Certainly there's a complexity argument to be made, because you don't actually need compression just to hold a bundle of files. But these days zip just works.
The perf measurement charts also make no sense. What exactly are they measuring?
Edit:
This reddit post seems to go into more depth on performance: old.reddit.com/r/selfhosted/comments/1qi64pr/comment/o0pqaeo/
And what's the point of aligning the files to be "DirectStorage-ready" if they're going to be JPEGs, a format that, as far as I know, DirectStorage doesn't understand?
And the author says it's a problem that "Metadata isn't native to CBZ, you have to use a ComicInfo.xml file.", but... that's not a problem at all?
The whole thing makes no sense.
Note that he doesn't quite say, when asked pointblank how much AI he used in his erroneous microbenchmarking, that he didn't use AI: https://reddit.com/r/selfhosted/comments/1qi64pr/i_got_into_...
Which explains all of it.
Kudos to /u/teraflop, for having infinitely more patience with this than I would.
It used to be a decent resource to learn about what services people were self hosting. But now, many posts are variations of, “I’ve made this huge complicated app in an afternoon please install it on your server”. I’ve even seen a vibe-coded password manager posted there.
Reputable alternatives to the software posted there exist a a huge amount of the time. Not to mention audited alternatives in the case of password managers, or even just actively maintained alternatives.
https://old.reddit.com/r/selfhosted/comments/1qfp2t0/mod_ann...
Every new readme, announcement post, and codebase is tailored to achieve maximum bloviation.
No substance, no credibility———just vibes.
I haven't read the reddit thread or anything but If the author coded it by hand or is passionate about this project, he will probably understand what we are talking about.
But I don't believe its such a big deal to have a benchmark be written by AI though? no?
The aspect of integrity checking speed in a saturated context (N workers, regardless if its multiple workers per file, or a worker per file), CRC32(C) seems to be nearly twice as fast https://btrfs.readthedocs.io/en/latest/Checksumming.html
ZIP can also support arbitrary metadata.
I think this could have all been backported to ZIP files themselves
"I got into an argument on Discord about how inefficient CBR/CBZ is, so I wrote a new file format. It's 100x faster than CBZ."
It has some charts, notes and comments
Here's the old.reddit link: https://old.reddit.com/r/selfhosted/comments/1qi64pr/i_got_i...
A multi-resolution image format would make more sense than optimizing the archive format. There would also be room for additional features like multi-language support, searchable text, … that the current "jpg in a zip" doesn't handle (though one might end up reinventing DJVU here).
There are already quite a few cbz archives in the wild that contain jxl encoded images. That's a multi-resolution format at least to the extent that it supports progressive decoding at fixed levels that range from 1:8 to as high as 1:4096. I think it might also support other arbitrary ratios subject to certain encoding constraints but I'm less clear on that.
Readers might need to be updated to make use of the feature in an intelligent manner though. The jxl cbzs I've encountered either didn't make use of progressive encoding or else the software I used failed to take advantage of it - I'm not sure which.
I didn't even realize random access is not possible, presumably because readers just support it by linear scanning or putting everything in memory at once, and comic size is peanuts compared to modern memory size.
I suppose this becomes more useful if you have multiple issues/volumes in a single archive.
I don’t understand what’s the point of any of this over a minimal subset of PDF (one image per page).
So, like ZIP?
> Uses XXH3 for integrity checks
I don’t think XXH3 is suitable for that purpose. It’s not cryptographically secure and designed mostly for stuff like hash tables (e.g. relatively small data).
Neither is CRC32. I'm pretty sure xxhash is a straight upgrade compared to CRC32.
Unclear; performance should be pretty similar to CRC32 (depending on implementation), and since integrity checking can basically be done at RAM read speeds this should not matter either way.
Do the emojis not show for you?
[edit]
If I download the README I can see them in every program on my system except Firefox. I previously had issues with CJK only not displaying in Firefox, so there's probably some workaround specific to it...
[Edit 2] If Firefox uses "Noto Color Emoji" (which Firefox seems to use as fallback for any font that doesn't have Emoji characters; fc-match shows a different result for e.g. :charset=2705) then I get nothing, but if I force a font that has the emoji in it (e.g. FreeSerif) then it renders. Weird.
---
For example they make a big deal about each archive entry being aligned to a 4 KiB boundary "allowing for DirectStorage transfers directly from disk to GPU memory", but the pages within a CBZ are going to be encoded (JPEG/PNG/etc) rather than just being bitmaps. They need to be decoded first, the GPU isn't going to let you create a texture directly from JPEG data.
Furthermore the README says "While folders allow memory mapping, individual images within them are rarely sector-aligned for optimized DirectStorage throughput" which ... what? If an image file needs to be sector-aligned (!?) then a BBF file would also need to be, else the 4 KiB alignment within the file doesn't work, so what is special about the format that causes the OS to place its files differently on disk?
Also in the official DirectStorage docs (https://github.com/microsoft/DirectStorage/blob/main/Docs/De...) it says this:
> Don't worry about 4-KiB alignment restrictions
> * Win32 has a restriction that asynchronous requests be aligned on a
> 4-KiB boundary and be a multiple of 4-KiB in size.
> * DirectStorage does not have a 4-KiB alignment or size restriction. This
> means you don't need to pad your data which just adds extra size to your
> package and internal buffers.
There are zip-based formats that align files so they can be mmap'd as executable pages, but that's not what's happening here, and I've never heard of a JPEG/PNG/etc image decoder that requires aligned buffers for the input data.
Is the entire 4 KiB alignment requirement fictitious?
---
The README also talks about using xxhash instead of CRC32 for integrity checking (the OP calls it "verification"), claiming this is more performant for large collections, but this is insane:
> ZIP/RAR use CRC32, which is aging, collision-prone, and significantly slower
> to verify than XXH3 for large archival collections.
> [...]
> On multi-core systems, the verifier splits the asset table into chunks and
> validates multiple pages simultaneously. This makes BBF verification up to
> 10x faster than ZIP/RAR CRC checks.
But that doesn't matter because to actually check the integrity of archived files you want to use something like sha256, not CRC32 or xxhash. Checksum each archive (not each page), store that checksum as a `.sha256` file (or whatever), and now you can (1) use normal tools to check that your archives are intact, and (2) record those checksums as metadata in the blob storage service you're using.
---
The Reddit thread has more comments from people who have noticed other sorts of discrepancies, and the author is having a really difficult time responding to them in a coherent way. The most charitable interpretation is that this whole project (supposed problems with CBZ, the readme, the code) is the output of an LLM.
It seems that JPEG can be decoded on the GPU [1] [2]
> CRC32 is limited by memory bandwidth if you're using a normal (i.e. SIMD) implementation.
According to smhasher tests [3] CRC32 is not limited by memory bandwidth. Even if we multiply CRC32 scores x4 (to estimate 512 bit wide SIMD from 128 bit wide results), we still don't get close to memory bandwidth.
The 32 bit hash of CRC32 is too low for file checksums. xxhash is definitely an improvement over CRC32.
> to actually check the integrity of archived files you want to use something like sha256, not CRC32 or xxhash
Why would you need to use a cryptographic hash function to check integrity of archived files? Quality a non-cryptographic hash function will detect corruptions due to things like bit-rot, bad RAM, etc. just the same.
And why is 256 bits needed here? Kopia developers, for example, think 128 bit hashes are big enough for backup archives [4].
[1] https://docs.nvidia.com/cuda/nvjpeg/index.html
[2] https://github.com/CESNET/GPUJPEG
[1] claims 15 GB/s for the slowest implementation (Chromium) they compared (all vectorized).
> The 32 bit hash of CRC32 is too low for file checksums. xxhash is definitely an improvement over CRC32.
Why? What kind of error rate do you expect, and what kind of reliability do you want to achieve? Assumptions that would lead to a >32bit checksum requirement seem outlandish to me.
[1] https://github.com/corsix/fast-crc32?tab=readme-ov-file#x86_...
What bothers me with probability calculations, is that they always assume perfect uniformity. I've never seen any estimates how bias affects collision probability and how to modify the probability formula to account for non-perfect uniformity of a hash function.
What makes you say this? I agree that there are better algorithms than CRC32 for this usecase, but if I was implementing something I'd most likely still truncate the hash to somewhere in the same ballpark (likely either 32, 48, or 64 bits).
Note that the purpose of the hash is important. These aren't being used for deduplication where you need a guaranteed unique value between all independently queried pieces of data globally but rather just to detect file corruption. At 32 bits you have only a 1 out of 2^(32-1) chance of a false negative. That should be more than enough. By the time you make it to 64 bits, if you encounter a corrupted file once _every nanosecond_ for the next 500 years or so you would expect to miss only a single event. That is a rather absurd level of reliability in my view.
Readme in SMHasher test suite also seems to indicate that 32 bits might be too few for file checksums:
"Hash functions for symbol tables or hash tables typically use 32 bit hashes, for databases, file systems and file checksums typically 64 or 128bit, for crypto now starting with 256 bit."
For detecting file corruption the amount of data alone isn't the issue. Rather what matters is the rate at which corruption events occur. If I have 20 TiB of data and experience corruption at a rate of only 1 event per TiB per year (for simplicity assume each event occurs in a separate file) that's only 20 events per year. I don't know about you but I'm not worried about the false negative rate on that at 32 bits. And from personal experience that hypothetical is a gross overestimation of real world corruption rates.
> It seems that JPEG can be decoded on the GPU [1] [2]
For a comic book the performance-sensitive part is loading the current and adjoining pages, which can be done fast enough to appear instant on the CPU. If the program does bulk loading then it's for thumbnail generation which would also be on the CPU.
Loading compressed comic pages directly to the GPU would be if you needed to ... I dunno, have some sort of VR library browser? It's difficult to think of a use case.
> According to smhasher tests [3] CRC32 is not limited by memory bandwidth.
> Even if we multiply CRC32 scores x4 (to estimate 512 bit wide SIMD from 128
> bit wide results), we still don't get close to memory bandwidth.
Look at https://github.com/corsix/fast-crc32 for example, which measures 85 GB/s (GB, GiB, eh close enough) on the Apple M1. That's fast enough that I'm comfortable calling it limited by memory bandwidth on real-world systems. Obviously if you solder a Raspberry Pi to some GDDR then the ratio differs.
> The 32 bit hash of CRC32 is too low for file checksums. xxhash is definitely
> an improvement over CRC32.
File checksums don't have the same size limit so it's fine to use 256- or 512-bit checksum algorithms, which means you're not limited to xxhash.
> Why would you need to use a cryptographic hash function to check integrity
> of archived files? Quality a non-cryptographic hash function will detect
> corruptions due to things like bit-rot, bad RAM, etc. just the same.
> And why is 256 bits needed here? Kopia developers, for example, think 128
> bit hashes are big enough for backup archives [4].
For archival you only need to compute the checksums on file transfer and/or periodic archive scrubbing, so the overhead of SHA256 vs SHA1/MD5 doesn't really matter.
I don't know what kopia is, but according to your link it looks like their wire protocol involves each client downloading a complete index of the repository content, including a CAS identifier for every file. The semantics would be something like Git? Their list of supported algorithms looks reasonable (blake, sha2, sha3) so I wouldn't have the same concerns as I would if they were using xxhash or cityhash.
Do LLMs perform de/serialization by casting C structs to char-pointers? I would've expected that to have been trained out of them. (Which is to say: lots of it is clearly LLM-generated, but at least some of the code might be human.)
Anyway, I hope that the person who published this can take all the responses constructively. I know I'd feel awful if I was getting so much negative feedback.
So the whole DirectStorage thing is just a nothingburger. The author glosses over the fact that decoding images on GPU is not possible (or at least very impractical).
It would be one thing if you were designing a format to optimize feeding data to an ML model during training but that's not even remotely what this is supposed to be.