More Optimizations Coming To LZHAM

[curaga]

Do they seriously trust compression schemes used by GPU vendors so little?

S3TC is lossy and bad quality, the newer ones are not supported in hardware? Contemporary hw does not support any lossless compression, nor enable bigger compression ratios by using bigger blocks for example.

[discordian]

Do they seriously trust compression schemes used by GPU vendors so little?

Nope, its just that the formats the GPUs understand natively are gimped for good reasons. They have to decode them pretty much on the fly and without much state.
Efficient compression algorithms however drag several MB of Tables along, if you ever tried to peel a single small file from a solid lzma archive then you may have noted that it can take just as long as decompressing the whole archive.

Civ5 has the textures compressed efficiently on HDD, then AFAIR unpacks them (CPU) and re-compresses them via GPU so the GPU can then directly decode them. There is compression-code for just that from Nvidia atleast, so I am not sure how custom their compression is (I guess not at all).

Btw, S3TC isnt state-of-the-art for quite a while. Still any format for realtime decompression of random small blocks will have fundamental limitations against any serial big-block formats.

[discordian]

This part doesn't make much sense to me.

They are different forms of compression, the one used to store stuff on disk has way more compression ratio (and/or might even be lossless) but needs to be processed serially, the one used during the game needs to fetch randomly small groups of pixels and is ideally supported by hardware directly.
Since not many games actually do this, you aren't alone in questioning the value.

Think of backing up your music as FLAC, and then compressing it to mp3 because one of your players doesn't support it.

You can read the paper about Civ5 texture compression here