View source for Google Summer of Code/2020

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 | style="padding-left: 1em; padding-right: 1em;" | Welcome to the Kodi [https://summerofcode.withgoogle.com/ Google Summer of Code] ideas page for 2020. We are pleased to announce that we have been accepted as an official [https://summerofcode.withgoogle.com/archive/2020/organizations/6555254004383744/ GSoC mentor organization] this year.
We encourage interested students of all ethnicities and genders to review some of the ideas on this page and feel free to provide input on any ideas you may have in the '''[https://forum.kodi.tv/forumdisplay.php?fid=301 Kodi GSoC 2020 subforum]''' so we can open a dialogue about any project you’d love to cover. To propose a project, see '''[[#Students project proposal ideas|Students' project proposal ideas]]'''.

From March 25<sup>th</sup> to April 9<sup>th</sup> any interested students may apply at the [https://summerofcode.withgoogle.com/ GSoC home page] to work with Kodi. After that, Google will notify applicants whether we get to work together according to the [https://summerofcode.withgoogle.com/how-it-works/#timeline GSoC schedule].
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== About Us ==
As there may be many students who have landed here as a result of GSoC but are unfamiliar with the project, here are a few resources that may help explain why we exist.

:Kodi (formerly known as XBMC) is an award-winning free and open source (GPL2+) software media player and entertainment hub for digital multimedia, designed around the ten-foot interface (living room) environment. Created in 2003 by a group of like-minded programmers, Kodi is a non-profit project operated and developed by volunteers located around the world. More than 500 software developers have contributed to Kodi alongside more than 100 translators who have expanded its reach, resulting in it currently being available in over 60 languages. For more information, please see the page '''[[Kodi]]'''.<br />

To get an idea of what Kodi is truly capable of you really must see it for yourself. Here are a few user-created videos that will let you do just that:<br />
{| class="center" style="margin-top: 1em; text-align: center; width: 100%;"
 | {{YouTube|NcogPuSo-DU}}
 | {{YouTube|4asUCtE0ONU}}
 |- style="padding-top: 1em;"
 | '''Kodi with the default Confluence skin'''
 | '''Kodi with Aeon Nox skin'''
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 | colspan="2" style="padding: 2em;" | <hr style="width: 75%;" />
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 | {{YouTube|4NR57ELY28s}}
 | {{YouTube|e_0PB5hfz_k}}
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 | '''Kodi on Raspberry Pi'''
 | '''Kodi's new PVR functionality'''
|}

Kodi is written primarily in C++ and runs on a variety of platforms, including Android, iOS, Linux, MacOS and Windows. It has been ported to work on several low-power platforms including the Raspberry Pi and several Android TV "boxes."

Kodi was a GSoC mentoring organization in 2008, 2012, 2013, 2015, 2017, 2018, 2019 and had team members involved in GSoC for other projects during 2011.

Students will need to review the overview of a good project proposal, follow the outline for proposals when applying and review the list of project ideas detailed below. They are also welcome to propose ideas that aren't on the list and are encouraged to indulge their creativity as much as they can.

=== Mentors ===
All mentors and backup mentors are extremely experienced in the Kodi codebase and will assist students in getting familiarized with it and quickly identify projects that are both achievable for someone new to the internal workings of Kodi while still being desirable to the wider Kodi community.

== Prerequisites ==
C++ coding skills, basic familiarity with Git, and a solid understanding and interest in programming. A facility with quickly understanding existing code is beneficial.

== Project Proposals ==
=== Overview ===
Qualifications for a good Summer of Code proposal:
* Discrete, well-defined, modular
* Comprised of a series of measurable sub-goals
* Based on open specs that are available free of charge
* Based on complete specs
An example of a good proposal is the implementation of a new feature or function that is not yet available in Kodi.

An example of a less desirable proposal is one that's not as measurable, such as refactoring an existing API. Bad proposals tend to be ones that would require touching a lot of core code.

To reiterate:
* Localized/isolated code projects = ''good''
* Global code refactoring = ''bad''
* A project should have a set of subgoals, so even if the end goal turns out to be too big some of the parts will be of benefit.
* Not too big! This is an important problem when choosing a project, while it is fun to think about solving a grand project its not always realistic. Its better to finish a smaller project than to start a grand one.

=== Where to submit proposals ===
In addition to submitting to the [https://summerofcode.withgoogle.com/ Google Summer of Code] website, you are highly encouraged to submit your idea/proposal to the [https://forum.kodi.tv/forumdisplay.php?fid=293 Kodi forum] for discussion. Any proposal not submitted to the forum for discussion will likely not be considered.

=== Outline for proposals ===
{{Divbox|blue||
PROJECT TITLE GOES HERE

* '''Name:'''
* '''forum/e-mail:'''
* '''Summary:''' A somewhat small but explanatory walk through of the project. It should not be overly detailed just enough to understand the problem trying to be fixed and how this project opt to solve it.
* '''How will I achieve this:''' Explain how the project will be done, what technologies are needed and how to implement them.
* '''What will the project focus on:''' Explain what the project will focus on, what is the important parts of the project.
* '''Benefits:''' Who will benefit and why from this project. Think about what a user or developer may need or do to benefit from it. Why does it benefit many users.
* '''Goals:''' What is the goal of the project, a project may not always solve the problem entirely as it may take to much time. Think hard about what can be accomplished during a summer with your skill and deduct that quite a bit. If the project can't be done after this perhaps it's better to opt for a smaller one or one with subgoals.
* '''What does it touch in Kodi:''' Think about what parts of the code this may touch, Kodi is a big application and a lot of the code is spread out and very complex. If a project touches to much it may be impossible to complete.
* '''Requirements:''' What is needed to complete the project, what code language knowledge what hardware, etc.
* '''Possible mentors:''' Place to add possible mentors (Team-Kodi will add this). 
}}

== Team-Kodi proposal ideas up for discussion ==
=== Explore building binary addons in rust ===
'''Description:''' While Kodi has python addons, it can also handle binary addons. But these need to be build one by one for each platform and also might fail on errors. Rust might help with both of those problems and more. The idea is to use the api we have but via rust ffi and see where that leads us.

'''Expected outcome:''' Documentation and templates on how to use rust with kodi. In the best case also one or two example addons.

'''Skills preferred:''' C++, Rust, C

'''Possible mentors:''' spiff, Razze, velocity

'''Difficulty:''' Hard

'''Type:''' Binary addon development

=== A new web interface ===
'''Description:''' Kodi has a webinterface by the name of chorus2 (https://github.com/xbmc/chorus2) which is written in coffeescript and as it stands no team member is able to work on coffeescript. So the idea would be to implement a new interface, in a newer language. I would like to see Elm or Svelte, but others would be fine too, as long as we would be able to maintain it.

'''Expected outcome:''' A new webinterface (can be redesigned) or a port of the old one.

'''Skills preferred:''' HTML, CSS, Javascript, Typescript, Elm

'''Possible mentors:''' Razze

'''Difficulty:''' Medium

'''Type:''' Webinterface development

=== Better profile support ===
'''Description:''' Profile support inside Kodi remains extremely hacked together. Improving profile projects would likely be broken down into smaller chunks to make each chunk truly achievable in a summer. Database handling for profiles needs to be reviewed and changed so that the user experience is more streamlined. It should also be possible to better guard code paths that need to check for specific profile rights. 

'''Expected outcome:''' Profiles should be more user-friendly than before and not be an afterthought. Being able to easily add more profile features is the big ultimate goal, as we want to support profiles for kids that automatically hide media that's not for them. Just as an example.

'''Skills preferred:''' C++

'''Possible mentors:''' spiff

'''Difficulty:''' Hard

'''Type:''' Core development

=== Replacing depends with a CMake-based system ===
'''Description:''' Kodi has its own system for building the many libraries Kodi depends on that supports most platforms (Linux, Android, OS X, iOS) and cross-compiling called depends. At the moment, it is implemented with autotools and hand-crafted Makefiles. This has lead to a lot of code duplication, poor maintainability, and not being very user-friendly. Also, it does not currently work on Windows. This task would be about replacing the current system with a new implementation in CMake that has better maintainability.

'''Expected outcome:''' A CMake-based dependency build system that offers roughly the same features as depends (i.e. all required libraries covered, diverse platform support, cross-compilation). If the solution can also be applied to Windows by e.g. adding minimal CMake files to replace some UNIX-only build systems, that would be a big plus, but it is not necessary.

'''Skills preferred:''' CMake, shell scripting, general familiarity with UNIX/Linux

'''Possible mentors:''' wsnipex

'''Difficulty:''' Medium

'''Type:''' Infrastructure/Automation

=== Integrate TUF (The Update Framework) ===
'''Description:''' Kodi uses a self-built mechanism for installing and updating add-ons from add-on repositories. Unfortunately, it is not very secure. This project would be about replacing the add-on repository code with the usage of TUF (The Update Framework), a quite recent library that solves many common security problems for updaters. TUF does not currently have a C or C++ implementation. The reference implementation is in Python, which we do not want to integrate with C++ for this core piece of application code. Due to security concerns, we also do not want to implement TUF ourselves. That leaves using rust-tuf, an experimental Rust implementation. First step would be to write a C wrapper library so that we can use it from Kodi.

'''Expected outcome:''' Add-on repository in Kodi using TUF that builds and works on all supported platforms (beware, there are quite a lot) and is integrated into the Kodi add-on infrastructure (i.e. there are also tools to generate valid repositories). It should support all core add-on functionality (be able to list, install, and update add-ons).

'''Skills preferred:''' C++, Rust, Python (for creating the repository the TUF reference implementation could be used)

'''Possible mentors:''' yol

'''Difficulty:''' Hard

'''Type:''' Risky/Exploratory (rust-tuf is unstable and there is also a lot of work to be done on the backend side)

=== Automatic add-on checker for binary add-ons ===
'''Description:''' Kodis add-on checker checks each Kodi add-on PR on GitHub for certain problems, which ultimately makes reviewing Python add-ons easier for the team. But the other type of add-ons, binary add-ons is not being checked so far, which makes reviews and coding guidelines hard to handle. Thus it would be nice to also check those add-ons, either via the current checker written in Python or a new binary add-on specific checker. Goals would include checking the addon.xml, the C++ code and a check for potentially malicious code.

'''Expected outcome:''' Being able to run the checker against all binary repo PRs on GitHub.

'''Skills preferred:''' Python, C++

'''Possible mentors:''' Razze

'''Difficulty:''' Hard

'''Type:''' Low-hanging fruit

=== Achievements in RetroPlayer engine ===
'''Description''': Retroarch has developed support for achievements in certain select libretro cores. This project would consist of porting whatever work might be portable and otherwise integrating the existing libretro achievement system into Kodi's RetroPlayer implemented using Kodi's UI system. Could be tackled a few different ways, including simply linking the user to the retroachievements.org or creating a full achievement database in Kodi.

'''Expected Outcome''': Users should be able to see their achievements in Kodi. Player manager and Player profile support may be in development concurrently, so thought should be given to those systems.

'''Skills preferred''': C++, Python, possibly PHP

'''Possible mentor''': garbear, velocity

'''Difficulty''': Medium

'''Type''': Fun/Peripheral

'''Notes''': Garbear has broken down the Retroplayer project into manageable pieces including input, core, game add-ons, peripheral add-ons, netplay, a game library implementation, and shaders to do things like emulate a CRT monitor.  This is one example, but many pieces are currently being worked on or are near completion, and many more could use help from a student familiar with the area. Visit the retroplayer section of the Kodi forum to see all the major projects still to do.

=== Saved game manager for RetroPlayer engine ===
[[File:Saved game manager.png|thumb|right|400px|Saved game manager from 2016]]
'''Description''': Kodi excels at managing large movie, music, and (with add-ons) game libraries. However, savestates and in-game saves are simply stored next to the ROM or in a hard-coded folder.

This project would consist of designing a user interface for saved game management. Some database work will probably be required. As a stretch goal, automatic saved-game captioning can be performed using the "Rich Presence" feature of RetroAchievements.org.

In 2016, Garbear created an experimental saved game manager - see https://github.com/xbmc/xbmc/pull/11034. It may be possible to re-use ideas and code from this PR. Here's what the saved game manager looked like at the time:

'''Expected Outcome''': Users should be able to manage their save states and in-game saves in Kodi.

'''Skills preferred''': C++, optionally Python

'''Possible mentor''': garbear, velocity

'''Difficulty''': Medium

'''Type''': Fun/Peripheral

=== Runahead for RetroPlayer engine ===
'''Description''': This feature, pioneered by libretro (see [https://www.libretro.com/index.php/retroarch-1-7-2%E2%80%8A-%E2%80%8Aachieving-better-latency-than-original-hardware-through-new-runahead-method/ Achieving better latency than original hardware through new runahead method]) allows for input latency better than the original console!

'''Expected Outcome''': Implemented runahead input

'''Skills preferred''': C++

'''Possible mentor''': garbear, velocity

'''Difficulty''': Medium

'''Type''': Fun/Peripheral

=== Player Manager for RetroPlayer add-on ===
[[File:Player manager.png|thumb|right|400px|Player manager concept art]]
'''Description''': Currently, player assignment and controller selection is hard-coded. This project would allow the user to configure which controllers are connected to the virtual console, enabling multiplayer in games that are currently hard-coded to single player.

A player management concept is [https://github.com/garbear/xbmc/issues/87 outlined here]. Ideas and code from the issue can possibly be re-used in this project.

'''Expected Outcome''': Players can change virtual input devices and choose which player number they are

'''Skills preferred''': C++

'''Possible mentor''': garbear, velocity

'''Difficulty''': Medium

'''Type''': Fun/Peripheral

=== <insert feature from RetroArch here> ===
'''Description''': RetroArch is an amazing, full-featured emulator system. Many of these features would make good GSoC projects!

'''Expected Outcome''': Feature from RetroArch is implemented

'''Skills preferred''': C++, optionally Python

'''Possible mentor''': garbear, velocity

'''Difficulty''': Various

'''Type''': Fun/Peripheral

=== Game-theoretic engine for RetroPlayer engine ===
'''Description''': Currently, Kodi's game engine (RetroPlayer) is based on VideoPlayer - games act as "codecs" that accept input and produce audio and video streams. While this rocks for performance (we've even mirrored zero-copy support from VP), it makes many features, such as rewind, runahead, and netplay difficult to integrate.

The project is to implement the emulation equation described by the Special Theory of Emulation introduced in [https://github.com/garbear/xbmc/issues/89 Reinforcement Learning Bots], where S is State and A is Action:

<span style="font-family: 'Linux Libertine',Georgia,'Times New Roman',serif; font-size: 1.28em; font-weight: 500; line-height: 1.33em;">''S''<sub>0</sub>&nbsp;=&nbsp;&empty;</span><br />
<span style="font-family: 'Linux Libertine',Georgia,'Times New Roman',serif; font-size: 1.28em; font-weight: 500; line-height: 1.33em;">''A''<sub>0</sub>&nbsp;=&nbsp;&empty;</span><br />

<span style="font-family: 'Linux Libertine',Georgia,'Times New Roman',serif; font-size: 1.28em; font-weight: 500; line-height: 1.33em;">''S''<sub>''t''+1</sub>&nbsp;=&nbsp;''PlayFrame'' ( ''S<sub>t</sub>'' ,  ''A<sub>t</sub>'' )</span><br />
<span style="font-family: 'Linux Libertine',Georgia,'Times New Roman',serif; font-size: 1.28em; font-weight: 500; line-height: 1.33em;">''A''<sub>''t''+1</sub>&nbsp;=&nbsp;''GetInput'' ( ''S''<sub>''t''+1</sub> ,  ''A<sub>t</sub>'' )</span><br /><br />

The equation results in the time series:

<span style="font-family: 'Linux Libertine',Georgia,'Times New Roman',serif; font-size: 1.28em; font-weight: 500; line-height: 1.33em;">(''S''<sub>0</sub>,&nbsp;''A''<sub>0</sub>,&nbsp;''S''<sub>1</sub>,&nbsp;''A''<sub>1</sub>,&nbsp;''S''<sub>2</sub>,&nbsp;''A''<sub>2</sub>,…)</span>

The emulation equation describes all of emulation in a game-theoretic manner. With such an engine, powerful features become incredibly easy:
* When emulation is a time series, rewind is just decrementing t
* Runahead is just replacing an A several t's ago
* Netplay is also possible - just run a consensus algorithm like RAFT over the State/Action pairs.

'''Expected Outcome''': Games play using the new engine. Rewind is now easy. Runahead is now easy. Netplay is still hard, but the emulation equation turns netplay from a networking problem into a consensus problem.

'''Skills preferred''': C++

'''Possible mentor''': garbear, velocity

'''Difficulty''': Advanced

'''Type''': Fun/Peripheral

=== Reinforcement learning bots for RetroPlayer engine ===
'''Description''': Same as the above, but implement the emulation equation described by the General Theory of Emulation in [https://github.com/garbear/xbmc/issues/89 Reinforcement Learning Bots].

'''Expected Outcome''': Super-human gaming bots take over the world

'''Skills preferred''': C++

'''Possible mentor''': garbear, velocity

'''Difficulty''': Lower circles of Hades

'''Type''': Fun/Peripheral

=== Retroverse ===
{{Float|right|{{YouTube|8dinUbg2h70}}}}
'''Description''': This project introduces the Retroverse: an infinitely-rewindable branching history of all gameplay.

Braid creator Jonathan Blow gave a presentation titled ''The Implementation of Rewind in Braid'' (at right). In 2013, Themaister [https://github.com/garbear/xbmc-retroplayer/commit/97e52df8a2f82a36952c8bcbebc133b3efc1babe donated] Braid-esque rewind to Kodi. This became the basis of the [https://github.com/xbmc/xbmc/blob/master/xbmc/cores/RetroPlayer/streams/memory/IMemoryStream.h memory streaming API] in RetroPlayer.

Recall how Blow describes his rewind feature: "Record full world state for every frame always; do not drop frames. Compress data somehow." The challenge of this project is to figure that out, somehow.

Does recording hundreds of hours of gameplay sound impossible? Assume deterministic emulation. The State can be fully reconstructed from the Action of the previous timestep, so only the Action needs to be saved. The Atari 2600, released in 1977, has 5 buttons, needing 5 bits. With a 5 bit frame size, you can store around 850 years of continuous (or nonlinear) Atari 2600 gameplay on a 1TB drive. Still seem impossible?

'''Expected Outcome''': Implement the <code>CNonlinearMemoryStream</code> class referenced in <code>[https://github.com/xbmc/xbmc/blob/master/xbmc/cores/RetroPlayer/streams/memory/IMemoryStream.h IMemoryStream.h]</code>. Enable LZ4 and/or RLE compression of savestate diffs. Enhance autosave by using interpolation to drop "base frames". Store a tree instead of a buffer!

'''Skills preferred''': C++

'''Possible mentor''': garbear, velocity

'''Difficulty''': Advanced

'''Type''': Fun/Peripheral

=== Using fuzz testing to fuzz test Kodi ===
'''Description:''' Adding fuzz testing to Kodi would be very valuable to find problems in the current code base. Especially security problems. First step would be choosing a framework either American fuzzy lop, libFuzzer or other similar projects. After we decided on that it would be time to start to fuzz different methods that are widely used in Kodi and try to expose flaws in those. If this leads to success, it should be documented and made repeatable.

'''Expected outcome:''' Being able to easily add more fuzz tests and having the process to do this documented.

'''Skills preferred:''' C++, CMake 

'''Possible mentors:''' Razze

'''Difficulty:''' Medium

'''Type:''' Risky/Exploratory

=== inputstream.adaptive binary add-on ===
'''Description:''' inputstream.adaptive is a binary kodi inputstream addon written in C++ and handles multi bitrate streams provided in DASH / Smoothstream manifest or HLS multi bitrate playlists. The add-on provides demuxed / encoded packets to Kodi and Kodi renders the data with its internal video player. Digital Rights Management (DRM) is implemented in inputstream.adaptive to allow playback of protected media. inputstream.adaptive is used by many (> 100) addons to play (legal) encrypted media.<br />The addon sources are still hosted in [https://github.com/peak3d/inputstream.adaptive my own Git repository], but I'll hand over the sources to the Kodi repository if someone is interested on working at one of these two most urgent topics below.

==== Bitrate switch ====
'''Description:''' In the current inputstream.adaptive implementation a stream resolution / bitrate is selected at start time. Because of network fluctuations / manual window / screen changes or performance stats of rendered frames it should be possible to switch seamless to lower / higher stream representations.

'''Expected outcome:''' Automagically select / change seamless stream depending on external factors.

'''Skills preferred:''' C++, CMake

'''Possible mentors:''' peak3d

'''Difficulty:''' Medium

'''Type:''' Media playback

==== Read ahead ====
'''Description:''' Currently stream segments are downloaded on request (that is kodi is requesting more data to display). Because the kodi videoplayer internal buffer is small (8 seconds), network fluctuation can lead to bad user experience (stream interruption). What users want is that inputstream.adaptive buffers a configurable amount of time ahead to bypass this issue.<br> Buffering ahead in multi bitstream is not only a technical task, there are numerous resolutions / bitrates for the same movie time segment in the manifest from which the "best" one should be buffered. The concept of what to read will be an not trivial engineering task.<br />Bitrate switch (see previous topic) will be a prerequisite to "Read ahead" because on low network times lower bitrate streams are read compared to good network times. 

'''Expected outcome:''' Implementation of read ahead logic for multi bitrate streams, user configurable.

'''Skills preferred:''' C++, CMake

'''Possible mentors:''' peak3d

'''Difficulty:''' Medium

'''Type:''' Media playback

=== Other ideas ===
These ideas still need expanding and/or assigned a potential mentor. If one of these ideas interests you, feel free to ask for more info in the GSoC 2020 forum area. We may be able to assign a mentor if enough interest is shown.
* Visual Studio Code extension to validate/highlight syntax for Kodi Add-ons (possible mentors: velocity)
* Using fruit or similar to use DI in Kodi and write tests
* High quality scalers for OpenGL(GLSL). Scale Y and UV plane separately (possible mentors: velocity)
* Support downloading of of media items (the actual file not just the metadata) from another Kodi instance (e.g. through UPnP) into the local library. This could be done in a "send to" way and in a "download" way and it could also be combined with transcoding depending on the target device.
* UPnP device profiles. A Pull Request already exists that goes in that direction and the problem is that right now we can only really provide device-specific MIME type hacks, but if we have transcoding we'll definitely need this
* Implementing a performance critical element of Kodi in rust

=== More ===
We feel it is important to note that, while we are interested in a focus on the listed three areas, we would like to stress passion, expertise, and creativity above all else. If you would like to do something completely different, definitely send in that proposal. The ideas listed above are, as always, merely suggestions. We will be interested in any idea, so long as you can communicate your interest, your background, and your solution the problem.

== Students project proposal ideas ==
Submit your own proposals on the '''[https://forum.kodi.tv/forumdisplay.php?fid=301 Kodi GSoC forum]'''. They can be as big or as small as you feel you can comfortably accomplish between '''PROJECT START DATE''' and '''PROJECT END DATE'''. In the end, it's better to have a smaller, completed project, rather than a larger, incomplete project.

To submit a proposal idea:
# Copy the text from '''[[#Outline for proposals]]'''.
# Create a new forum post '''[https://forum.kodi.tv/forumdisplay.php?fid=301 HERE]''' and paste the text.
# Fill out everything using your specific proposal.


[[Category:Google Summer of Code]]