Discourage the use of vf(select) as it's slow

[ishitatsuyuki]

av1an falls back to vf(select) if VS is not installed. Unfortunately it decodes the entire video until the crop point and is extremely wasteful of resources.

It should be either strongly discouraged from use or replaced with a proper trimming method (see https://stackoverflow.com/questions/18444194/cutting-the-videos-based-on-start-and-end-time-using-ffmpeg).

[shssoichiro]

Ideally, yes, we would want to make the select method faster. We want to make sure we do that in a way that is frame accurate, so for the time being I'll add a warning to users who select the "select" method. I'll leave this ticket open re. changing the method.

[redzic]

Perhaps we should just remove the select chunk method altogether? I'm not really sure if there's a real use case for it anyway.

[ishitatsuyuki]

When I didn’t have VS installed select was the default chunking method. Not sure if there are other fallbacks.

[redzic]

It shouldn't be possible for av1an to choose select chunking on its own, see

Av1an/av1an-core/src/vapoursynth.rs

Lines 45 to 53 in c7f3874

	pub fn best_available_chunk_method() -> ChunkMethod {
	if is_lsmash_installed() {
	ChunkMethod::LSMASH
	} else if is_ffms2_installed() {
	ChunkMethod::FFMS2
	} else {
	ChunkMethod::Hybrid
	}
	}

Are you sure it was select chunking that it chose and not hybrid chunking? Hybrid chunking should at least avoid decoding from the beginning for each chunk, but it's still not as good as VS chunk methods.

[ishitatsuyuki]

Hmm, I'm actually not sure. If what you say is true then it would have been the hybrid chunking method. I'll retest when I have time.