1

I have this script which I am working on to encode a video into smaller file size:

echo off
set arg1=%1
set _filename=%~n1
set _extension=%~x1
shift
ffmpeg -i %arg1% -c:v h264_amf -crf 18 -preset slow -c:a aac -b:a 128k -movflags +faststart -vf scale=-2:480,format=yuv420p %_filename%.480P%_extension%

It accepts one argument which is the video file and outputs a new file.

Testing with a video file size of 815,050 KB the output was even bigger 1,554,650 KB specifically.

I'm using h264_amf for the reason I am encoding on a machine with AMD GPU on Windows.

My goal here is to convert a ton of videos to about 500MB (or lower if the input size is lower than 500MB) each regardless of the quality since it will be played in a AI-enhancing video player so quality of the output is not important.

What's the correct ffmpeg parameters to achieve this?

2

h264_amf does not support -crf or -preset. If you want a specific output file size with this encoder then use -rc cbr and set the appropriate bitrate with -b:v.

Example for 1000 second input with approximate 500 MB output:

(500 MB * 8000) = 4000000 kb / 1000 seconds - 128kb audio bitrate - ~1% muxing overhead = -b:v 3832k

Simple example command:

ffmpeg -i input -c:v h264_amf -rc cbr -b:v 3832k -c:a aac -b:a 128k output.mp4

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.