There seems to be multiple people at videolan dunking on rav1d, in notable part due to how it was done (transpile C to Rust, and cleanup afterwards). Perhaps they're Rust purists and don't think that's how it should have been done. Or perhaps they're not happy that rav1d proclaims that Rust is (almost) as fast as C when all the performance engineering efforts went in the ASM bits, that were copied verbatim from dav1d.

My best guess would be for the same reasons the ffmpeg twitter account has shown a lot of vitriol too: funding taken away from the original project towards another effort.

I would guess the author is young and smart, but hasn't spent much time working with others. I've seen this in other developers with lots of potential. It usually takes a few years of mentorship to smooth the rough edges.

I think the ffmpeg / libav controversy definitely showed that codec implementation is an area which doesn't attract only well adjusted people. Emulators have the same issue. It seems to be common about this very technical, very low level projects.

You sometimes get contributors which are very attached to their work and have strong feelings about how things should be done with the deadly combo of low / still developing social skills.

It definitely is oddly aggressive. They could just say that the rav1d bounty motivated them to look for improvements in dav1d and it would be an awesome result. There's nothing like healthy friendly competition. But this isn't it.

> making tools for more convenient work with C/C++ projects on Rust (as Python) is a more useful thing than trying to replace an already working dav1d solution (or any FOSS infrastructure) that has been tested by time, many contributors and most vulnerabilities have been closed. New projects will also have performance and vulnerability issues. No need to waste your time writing another bike, there are much more useful things.

This is their rationale, which you might disagree with, but I can’t notice any “vitriol” you’re talking about. Other people might have different opinions than yours about their favourite language, and that’s fine.

Well apparently the so called just 5% slower than dav1d is not true according to other benchmark, it's much slower.

It makes sense that rav1d would need a bunch of repr(C) because the initial conversion is just mindlessly derived from the C, so if there's C which just bit-copies part of a data structure this cannot possibly work in Rust unless we explicitly say "This structure needs to be laid out the same as in C".

It also sounds as though at least some of this "speed up" was assuming dav1d doesn't need big integers where actually it does, but only for larger images. I can well imagine that DVD resolution works fine with 16-bit variables where the Ultra HD blows up nastily.

> Even if rav1d closes the gap, who will ship rav1d over dav1d? More than 85% of dav1d is hand written assembly that rav1d takes as-is and calls via unsafe blocks. Is this really memory safety?

> The dav1d improvements must continuously be backported to rav1d, see the 82 closed PR's here [3]. Who is going to pay for this maintenance in perpetuity?

No one?

Isn't the point of rav1d to show that it's possible to write a performant encoder in semi-idiomatic Rust and that it doesn't have to be very different from one written in C?

It seemed pretty clear to me that rav1d was supposed to be a fun "research" side-project from its author shared with everyone and with an unclear future which will depends of what the community wants to actually do with it but I might be completely wrong.

Thanks! Is this the same hardware used here http://paste.debian.net/1374884?

Can you share what system was used (ARM CPU, OS, etc.)?

> The dav1d improvements must continuously be backported to rav1d, see the 82 closed PR's here

so basically the work is done in dav1d, but claimed in rav1d.

It really makes rust look like a parasite.

> Wouldn't -O3 with -Ofast do all code optimization for programmer.

No?

> Contributor dav1d claims 1-3% growth after his optimization, depending on video dataset payload. He nullified 1% optimization in rav1d, if the real growth was 3%, rav1d will not soon be able to equalize benchmark results.

Aren't you the contributor? (You have a very unique writing voice)

> Another question in theory can Rust be faster than C? If all possible optimizations are applied.

I don't see why not?

Other than that:

A) Great work!

B) Unsolicited advice, apologies: your technical acumen is being outshadowed by projection of motivations.

They're just programming languages.

There's no way to say one is definitely better than the other, and no guarantee one will be faster or slower than the other.

Your forebears had similar arguments about C and assembler.

Yet, neither of us is surprised to find there is no asmav1d. (and that's much more clean-cut of an argument w/r/t speed!)

(I don't think it was the goal of a long-running FOSS project to advertise Rust is almost as fast as C when they offered a bounty)

> Another question in theory can Rust be faster than C? If all possible optimizations are applied.

Very likely not at this stage, and maybe not for years to come. But I'll take increased memory safety and elimination of entire class of bugs for 1-3% performance loss even on the most critical paths (with many actual wins for Rust in many other cases).

While I do get what huge battery life implications might 5% differences in decoders make, I believe the current political climate mandates we use the most secure code we can and sacrifice smidgen bits of performance here and there for it.

It was known for decades that at one point we'll have to roll up our sleeves and pay up the security tech debt.

Sorry for the slightly philosophical message but I've no desire to comment on the actual tech details here.