[FFmpeg-devel] Question about av_frame_is_writable

[Jean Delvare]

Hi all,

Can av_frame_is_writable() ever return 1, and if so, when?

Context: I am testing corner cases of the delogo filter. To my
surprise, even for a simple test case such as:

$ ffmpeg -f lavfi -i "color=color=white:size=24x24" -frames:v 1 -vf "delogo=7:3:8:8" -f image2 debug.png

av_frame_is_writable() returns 0, which disables direct mode of the
delogo filter and forces the allocation of a new buffer. My
understanding was that we were trying to avoid allocation and data copy
as much as possible, for performance reasons, and with such a simple
filter graph I can't see why we can't modify the video data in-place.
Can someone enlighten me?

Thanks,
-- 
Jean Delvare
SUSE L3 Support