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Balrogg: Demonically compacting (up to 15%) lossless Vorbis/Opus recompressor
- EdSchouten 1mo agoInteresting that it doesn’t use the same open source license as Vorbis/Opus itself. Otherwise improvements like these could be upstreamed?
- merbanan 1mo agoVorbis sends the entropy tables in the actual file at the start. https://www.xiph.org/vorbis/doc/Vorbis_I_spec.html#x1-470003 https://www.xiph.org/vorbis/doc/Vorbis_I_spec.html#x1-470003 If you have the complete file you can calculate the optimal ones. In a streaming scenario that does not work and you have use something you think is good.
- eru 28d agoI wonder if you could send new tables every so often in your stream?
- BoingBoomTschak 1mo agoThose .blr extensions in the examples are making me doubt: the result is still conformant and playable ogg Vorbis/Opus, right?
- sinnet3000 1mo agoFrom what I can see, it's more like a specialized ZIP-like compressor for Vorbis/Opus files. You archive them on blr, and decompress them back to the original format.
- ncruces 29d agoKinda like what Dropbox Lepton did for JPEG back then. https://github.com/dropbox/lepton https://github.com/dropbox/lepton
- BoingBoomTschak 29d agoAh, it's basically a PAQ context.
- embedding-shape 29d agoSimpler: it's basically ZIP but specific to one format.
- bigC5560 1mo agoI just tested this out for myself and I was unable to play the .blr file in VLC or using ffplay. It is not recognized as anything by ffprobe either. So it seems like you need to decompress it to play it in a standard player unfortunately.
- RicoElectrico 29d agoThere is a long history of compressors that replace the entropy coding layer of a codec with something else entirely. This is exactly it.
- tux3 1mo agoSo, it looks like this tries to build a model (or rather, multiple layers of models combined with something called context mixing[0]), potentially analyzing the whole file first? Is it fair to call this a very fancy entropy coder, replacing the last phase of what a traditional audio codec does (the lossless part, after quantization)? I like the code style, this is pretty nice C. It's refreshing to see human code. [0]: https://en.wikipedia.org/wiki/Context_mixing https://en.wikipedia.org/wiki/Context_mixing
- RicoElectrico 29d ago> I like the code style, this is pretty nice C. Or is it? https://github.com/iczelia/balrogg/blob/7008bdc10ff25ad871052011ef4654473c9adb47/src/cm.c#L92 https://github.com/iczelia/balrogg/blob/7008bdc10ff25ad87105...
- tux3 29d agoI admit I'm not a fan of the loop macros, or writing constants like 0xd80000 in decimal, or having all of that code inlined with no further explanation or git history. But I think it's just that this file is lifting parts of the logic from PAQ8 (the inlined num_states/next_state named in a comment sure look exactly like PAQ functions translated into C, which, kudos to PAQ for having extensive comments in their code by the way). I'm a bit disappointed that PAQ isn't mentioned in the README, and only very obliquely in the code, if that's where those functions come from. PAQ is GPLv3, at least a mention could have been nice (assuming I'm not wrong about the source of that logic).
- palaiologos 29d agoI use the PAQ terminology as it is likely to be familiar to other compression experts. However, the lineage to PAQ is very, very limited, and many other compressors also re-use its common ideas.
- tux3 29d agoI see, my bad. I tried to follow the comment and jumped to conclusions, sorry about that.
- sinnet3000 1mo agoThe git username sounded familiar, it's from the same developer that created bzip3.
- slyall 28d agoYes. https://github.com/iczelia/bzip3 https://github.com/iczelia/bzip3
- functionmouse 29d agoWhy was this written with explicit Windows 95 support? Just 'cuz?
- lightedman 29d agoProbably the same reason it was written with explicit DOS support.