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• How to find the offset by which the each video must be delayed to sync them perfectly ?

  19 janvier 2023, par PirateApp

  

  


  Let me explain my use case a bit here

  


  


  • We are 4 of us playing the same game

    


  


  • 3 of us recording mkv using OBS studio at 60 fps, 4th guy recording with some other tool at 30 fps

    


  


  • Each mission starts at a cutscene and ends with a cutscene

    


  


  • I would like to create a video like the image you see above starting at ending at the same points but the intermediate stuff is basically what each player is doing in the game

    


  


  • Currently, I follow a process slightly complicated to achieve this and was wondering if there is an easier way to do this

    


  


  • My current process

    


  


  • Take a screenshot from one of the videos of the cutscene

    


  


  


  Run a search for this screen inside the other videos using the command below

  


  ffmpeg 
  -i "video1.mkv"
  -r 1
  -loop 1
  -i 1.png
  -an -filter_complex "blend=difference:shortest=1,blackframe=90:32"
  -f null -


  


  


  • It gives me a result like this in each video

    


    [Parsed_blackframe_1 @ 0x600000c9c000] frame:263438 pblack:91 pts:4390633 t:4390.633000 type:P last_keyframe:263400

    


  


  


  Use the start time from each of the results to create a split screen video using the command below

  


  ffmpeg 
  -i first.mkv
  -i second.mkv
  -i third.mkv
  -i fourth.mp4
  -filter_complex " 
    nullsrc=size=640x360 [base];
    [0:v] trim=start=35.567,setpts=PTS-STARTPTS, scale=320x180 [upperleft]; 
    [1:v] trim=start=21.567,setpts=PTS-STARTPTS, scale=320x180 [upperright];
    [2:v] trim=start=41.233,setpts=PTS-STARTPTS, scale=320x180 [lowerleft]; 
    [3:v] trim=start=142.933333,setpts=PTS-STARTPTS, scale=320x180 [lowerright];
    [0:a] atrim=start=35.567,asetpts=PTS-STARTPTS [outa]; [base][upperleft] overlay=shortest=1 [tmp1];


  


  


  • As you can see, it is a complex process and depends completely a lot on what image I am capturing. Sometimes, I find out that stuff is still slightly off in the beginning or end because the images dont match a 100%. My guess is that the frame rate is different for each video not to mention 3 of them are mkv inputs and one is an mp4 input

    


  


  • Is there a better way to get the offset by how much each video should be moved to sync them perfectly ?

    


  


  • The only way that I can think of is to take 1 video

    


  


  • Take a starting timestamp and an ending timestamp, say with a total duration of 30s

    


  


  • Take the second video

    


  


  • Start from 0 to 30s and compare the frames in both videos, set a score

    


  


  • start from 0.001 to 30.001 and compare the frames, set a score

    


  


  • start from 0.002 to 30.002 and compare the frames, set a score

    


  


  • Basically increment the second video by 0.001 second each time and find out the part with the highest score

    


  


  • Any better way of doing this ? I need to run this on 100s if not 1000s of videos

    


  


  


• How do I sync 4 videos in a grid to play the same frame at the same time ?

  28 décembre 2022, par PirateApp
  

  • 4 of us have recorded ourselves playing a game and want to create a 4 x 4 video grid

  


  • The game has cutscenes at the beginning followed by each person having their unique part for the rest of the video

  


  • I am looking to synchronize the grid such that it starts at the same place in the cutscene for everyone

  


  • Kindly take a look at what is happening currently. The cutscene is off by a few seconds for everyone

  


  • Imagine a time offset a,b,c,d such that when I add this offet to each video, the entire video grid will be in sync

  


  • How to find this a,b,c,d and more importantly how to add it in filter_complex

  


  


  I used the ffmpeg command below to generate a 4 x 4 video grid and it seems to work

  


  ffmpeg
    -i nano_prologue.mkv -i macko_nimble_guardian.mkv -i nano_nimble_guardian.mkv -i ghost_nimble_guardian_subtle_arrow_1.mp4
    -filter_complex "
        nullsrc=size=1920x1080 [base];
        [0:v] setpts=PTS-STARTPTS, scale=960x540 [upperleft];
        [1:v] setpts=PTS-STARTPTS, scale=960x540 [upperright];
        [2:v] setpts=PTS-STARTPTS, scale=960x540 [lowerleft];
        [3:v] setpts=PTS-STARTPTS, scale=960x540 [lowerright];
        [base][upperleft] overlay=shortest=1 [tmp1];
        [tmp1][upperright] overlay=shortest=1:x=960 [tmp2];
        [tmp2][lowerleft] overlay=shortest=1:y=540 [tmp3];
        [tmp3][lowerright] overlay=shortest=1:x=960:y=540
    "
    -c:v libx264 output.mkv


  


  My problem though is that since each of us starts recording at slightly different times, the cutscenes are out of sync

  


  As per the screenshot below, you can see that each video has the same scene starting at a slightly different time.

  


  Is there a way to find where the same frame will start on all videos and then sync each video to start from that frame or 20 seconds before that frame ?

  


  

  


  UPDATE 1

  


  i have figured out the offset for each video in millisecond precision using the following technique

  


  take a screenshot of the first video at a particular point in the cutscene and save image as png and run the script below for the remaining 3 videos to find out where this screenshot appears in each video


ffmpeg -i "video2.mp4" -r 1 -loop 1 -i screenshot.png -an -filter_complex "blend=difference:shortest=1,blackframe=90:32" -f null -


  


  Use the command above to search for the offset in every video for that cutscene

  


  It gave me this

  


  VIDEO 3 OFFSET

  


  [Parsed_blackframe_1 @ 0x600003af00b0] frame:3144 pblack:92 pts:804861 t:52.399805 type:P last_keyframe:3120

[Parsed_blackframe_1 @ 0x600003af00b0] frame:3145 pblack:96 pts:805117 t:52.416471 type:P last_keyframe:3120


  


  VIDEO 2 OFFSET

  


  [Parsed_blackframe_1 @ 0x6000014dc0b0] frame:3629 pblack:91 pts:60483 t:60.483000 type:P last_keyframe:3500


  


  VIDEO 4 OFFSET

  


  [Parsed_blackframe_1 @ 0x600002f84160] frame:2885 pblack:93 pts:48083 t:48.083000 type:P last_keyframe:2880

[Parsed_blackframe_1 @ 0x600002f84160] frame:2886 pblack:96 pts:48100 t:48.100000 type:P last_keyframe:2880


  


  Now how do I use filter_complex to say start each video at either the frame above or the timestamp above ?. I would like to include say 10 seconds before the above frame in each video so that it starts from the beginning

  


  UPDATE 2

  


  This command currently gives me a 100% synced video, how do I make it start 15 seconds before the specified frame numbers and how to make it use the audio track from video 2 instead ?

  


  ffmpeg
    -i v_nimble_guardian.mkv -i macko_nimble_guardian.mkv -i ghost_nimble_guardian_subtle_arrow_1.mp4 -i nano_nimble_guardian.mkv
    -filter_complex "
        nullsrc=size=1920x1080 [base];
        [0:v] trim=start_pts=49117,setpts=PTS-STARTPTS, scale=960x540 [upperleft];
        [1:v] trim=start_pts=50483,setpts=PTS-STARTPTS, scale=960x540 [upperright];
        [2:v] trim=start_pts=795117,setpts=PTS-STARTPTS, scale=960x540 [lowerleft];
        [3:v] trim=start_pts=38100,setpts=PTS-STARTPTS, scale=960x540 [lowerright];
        [base][upperleft] overlay=shortest=1 [tmp1];
        [tmp1][upperright] overlay=shortest=1:x=960 [tmp2];
        [tmp2][lowerleft] overlay=shortest=1:y=540 [tmp3];
        [tmp3][lowerright] overlay=shortest=1:x=960:y=540
    "
    -c:v libx264 output.mkv


  


• ffmpeg with cuda and concat videos [closed]

  15 septembre 2024, par Petr Šimůnek

  I have a ffmpeg command with nvidia hw support that I want to join two videos :

  


  /home/videotest/ffmpeg-dev/ffmpeg -benchmark -hide_banner -loglevel warning -y -hwaccel_device 0 -hwaccel cuda -hwaccel_output_format cuda -i /mnt/video-storage/test/cuda/surfing/intermediate1.mp4 -i /mnt/video-storage/test/cuda/surfing/intermediate2. mp4 -filter_complex 'hwupload_cuda,[0:v:0][0:a:0][1:v:0][1:a:0]concat=n=2:v=1:a=1 [outv] [outa]' -map [outv] -map [outa] -pix_fmt yuv420p -c:v h264_nvenc -preset p6 -profile: v high -force_key_frames 'expr:gte(t,n_forced*5)' -bf 0 -movflags +faststart -b:v 3000k -maxrate 4000k /mnt/video-storage/test/cuda/surfing/game.mp4

  


  I get an error message after starting :

  


  Impossible to convert between the formats supported by the filter 'graph 0 input from stream 0:0' and the filter 'auto_scale_0' [fc#0 @ 0x61ae2b37a1c0] Error reinitializing filters!

  


  I can't figure out how to remove it. Can you help me ? Thank you.

  


  If I use nvdec/nvenc instead of cuda, this error does not appear and the video is created fine.