Add transcoding to AV1 to default set

[petterreinholdtsen]

For this to work in production, a new fileformat 'av1' must be
added.

Fixes #127

[petterreinholdtsen]

The travis test fail with "Unknown encoder 'libaom-av1'" because ffmpeg on the test machine is too old. I suspect the same is the case on the transcoding host, so we need to upgrade both before we put this change into production.

[odinho]

I also guess this will be slow as molasses.

Maybe add a special field to the Video that decides whether it should do this or not? Well, actually, we don't really have a lot of traffic, just NUUG and P7, so it can probably use a lot of time to churn on that. But this might be something we have to ax or throttle if we start getting more people running.

I've wanted to split move_and_process responsibilities to also have a batchprocess or another service that does such lower-priority things. Kinda like the off-time thingy you made, but it's own file, it's own service only doing that. That way, we can quickly get JPEG preview, and some metadata and leave all the rest to further processing. ogv vod stream would probably be the next thing that should run in mid-priority, and then broadcast, - and finally at batch priority any extras such as AV1.

But the nice thing is that we don't really have to do it, yet, since we're not seeing these problems yet. But it's good to have in the back of our minds so our designs doesn't shut the possibility out later.

[petterreinholdtsen]

I guess the daemon should be able to run several transcoders in the background and in parallell, to avoid blocking completely while a slow transcoder is running. It would reduce the impact on horribly slow transcoders as the av1 one.

[odinho]

My loose plan is just to run several instances of the same program. We can easily nice it and also say a program should do --only-mime video/ogv or some such. The moving part should then be split out of course, and the way it picks jobs is a bit different. Whay do you think?

[petterreinholdtsen]

I suspect it is best to have one controller for all transcoding, to reduce the chance of overloading the machine with too many parallell processes. Perhaps it is better to extend the 'period' system(#159) to run background processes, and do av1 transcoding when there is little else to do?

[odinho]

Not overloading the machine is the kernel's job. :) We'll just have a niceness on all the processes. It shouldn't be a big problem to always have some jobs running - the scheduler of the OS will make sure important things gets done timely enough.

But it's possible to do it during idle as well. We'll just do whatever is simplest and iterate when we get to the point. 🤷‍♂️