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• FFmpeg - Change resolution of the video with aspect ratio

  18 septembre 2024, par Arthur

  all.

  



  How to change resolution of the video with aspect ratio with FFmpeg ?

  



  There are options 
http://manpages.ubuntu.com/manpages/oneiric/man1/ffmpeg.1.html

  



         -s size
       Set frame size. The format is wxh (ffserver default = 160x128,
       ffmpeg default = same as source).  The following abbreviations are
       recognized:


  



  and

  



         -aspect aspect
       Set the video display aspect ratio specified by aspect.

       aspect can be a floating point number string, or a string of the
       form num:den, where num and den are the numerator and denominator
       of the aspect ratio. For example "4:3", "16:9", "1.3333", and
       "1.7777" are valid argument values.


  



  For example, I have two input videos :

  



  

  • with 200*400 resolution

  


  • with 400*700 resolution

  


  



  I need to make output video with 100*200 resolution.

  



  If I will run ffmpeg with -s 100x200, then second video will have bad aspect ratio.

  



  How can I limit output video by width, with auto aspect ratio by height ?

  



  For example, I want specify for the output video only width 100px and ffmpeg must automatically calculate height with right aspect ratio.

  



  For first video it will be :

  



  200/100=2

  



  400/2=200

  



  Ie 100x200

  



  For second video it will be :

  



  400/100=4

  



  700/4=75

  



  Ie 100x75

  



  Is it possible ?

  


• How I can receive MJPEG stream via RTSP with resolution more than 1080p

  21 septembre 2018, par chuchuchu

  There is a problem :
  When I get a video stream with a resolution of 1080 and below - everything is fine.
  But if I select a stream with a resolution higher than 1080 on the camera, an error occurs.
  FFMPEG :

  [mjpeg @ 0x7f5488003e40] [IMGUTILS @ 0x7f5494acb4f0] Picture size 0x0 is invalid

  If I open a stream in the player I get a disparate image :

  [mjpeg @ 0x7fd9f8043b20] error y=91 x=16
  
  [mjpeg @ 0x7fd9f8043b20] error dc

  I repeatedly recompiled and reinstalled various versions of the ffmpeg, the problem is not solved.

  I suspect that there is a restriction for video stream over 1080p, but I can not find any description or solution.
  And I found next string in rfc "RTP Payload Format for JPEG" :

  The maximum width is 2040 pixels.

  but it is dated 1998. I know for certain that this stream on the RTSP receives in the resolution I need, but I can not understand how.

  Please, tell me the way to the solution. I’m using Ubuntu 16.04 amd64.
  Perhaps there is an alternative way to receive a rtsp-stream without using a ffmpeg ?? Since all ways known to me are using ffmpeg.

• Standardizing many mp4 files into same resolution

  22 novembre 2018, par Cowfod

  I have a huge collection of Instagram videos in different resolutions and with different audio codecs.

  Some videos are 640x640, others are 640x800. You get the picture.

  When I try to concat the videos, the video and audio go out of sync in the final output and the in some places the audio is slowed down(?).

  This is my ffmpeg concat command :

  ffmpeg -i "$(cat /home/list.txt)" -c:v copy -c:a copy /home/output.mp4

  list.txt contains over 800 clips and is formatted correctly :

  file 'clip1.mp4'
  
  file 'clip2.mp4'
  
  file 'clip3.mp4'
  
  etc...

  I believe the issue is due to all the different resolutions and different codecs used, so how can I standardize my collection of clips in order to concat them into a working video file ?