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• FFMPEG : Encoding WEBM with fast-seek and copyts leads to wrong video lenght

  1er février 2020, par TheOverlord2D

  I’m trying to convert a scene from a soft-subbed MKV file into a hard-subbed WEBM file with two-pass. The video encodes fine, but the file shows the wrong length when opened on a media player (it’s showing as if I had encoded the original file from the starting point all the way to the end).

  This is the command I’m using :

  set timestamp=-ss 12:59.069 -to 16:14.277
  
  
  
  ffmpeg -y %timestamp% -copyts -i source.mkv -shortest -c:v libvpx-vp9 -pass 1 -b:v 0 -crf 33 -threads 8 -speed 4 -tile-columns 6 -frame-parallel 1 -an -sn -vf scale=-1:720,subtitles=source.mkv -f webm NUL
  
  ffmpeg -y %timestamp% -copyts -i source.mkv -shortest -c:v libvpx-vp9 -pass 2 -b:v 0 -crf 33 -threads 8 -speed 2 -tile-columns 6 -frame-parallel 1 -auto-alt-ref 1 -lag-in-frames 25 -c:a libopus -b:a 64k -sn -vf scale=-1:720,subtitles=source.mkv -f webm out.webm

  When opening the video in MPC-BE, the video plays regularly until around the point shown on https://i.stack.imgur.com/6bRwc.png (which is where the scene I wanted to cut out ends) then it just skips to the end of the file, and this wrong length is giving me all sorts of issues when I try to use the encoded video.

• Jerky Video from Jpgs encoded with ffmpeg [closed]

  16 février 2012, par Glstunna

  I have a bunch of jpg snapshots taken from a 3d program at perfect time frames.
  But when I have the videos compiled/encoded into a video by ffmpeg, I notice an annoying jerkiness. The jerkiness is not that pronounced, but enough to be annoying, especially during slow camera pans.

  This is what I use :

  "ffmpeg-lgpl.exe" -y  -r 29.97 -i "C:\vidsnaps\vid_%d.jpg" -b 8000k "C:\Users\peki.ICE\Documents\macbattle.mpg" 

  I chose mpg (mpeg1video) because that is the format readily available in all end-user systems like XP without downloading extra codecs. The video images are guaranteed to match that framerate 29.97 as the camera in the 3d program pretty much waits for each frame to be dumped to file before moving to the next one.

  What other fancy ffmpeg flags do I have to set for this thing to stop being jerky.

  EDIT : see video example here and notice the light jerk/stuttering.
  http://www.youtube.com/watch?v=g-slsJBZA2w&feature=youtu.be

• yt-dlp how to download a specific video using timestamps, and limiting the download resolution ?

  30 septembre 2023, par ignacM

  I am running a python program to download a video, this is the command I use :

  


  command = ['powershell.exe ffmpeg',
                   '-ss', str(start),
                   '-i', '$(yt-dlp',
                   '-f', 'bestvideo[ext=webm]',

                   '-g', '"%s")' % (url_base + video_identifier),
                   '-t', str(end - start),
                   '-c:v', 'libx264', '-c:a', 'copy', '%s' % output_filename]

command = ' '.join(command)
output = subprocess.check_output(command, shell=True, stderr=subprocess.STDOUT)


  


  This prints something like
powershell.exe ffmpeg -ss 10 -i $(yt-dlp -f bestvideo[ext=webm] -g "https://www.youtube.com/watch?v=Z15erfLqNKo") -t 10 -c:v libx264 -c:a copy C :\Users...\video.mp4

  


  This works perfectly fine. However, I tried to download a video that had very high resolution (4K) and I want to limit the resolution when downloading. I have found that placing [height<=1080] as so should work :

  &#xA;

  powershell.exe ffmpeg -ss 10 -i $(yt-dlp -f bestvideo[ext=webm][height<=1080] -g "https://www.youtube.com/watch?v=Z15erfLqNKo") -t 10 -c:v libx264 -c:a copy C :\Users...\video.mp4

  &#xA;

  However this does not work for me and gives me the error :&#xA;Error command "" returned non-zero exit status 1.&#xA;Output : b'The system cannot find the file specified.\r\n'

  &#xA;

  I also have noticed that only limiting the resolution does not work for me either :

  &#xA;

  powershell.exe ffmpeg -ss 10 -i $(yt-dlp -f bestvideo[height<=1080] -g "https://www.youtube.com/watch?v=Z15erfLqNKo") -t 10 -c:v libx264 -c:a copy C :\Users...\video.mp4

  &#xA;

  Actually, placing [height<=1080] after bestvideo never works, no matter what I do.

  &#xA;

  What could be the problem ? Or what command can I run to achieve both tasks (limit resolution and download specific timeframe (not whole video and cutting it)) ?

  &#xA;