Google Summer of Code (GSoC) 2021 ideas page

Welcome to our ideas page. It's great you want to start early. Please join us in our slack channel! (we'll leave as an exercise to you to find it --- it's on our website).

This is an "new way of doing things year". GSoC projects are now supposed to take around 175 hours and we've adapted our ideas to reflect that. If you think any idea is too long or too short please let us know - we still need to fine tune this!

As you will see, this year has a lot of Rust. The reason is simple: Security. Our C code base has known (and we suspect, a lot of unknown) security issues caused by the usual memory management in C. Lots of people have touched the code over the years, and it shows.

There's also Flutter, which we love, and more.

We will provide resources for students --- we'll give access to a high-speed server, all our samples (we'll even ship a portable drive with them anywhere in the world, so don't worry about slow connections) and various other perks.

You are welcome to check out the page (actual ideas at the bottom of the page, with each project having it's own separate page as well) and start early in the community bonding process as well as learning a bit about our code ethics and practices. And of course, we'd love you to stay around even if we are not invited to GSoC or if we cannot invite you as a student.

The ideas we currently have

Important: If you have something else in mind that relates to subtitles and accessibility please get in touch. We prefer that you do something that you are passionate about even if it's something we hadn't considered.

After you check out our ideas please continue reading to the bottom of the page to get information about who we are, how we collaborate, what resources we will provide to you, etc.

Some tasks descriptions are still vague. We know that. Feel free to get in touch for questions, or just check their page from time to time. We will update the descriptions often.

CCExtractor Rust rewrite

NameDescriptionTech you need to knowTech you will learnDifficulty
Initial Rust scaffoldingSet up the base Rust infrastructure. Build with cargo. FFI.(Some) Rust, Some (C)A lot of Rust + C interoperability. CCExtractor internalsMedium
Rewrite 708 decoder in RustCEA-708 is the American standard for digital subtitles. We have a reasonably good (meaning, easy to understand, and it was written when we knew what we were doing) C base. We'd like to port it to rust. We will provide you with the official technical standards.(Some) Rust, Some (C)Digital subtitles Working with standards.Medium
Rewrite 608 decoder in RustCEA-608 is the American standard for analog subtitles. It also carries things like emergency alerts, basic TV guide, and content classification. We have a complete implementation in C that works OK (possibly with some bugs) but that is not really very well organized. We'd like to port it to rust. We will provide you with the official technical standards.(Some) Rust, Some (C)Analog subtitles, XDS Working with standards.Medium
Rewrite the OCR subsystem in Rust.We use tesseract to OCR bitmap based subtitles. It's a great library, but because its input is a bitmap that is preprocessed (so provide a reasonable input) there's lots of places in which there can be buffer overruns, underruns… many of the problems that Rust shines on are evidenced here. So a Rust rewrite of this would be a big win.OCR Rust FFITesseract Imaging OCRMedium

Core subtitle tool (CCExtractor itself)

NameDescriptionTech you need to knowTech you will learnDifficulty
Add support for DTMB countriesDTMB is the standard for Chinese TV, also implemented by countries such as Cuba. What kind of student is ideal for this task? One with lots of analytic skills and patience. If you are one of those, don't disregard this task just because you don't speak (or maybe, even care) about Chinese. The experience on dealing with this will be extremely valuable in the future.We will use part of the organization funds to buy standard documents you might need, a capture device, and in general, anything required to make your life easier.CDTMB Video standards Hardware ResearchUnknown
Add Japanese supportCaptions are used by people all over the world on a regular basis. Most of us are familiar with regular horizontal captions at the bottom of the screen, but did you know that in Japan a common position for captions is vertically on the right or left side of the screen? Come learn more about what Japanese audiences need out of captions as well as how captioning standard likes IMSC and WebVTT support these features.Japanese (or be good with foreign languages)DependsSuspected hard

Artificial Intelligence and clever algorithms

NameDescriptionTech you need to knowTech you will learnDifficulty
Poor man's Rekognition (III)Amazon Rekognition is a (paid) service that is able to identify celebrity faces in a picture. Last year we did some work towards creating a free alternative. This year we want to improve on the past work.Your choiceAI Computer visionUnknown
Poor man's TextractAmazon Textract a (paid) service that "automatically extracts text and data from scanned documents. Amazon Textract goes beyond simple optical character recognition (OCR) to also identify the contents of fields in forms and information stored in tables". We want to build a free alternative that provides an output of similar quality.Your choiceAI Computer vision OCRUnknown

Support tools we and other orgs use as part of their development process

NameDescriptionTech you need to knowTech you will learnDifficulty
The sample platform (/ continuous integration) projectThe sample platform is a good way to help new contributors to check if their code doesn't introduce any regressions. It's pretty stable, but is often hard to interpret for new contributors, and still pretty slow if the queue builds up. We want to move the platform towards GCP (Google Cloud Platform) and run the tests on disposable instances rather than through KVM. This project is guaranteed to be selected if the proposal is good.Git PythonGoogle Cloud API's GitHub Actions GitHub API's Continuous Integration (CI) Automated deployments GitHub integrationMedium/Hard

Multimedia (misc)

NameDescriptionTech you need to knowTech you will learnDifficulty
Improve our reference channel for RokuRoku is currently the most common media streamer. It's cheap and neutral (it's not in any "fight"). Unfortunately, there aren't any good open source channels, so if you want to start your own you have to start from scratch. Last year we started a new channel everyone can use as a starting point. We'd like to continue working on it, adding new features. We will send a free Roku to our student for development.NoneBrightscript Roku Video StreamingMedium


NameDescriptionTech you need to knowTech you will learnDifficulty
ruTorrent mobile interface (II)ruTorrent is a popular web interface for rTorrent, which is possibly the most used BitTorrent client in linux. Last year we started a new project to write a Flutter based interface and was successful and it's gaining traction on its own. We want to work on that project and include new features.FlutterBitTorrentMedium
support more torrent clientsWe'd like to add support for other clients to our ruTorrent mobile interface (which of course will get a new name): Flood and Deluge.FlutterAPI, TeamworkMedium
CCExtractor's GUI in FlutterOver the years there's been a few attempts to replace the GUI for our core tool, CCExtractor, but none have been really successful. Using flutter, let's write a modern GUI.FlutterCCExtractorMedium
BeaconWe have a short version on this as a qualification tool (which you should do first) but this is actually a complete project we expect to become very popular.FlutterScalabilityMedium


We use jesec/rtorrent. It provides a more modern base with Bazel/CMake and C++ 17 (instead of autotools and C++ 0x). Plus, your works are guaranteed to be incorporated if they match expectations.

NameDescriptionTech you need to knowTech you will learnDifficulty
a modern RPC interfacerTorrent currently uses an antique XMLRPC interface, which is limited in capability, not scalable, hard to use, insecure and low-performance. Community needs a modern RPC interface with full bidirectional, stream processing, incremental data loading and high concurrency capabilities, which allows real-time events for RPC users, reduced serialization/transfer overheads, potentially better security (with authentication and/or TLS), etc.C++RPC, Event LoopMedium/Hard
asynchronous name resolutionUDP tracker name resolution is not asynchronous at the moment, which causes blocking in the main thread and can block (timeout) other ongoing/incoming connections/transfers. c-ares or libwebsockets implementation is preferred, as c-ares is already used by curl, which rTorrent depends on, while libwebsockets may be used by a future WebSockets RPC interface.C, C++Threading, Event LoopMedium
improve scalability - on startIt takes 3 minutes to load 28890 entries from the session directory on start. Only 1 core is used. Deal with this situation, potentially by making the session functions thread safe and spawning more threads for the tasks.C++ThreadingMedium
improve scalabilityrTorrent has a well-defined threading behaviour, which makes it stable and light on resources. There are 3 permanent threads only: main, disk and scgi. However, in the age of Gigabit/10G connections, 3 threads are often not sufficient. Implement a new threading model with better scalability.C++ThreadingHard
scheduling/queuingIn some cases, users might want to download a series of torrents one-by-one without having to manually start the next when the previous is completed. Implement a scheduler along with a queue to allow users to limit the number of maximum simultaneous downloads. Enqueue if the user adds a download or decrease the limit. Dequeue when a download is completed or the user increases the limit. Keep the queue state across reboots.C++SchedulingMedium

New things we're currently interested on

NameDescriptionTech you need to knowTech you will learnDifficulty
Mouseless for LinuxMouseless is a nice tool to practice keyboard shortcuts for a few popular apps. Unfortunately it's only available for Mac. We'd like to create an open-source Linux version that can be easily extended.Your choice??Unknown
BitTorrent over TLSBitTorrent protocol is not secure. Its encryption mechanism is outdated and weak. Even for obfuscation, it is ineffective. Nowadays, even an entry-level gateway has the capability to detect and block BitTorrent traffic at little to no risk. The BitTorrent community would benefit from a new standard encryption mechanism that allows strong encryption, forward secrecy and resistance to censorship.DependsNetworking, StandardizationHard
The next peer-to-peer protocolBitTorrent is of course the world's most used peer to peer protocol. It's great, but it was designed before the cloud was ubiquitous and it doesn't make use of the places where you have the most storage or the most bandwidth. Can we design something for the next decade?DependsPeer-to-peer, cloudUnknown
Linux tuning for network throughputCome up with a system that tunes the linux kernel to maximize network throughput for a number of workloads, such as web server or BitTorrent. We will provide access to a server with a huge pipe (10 Gbit/s, SSD, lots of cores) and your job is to build a tool that maximizes the throughput (and prove it!)LinuxKernel internals, NetworkingHard

About us

We are a small org, which means that your contribution will have a large impact. It's not going to mean a 0.5% improvement on a big project --- it's going to be more than 10% on a medium size one. If you like challenges and want a chance to shine this is your place.

We have we think statistically amazing continuity in the team: Most GSoC students from all the past years are still involved, even if they are no longer eligible as students. They still contribute code, and they mentor both in GSoC and the sister program GCI. As mentors, they also come to the Summer of Code summit which traditionally takes place in October.

We have mentors all over the world (North America, Europe, Asia and Australia), so time zones are never a problem. Our main channel of communication is a Slack channel to which everyone is welcome. We expect all accepted students to be available on Slack very often, even if you don't need to talk to your mentor. This will help you ask questions when necessary, and you might be able to help others out as well while working on your project.

Exception: If your country (such as Russia) has banned Slack please get in touch in we'll work out a solution with you. We absolutely want you to participate.

A mailing list is also available for those that prefer email over slack. It's a new mailing list (the old one hasn't been used in a long time) but it's read by everyone involved in GSoC.

All our top committers will be mentoring. Many of them are former GSoC students or winners of GCI.


All accepted students get a programming book immediately after being accepted, with the hope that they read them before the coding starts. We want to see if this increases the quality of the work. So far we have selected these three books (pick one), but we're open to suggestions: Clean Code, Elements of Programming Interviews in Python, Cracking the code interview.

We will also provide to all accepted students: - 6 months of access (from the acceptance date) to all courses in - 12 months of access (from the acceptance date) to backtobackswe, which is a fantastic resource to learn algorithms, prepare for coding interviews, and in general learn fundamentals.

The student working on CEA-708 will also receive a copy of the latest CEA-708 specification document.

About what we use

This is what we use today. It doesn't mean this is what we want to continue using. Probably not --- we're really open to change. We're just describing the status quo so you know what you are getting into :-)

The core tool that names the organization (CCExtractor) is a command-line program written in C (not C++).

The current Windows GUI is written in C #, and we have another GUI for Linux that's written with Qt, and a small GUI that's integrated into the main program (C). In we're being honest, nothing is great. Good news for you is that you can start over if you want.

The testing tool we use to run regression tests is mainly written in Python, but it also used Javascript, CSS and some shell scripting. The Test suite is written in C#. One of the projects this year is about replacing it.

The prototype real time subtitle website is written in NodeJS.

We also have a number of support tools that do a number of different things, from downloading subtitles from streaming services to translating them with Google Translate or DeepL. Most of them are written in Python, but since they are small tools that do their job you don't need to worry much about them.

For totally new things you can use whatever tool you feel is best for the job.

About sample media and other resources

We work with huge files. Not all of them are huge, but many are. We know that many students don't have access to high speed internet. To those students we will ship (as soon as they are selected) a portable hard drive with all our samples. So if your internet connection is not good, don't worry --- as long as you can plug a USB drive to your development computer you can participate with us.

We also have a shared Linux development server with lots of storage and a Gigabit uplink. Students get an account on it and they are welcome to use it. There's nothing there except our own work, so it's a trusted environment (for a server that is connected to internet of course).

The sample platform also hosts a bunch of samples, both which are small or decently sized.

Some projects have specific requirements: For example to add support for JokerTV you will need a physical JokerTV device. We will send one to the student that takes this project well before GSoC starts. The LiveTV project requires a subscription to YouTube with LiveTV (whatever it's called this week) and Hulu. We will pay for those. If your project requires some cloud resources (Google Compute Engine, for example), we will pay for that, too.

In general, you are not expected to pay for anything (other than your own development computer and internet, of course) related to any project.

If you need anything not mentioned (such as a book) let us know. Within reason, we'll help you.

About the projects and getting accepted

Qualification: Our selection system is based on several factors. Of course no student ranks in all criteria, so don't worry when you read the list below.

Work on our core tool: Even if you are going to be working on something totally different. This might seen counter intuitive, but the thing is if you prove you can dig into our (messy) code base, find yourself your way around it, and fix a few bugs, you are just the kind of person we can trust to "figure things out". GSoC is among other things, a learning experience. No matter what project you decide to work on, there's going to be roadblocks, things you don't know how to do, etc. So we really like it when students embrace those situations.

Qualification tasks specific to the project: The detail page for some projects contains specific qualification tasks that apply to them.

Contributions to existing open source projects: This can be anything. From a good GitHub profile to pull-requests sent to any other existing project, participation in hackathons, Google Code-In, past GSoCs and so on.

A good proposal: This is the one criteria that is non-negotiable. Your proposal has to be good, period.

Project popularity: Some ideas just have more competition, so if participating in GSoC is a top priority for you (over working on a specific project), consider applying to one of the "niche" ideas. After all, that's a great way to get your foot in the door :-)

Best core tool tasks

We're added a difficulty level to all our open issues on GitHub. Best thing you can do is head there and see if you are able to fix some of the easy ones and work your way up. We don't expect you to be able to do the hard ones but we'd be impressed if you did :-)

For some of the easy ones you don't even need to know C. Just being able to compile CCExtractor and dig around a bit will be enough.

The sample platform's issues are tagged with "gsoc-proposal-task", so you can easily see what you can work on.

Take home qualification tasks

If instead of working on existing code you'd prefer to show us your skills working on something new, you can pick one of these projects.

Community etiquette

It goes without saying that everyone in the community has to be polite and respectful, and consider everyone else a member of a team and not a competitor.

All developers are part of the team, by the way. Our Slack channel has mentors, code-in participants, other students, or developers and users that are none of the above but they all play some kind of role in CCExtractor's community.

Part of being respectful is giving consideration to everyone else's time. Most of us have day jobs, and as such are limited in the time we can use to guide you. We'd like to spend it on quality discussions, and not on things that are for example written on this website, things that you can easily retrieve by reading documentation on used libraries or on the software's help screen. Asking this kind of questions in the Slack channel shows little respect for our time. This doesn't mean you can't ask questions, but remember that being a clueless user and a lazy developer are two very different things. If you ask those questions you will probably get an answer as if you were a clueless user (polite no matter what), but if you apply to GSoC you will be considered a lazy developer. Google is your friend ;)

Tell things as you see them. Politely -you're not Linus-, but don't sugar-coat it. We know some parts of our code is poorly written, poorly documented, etc. It stands out, so you will know when you dig in. No one is going to be offended by having that code rewritten or refactored. Peer review applies to everybody's work and is done by everybody.

Cross project proposals

Because we use a number of libraries and in fact "are a library" ourselves (meaning other programs can link CCExtractor as a library, or invoke the binary) we interact with other communities and their software. From time to time there's a chance to do something interesting that affects CCExtractor and something else (FFmpeg comes to mind, but also Kodi, VLC, libGPAC, Red Hen, to mention just a few of our friends that typically participate in Summer of Code). So how does this work? As long as the work benefits CCExtractor and it's part of your summer project, we're OK with you spending some time on the other project. For example if you are improving our MP4 support, for which we use libGPAC, and need to fix or improve something on libGPAC you are welcome to do so. If you do, make sure you submit your changes to their maintainers and follow through with their merge process.

Your proposal

You can propose to do any of the following ideas, or you can bring your own. In any case, make sure you run them by us before you actually submit your proposal.

At the very least your proposal needs to

  • Explain what you want to do, why it is important to you (don't make up a story here — the reason can be that you need it, that you just think it's cool, that you have an itch to work on it, etc), and why it could be important or useful to us.
  • Explain how you intend to accomplish the goal, in enough detail that makes it clear that you have done your homework. For example, “I will modify the CCExtractor binary so that it's able to convert audio to text with perfect accuracy” is the same thing as sending your proposal to the trash. You need to have a plan.
  • Detail the timeline explaining what the expected progress is for each week or every two weeks (pay special attention to the milestones within the GSoC timeline itself, of course) and how we should validate the results.
  • Detail what kind of support you will need from us. For example, if you are going to need test streams, hardware, access to a server, etc, let us know, so we can prepare everything for you as soon as possible.
  • Detail your expected working hours in UTC. We're used to weird working schedules, so don't worry about working in the middle of the night, or weekends instead of other days, etc. Knowing your hours may help us to match you better with a mentor.
  • Mention your planned absences. We don't need you to detail what you will be doing when you are not working of course, but if you are going away for any reason we need to know so we don't think you've abandoned.
  • Link to your GitHub (or any other repository) profile, if you have one, so we can take a look at your previous work.
  • GSoC is a coding program: This means that ideas that are about testing (unless it involves coding something to test our programs ;) ), website design, etc, are out.
  • However, we want to have good documentation: Make sure you have time to write a good technical article explaining your work.
  • Be realistic and honest with the timeline. Consider each week you should work around 30 hours. If your timeline reserves a lot of time for minor things we'll think that you are not going to be working full-time in GSoC. On the other hand if you promise to do things in a lot less than that it seems realistic to us it will seem that you don't really know how much work things take.
  • If you are going to be using 3rd party libraries (that's OK), make sure to validate that their license is compatible with GPLv2 (which is ours). List the libraries in your proposal. Check that they are cross-platform. If you will need to extend those libraries in any way please explain. In this case, your proposal should include time to get that extension submitted to the maintainers (we love to contribute to other projects).

Something else: Mentors often have their fingers in several pies. If you send the same proposal to several orgs everyone will know. So do yourself a favor and don't do that. You can apply to several organizations and that's totally fine, but each organization will want to see that you have put the time to write a great proposal that is focused on them.

Useful resources

A great resource for GSoC.