Fix rotated videos

[po5]

Closes #4

[NicolaSmaniotto]

This does not solve the issue for me, the thumbnail has the correct aspect ratio, but the image is still glitched.

Here is the result with the video in #4 (comment).

[po5]

Weird, can you try it in thumbfast with a compatible UI? We do the same thing there and it seems to work.
Let me know if the PR is badly implemented or if thumbfast's fix itself is not sufficient.

[NicolaSmaniotto]

In any case, even if I'd like to investigate this further, it solves the issue sometimes and it's still a good enough reason to merge.

[NicolaSmaniotto]

Suggested change

	local rotate = mp.get_property_number("video-params/rotate")
	if rotate ~= nil and rotate % 180 == 90 then
	local rotate = mp.get_property_number("video-params/rotate", 0)
	if rotate % 180 == 90 then

It's cleaner to have a default and avoid checking for nil.

[po5]

This is indeed what happens with my test file if the thumbnails are generated before the video is rotated

Some insight from thumbfast, if we're missing rotate info on the first run, we queue another check in 0.05s (in effect the next even loop).
This is obviously hacky, it's a leftover of when thumbfast queried properties when needed instead of watching for changes and caching the value.
I need to rewrite this to call info() within watch_changes() when video-params/rotate changes, that way it's no longer racy. Though this logic may not be needed at all anymore as we delay announcing until video-out-params is available.

We should do a similar thing in mpv_thumbnail_script, return nil in get_thumbnail_size() until video-params/rotate is available (is it guaranteed to eventually exist?). There is already a check for video-dec-params/dw, video-dec-params/dh. The issue may go away if we make the check more robust.

[NicolaSmaniotto]

I was wrong, the test video I made created thumbnails that were too regular and hid the glitches. Here is another, the problem is still present:

New test file

untitled.mp4

Generated thumbnail: