Balrogg: Lossless Vorbis/Opus recompressor shrinks files up to 15%
Balrogg: Demonically compacting (up to 15%) lossless Vorbis/Opus recompressor
Balrogg is a new open-source tool that losslessly recompresses Ogg Vorbis and Opus audio files, typically reducing them by 8-12% and 3-8% respectively, with up to 15% savings. It works by optimizing the bitstream without altering the decoded audio. The project is written in C99, supports batch processing, and offers effort levels from -1 to -9, balancing compression ratio and speed. It refuses files it cannot reproduce exactly and has been tested on Windows 95 and MS-DOS, showcasing its portability.
Archives are typically 8-12% smaller than `.ogg` files and 3-8% smaller than `.opus` files.
- tux3
So, 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.
- merbanan
Vorbis sends the entropy tables in the actual file at the start.
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.
- sinnet3000
The git username sounded familiar, it's from the same developer that created bzip3.