Hello,
I have been experimenting with using the video crop and transpose
filters with ffmpeg (version 2.5.2 on Windows) to convert 4K video into
1080p video without scaling. When I combine these filters in a 1 pass
operation, I get an output (File4.mp4) that is about 4X larger than it
should be. But, when I split the same operation into 2 passes, I get an
output (File3.mp4) that seems to be the correct size. The details are:
Crop and transpose in 1 pass:
ffmpeg -i File1.mp4 -vf crop=1080:1920:0:0 -vf transpose=2 File4.mp4
File sizes in bytes:
File1.mp4 79,889,077 (Input 4K Video)
File4.mp4 25,918,758 (Excessive Size)
Crop and transpose in 2 passes:
ffmpeg -i File1.mp4 -vf crop=1080:1920:0:0 File2.mp4
ffmpeg -i File2.mp4 -vf transpose=2 File3.mp4
File sizes in bytes:
File1.mp4 79,889,077 (Same Input 4K Video)
File2.mp4 6,994,548
File3.mp4 5,777,801 (Correct Size)
All of these files can be played with ffplay, but I use other video
players and they have trouble playing File4.mp4.
It is not a big problem to use 2 passes, but I'm curious if this is a
known issue or am I missing something?
Thanks, Clay
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