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• GoPro (MP4) video timestamp sync with precision of milliseconds

  3 février 2021, par Raphael Ottoni

  I need your help with a data sync problem... I m currently trying to sync my GoPro video with real world time (a.k.a my notebook). I manage to sync date and time of my notebook and my GoPro 3+ black perfectly. The problem is that when the GoPro save the files in disk it round up the milliseconds on the creation_time (the milliseconds is always 000000) . Thus, turning the perfect sync impossible. In attachment is a picture of the meta information (extracted by ffprobe) of the MP4 video.

  



  My question is : What I have to do, so the GoPro actually save the creation_time with precision of milliseconds ?

  



  Another small question : Looking at the attachment figure, we see the "timecode" which is a time synchronization data in the format of hours:minuts:seconds:frame. I was thinking that I could use the "frame" value to calculate the missing milliseconds value. If we take this attachment, as a example, we can see that the frame value is "36". Meaning that the millisecond that it started to record was the one associated with the 36th frame of the FPS (in this video : 60fps) value : Some thing like 1000/60 * 36 which is 600 milliseconds, thus the actual creation_time of this video would be : 2017-07-19T18:10:34.600

  



  Is this logic right ? it didn't work ! I don't know what else to do.

  



  P.S : I need this kind of time precision because I will sync the video frames with a external sensor data that is recorded at 11hz.

  



  Please Help

  



  

  



  update

  



  I forgot to mention, even if you check the original raw file information, inside the GoPro SSD card, using "stats" to read the creation time (see attachment) it still has the same timestamp without milliseconds.

  



  

  


• FFMPEG xstack not recognizing inputs

  12 août 2020, par Josh

  I'm trying to arrange three input videos into a single output video using ffmpeg's xstack. I currently have the operations working with a vstack followed by an hstack, but would like to combine them into an xstack for performance.

  


  I've tried copying the syntax from multiple locations such as :

  


  https://trac.ffmpeg.org/wiki/Create%20a%20mosaic%20out%20of%20several%20input%20videos%20using%20xstack

  


  Vertically or horizontally stack (mosaic) several videos using ffmpeg ?

  


  My command is as follows :

  


  


  C :\ffmpeg\bin\ffmpeg.exe -i states_full.mp4 -i title.mp4 -i graphs.mp4" -filter_complex "[0:v] setpts=PTS-STARTPTS, scale=qvga [a0] ; [1:v] setpts=PTS-STARTPTS, scale=qvga [a1] ; [2:v] setpts=PTS-STARTPTS, scale=qvga [a2] ; [a0][a1][a2]xstack=inputs=3:layout=0_0|w0_0|w0_h0[out] " -map "[out]" -c:v libx264 -t '30' -f matroska output.mp4

  


  


  The command always errors out at the same spot, with the same error message :

  


  


  'w0_0' is not recognized as an internal or external command,
operable program or batch file.

  


  


  Some odd behavior is that even when I change the layout section to :

  


  layout=w0_0|0_0|w0_h0


  


  The error message is still on the middle '0_0' meaning it may be an error in formatting.

  


  This issue is very strange, as the vstack and hstack still work, only the xstack fails.

  


• ffmpeg concat .dv without errors or loss of audio sync

  29 mars 2022, par Dave Lang

  I'm ripping video from a bunch of ancient MiniDV tapes using, after much trial and error, some almost as ancient Mac hardware and iMovie HD 6.0.5. This is working well except that it will only create a contiguous video clip of about 12.6 GB in size. If the total video is larger than that, it creates a second clip that is usually about 500 MB.

  


  I want to join these two clips in the "best" way possible - meaning with ffmpeg throwing as few errors as possible, and the audio / video staying in sync.

  


  I'm currently using the following command line in a bash shell :

  


  for f in *.dv ; do echo file '$f' >> list.txt ; done && ffmpeg -f concat -safe 0 -i list.txt -c copy stitched-video.dv && rm list.txt

  


  This seems to be working well, and using the 'eyeball' check, sync seems to be preserved.

  


  However, I do get the following error message when ffmpeg starts in on the second file :

  


  Non-monotonous DTS in output stream 0:1 ; previous : 107844491, current : 107843736 ; changing to 107844492. This may result in incorrect timestamps in the output file.

  


  Since I know just enough about ffmpeg to be dangerous, I don't understand the significance of this message.

  


  Can anyone suggest changes to my ffmpeg command that will fix whatever ffmpeg is telling me is going wrong ?

  


  I'm going to be working on HD MiniDV tapes next, and, because they suffer from numerous dropouts, my task is going to become more complex, so I'd like to nail this one.

  


  Thanks !

  


  as suggested below ffprobe for the two files

  


  Input #0, dv, from 'file1.dv' : Metadata : timecode : 00:00:00 ;22 Duration : 00:59:54.79, start : 0.000000, bitrate : 28771 kb/s Stream #0:0 : Video : dvvideo, yuv411p, 720x480 [SAR 8:9 DAR 4:3], 25000 kb/s, 29.97 fps, 29.97 tbr, 29.97 tbn Stream #0:1 : Audio : pcm_s16le, 48000 Hz, stereo, s16, 1536 kb/s

  


  Input #0, dv, from 'file2.dv' : Metadata : timecode : 00:15:06 ;19 Duration : 00:02:04.09, start : 0.000000, bitrate : 28771 kb/s Stream #0:0 : Video : dvvideo, yuv411p, 720x480 [SAR 8:9 DAR 4:3], 25000 kb/s, 29.97 fps, 29.97 tbr, 29.97 tbn Stream #0:1 : Audio : pcm_s16le, 48000 Hz, stereo, s16, 1536 kb/s