This page lists the suggested tasks to build a 175 hour (medium sized) or 350 hour (large project) for Google Summer of Code 2022. The ideas are already assigned to example project, but you are encouraged to use them for building your own project adding your own ideas and make it suit perfectly to you, your skills and your time line.

If you are interested in applying to GSoC, read GSoC Advice before applying or getting involved. Only beginner contributors that are active members of the Mixxx community are accepted. If this is not the case yet, just say hello at https://mixxx.zulipchat.com and discuss your Ideas and use cases with us.

Some Controller mappings have implemented a Spin-Up/Spin-Down to mimic the inertia of a turn table. This should be moved into the engine, so that it is accessible without a controller.

Part of the project is to record the spin up of a real turn table to get to know of the real acceleration curve and model this via software. You may also deal with the BPM sync feature, in a way that the spin up and down integrates faultlessly into a mix.

https://bugs.launchpad.net/mixxx/+bug/1692261

• Expected Outcome: A flawlessly working spin up and down effect accessible without controller
• Skills: Good understanding of sound processing, C++
• Possible Mentor: Owen Williams
• Difficulty: Medium
• Size: 350 h

Our scratching algorithm suffers from jitter noise created by the latency of the midi messages. It also suffers from a so called sticker drift, an incrementing offset shifting away form the original scratch sample. Part of this project is to filter the discrete messages from the controller in a way that you can either "play" the track without much wobbling by turning the jog wheel, and keep the position during scratching.

We may also make use of the time stamps of the midi messages. https://bugs.launchpad.net/mixxx/+bug/1157573

The required controller can be provided as a loan.

• Expected Outcome: Wobble fee scratching using a joggwheel
• Skills: Good understanding of real time processing, C++
• Possible Mentor: Daniel Schürmann
• Difficulty: Hard
• Size: 350 h

Currently crossfader changes are stretched on audio buffer time to avoid pop sounds. This is too long for some scratching styles. During this project you need to dive into the audio engine code find the code that is responsible for crossfading and make it independent from the audio buffer size.

https://bugs.launchpad.net/mixxx/+bug/1703475

• Expected Outcome: Cut type crossfader curve, suitable for scratching.
• Skills: Good understanding of sound processing, C++
• Possible Mentor: Daniel Schürmann
• Difficulty: Medium
• Size: 175 h

Mixxx uses a linear resample when scratching. This is blazing fast, but the sound can be improved. Here Mixxx should provide more resample options. This project involves to review the already used resample libraries RubberBand and Soundtouch and compare them with other candidates. The one with the best Sound/CPU load trade of shall be selected. Make sure that it supports on the fly changing of the sample rate without artefacts. This project may also involve to contribute a missing feature to such library.

https://bugs.launchpad.net/mixxx/+bug/1775164

• Expected Outcome: Optional replacement of the linear resampler.
• Skills: Good understanding of sound processing, C++
• Possible Mentor: Owen Williams
• Difficulty: Easy
• Size: 175 h

If a controller is accidentally unplugged it has to be manually reconfigured, which is a party stopper. Mixxx should do it automatically. This project has two stages, fist behave like a real DJ: fix the issue but faster. So the the time of silence on the dance floor is kept short. The advance stage of this project is to implement real Hot Plug And Play. In order to that you likely need to touch the low level inside third party libraries.

The required controller can be provided on loan.

• Expected Outcome: Re-power the controller and continue to use it, on your target platform.
• Skills: Good understanding of the USB stack, C++
• Possible Mentor: Daniel Schürmann
• Difficulty: Easy / (Hot Plug And Play = Difficult)
• Size: 175 h / (Hot Plug And Play = 350 h)

Mixxx should be able to continue playing after cumming back from the suspend state of the PC. This requires to detect the faulty state after resume and reinitialize the required parts of Mixxx.
https://bugs.launchpad.net/mixxx/+bug/1744641

• Expected Outcome: The sound output shall continue after sleep.
• Skills: Good understanding of the USB stack, C++
• Possible Mentor: Daniel Schürmann
• Difficulty: Difficult
• Size: 175 h

Mixxx should look up our download page and automatically update itself in case an update is available. This shall be implement using Sparkle on MacOS and WinSparkle on windows like Wireshark.

• Expected Outcome: A working update notifier, frontend and server part.
• Skills: Experience with MacOs and Windows, C++
• Possible Mentor: Daniel Schürmann
• Difficulty: Easy
• Size: 175 h

Mixxx shall suggest compatible tracks matching the current playing one. The feature may use existing meta data like bpm genre and key or tab online resources like LastFM and similar. https://bugs.launchpad.net/mixxx/+bug/889898

• Expected Outcome: A dynamically changing list of suggested tracks.
• Skills: Experience with web services, C++
• Possible Mentor: Daniel Schürmann
• Difficulty: Medium
• Size: 350 h

There should be an independent effect for pitch shifting. In addition to our main pitch shift feature this should be implemented as an independent effect with a wider range of parameter values. This can be implemented by a independent instance of RubberBand or other suitable library. https://bugs.launchpad.net/mixxx/+bug/1299035

• Expected Outcome: An additional effect for chipmunk voices.
• Skills: Experience with sound processing, C++
• Possible Mentor: Daniel Schürmann
• Difficulty: Easy
• Size: 175 h

As always with Summer of Code, you aren't limited to the suggestions we've made here. If you've got a great idea for a project involving Mixxx then we're looking forward to hearing about it. We recommend spending more than a few days using Mixxx and participating in the community to develop a better understanding of areas where Mixxx could use improvement. Our bug tracker is full of wishlist bugs and other ideas scattered throughout, so if you browse through it, you may find many more ideas for GSoC projects.

IMPORTANT: You should contact us first to get feedback if you're going to submit a proposal for your own project idea! We very rarely approve ideas students propose. If you're not already experienced with DJ equipment, we recommend sticking with one of the ideas above.