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• avfilter/vf_vif : Remove superfluous ' ;'

  19 février 2021, par Andreas Rheinhardt

  avfilter/vf_vif : Remove superfluous ' ;'
  Inside a function a superfluous ' ;' is just a null-statement ; yet
  
  outside it is invalid, even though compilers happen to accept them.
  
  They (at least GCC and Clang) only warn about this when on -pedantic.
  Signed-off-by : Andreas Rheinhardt <andreas.rheinhardt@gmail.com>
  

  • [DH] libavfilter/vf_vif.c

• How to change resolution of a video.mp4 file stored on the AWS S3 ?

  10 octobre 2018, par Aman

  I’m using AWS S3 to store my video and audio files. Before I upload any video file, I convert the video file into different resolutions from my laptop using ffmpeg and then I upload those files onto my AWS S3 account. I want to know if its possible to convert the video file stored on my AWS S3 to different resolutions. As in the conversion to happen on the AWS.

  I’m using ffmpeg command in CMD : ffmpeg -i video.mp4 -s 256x144 -c:a copy video_144p.mp4

• ffmpeg, how to extract single frame, 0.5 seconds before the end ? [duplicate]

  24 avril 2020, par Tonny

  I've got a bunch (several 100) of videos (all different frame-rates and different lengths).
  
Each has an end-title during the last second of the video, that shows some important information I need to check.
  
Playing each video in a player, scrolling to the end and trying to pause it in the last second is just to cumbersome/time-consuming.
  
Grabbing a frame at that position and saving it as an image for each video lets me quickly check the info using the image-preview in my file-manager. Which is much more efficient.

  



  ffmpeg can capture single frames and write them to a jpg or png, but I am at a loss how to extract a frame in the middle of that title sequence. 0.5 seconds before the end of each video would be the sweet spot. (There is a animation effect during that 1 second sequence that makes the text in the video sometimes hard to read, but exactly in the middle the visibility is best.)
  
As far as I can tell ffmpeg can't use offsets "from the end", so I assume ffprobe is probably needed to analyze the video and on basis off that the correct ffmpeg command can be generated.

  



  I can handle the scripting around it to batch-process all the files.
  
Problem is that I'm very unfamiliar with video in general, ffmpeg and ffprobe in particular. I need some help to get started.
  
If someone can explain to me how to get from the full video 'clip.mp4' to the single frame 0.5 seconds before the end in 'clip_frame.jpg' I would be most grateful.