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• I want to crop videos with black frames on top and bottom

  10 février 2019, par jennie

  I want to crop videos with black frames on the bottom and top according to the frame rate as described in the video after crop

  how with ffmpeg ? How to crop Black Bars from Video

  Can you help me ! thank you so much !

  I want to crop videos with black frames on the bottom and top follow the scale as described in the video .

  Example image video

  video image after crop

  video after crop

• What is the most efficient way of stacking two videos using ffmpeg ?

  4 octobre 2024, par technical_difficulty

  I want to stack two videos of a talk together vertically using ffmpeg. One shows the presentation (slides) and one shows the speaker. Since I want to do this for several talks, I'd like to do this in a more general way and as efficiently as possible. Most of the time the videos have different resolutions and aspect ratios.

  


  My current workflow is :

  


  


  1. Scale the video with the lower resolution up to match the resolution of the other video :
ffmpeg -i video1.mp4 -s 1920x1080 -c:a copy video1_upscaled.mp4

     


  


  2. Stack the two videos :
ffmpeg -i video1_scaled.mp4 -i video2.mp4 -filter_complex vstack=inputs=2 combined.mp4

     


  


  


  The videos are between one and two hours long and the commands do take a while to complete. Is there any way of saving some time ?

  


  Would it be faster to put black bars/borders around the smaller video instead of scaling it to the size of the other one ? Can the stacking be done in a more efficient way ? Would it help a lot if those two steps were combined into one ?

  


  Some information that might be relevant :

  


  

  • it's always exactly two videos to stack vertically, one above the other

  


  • the quality of the video is not incredibly important, both having the resolution of the video with the lower resolution would be perfectly fine

  


  • disk space is not an issue

  


  • the resolution and aspect ratio of the videos are known (use any for your example)

  


  • both videos have the same audio

  


  • both videos have the exact same length

  


  


• FFMpeg : 2 pass encoding, first with CRF and second with maxrate of first pass average bitrate ?

  28 septembre 2022, par Alireza Rinan

  I usually do conversions with ffmpeg 1 pass CRF 22 with maxrate 1400k for some movies to convert them to 720p and generate smallest size with best quality, the parameters I use is :

  


  c:v libx264 -vf format=yuv420p,scale=1280:-2 -crf 22 -maxrate 1400k -bufsize 7000k


  


  Doing this too much I found that apart from the black bars that reduces bitrate, the color theme, number of high movement scenes... etc affects the bitrate too much, CRF 22 makes sure you get constant quality at every scene, that makes bitrate reaches my maximum 1400k at some scenes while the reset of the scenes in some movies are barely 800k, this result the average bitrate for a same movie reaches for example about 1100k, for these movies I do the encoding again with lower maxrate
(Ex:1100k) and I get same quality with lower average rate 1000k.

  


  Now I'm wondering is there any automated method in 2 pass to get same result ?
For example doing the first pass in CRF 22 and the second pass at average bitrate of first pass to lower the quality of those bitrate rages in first pass ?