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cadaver
Registered: Feb 2002
Posts: 1160 |
Exomizer on-the-fly loading/decompressing
Hey,
anyone want to share, what is the lowest disk interleave you've managed to use with on-the-fly Exomizer decompression while loading?
I'm currently at 11, using 2-bit transfer and a lame drivecode (using jobcodes only) + 1 sector buffering. However I don't think the drivecode is the problem; if I try to decrease to IL 10 the C64 often doesn't have to wait for the drive at all for the next sector's data, but occasionally the depack will take too long, resulting in missed revolution.
I've already done some optimization to the depack routine, including inlining getting a single bit (literal/sequence decision, and reading the gamma).
Don't think I would switch to another packer just for speed, but nevertheless interested in any battle stories. |
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Krill
Registered: Apr 2002
Posts: 2980 |
Quoting BitbreakerRegarding the size of the exomizer depacker (including tables) this would just be a small addition. Right, why does it have to be exomizer in the first place, which is neither fast nor small? :) |
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cadaver
Registered: Feb 2002
Posts: 1160 |
My top priority is still the compression ratio, over loading speed or runtime size.
Also, I have cases where a file is not only a single packed stream, but might consist of..
- first subfile memory allocation info (3 unpacked bytes)
- first subfile packed stream
- second subfile..
in which case out-of-order loading would need to support reading those unpacked bytes in between the packed streams.
+ have to support also Kernal loading with preferably drop-in replacements for opening a file and reading a byte, without any mandatory buffering. In this case Exomizer's API allows the easiest replacement, though the performance is not optimal compared to e.g. Doynamite, which always reads from a buffer. |
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Krill
Registered: Apr 2002
Posts: 2980 |
You don't want any of those pesky crackers come up with a shorter version, eh? :)
So yes, if 3 bytes shorter is what you want, and having the best pack ratio so far, then exomizer indeed.
The subfiles could be split into separate files for unpacked and ooo-loading. Then slap "IFFL"-style loading on top to make up for the block granularity overhead.
Kernal loading is not a problem, as ooo-loading and buffer-based depacking do not contradict it. My loader has Kernal load fallback and still supports ooo-loading and Doynax LZ. |
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cadaver
Registered: Feb 2002
Posts: 1160 |
I'll stop when I reach 0 blocks free on the diskside, so using Exo allows to cram the most content in :) |
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lft
Registered: Jul 2007
Posts: 369 |
Nah, you don't stop when you reach 0 blocks free. That's the starting point. From there on, you have to do some actual thinking about how to best represent each individual effect/level/whatever based on its content, to produce optimal input for the generic cruncher.
I admit I have limited experience of this for C64. For other platforms, though... |
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cadaver
Registered: Feb 2002
Posts: 1160 |
In MW4, I remember shuffling some dialogue around to improve compression, as well as saving only one way facing sprites (generate the flipped ones at runtime after loading) quite late into the project, when I had hit 0 blocks. This time I'm already doing the sprite flipping from the start though.
But yeah, something like reordering tiles/chars in levels (or patterns in songs) has the potential to save some additional space, without changing anything functionally. |
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Krill
Registered: Apr 2002
Posts: 2980 |
Why is adding another disk side not an option? :)
(Since you want Kernal loading as a fallback, denser custom formats and extended tracks are out of the question. Oh, and i guess you're using the directory track for storage already?) |
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cadaver
Registered: Feb 2002
Posts: 1160 |
I want to see the crackers reaction when they want to add an intro, but there's no space free :) Ie. do they use IFFL, add a "boot side", improve compression or what?
If we're being serious, a boot side would always be an option (free around 100 blocks), actual in-game disk flipping less preferable since you travel back and forth, and I'm not using the directory track yet. But I don't even know yet if I'll run into serious trouble, if I have extra space in the end then I'll just add extra cutscene pictures, movie credits end sequence or such. |
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algorithm
Registered: May 2002
Posts: 705 |
What lft also mentioned in a previous post. Its just as important (if not more important) to transform the data to make it more compressible or generate it before the packing. Even just simple methods such as low/high nibble swaps from byte pairs (for bitmap data) or delta for samples. |
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Didi
Registered: Nov 2011
Posts: 487 |
Don't expect any cracker to be really bothered by a full disk. ;-) |
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