On Fri, Oct 8, 2021 at 2:11 PM Michael Koch <astroelectro...@t-online.de> wrote:
> I'd like to suggest to revert this patch for the v360 filter: > http://ffmpeg.org/pipermail/ffmpeg-cvslog/2020-October/124887.html > > Why should it be reverted? > -- Because after this patch, the yaw, pitch and roll angles have a > different meaning. If they are set in the command line, they are > interpreted as absolute angles. However if they are sent via sendcmd, > they are interpreted as relative angles. > -- As far as I know, no other filter has such behaviour where an option > gets a different meaning if it's set via sendcmd. > -- It's impossible to test a rotation in the command line, and later set > the same rotation via sendcmd. The result would be totally different. > -- It breaks previously correct behavior. See for example chapters 2.111 > and 2.115 in my book: > http://www.astro-electronic.de/FFmpeg_Book.pdf > -- It's undocumented. > -- I don't see any workaround to simulate an absolute rotation with > relative rotations. I've tried it but it doesn't work. It might work for > one rotation axis, but if two or three axes are involved simultaneously, > it gets extremely complicated. > > Why was this patch made? > -- Because there was a problem with gimbal lock in some rare cases. I > never saw this problem. > Invalid reasoning. Absolute rotations give those issues. Using linear interpolation for absolute or relative rotation is flawed approach and give various broken results for non-trivial rotations. Filter is meant to be used interactively and not via sendcmd. > What's the correct way to solve this problem? > -- Most important is to revert this patch. That means there will be > gimbal lock in some rare cases. The user has to take care of it, and > avoid these rare cases. > -- New options could be added for relative rotations: rel_yaw, > rel_pitch, rel_roll. Then the user could decide if he prefers absolute > or relative rotations. However from my point of view, I don't need > relative rotations. > > See also ticket 9447. > > Michael > > _______________________________________________ > ffmpeg-devel mailing list > ffmpeg-devel@ffmpeg.org > https://ffmpeg.org/mailman/listinfo/ffmpeg-devel > > To unsubscribe, visit link above, or email > ffmpeg-devel-requ...@ffmpeg.org with subject "unsubscribe". > _______________________________________________ ffmpeg-devel mailing list ffmpeg-devel@ffmpeg.org https://ffmpeg.org/mailman/listinfo/ffmpeg-devel To unsubscribe, visit link above, or email ffmpeg-devel-requ...@ffmpeg.org with subject "unsubscribe".
