On 20/01/2021 03:06, owen s wrote:
with software libx264 using crop filter
crop=width:heigh:x:y, i could crop around a specific point. using
h264_vaapi and -vf crop=width:height
doesn't control the crop location.

also with libx264 -video_size=widthxheight worked, but with h264_vaapi, the
video resolution comes out to be the max size of the video framebuffer
65535x65535 in my case.

Can I set where the h264_vaapi crop x,y position and how do I control the
resolution after using h264_vaapi?

log file: http://0x0.st/-ifF.txt

This crops your 2560x1440 input to 2560x1440 so it is unsurprising that nothing 
happens.

More generally, cropping is supported by VAAPI filters but not by the encoder 
(due to internal API constraints which probably derive from actual hardware 
constraints).

Therefore, you should crop either before upload (if you are uploading) or before 
applying a filter (when staying in VAAPI surfaces).  If you aren't filtering at 
all (pure decode->encode), then you need to insert a null scale before the 
encode (which is an extra copy, but can't be avoided when the encoder doesn't 
support that input).

So:

ffmpeg -i ... -vf crop=...,format=nv12,hwupload -c:v h264_vaapi ...

ffmpeg -hwaccel vaapi -hwaccel_output_format vaapi -i ... -vf 
crop=...,scale_vaapi=... -c:v h264_vaapi ...

- Mark
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