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• formula to calculate video dimensions for target aspect ratio

  23 avril 2015, par Nevoxx

  i currently building an application that converts videos to a specific dimension under consideration of the target aspect ration.

  the target resolution must always be 1280x720, i want to fit the uploaded video in this size using black bars.

  can anyone point out a formula to calculate the target video dimensions without changing it’s aspect ratio ? if the target with is smaller then 1280x720 i’ll add the missing pixels as black bars.

  i’m using ffmpeg with the "-vf scale=1280x720,pad=?:?:black" command

  (sorry if my english is not that great)

• FFMPEG Concatenate multiple videos causes : Too many invisible frames

  2 décembre 2019, par Silmood

  i’m trying to concatenate multiple .webm files in a single one. One of these files is a simple black video generated with the next command :

  ffmpeg -f lavfi -i color=c=black:s=1920x1080:d=5.2 black.webm

  Then this is concat_list.txt

  file 'black.webm'
  
  file '1.webm'
  
  file '2.webm'
  
  file '3.webm'

  Finally i try to concatenate files with :

  ffmpeg -f concat -i concat_list.txt -c copy video.webm

  The result is a long list of this message :

  [AVBSFContext @ 0x7fcecef00180] Too many invisible frames
  
  [AVBSFContext @ 0x7fcecef00180] Failed to receive packet from filter vp9_superframe for stream 0

  Complete log

  The problem seems to be the black.webm file. I removed it from the concat_list.txt and everything works fine.

  It’s important to mention that none of these files has an audio stream.

• ffmpeg failed to drawbox and set volume

  27 janvier 2021, par Hussam Al-Barodi

  I don't know what is wrong in my command with ffmpeg.
Lets say I have a video and I want to make a black screen with muted audio between 20-30 seconds. So what I wrote is :

  


  ffmpeg -i input.mp4 -filter_complex "[0:v]trim=0:20[0v];[0:a]atrim=0:20[0a];[0:v]trim=20:30,drawbox=color=black:t=fill[1v];[0:a]atrim=20:30,volume=0[1a];[0:v]trim=30:60[2v];[0:a]atrim=30:60[2a];[0v][1v][2v]concat=n=3:v=1:a=0[outv];[0a][1a][2a]concat=n=3:v=0:a=1[outa]" -map [outv] -map [outa] output.mp4


  


  Now, I expect to have a video with 1 min length where the seconds between 20 & 30 are muted with black screen, but what I got is :

  


  20 sec correct
20 sec freezing video with no audio
40 sec black video with no audio
30 sec correct


  


  Can anyone help and tell me what is wrong in the command line ?