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• 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

  


• 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.

  


• Music Video Idiosyncrasies

  18 juin 2011, par Multimedia Mike — General

  So I’m watching a fairly recent music video for a song named "XXXO" from an artist named M.I.A. when I’m suddenly assaulted by this imagery :

  
  
  

  ... and I enter nervous convulsions. You see, while this might seem to be an odd video effect to the casual viewer, to a multimedia hacker, it appears to be deliberately antagonistic. To anyone who has written a video codec, this scene looks like an entire casserole of video bugs, combining creeping plane offsets errors, chroma problems, and interlacing havoc. The craziest part is to realize that this is probably some kind of standard video effect / filter type. Upon a repeat viewing, I realized that the entire video sort of looks like an amateur video editor’s first week using video software.

  Elsewhere in the video, a YouTube-style video frame vortex highlights the proceedings. I guess I need to come to terms with the fact that the ubiquitous player frame is just part of the digital Zeitgeist now :

  
  
  

  Vintage Video Strangeness
  I’m a long-time music video junkie but I have a tendency of examining them entirely too closely. I first saw Paula Abdul’s video for "Cold-Hearted" when I was just starting to understand multimedia technology and how it interacted with emerging home computers. Imagine how confused I was when I tried to make sense of the actions performed by our eMaestro "Chuck" whom Paula has instructed to "hit it". First, he hits a key followed by 3 quick strikes on a second key :

  
  
  

  Then, the "start music" action is apparently bound to a particular key on the electronic keyboard :
  
  

  
  
  

  Which kicks off the electronic metronome on the computer. Each identical-sounding beat quizzically maps to a different frequency transform :

  
  
  a one...
  
  and a two...
  
  and a three...
  

  I had no trouble believing things up to this point. But even though I didn’t understand what was going on with that frequency transform, I knew that it must have had something to do with the audio. And if the audio was the same, the visualization ought to be the same. Though, to be fair, I will concede that the first and third ticks pictured bear some mutual resemblance.

  Anyway, the software is probably real even if the keyboard interaction was stylized. Can anyone identify the software ? What about the computer ? This is perhaps the best view the video gives us :

  
  
  

  So, remember, don’t base your understanding of technology — or anything, really — on stylized media representations. Don’t even get me started on the movie "Sneakers." That had me confused about cryptography and computer security for many years.