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• How to save a vedostream on an event using ffmpeg

  26 janvier 2015, par Ludo

  I want to record short video sequences of an online stream (IP CCTV or Internet) on a defined event.

  For example : I want to have two minutes before and one minute after an event occures stored in a output file.

  Is it possible to do this using ffmpeg (avconv) and what are the parameters to use.

  Thanks for your help !

• FFMPEG - Download video in parts and concat, stutter at concat points

  23 juillet 2022, par rnbwSmn

  My goal is to download a video (or M3U8) in parts/chunks which I can later concat.

  


  For context, I would like to download videos in an Android Service which may be stopped at any time, so I think chunking is the right approach.

  


  After some time I got the "downloading the parts" right, using this. I would later put that in a function, and for now I chose the chunks to be 30 seconds long.

  


  %offset% = 30 * %part%

ffmpeg -ss %offset% -t 30 -i INPUT_FILE -avoid_negative_ts 1 out%part%.mp4


  


  The first line is just pseudocode, part is starting at 0.
This works fine, downloading 30 second long .mp4 files.

  


  After that I tried merging them together into a single .mp4. For the tests I only downloaded the first few parts.

  


  Concat command :

  


  ffmpeg -safe 0 -f concat -i concat.txt -c copy final.mp4


  


  This would be a very short concat.txt file :

  


  file 'out0.mp4'
file 'out1.mp4'


  


  The concat works but has one problem : At the point where both files are actually combined, so at 30 seconds, there is a small stutter in video and audio.

  


  So what I think is going on is that I download parts that are 30s long, starting at multiples of 30s so there is a small overlap ? In the "Details" part of the Windows file properties it also shows a length of 31 seconds, so the video is even longer than I want.

  


  I tried setting the duration of each part in the concat.txt, both to 30s and to 30s - 1 frame

  


  23.98 fps -> 1/23.98 spf = 0.0417s


  


  But with a duration of 30 as well as 29.9583, although it is better, there is still a small stutter.

  


  file 'out0.mp4'
duration 29.9583
file 'out1.mp4'
duration 29.9583


  


  I also tried with a different fileformat, .ts files, but the stutter was still there. I still think my timings are not quite right, but at this point I don't know where the problem is exactly. What do I need to change to remove the small stutter ?

  


• Anomalie #4660 (Nouveau) : #INTRODUCTION et introduction explicite

  11 février 2021, par Maïeul Rouquette

  Spoiler : ca attendra la 3.4 , mais j’expose maintenant le problème

  Sur un site, j’ai
  1. D’une part des gens qui mettent des <intro></intro> dans leurs articles, avec parfois plus de 600 caractères
  2. D’autre part des gens qui n’en mettent pas, et dans ce cas le découpage à 600 caractères devrait venir en fallback.

  Sauf qu’actuellement, même si on a une intro explicite, cela nous coupe à 600 caractères (ou constante/valeur).

  Mon contournement, qui est moche :

  []
  

  Idéalement il faudrait pouvoir avoir un comportement qui permette, si jamais #INTRODUCTION se base sur les intro explicites, de ne pas couper.

  Mais comme disait tcharlss, on est dans une double impasse :
  - d’une part on ne peut pas régler cela à coup d’une constante, car il y a des cas où il faut EFFECTIVEMENT couper automatiquement (genre les listes d’objets).
  - d’autre part, on ne peut pas rajouter un 3ème paramètre à #INTRODUCTION, car sinon on en fini pas au niveau des signatures.

  Une solution serait d’avoir des paramètres nommées, mais ca n’existe pas encore dans le compilo (bien qu’il y ait des pistes pour cela dans le plugin saisies)