[SOLVED] ffmpeg doesn't actually resize video

[yetanotherlogin]

Hello

For some reason, I can't get ffmpeg to resize a 848x480 video (H264/AAC) to 640x480.

I tried the following commands, but both end up with the same original size, although VLC says the output video is 640x480:

ffmpeg.exe -report -i input.mp4 -shortest -c:v libx264 -vf scale=640:480 -pix_fmt yuv420p -strict experimental -c:a aac -ab 128k -ar 48000 -strict -2 -f mp4 output.mp4

ffmpeg.exe -report -i input.mp4 -shortest -c:v libx264 -s 640x480 -pix_fmt yuv420p -strict experimental -c:a aac -ab 128k -ar 48000 -strict -2 -f mp4 output.mp4

Any idea why?

Thank you.

[Baldrick]

What do you identity the video frame size with? ffmpeg, Mediainfo?

[yetanotherlogin]

I just play the output video in VLC and check Tools > Codec Information.

Are "-vf scale=640:480" or "-s 640x480" the right switches to change the size of a video, or should I use something else?

[jagabo]

I tried both your command lines and they both worked. A random 1280x720 video was resized to 640x480. It was properly flagged to play back at the original 16:9 aspect ratio. Are you looking to squish the video so it plays 4:3 instead of 16:9?

[yetanotherlogin]

Thanks for the feedback.

I was just trying to convert a video so that it would go from 848x480 to a more standard 640x480. I'll investigate further.

[jagabo]

848x480 is a ~16:9 aspect ratio. 640x480 is a 4:3 aspect ratio. The issue isn't what frame size you want, ffmpeg is giving you that, it's what aspect ratio you want the video displayed at.

[yetanotherlogin]

Thanks for the info. I'll read up about changing aspect ratio.

[jagabo]

If you want the resulting video to display 4:3 add "-aspect 4:3". For example:

ffmpeg.exe -report -i input.mp4 -shortest -c:v libx264 -vf scale=640:480 -aspect 4:3 -pix_fmt yuv420p -strict experimental -c:a aac -ab 128k -ar 48000 -strict -2 -f mp4 output.mp4

[yetanotherlogin]

Thank you.