[terrelln]

Meta drove the Zstandard content encoding, but Google drove the adoption of Zstandard in Chrome.

The faster Brotli levels could probably be made to match Zstandard’s compression speed. But we’ve invested a lot in optimizing these levels, so it would likely take significant investment to match. Google is also contributing to improving the speed of Zstandard compression.

A cheaper conversion from Zstandard to Brotli is possible, but I wouldn’t really expect an improvement to compressed size. The encoding scheme impacts how efficient a LZ coding is, so for Brotli to beat Zstandard, it would likely want a different LZ than Zstandard uses. The same applies for a conversion from Brotli to Zstandard.

[lifthrasiir]

The conversion is meant to avoid the expensive backreference optimization when it has been already done once by Zstandard, because you can't prepend a Zstandard bitstream with a Brotli bitstream without turning one to another. But well, I think such hybrid scheme is hard to make when the latency is at stake.