CODEWITHSUNDEEP
ffmpeg
user270700
user270700

Reputation: 759

decreasing video resolution using ffmpeg increases file size

I try to decrease video resolution using ffmpeg by,

ffmpeg -y -hide_banner -loglevel panic -i "input.mp4" -vf "scale=-1:256" -q:v 1 -c:a copy -threads 1 "output.mp4"

But the video file size is increased. The original height is larger than 256. Why the file size is increased though the resolution is decreased?

Upvotes: 1

Views: 604

Answers (2)

Amal Irfan KC
Amal Irfan KC

Reputation: 1

I had just some suggestions, but then I decided to test them out.

https://trac.ffmpeg.org/wiki/Encode/VP9

this page shows some methods to configure the quality.

I tried average, constant and constraint quality mode.

the video is 2.4 MB, after resize the 7.8 seconds long video file's sizes are around: 2.7MB, 4MB, 2.0MB; respectively.

this is how to use constraint quality:

ffmpeg -i input -crf 30 -b:v 2M output

or

ffmpeg -i input -minrate 500k -b:v 1000k -maxrate 2000k output

when using crf, lower the value higher the file size and quality.

Upvotes: 0

szatmary
szatmary

Reputation: 31101

Because bitrate and resolution are independent variables. -q:v 1 basically means to use as many bits as necessary to keep the video nearly identical to the (scaled) input.

Upvotes: 1

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