Support for GIF looping in recorded video output

[ztangent]

Description

Adds the loop option to the VideoStreamOptions struct, and adds loop as a keyword argument to VideoStream, which is passed on to FFMPEG. This allows control over the number of times a GIF is looped for videos produced by record.

Type of change

• New feature (non-breaking change which adds functionality)

Checklist

• Added an entry in NEWS.md (for new features and breaking changes)
• Added or changed relevant sections in the documentation
• Added unit tests for new algorithms, conversion methods, etc.
• Added reference image tests for new plotting functions, recipes, visual options, etc.

[asinghvi17]

This looks pretty cool!

Is there a way to test that this works in tests? For example, if I try to set loop=2 and load it using ffmpeg, would I get 2x the frames and time?

[asinghvi17]

Suggested change

	(loop === nothing) && (loop = 0)
	isnothing(loop) && (loop = 0)

[ztangent]

I was trying to maintain consistency with the earlier lines of code by using === instead of isnothing, but if you prefer it this way, happy to switch!

[ztangent]

@asinghvi17 Unfortunately I don't think there's an easy way to check based on the number of frames, or length of the video, alone -- it looks like the loop count for animated GIFs is stored somewhere in the header of the file (see https://en.wikipedia.org/wiki/GIF#Animated_GIF) and I'm not sure how to use FFMPEG to look up that number. Maybe it's possible to just look at that byte number (31D) directly?

[SimonDanisch]

Thanks!