM alone, but
  
  there is a flag for SVE-I8MM (added in WinSDK 10.0.26100 and
  
  recent versions of mingw-w64). If SVE-I8MM is available, we can
  
  assume that I8MM is available.
  While HW supporting these features isn't yet commonly running
  
  Windows, this at least allows detecting and running the I8MM codepaths
  
  in Windows builds in Wine (possibly running in QEMU).
  Signed-off-by : Martin Storsjö <martin@martin.st>
  

  • [DH] libavutil/aarch64/cpu.c