Add RNNoise for neural network-based audio noise reduction

[phreed]

RNNoise is a noise suppression library based on a recurrent neural network developed by the Xiph.Org Foundation. This recipe provides:

• Cross-platform build support (Linux, macOS, Windows)
• Proper CMake configuration with custom CMakeLists.txt
• Nushell-based build script for consistent cross-platform builds
• Comprehensive testing for library and header installation
• pkg-config support on Unix platforms
• Custom CMake configuration template (rnnoise-config.cmake.in)

Key features of RNNoise:

• Real-time noise suppression using deep learning
• Optimized for speech enhancement with low computational overhead
• Works on 48 kHz mono audio streams
• GRU-based recurrent neural network architecture
• Effective at removing background noise and enhancing voice quality

This library is particularly useful for VoIP applications, streaming services, and any real-time audio processing scenarios requiring noise reduction capabilities.

Checklist

• Title of this PR is meaningful: e.g. "Adding my_nifty_package", not "updated meta.yaml".
• License file is packaged (see here for an example).
• Source is from official source.
• Package does not vendor other packages. (If a package uses the source of another package, they should be separate packages or the licenses of all packages need to be packaged).
• If static libraries are linked in, the license of the static library is packaged.
• Package does not ship static libraries. If static libraries are needed, follow CFEP-18.
• Build number is 0.
• A tarball (url) rather than a repo (e.g. git_url) is used in your recipe (see here for more details).
• GitHub users listed in the maintainer section have posted a comment confirming they are willing to be listed there.
• When in trouble, please check our knowledge base documentation before pinging a team.

[github-actions]

Hi! This is the staged-recipes linter and your PR looks excellent! 🚀

[conda-forge-admin]

Hi! This is the friendly automated conda-forge-linting service.

I just wanted to let you know that I linted all conda-recipes in your PR (recipes/rnnoise/recipe.yaml) and found it was in an excellent condition.

[phreed]

@conda-forge/help-c-cpp review-requested

[traversaro]

Can you explain in a comment how this two are related? This can be useful for future maintainers.

[traversaro]

This seems AI-generated and a bit difficult to mantain. While simple README for recipes make sense, I am not sure if this is particularly useful, what do you think?

[traversaro]

Thanks for the contribution @phreed ! Just to understand, conda-forge has full support for building packages with autotools (also on Windows), see for example:

• https://github.com/conda-forge/ffmpeg-feedstock/tree/main/recipe
• https://github.com/conda-forge/ipopt-feedstock/tree/main/recipe

or you can search for any use of the autotools_clang_conda helper package. There is any specific reason for not using those tools instead of having a custom CMakeLists.txt in the recipe that may diverge w.r.t. to upstream?

[phreed]

Thanks for the contribution @phreed ! Just to understand, conda-forge has full support for building packages with autotools (also on Windows), see for example:

* [conda-forge/ffmpeg-feedstock@`main`/recipe](https://github.com/conda-forge/ffmpeg-feedstock/tree/main/recipe?rgh-link-date=2025-10-11T16%3A09%3A35Z)

* [conda-forge/ipopt-feedstock@`main`/recipe](https://github.com/conda-forge/ipopt-feedstock/tree/main/recipe?rgh-link-date=2025-10-11T16%3A09%3A35Z)

or you can search for any use of the autotools_clang_conda helper package. There is any specific reason for not using those tools instead of having a custom CMakeLists.txt in the recipe that may diverge w.r.t. to upstream?

I will take a look at those two feedstocks.
I was under the impression that cmake was preferred over autotools on conda-forge (especially when Windows is involved).
I guess that was wrong?

[conda-forge-admin]

Hi! This is the friendly automated conda-forge-linting service.

I wanted to let you know that I linted all conda-recipes in your PR (recipes/rnnoise/recipe.yaml) and found some lint.

Here's what I've got...

For recipes/rnnoise/recipe.yaml:

• ❌ This recipe is using a compiler, which now requires adding a build dependence on ${{ stdlib("c") }} as well. Note that this rule applies to each output of the recipe using a compiler. For further details, please see META: {{ stdlib("c") }} migration conda-forge.github.io#2102.

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