A while ago, me and Mattrizzle from dkc-atlas figured out how the DMA code from the DKC series worked, and I found out that the animated sprites didn't have any pixel-level compression. The only space saving technique was carefully placed 8x8 and 16x16 sprites, which also saved on vram space and DMA bandwidth.
It makes me wonder if the DKC games were able to fit so many frames without compressing the tile patterns that make up the objects, was compressed graphics really that widely use, and were they really necessary for most games? I think most people were lazy about metasprites, and just used big rectangular metasprites like 32x32 or 32x64.
Two words: Lunar Compress.
Super Mario World graphics are compressed. Contra (U) graphics are compressed. Levels are pretty much always compressed, be it through object-based maps (Super Mario series) or meta-metatiles (Mega Man series, Blaster Master, Sonic series). Perhaps compression was more common before 32 Mbit carts became expected. Some Super NES coprocessors, in fact, exist for the sole purpose of compression (SDD1 and SPC7110).
By careful 8x8 placement, do you mean something like
this example?
Why does SFA2 have such long load times? Why have a compression chip if you're not going to use it in real time?
I haven't reverse engineered the game so I don't know but I suspect the long loading times are for the voice samples that are transfered to the SPC700, and have nothing to do with the graphics compression chip.
Is this SNES specific? I imagine that NES games are limited in the kinds of compression they use because of the little amount of RAM (when they didn't have extra RAM in the cart). A lot of them didn't even need graphics compression because they use CHR-ROM.
But no matter the console, storage space always becomes cheaper later in its life, and effects that need tons of uncompressed data in order to be performed in realtime start to become tempting to developers.
I used a form of compression in the FF2e/FF2j intro replacement for Neo Demiforce (for the graphics) -- I had to, because the amount of free space in FF2j was extremely limited.
So in other words, compression was widely used, but the difference was subtle, because tighter compression would've been a strain on the hardware.
I wonder if it is possible, with more elaborate compression schemes, to fit Dark Stalkers arcade game onto a 32meg cartridge, because the sprites in that game look like they can be compressed to death. There are plenty of places where the same color is repeated 50 pixels in a row.
Yes, that game appears to be
flat shaded.
Decrypt the Darkstalkers ROMs and zip up the decrypted ROMs to get an estimate of what compression can do. There are stronger codecs than DEFLATE used in Zip, and there are faster ones, but it should give you an idea.