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• Given 2 input videos of different lengths at 60 FPS with multiple common sections in between, what is the best way to sync them at the common section ?

  27 janvier 2024, par PirateApp

  
input vs output

  


  

  • In my actual case, there are 4 videos (basically gaming videos recorded from 4 different machines)

  


  • Each video may start or end at different duration (manually controlled by people starting and stopping recording and therefore their lengths vary slightly)

  


  • Each video has one or more common sections (basically a cutscene playing at the same time)

  


  • The distance between the common sections is the same in every video

  


  • How do I sync the videos at the common section ?

  


  • Basically I want to create a split screen video such that the common part plays at the same time on all the sub parts of the video

  


  • Keep in mind that the common sections wont be EXACTLY equal (because of graphics differences between machines but highly similar like dx9 vs dx11 or gamma)
What have I tried ?

  


  • Naive approach

  


  • Start video 1 at 0, start video 2 at 0.017, render the whole thing and check if it is in sync

  


  • Start video 1 at 0, start video 2 at 0.033, render the whole thing and check if it is in sync

  


  • Basically loop through the length of the video at each frame interval, render the full video and check if we get a synced version

  


  


  This sounds like a terrible idea honestly

  


    for (t1 in length of video a) {
    for (t2 in length of video b) {
       render a video with a and b starting at t1, t2 respectively
       increment t2 by 0.017 for b
    }
    increment t1 by 0.017 for a
  }


  


  Final output with 4 videos should look like this all synced at common sections


  


  Any better ideas ?

  


• Mac terminal command to list files and sort by date to use in ffmpeg

  22 septembre 2020, par Jeff

  I am using a gopro to film a bunch of videos. I want to then take those videos directly from the SD card folder and concatenate them into a single video (bypass an editor) by using FFMPEG.

  


  I'm currently able to stitch together "chaptered" videos with the following example command on my Mac (10.13) :

  


  ffmpeg -f concat -safe 0 -i <(for f in /sdcardfolder/100GOPRO/GH*488.MP4; do echo "file '$f'"; done) -c copy /folder/video.mp4

  


  The reason for this is that the ffmpeg command requires a text file that looks like this :

  


  


  file '/folder/GH016992.MP4'

  
file '/folder/GH036990.MP4'

  
...

  


  


  The real command is this, which generates the list of files in the right format with file in front of each one and can be embedded into the ffmpeg command :

  


  for f in /Volumes/GoPro8/DCIM/100GOPRO/GH0*71*.MP4; do echo "file '$f'"; done

  


  I want to add 2 changes to this :

  


  


  1. List the files in date order (ascending) : I want the list of files to be in date order. But I can't figure out how to add a -sort or something to the for f in command.

     


  


  2. Allow a more robust set of file matching/filtering : Right now I can add basic regex like GH*488.MP4 or, with chapters which increments the first number, something like GH0[123]488.MP4 would work to just get the first few. But when I change it to be more flexible like GH0[0-9]71[0-9][0-9].MP4 - which would be necessary to match all files that were recorded yesterday, but nothing before then, the command doesn't like this regex. It seems to only accept a *.

     


  


  


  I looked at a few examples like https://opensource.com/article/19/6/how-write-loop-bash but there wasn't much more than just listing files.

  


  This boils down to a terminal command and isn't really related to FFMPEG but I hope it's helpful context.

  


  I imagined it would be something like this, but this definitely doesn't work :

  


  for f in (find /Volumes/GoPro8/DCIM/100GOPRO/GH0[0-9]71[0-9][0-9].MP4 -type f | sort); do echo "file '$f'"; done

  


  I'd appreciate any help ! Thanks !

  


  Update

  


  It looks like sorting isn't easy with Mac tools so I gave up and wrote a much simpler Ruby script that could execute everything for me. This is not really an answer to my question above but it is a solution.

  


  Here I can easily write the text file necessary for ffmpeg and I can also filter files with a regex on the name, filter for a particular date, and size. Then, via the script, simply execute the ffmpeg command with args to concat files. I can also have it immediately resample the file to compress it (gopro videos are giant and I'm ok with a much lower bitrate if I want to save raw footage).

  


  I got lucky with this Dir.entries in Ruby - it seems to automatically sort by date ? I don't know how to sort it otherwise.

  


  PATH = '/Volumes/GoPro8/DCIM/100GOPRO/'
NEW_FILENAME = '/folder/new-file.mp4'
video_list = '/folder/ffmpeg-list.txt'

# create the text file
File.delete(video_list) if File.exist?(video_list)
i = 1
Dir.entries(PATH).each do |f|
    d = File.mtime(PATH + f)
    size = File.size(PATH + f)
    if f.match(/GH0.*.MP4/) && d.to_s.match(/2020-07-30/) && size.to_i < 1000000000
        puts "#{i}\t#{f}\t#{d}\t#{size}"
        File.write(video_list, "file #{PATH + f}\n", mode: "a")
        i= i+1
    end
end

command = "ffmpeg -f concat -safe 0 -i #{video_list} -c copy #{NEW_FILENAME}"

puts "executing concatenate..."
puts command
system(command)


  


• mac terminal ffmpeg batch recursive conversion preserving directory structure

  13 avril 2020, par kidnim

  i'm using ffmpeg on mac to batch convert .flv to .mp4 files. i'm trying to find all files in subdirectories of the current directory and save new files in the same directory.

  



  for instance starting with :

  



  subdirectory1/video1.flv
subdirectory1/video2.flv
subdirectory2/video1.flv


  



  and ending with

  



  subdirectory1/video1.mp4
subdirectory1/video2.mp4
subdirectory2/video1.mp4


  



  i've gotten this far but can't figure out how to save with preserved recursive directories

  



  for i in  `find -name . "*.flv"`; do ffmpeg -i "$i" "${i%.*}.mp4"; done