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• ffmpeg - How to change the filter-paramaters depending on time oder framenumber ?

  2 mars 2020, par LookAndSee

  Hallo to all userse and helpers here in this forum ! Thank you, i am new and i have found allready a lot of solutions.

  Now I want to ask, if someone can help me :

  I have a Movie about 30 seconds made of 1 image.
  Now I want to pixelate depending on time or framenumber - every time a litlle bit less.
  My code so far :

  ffmpeg -i in.mp4 -vf scale=iw/n:ih/n,scale=niw:nih:flags=neighbor out.mp4

  where n should be the framenumber 1 to 900.
  this scould also be t+1 for slower change.

  the stars are gone - so i mean n times iw:n times ih :

  error-massage :

  undefined constant or missing ’(’ in ’n’
  error when evaluating the expression ’ih/n’
  maybe the expression for out_w :’w/n’ or for out_h :’ih/n’ is self-referencing.
  failed to configure output pad on paresed_scale_0
  error reinitializing filters !
  failed to inject frame into filter network : invalid argument
  error while processing the decoded data for stream #0:0

  Do you have some suggestion plaese - Thank you in Advance

• Syncing decoded video using Ffmpeg

  30 juin 2012, par Infiniti Fizz

  I am using Ffmpeg to decode and play video files. I have currently got the video playing and the audio playing at as fast as the CPU can decode and display them. The problem is that I want to play the video and audio in sync using the system clock.

  I've searched around for some help but can't find anything substantial other than dranger's tutorial 05 but I don't really understand what he is doing because my program isn't written in the same way as his.

  I am using mjpeg files and so the pts seems to be retrieved every single time a frame is decoded, I have multiplied the pts by the time_base as dranger does to get the value in seconds but the resolution seems to be only seconds and so I get the value "6" 25 times and then "7" 25 times as the video runs at 25 frames per second.

  Is there not a more accurate value ? Or way to get a more accurate value and if so, how would I go about syncing to this value ? I am using SDL to display the value so can I just use a SDL_Delay() of the value I get ?

  Thanks for your time,

  Infinitifizz

• FFmpeg per stream metadata change with more audio streams

  22 août 2014, par tomasb

  I’m trying to change audio stream title for a movie which was originally with DTS sound. I have added AC3 version using -map parameter, want to keep both. My problem is that the AC3 audio stream bears DTS stream metadata. I am using FFmpeg 1.2

  Tried :

  ffmpeg -i movie.mkv -c copy \
  
  -metadata:s:1 title="AC3 5.1 640 kb/s" -y movie.temp.mkv 

  this partially works, but output file contains only 1 of each stream type, i.e. 1 video, 1 audio and 1 subtitle stream. When i try to get all the streams contained in my mkv like this :

  ffmpeg -i movie.mkv -map 0 \
  
  -metadata:s:1 title="AC3 5.1 640 kb/s" -y movie.temp.mkv 

  i am getting strange output :

  Stream mapping:
  
    Stream #0:0 -> #0:0 (h264 -> libx264)
  
    Stream #0:1 -> #0:1 (ac3 -> libvorbis)
  
    Stream #0:2 -> #0:2 (subrip -> ass)
  
    Stream #0:3 -> #0:3 (dca -> libvorbis)
  
    Stream #0:4 -> #0:4 (ac3 -> libvorbis)
  
    Stream #0:5 -> #0:5 (subrip -> ass)
  
  Press [q] to stop, [?] for help
  
  [libvorbis @ 0x12e5a40] Queue input is backward in time
  
      Last message repeated 19 times
  
  Queue input is backward in time      20kB time=00:00:01.05 bitrate= 156.8kbits/s    
  
  [libvorbis @ 0x12e5a40] Queue input is backward in time
  
      Last message repeated 17 times
  
  Queue input is backward in time      20kB time=00:00:01.99 bitrate=  83.0kbits/s    
  
  [libvorbis @ 0x12e5a40] Queue input is backward in time
  
      Last message repeated 5 times
  
  Queue input is backward in time=      20kB time=00:00:02.38 bitrate=  69.5kbits/s    
  
  [libvorbis @ 0x12e5a40] Queue input is backward in time
  
      Last message repeated 6 times
  
  Queue input is backward in time=      20kB time=00:00:02.87 bitrate=  57.5kbits/s    
  
  [libvorbis @ 0x12e5a40] Queue input is backward in time
  
  ...

  I have found information that FFmpeg’s attributes under linux are inconsistent when manipulating per stream metadata and doesn’t work as expected so I am looking for some alternative way how to proceed. (preferably with ffmpeg)

  Thanks for any help.