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• FFMPEG - How to reduce frame rate without slow motion effect ? [closed]

  4 avril 2024, par crater33

  I have an MP4 video that's 21 minutes long, that was shot on a GoPro Hero 9 Black at 2.7k and 240 frames per second using HEVC.

  


  I would like to use FFMPEG to reduce the frame rate, with the output being a video that is also 21 minutes long and 2.7k ... but with a frame rate of 120 frames per second. But when I use the command "ffmpeg -i input.mp4 -filter:v fps=120 output.mp4 I get a video that is 42 minutes long.

  


  I would like to tell FFMPEG to simply delete every other frame of the input video, while keeping the total length of the video the same. What command would I use to do that ?

  


  Also, how would I modify this command if I wanted the output to be encoded in AVC ?

  


  Thank you.

  


• Merging .flv chunks from stream site

  4 décembre 2016, par Iztooi

  I’m trying to download a video from an alternative version of the Ustream site. This site is apparently used for a DRM protection, in fact you can’t watch this video without having access to it through a login from this site.
  The video system should be the same used by ustream (same links), that is calling different flv chunks every x seconds and merging them into the stream (similar to an rtmp service, but it doesn’t use this protocol).

  I managed to download every .flv chunks composing this video, but i had issues on merging them into a single file. First of all these flvs files have some audio/video lags/problems, but since there is no other way to download this video i’m not complaining about lags.

  The real issue is that every flv file has an additive increase on the duration, despite having a normal size. Video duration is about 6 seconds, so the first chunk is 6 seconds long, the second chunk is 12 seconds long, although only the first 6 are visible (the remaining 6 are "corrupted"). If i try to merge (with ffmpeg or any video-joining software) all these files (about 600-700, for a total duration of 1 hour and 15 minutes) only the first two sections are visible, then I cannot see anything. (Being more clear, if i try to merge the first 2 chunks, file is 18 seconds long and i can see the first 12 ; if i try to merge the first 3 chunks, file is 36 seconds long and i can still only see the first 12 seconds.)

  Anyone has any idea ?

• How do I concatenate a specific audio recording to multiple different ones (at the beginning of each), in bulk ? [closed]

  28 septembre 2023, par catofws

  So I have an audio recording that's something like 10 seconds long, right ?

  


  That single audio recording needs to be added to the beginning of a lot of different ones, and I need to somehow be able to do it in bulk.

  


  I am talking about something very simple, literally adding that one specific 10 second long audio recording I have mentioned earlier to the beginning of the other ones, not overlapping with anything, thus extending the total duration by 10 seconds or so.

  


  Tried Audacity, works, but it's a long process that doesn't fit my purposes. If audacity can do it I know for sure that a simple script can accomplish this one very specific very simple task.

  


  I don't code.

  


  EDIT : Wanted to add that I am not expecting someone to write a whole script for me, but rather point to the right direction. I have a very basic idea of Python and I know that for my specific purpose I would need to use FFMPEG. I want someone to point me towards the right direction, what functions & libraries would I need to use to make such a script ?