Mixxx 2.4.0 Released -- New Major Version

We are proud to announce #Mixxx 2.4, a new major version of our free open source DJ software, available right now from https://mixxx.org/download/ . It's been two years since the last release due to the large number of great new features and important changes under the hood.

Full release announcement: https://mixxx.org/news/2024-02-16-mixxx-2-4-0-features/

What's New:

* EngineOS Export

Mixxx 2.4 adds support for exporting crates, playlists and the library to Engine DJ OS devices, including Denon and Numark standalone controllers. This allows users to prepare their tracks on a laptop using Mixxx and export them to a USB stick for use on a standalone controller at their gig.

Saved Loops

Mixxx 2.4 adds support for Saved Loops, which can be assigned to any Hot Cue slot. If you already have tracks from Serato DJ with Saved Loops, Mixxx 2.4 will import them automatically.

Effect Chains

Mixxx 2.4 introduces Effect Chains, a set of effects which can be saved and reloaded with all their parameters and individual Meta Knob mappings. Effect Chains can also be exported and imported, which allows you to share them with other Mixxx DJs.

Sync Lock Improvements

Mixxx 2.4 adds support for manually selecting the Sync Leader by clicking on the new button with the crown symbol next to the Sync button. This mode is useful when tracks have variable BPM.
All decks with sync enabled will follow the changing BPM of the Sync Leader.

Soundstretcher / Key-Shift Algorithms

Mixxx 2.4 now supports three different key shift algorithms:

- Soundtouch (Basic audio quality - medium CPU usage)
- Rubberband R2 (Good audio quality - higher CPU usage)
- Rubberband R3 (High audio quality - very high CPU usage)

Waveform Rendering Reworked

The waveform display has been rewritten, solving some longstanding performance issues, especially on macOS.

Apple Silicon Support

Mixxx now supports macOS ARM systems ("Apple Silicon") such as M1 natively and provides installation packages for those architectures. For macOS users, this increases the stability and performance of Mixxx on Apple silicon.

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@mixxx sounds like this will improve the quality of tracks that have their tempo decreased? This was the only thing in Mixxx that I wished was better

@earth_walker I'm not sure what you mean? Tempo detection has improved, if that's what you are referring to.

@mixxx when I changed the tempo of a track down to beat match (say from 120 BPM to 110 BPM) I noticed it sounded worse, like it was "breaking up" a little. I know changing the speed of a track without impacting audio quality is a complicated technology, but it sounded like these new algos would help with that?

@earth_walker Yes, if you have the Rubberband v3 library and a very fast CPU, it should sound much better!

@mixxx what do you consider as a recommended CPU for the new version of Rubberband?

@getimiskon I am able to use it on an Intel i7-1195G7 at 5ms latency but only one deck at a time -- it's very hungry.

@mixxx I currently have an older CPU (i5-8250U). I'll do some testing on my macOS setup, which has the least latency (hackintosh ftw). My laptop is definitely gonna scream, but it's gonna be fun.

@mixxx alright, I'll be honest, Rubberband R3 is neat. The audio quality is good. But as an option it's just impractical for actual use, for now at least. While on my laptop I don't have as many issues as I anticipated during my testing (had only some buffer underflows at 5.33ms, 48kHz), not being able to use it with more than a single track makes it useless. I would really like this to be improved over time, I'm curious to see if it can be further optimized to the point of becoming the standard in the future.
By the way, built-in noise gate when?

@getimiskon we do not have any audio engineers on our dev team so we rely on the wider open source community to create libraries. If another library appears that meets our needs (realtime performance, per-callback parameter modification, etc) then we will add support for it.

@mixxx @getimiskon

The Mac M2s are able to keep up with Rubberband R3 on multiple decks at ~5ms. This was running on Asahi Arch.

Unfortunately I don't own an x86/AMD64 machine with fast enough single thread performance to be able to do multiple decks at ~5ms.