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• ffmpeg seek and change select filter after starting

  15 avril 2023, par Ta946

  Im using python to create something like a video player, I've written an ffmpeg wrapper to read a video.

  


  I want to dynaamically seek after ffmpeg has already started running. Eg : read n frames, seek to frame 100, read n frames, seek back to frame 50, read n frames.

  


  Another thing my program needs to do is read every nth frame using ffmpeg's select filter. And be able to change n after it has already started running. eg : read every 2nd frame then change to read every 10th frame.

  


  I create the ffmpeg process using Popen with the following command :

  


  ffmpeg -i {path} -ss {seek_time} -f  rawvideo -pix_fmt bgr24 -vsync 0 -vf select="not(mod(n\,{skip_size}))" -


  


  I haven't found any way to seek or change select filter after ffmpeg starts.

  


  So I have to kill the Popen process, and create a new one with the updated seek_time and/or skip_size. Which creating a new process is extremely slow

  


  Is there a faster way to achieve this ?

  


• FFMpeg and Python Videos - skipping frames and resulting in incorrect video outputs

  29 septembre 2022, par S.A.D.

  I have a couple of videos recorded (I recorded them using opencv in python)- they are rougly 4 minutes long. I want to trim only 10s of each of them.

  


  Trimming them with FFMpeg tho (ffmpeg -i input.mp4 -ss 00:02:01 -t 00:00:10 -c:v copy -c:a copy output.mp4) results in an incorrect output.

  


  Whats incorrect about it ?

  


  

  1. When I open it with VLC media player, it shows it is indeed 10s long, but it plays only one second, from 9 to 10th second, and ends the video.

  


  2. I chose a specific fragment to be cut, and yet, the trimmed output is not this fragment - it is like, 10s earlier.

  


  


  I literary have no idea why this is happening - this sounds like some corrupted input file, and results in another corrupted output.
Why is this happening ? How to fix this ?

  


  Thanks tons

  


• I want to replace audio in a moflex file but ffmpeg says "Unable to find a suitable output format for 'CloudyWithAChanceOfMeatballs(3D).moflex'"

  26 septembre 2022, par Костянтин Мара

  What i do :

  


  ffmpeg -i CloudyWithAChanceOfMeatballs(3D)_400x240_1800kbps_23.976fps_2pass.moflex -i Cloudy.With.A.Chance.Of.Meatballs.2009.1080p.mp3 -c:v copy -c:a fastaudio -map 0:v:0 -map 1:a:0 -o CloudyWithAChanceOfMeatballs(3D).moflex


  


  and what i get :

  


  Input #0, moflex, from 'CloudyWithAChanceOfMeatballs(3D)_400x240_1800kbps_23.976fps_2pass.moflex':
  Duration: N/A, bitrate: N/A
  Stream #0:0: Video: mobiclip, yuv420p, 400x240, 23.98 fps, 23.98 tbr, 23.98 tbn
  Stream #0:1: Data: none
  Stream #0:2: Audio: fastaudio, 48000 Hz, stereo, fltp
Input #1, mp3, from 'Cloudy.With.A.Chance.Of.Meatballs.2009.1080p.mp3':
  Metadata:
    title           : --SCHUMAHER--
    encoder         : Lavf59.24.100
  Duration: 01:29:50.71, start: 0.023021, bitrate: 128 kb/s
  Stream #1:0: Audio: mp3, 48000 Hz, stereo, fltp, 128 kb/s
    Metadata:
      encoder         : Lavc59.33
[NULL @ 000002651fbaf540] Unable to find a suitable output format for 'CloudyWithAChanceOfMeatballs(3D).moflex'
CloudyWithAChanceOfMeatballs(3D).moflex: Invalid argument


  


  I'm not sure what could be the problem, before this i tried converting it to mp4 and then do something but because the video was in 3d, ffmpeg sort of shuffled those left and right frames into one, 2x long video. Help on this would also be welcome.