Questions regarding chdman performance (SIMD optimizations) and lossy CHD support

[7zxkv]

Hi! Thanks for developing OpenROM, it looks super promising.

I have two quick questions regarding the chdman backend used in the project:

• SIMD & Performance Optimizations: Does OpenROM bundle or support optimized builds of chdman, such as grouik1er-coder/chdman-simd? It includes SHA-NI, AVX2, LZMA ASM, and zlib-ng optimizations that significantly speed up the compression process.

• Lossy Compression Support: Is there any plan (or existing option) to support lossy CHD compression modes (e.g. for audio/video tracks), similar to what platforms like chdman.com or standard chdman flags offer?

Thanks again for the great work!

[ClausValcaTD]

Hey! Great questions 🎮

1. chdman-simd: We're aware of the SIMD fork — it's on our radar.
   We're currently evaluating it for inclusion as an optional
   "performance mode" binary. The concern is stability since it's
   not an official MAME build. We'll likely add it as an opt-in
   setting in a future release.

2. Lossy CHD: Not currently planned — OpenROM focuses on
   lossless preservation by default. That said, we could add
   a "lossy audio" flag as an advanced option for users who
   prioritize file size over perfect fidelity. Opening this
   as a feature request if anyone wants to track it!

Thanks for the detailed feedback — exactly the kind of
input that helps us improve 🙏

[7zxkv]

Thanks for the suggestion. Just to clarify, that's exactly what I did with this issue (#15): I submitted the idea here, describing the proposed improvements to chdman and CHD lossy compression.

So I believe the idea has already been submitted as a feature request. 🙂