Hi Paul, On Sat, 12 Dec 2015 12:03:39 +0000, Paul B Mahol wrote: > On 12/12/15, Jean Delvare <jdelv...@suse.de> wrote: > > 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? > > Non-refcounted frames are never writable. And color source is made of one > single > frame which is cloned multiple times. > Use different input file perhaps?
Thanks for the hint. That makes sense, and if I set the input to a still picture instead then av_frame_is_writable() indeed returns 1. However if I add replace "-frames:v 1" with "-loop 1 -frames:v 5", av_frame_is_writable() still returns 1. I expected the input picture to be cloned 4 times so it would no longer be writable, given your explanation above. Also if I change the input to a MPEG file, av_frame_is_writable() returns 0 again. So I still do not fully understand when frames are writable and when not. But -- Jean Delvare SUSE L3 Support _______________________________________________ ffmpeg-devel mailing list ffmpeg-devel@ffmpeg.org http://ffmpeg.org/mailman/listinfo/ffmpeg-devel
