Remove AVI, add standardized some codec and container support

[a1batross]

Xash3D engine supports video playback.

Unfortunately for us, the code is known to be tied to Windows system codecs. In theory, it allows game creators to use any codec they like to. However, for eight years there was no a brave enough person to bring some universal decoder library, like ffmpeg, which is 3-4x times heavier and more complex than the engine itself.

My decision is to drop AVI support completely and instead provide a popular container and codec support, to make it easier for modders to use the engine functionality.

I think that's adding support for WebM container and AV1 codec is good for future perspective. WebM is highly popular, and almost any video software should support it at this time. AV1 video codec on the other hand is a new codec introduced few years ago, that have better compression compared to VP9. My only concern is software decoding, it must be efficient. Support for hardware decoding would be nice, but it's an out of scope and can be discussed later when this issue will be resolved.

[SNMetamorph]

Will be this functionality expandable? In other words, will it be possible to add support for other formats/codecs on mod side?

[a1batross]

Let's make the prototype first.

[mittorn]

From wikipedia: WebM: as a matter of formality, AV1 has not been sanctioned into the subset of Matroska known as WebM as of late 2019 also: https://www.webmproject.org/docs/container/ So webm subset seems does not cover AV1 at all

[a1batross]

VP9 seems to be a better choice for now. Older codecs than VP9 will provide worse compression, but newer is not yet implement in hardware. And there is no reason to depend on proprietary codecs like AVC or HEVC.

+ why we should limit ourselves to subset of Matroska when we can just use Matroska itself?