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• 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


  


• Rails 5 with Carrierwave and S3 - creating multiple video formats for DASH streaming works but mpd file breaks

  22 novembre 2019, par Milind

  what I am doing -
  i have a Rails 5 app for video streaming(DASH MPEG) that uses FFMPEG to get encoded stream videos by converting any single video into multiple videos of multiple bit rates/size and primarily also MPD FILE that can be played easily on html video player, which i have already tested by manually running the ffmpeg scripts on the console that generates all the files.However, I want to automate this process and hence carrierwave comes into the pictures.
  Here, i use carrierwave to generate different versions(size/bitrate) of videos(mp4/webm) to upload to s3 but during running the version, where all the versions are successfully created in tmp folder, only the last version(mpd) that needs to create .mpd file, carrierwave creates a mp4 video file and just replaces the extension instead of actually creating the mpd file.

  So in the aws s3(screenshot added below), i can see my all versions and mpd file , but that mpd file which must be xml file is actually a mp4 video file or uploaded version file itself.
  I have also tried to create new file during the process, but it never works.
  Has some one encountered this problem ?

  any help will be greatly appreciated ?

  Ny code snippets below - model,uploader,output of script on the console during upload, s3 screenshot

     ##### models/video.rb ##########
  
  
  
      mount_uploader :video, VideoUploader  
  
  
  
     ####### uploaders/video_uploader.rb #########
  
  
  
      class VideoUploader < CarrierWave::Uploader::Base
  
  
  
  
  
      include CarrierWave::MiniMagick
  
      include CarrierWave::Video
  
      include CarrierWave::Video::Thumbnailer
  
      include ::CarrierWave::Backgrounder::Delay
  
  
  
      ####### for streaming ..first get the audio and then convert the input video into multiple bitrates/scale #######
  
  
  
      ###first get audio and then get all different versions of same video
  
      version :video_audio do
  
        process :get_audio
  
  
  
        def get_audio
  
          `ffmpeg -y -i "#{file.path}" -c:a aac -ac 2 -ab 128k -vn video_audio.mp4`
  
        end
  
  
  
          def full_filename(for_file)
  
            "video_audio.mp4"
  
          end
  
  
  
          def filename
  
            "video_audio.mp4"
  
          end        
  
      end 
  
  
  
      ####### similar to the above i have various version like ...#########
  
  
  
      version :video_1080 do...end
  
      version :video_720 do... end
  
      version :video_480 do ...end
  
      ...and so on..and all these versions are successfully created and uploaded to s3, however..in next version ...show it also creates a video file whereas i need a simple mpd file ONLY.
  
  
  
           ###this is where even after everything works, in S3, i can see a video file of version mpd and not actual mpd file
  
           version :mpd  do
  
             process :get_manifest
  
                ###here in the command below, the video.mpd file is successfully obtained but its uploaded as video.mpd file of added/uploaded video file and not a new mpd file
  
                ###tried with ffmpeg -f webm_dash_manifest -i too, but s3 still shows a mp4 file
  
                `MP4Box -dash 1000 -rap -frag-rap -profile onDemand -out video.mpd video_1080.mp4 video_720.mp4 video_480.mp4 video_360.mp4 video_240.mp4 video_audio.mp4 `
  
  
  
             end
  
            end
  
  
  
           ######### sidekiq console output - successful mpd is generated ################
  
                DASH-ing files - single segment
  
                Subsegment duration 1.000 - Fragment duration: 1.000 secs
  
                Splitting segments and fragments at GOP boundaries
  
                DASHing file video_1080.mp4
  
                DASHing file video_720.mp4                                  
  
                DASHing file video_480.mp4                                  
  
                DASHing file video_360.mp4                                  
  
                DASHing file video_240.mp4                                  
  
                DASHing file video_audio.mp4                                
  
               \[DASH\] Generating MPD at time 2019-11-22T00:01:59.872Z      
  
                mpd_1mb.mp4
  
                mpd_video.mpd

  this is what the uploaded files looks on s3, notice the video.mpd, its a mp4 video file just like others which should have been a simple mpd file of not more than 2kb.

  Is there something that I am missing ?
  Can Carrierwave do this or is it not made for this ?
  Do I have to write a callback and then programmatically upload files to s3, if carrierwave is not helping in this regard ?

  Kindly provide any suggestion or useful advice so that I can move ahead.

  

• Flutter_ffmpeg : At least one output file must be specified

  22 mars 2020, par Jehonadab Okpukoro

  I’m trying to crop a video with Flutter_ffmpeg package using this -i $inputPath -filter:v "crop=80:60:200:100" -c $outputPath, but I’m having this error message

  Running FFmpeg with arguments: [-i, /data/user/0/com.timz/app_flutter/Movies/flutter_test/1584827688309.mp4, -filter:v, crop=80:60:200:100, -c, /data/user/0/com.timz/cache/output.mp4].
  
  I/flutter (20728): ffmpeg version git-2020-01-25-fd11dd500
  
  I/flutter (20728):  Copyright (c) 2000-2020 the FFmpeg developers
  
  I/flutter (20728): 
  
  I/flutter (20728):   built with Android (5220042 based on r346389c) clang version 8.0.7 (https://android.googlesource.com/toolchain/clang b55f2d4ebfd35bf643d27dbca1bb228957008617) (https://android.googlesource.com/toolchain/llvm 3c393fe7a7e13b0fba4ac75a01aa683d7a5b11cd) (based on LLVM 8.0.7svn)
  
  I/flutter (20728):   configuration: --cross-prefix=aarch64-linux-android- --sysroot=/files/android-sdk/ndk-bundle/toolchains/llvm/prebuilt/linux-x86_64/sysroot --prefix=/home/taner/Projects/mobile-ffmpeg/prebuilt/android-arm64/ffmpeg --pkg-config=/usr/bin/pkg-config --enable-version3 --arch=aarch64 --cpu=armv8-a --cc=aarch64-linux-android24-clang --cxx=aarch64-linux-android24-clang++ --target-os=android --enable-neon --enable-asm --enable-inline-asm --enable-cross-compile --enable-pic --enable-jni --enable-optimizations --enable-swscale --enable-shared --disable-v4l2-m2m --disable-outdev=v4l2 --disable-outdev=fbdev --disable-indev=v4l2 --disable-indev=fbdev --enable-small --disable-openssl --disable-xmm-clobber-test --disable-debug --enable-lto --disable-neon-clobber-test --disable-programs --disable-postproc --disable-doc --disable-htmlpages --disable-manpages --disable-podpages --disable-txtpages --disable-static --disable-sndio --disable-schannel --disable-securetransport --disable-xlib --disable-cuda --disable-cuvid --disa
  
  I/flutter (20728):   libavutil      56. 38.100 / 56. 38.100
  
  I/flutter (20728):   libavcodec     58. 65.102 / 58. 65.102
  
  I/flutter (20728):   libavformat    58. 35.101 / 58. 35.101
  
  I/flutter (20728):   libavdevice    58.  9.103 / 58.  9.103
  
  I/flutter (20728):   libavfilter     7. 70.101 /  7. 70.101
  
  I/flutter (20728):   libswscale      5.  6.100 /  5.  6.100
  
  I/flutter (20728):   libswresample   3.  6.100 /  3.  6.100
  
  I/flutter (20728): Trailing option(s) found in the command: may be ignored.
  
  D/flutter-ffmpeg(20728): FFmpeg exited with rc: 1
  
  I/flutter (20728): Input #0, mov,mp4,m4a,3gp,3g2,mj2, from '/data/user/0/com.timz/app_flutter/Movies/flutter_test/1584827688309.mp4':
  
  I/flutter (20728):   Metadata:
  
  I/flutter (20728):     major_brand     : 
  
  I/flutter (20728): mp42
  
  I/flutter (20728): 
  
  I/flutter (20728):     minor_version   : 
  
  I/flutter (20728): 0
  
  I/flutter (20728): 
  
  I/flutter (20728):     compatible_brands: 
  
  I/flutter (20728): isommp42
  
  I/flutter (20728): 
  
  I/flutter (20728):     creation_time   : 
  
  I/flutter (20728): 2020-03-21T21:54:56.000000Z
  
  I/flutter (20728): 
  
  I/flutter (20728):     com.android.version: 
  
  I/flutter (20728): 9
  
  I/flutter (20728): 
  
  I/flutter (20728):   Duration: 
  
  I/flutter (20728): 00:00:07.17
  
  I/flutter (20728): , start: 
  
  I/flutter (20728): 0.000000
  
  I/flutter (20728): , bitrate: 
  
  I/flutter (20728): 3870 kb/s
  
  I/flutter (20728): 
  
  I/flutter (20728):     Stream #0:0
  
  I/flutter (20728): (eng)
  
  I/flutter (20728): : Video: h264 (avc1 / 0x31637661), yuv420p(tv, bt709), 720x480, 3854 kb/s
  
  I/flutter (20728): , SAR 1:1 DAR 3:2
  
  I/flutter (20728): , 
  
  I/flutter (20728): 29.44 fps, 
  
  I/flutter (20728): 29.83 tbr, 
  
  I/flutter (20728): 90k tbn, 
  
  I/flutter (20728): 180k tbc
  
  I/flutter (20728):  (default)
  
  I/flutter (20728): 
  
  I/flutter (20728):     Metadata:
  
  I/flutter (20728):       rotate          : 
  
  I/flutter (20728): 270
  
  I/flutter (20728): 
  
  I/flutter (20728):       creation_time   : 
  
  I/flutter (20728): 2020-03-21T21:54:56.000000Z
  
  I/flutter (20728): 
  
  I/flutter (20728):       handler_name    : 
  
  I/flutter (20728): VideoHandle
  
  I/flutter (20728): 
  
  I/flutter (20728):     Side data:
  
  I/flutter (20728):       
  
  I/flutter (20728): displaymatrix: rotation of 90.00 degrees
  
  I/flutter (20728): 
  
  I/flutter (20728):     Stream #0:1
  
  I/flutter (20728): (eng)
  
  I/flutter (20728): : Audio: aac (mp4a / 0x6134706D), 48000 Hz, mono, fltp, 12 kb/s
  
  I/flutter (20728):  (default)
  
  I/flutter (20728): 
  
  I/flutter (20728):     Metadata:
  
  I/flutter (20728):       creation_time   : 
  
  I/flutter (20728): 2020-03-21T21:54:56.000000Z
  
  I/flutter (20728): 
  
  I/flutter (20728):       handler_name    : 
  
  I/flutter (20728): SoundHandle
  
  I/flutter (20728): 
  
  I/flutter (20728): At least one output file must be specified

  I’ve been cracking my head with this for the past two days, kindly share your thoughts on what might wrong.