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• Normalise video aspect ratio with ffmpeg

  4 juillet 2022, par Benjamin Tamasi

  I'm parsing a video stream from an application that receives an h264 stream and writes it to a file. (The frame data is an unencrypted depacketized H.264 elementary stream).

  


  I use ffmpeg to resize it to a fixed resolution. (I overlay it on a black canvas with -f lavfi -i color=c=black:s=1920x1080:r=30) and -filter_complex [1][0]scale2ref=w='if(gt(mdar\,dar),iw,oh*mdar)':h='if(gt(mdar\,dar),ow/mdar,ih)'[2mp4][base];[base][2mp4]overlay=x='(W-w)/2':y='(H-h)/2':eof_action=pass[vout]

  


  My issue is, that since this stream is coming from a phone's camera, whenever the orientation of the phone changes, the stream's aspect ratio changes. It can go from portrait to landscape, and back, in the same stream. When I open the file in vlc, it handles it quite nicely by resizing the window of the player to match the aspect ratio as it changes.

  


  How can I "normalise" the video, so it's always nicely overlayed on my black canvas as the aspect ratio changes ? Currently it's just using the initial aspect ratio, and if that changes mid stream, it will ignore the change, effectively distorting the stream by squishing or stretching it.

  


  Is there some way I can get ffmpeg to do this ?

  


• Creating marketing videos

  7 juin 2020, par Cengiz

  I am trying to create a marketing video with multiple images (png/jpg) after adding texts on every single image and of course with their duration. Therefor, I use several ffmpeg commands, because I am not able to do it with just one command.

  



  How can I define a text and a duration for every image before adding it to the video ?

  



  My example batch file :

  



   !/bin/bash

  



  echo "[Start]"
ffmpeg \
 -i '01.jpg' \
 -vf drawtext="\text='Stack Overflow' : fontcolor=white : fontsize=24 : box=1 : boxcolor=black@0.9 : boxborderw=5 : x=(w-text_w)/2 : y=(h-text_h)/2" \
 -codec:a copy \
 -y 'out-a.mp4'
ffmpeg \
 -i '02.jpg' \
 -vf drawtext="\text='Another Text' : fontcolor=white : fontsize=24 : box=1 : boxcolor=black@0.9 : boxborderw=5 : x=(w-text_w)/2 : y=(h-text_h)/2" \
 -codec:a copy \
 -y 'out-b.mp4'
ffmpeg \
 -i '03.jpg' \
 -vf drawtext="\text='Hello World' : fontcolor=white : fontsize=24 : box=1 : boxcolor=black@0.9 : boxborderw=5 : x=(w-text_w)/2 : y=(h-text_h)/2" \
 -codec:a copy \
 -y 'out-c.mp4'
ffmpeg \
 -i out-*.mp4 \
 -vf scale=768x420 \
 -c:v libx264 \
 -r 30 \
 -pix_fmt yuv420p \
 -y 'output.mp4'
echo "[End]"

  



  Thanks to all
Cengiz

  


• ffmpeg - Text fontcolor is changed (faded) because of alpha(I think). Is there any possibility to avoid this behavior ?

  13 mai 2019, par Bedrule Paul

  I am using following command

      ffmpeg -i ~/Desktop/input.mp4 -filter_complex  "color=black:100x100[c];\
  
  [c][0]scale2ref[ct][mv]; \
  
  [ct]setsar=1,split=1[t1]; \
  
  [t1]drawtext=text='Test Text 1':fontsize=36:fontcolor=#13348b\
  
  ,split[text1][alpha1]; \
  
  [text1][alpha1]alphamerge,rotate=30:ow=rotw(30)\
  
  :oh=roth(30):c=black@0[txta1]; \
  
  [mv][txta1]overlay=x='min(0,-H*sin(30))+500':\
  
  y='min(0,W*sin(30))+350':shortest=1" \
  
  ~/Desktop/result.mp4 -y

  I think alpha is the problem, but I don’t know how to avoid it.