Wiki > Main > SummerOfCode2010 (compare)
Difference: SummerOfCode2010 (r76 vs. r75)
If you are considering applying to Rockbox (or any other organization, in fact), you may want to have a look at this wiki page: http://code.google.com/p/google-summer-of-code/wiki/AdviceforStudents . It contains a lot of good advice about what you should expect during the Summer of Code and helps you create a good proposal.
Please use the template from GSoCApplicationTemplate2010 as a guideline when submitting your application to google.
If you're serious about working on Rockbox for SoC, then the best way you can show us is to start getting involved in the project before you make your application - i.e. download the code, hang out in our IRC channel, subscribe to our mailing lists, and start submitting patches.
The following list are the main project ideas the Rockbox project would like to see completed for SoC 2010. Applications for these projects are more likely to be accepted.
If you are a student planning on applying, please come into our IRC channel on FreeNode and talk to us about it! Please do not contact possible mentors personally at this stage.
Rockbox is a replacement firmware for portable audio players - it consists of a kernel, hardware drivers and a music-playing application and completely replaces the existing software on a device (although dual-booting is normally available). Portable devices which allow third party applications to run within the retail OS are becoming increasingly popular and this project would take the "application" part of Rockbox and run it on such a device.
Rockbox can currently be compiled to run as a "UI Simulator" on a PC using SDL for the UI. This can be used as a basis of this project, but requires restructuring the Rockbox code to use create a clean "Application" target, instead of a simulator.
The student is free to choose any such device to port Rockbox to, but the following are potential targets:
Some further background information is available at http://daniel.haxx.se/blog/2010/02/15/the-rockbox-future-is-an-app/
A mid-term goal could be to undertake the refactoring of the existing Rockbox code and produce a Rockbox application capable of running in a dexktop environment using SDL
The remaining part of the summer could be spent porting this Rockbox application to a portable device.
Windows Media Audio (WMA) is a set of four audio codecs:
Rockbox currently just supports WMA Standard, as well as a parser for the ASF container format WMA audio is usually stored in.
This project would extend Rockbox's WMA support by porting existing open source WMA Professional and WMA Voice decoders from [[http://www.ffmpeg.org][ffmpeg]. There is no existing open source decoder for WMA Lossless.
During GSOC2008 a floating point WMA Pro codec was implemented for ffmpeg. This project would port this codec to Rockbox by removing all floating point code, streamlining memory usage, and adding assembler optimisations for at least some Rockbox devices (ARM, Coldfire and MIPS).
Similarly, there is a floating point WMA Voice codec in ffmpeg which would need the same treatment.
A student could either propose to port both codecs by mid-term, and then spend the rest of the summer optimising and bug-fixing, or to completely implement one codec by mid-term, and then the second by the end of summer.
We would expect by the end of the summer to have two new working codecs in Rockbox, with some degree of optimisation
Rockbox's core function is audio playback, and the efficiency at which Rockbox can do that has a direct impact on the battery run-time of the portable devices Rockbox runs on - codecs can never run too efficiently.
A project to work on codec optimisation assumes a student with some knowledge of either assembly programming, digital signal processing, or processor optimization, but not necessarily an extensive knowledge of audio compression. Learning about fixed-point arithmetic maybe needed for some of the codecs projects too. Mentoring will be provided to bring a student's knowledge up to par during the project. If in doubt, ask in IRC about any of these proposals, or come up with one that suits you.
Possible optimisation work includes:
Rockbox has a fixed point MP3 decoder based on libmad. Unfortunately libmad is not particularly fast even after extensive optimization. For example, on ARM7TDMI?, Rockbox uses 38MHz for 128k MP3. The official ARM decoder uses 29MHz, a difference of almost 25%. Other libraries exist for decoding mp3, each with their own strengths and weaknesses. In this project, a student would explore the performance of each of the major components of our decoder and then evaluate possible replacements in other codec libraries (ffmpeg, etc) or implement their own code based on algorithms in the literature. The goal would be to produce a decoders using either the best known algorithm or best known open source code for each step in the decoding process. The resulting improvements to Rockbox would reduce power consumption and provide the open source community with substantially more efficient embedded MPEG codecs.
Rockbox has a fixed point AAC decoder based on libfaad. Unfortunately libfaad is not particularly fast even after extensive optimization. For example, on ARM7TDMI?, Rockbox uses over 120MHz for 64kbps AAC-HE. The Helix ARM decoder uses only 60 MHz - a difference of over 100%. FFmpeg provides a much more efficient, but floating point decoder. In this project, a student would explore combining some or all of the ffmpeg decoder into Rockbox, either replacing or augmenting libfaad, but it's much preferable to replace libfaad completely. The ffmpeg decoder would be converted to fixed point and optimized for embedded decoding. The resulting improvements to Rockbox would reduce power consumption and provide the open source community with substantially more efficient embedded MPEG codecs.
Some new rockbox targets run on MIPS CPUs. In this project, a student would review various ARM assembly optimizations added to MP3, Vorbis, AAC, WMA and FLAC and then port them to MIPS. This would ensure that rockbox's exceptionally fast codec library can be used efficiently on MIPS CPUs, and also provide fast embedded MIPS codecs for formats that currently lack them.
Create a stand alone command line version of the rockbox codec api functions so that rockbox codecs can be compiled and tested outside of rockbox, much as ffmpeg codecs can be tested from the command line. Then optimize codecs in order to fit into certain memory or CPU usage goals. Introduce standard, optimized library functions for common tasks to complement the existing IMDCT library (such as bitstream parsing, huffman decoding, etc). The goal of this project would be to improve the performance and memory usage of rockbox codecs, while making them accessible to other embedded projects.
Due to the open scope of this project idea we would rely on the student to provide project goals.
Rockbox currently has limited video playback via the mpegplayer plugin. This can play MPEG program streams containing MPEG-1 or MPEG-2 video and MPEG audio.
There are many areas where Rockbox's video playing capabilities can be improved, including support for more video/audio codecs, support for different container formats, making use of hardware video acceleration or integrating video playback into Rockbox's core audio playback engine (allowing mixed audio/video playlists).
An initial step that any project to enhance video playback in Rockbox would be to refactor the existing mpegplayer plugin to implement an infrastructure for multiple video/audio codec or container format support.
Some specific proposals:
A student undertaking this project could propose to implement a number of the smaller features proposed above, or a single large feature.
The precise skills depend on the tasks the student decides to undertake for this project.
The goals would depend on the precise enhancements the student proposes to implement.
However, we would expect a summer's work to involve implementing the infracture for multiple audio/video codec and container support and then adding a new video codec. In addition, existing Rockbox audio codecs (e.g. AC-3 and AAC) could be implemented as part of this project.
The following list are ideas for other projects that are wanted, but less likely to be accepted. These are only ideas and suggestions, students are free to make up and describe their own project when they apply.
NOTE: This is not a general wish list for Rockbox features. Don't add a project here without discussing it with the Rockbox developers first.
Rockbox currently supports speaking menus and filenames by premade voice clips. While this feature is especially for visually impaired people it has the major drawback that it doesn't work with texts that can't get prerendered easily. Examples for such texts are the database view (metadata from the files' tags) and filenames the user changed on the player (until a new voice clip is generated).
Adding a lightweight Text To Speech (TTS) engine would allow to overcome these problems. This will make more parts of Rockbox accessible to people that can't use the usual, graphical interface. An enginge that might be suited is espeak (the last version that is GPLv2+ is 1.26). Another possiblity could be flite.
Rockbox has an extremely complicated playback engine that can be run on many different devices as well as a PC simulator. Unfortunately, the PC simulator simulates the entire rockbox GUI, making it extremely difficult to reproduce some playback bugs due to timing issues and preventing automated testing. At the same time, the enormous number of features in the playback engine means that most changes seem to break obscure use cases.
Adding a simple interface for scripting rockbox actions would allow more easily reproducing problems identified on target, and allow for automated testing of changes to the playback engine. In this project a student would add the ability to compile rockbox's playback engine on PC without a GUI. Instead commands would be implemented by a test driver, a simple script that sequentially issued actions to the playback engine and recorded the result. Finally, the student would introduce a number of example tests for the playback engine involving common tasks such as changing tracks, seeking through an audio file, and building a playlist.
Port buflib from the pluginlib over to the core and use it to allocate big buffers in a more dynamic way.
Rockbox has no malloc() for various reasons (WhyNoMalloc). However, time has shown that fixed size static buffers limit us a lot: Either they're too big and waste precious RAM which often directly translates into a loss of battery life or they are too small and limit our users when it comes to customizability. As Rockbox runs on a wide range of targets, some with large hard disks and some with small flash based memory, some with small greyscale screens and others with large color screens, choosing appropriate buffer sizes gets harder and harder. The pluginlib has a powerful buflib library which is handle-based able to move/resize/compact allocated and unused memory.
This project would involve porting it over to the core and adapt some parts of Rockbox to use it so that we can get rid of many fixed size buffers. Most work would be spend on making the code base aware of the fact that memory may move and to make the audio buffering engine handle an audio buffer that changes its size and location at runtime.
The student would be expected to port the buflib, and adapt a simple part of rockbox (e.g : a codec) to use it, as a proof-of-concept. Then work would continue by adapting more parts of rockbox as time allows, starting with the playback code.
The current radio code is mostly in apps/recorder/radio.c and is a big mess of tuning/ presets handling/ the actual radio screen/ etc. The ideal outcome of this project would be to split that one file into separate files handling radio presets, the driver layer, and a GUI layer.
http://www.rockbox.org/tracker/task/9573? might be a good starting point.
The student would be expected to extract the different parts of the existing code into separate modules and come up with a clean radio interface (building on the existing tuner_get/set() system). Another major goal would be to update the GUI code (radio_screen() ) to update it to fully use the action system and get out of the #ifdef hell which is still there. Lastly the presets should be moved out and made cleaner.
Many targets feature both internal storage and a slot for external storage to be inserted (SD card slot, etc). Currently Rockbox shows the SD/MMC/... card as a separate volume (on one currently in development device, it even shows an external card as the main file system and the internal one as a separate storage, because it's can't be writteb for now).
Ideally, Rockbox could (optionally) show both the internal storage and the external card(s) as a single filesystem. The volumes would of course need to have certain priorities (for filename collisions, writes, etc), however it should be presented to the user and behave as one filesystem. They are several reasons to use such a system, some of them are:
This is not a trivial task, particularly because it probably means fiddling with different code layers like the storage API, directory and tag cache.
A mid term goal could be to implement the union file system for the storage API part, not taking into account caching and not investigating too much which parts of the rockbox code have to be updated. The focus would be on functionality, user settings can be implemented later. Special care will be taken about the fact that this is dynamic: the user can eject an external card and the code has to handle that !
The remaining part of the summer could be spent on fixing the directory cache if needed and updating the rest of the code to take the unionfs into account (or not !). Updating the tag cache can also be needed (this part is really tricky, there are decisions to take).
Rockbox uses a plugin architecture for some of its features, mainly codecs and what are actually called "Plugins" in the user interface. Currently, only one plugin of each type can be loaded at a time. There is a demand to be able to run multiple plugins in parallel. This is not possible currently, because plugins are compiled at a fixed address at the start of the plugin buffer. The project would mean to create a framework which allows plugins to be compiled and linked with relocation information, to be resolved at load time. It would probably also mean finding new file format for the plugins, such as coff or elf (or look at elf2flt). Of course part of the job is to adapt the core plugin loader to handle more than a single plugin and a new file format too.
Reasons for this ability to run multiple plugins are:
This project requires a basic understanding of the compile-assemble-link chain and to get known to various alternative binary formats. It may even require changing an existing format to fit our needs.
The mid-term goal would be to have the new loader working and demonstrated, but not necessarily fully integrated yet.
By the end of the summer, we'd expect to have both plugins and codecs working with the new system, as well as working visualisation plugins for the WPS, and possibly USB plugins.
Since virtually all new DAPs coming to market contain an ARM core, a well working ARM emulator would be extremely useful many aspects of Rockbox development.
An emulator could be used to help reverse hash/encryption algorithms used in many retail firmwares (such as Apple, Sandisk, Creative players), to help determine addresses of memory mapped hardware, and to optimize codecs by allowing more detailed analysis of memory/IRAM/etc.
A simple but only semi-functional Windows emulator exists for the Sansa E200 series which emulates much of the PortalPlayer hardware. It currently can boot some builds of rockbox, but is not stable enough to be very useful.
This project could resume work on that emulator (or pick another to use), first getting it to run rockbox or a retail (Sandisk, Apple, etc) firmware without instability. This would involve a process a lot like porting rockbox, but in reverse. Starting with the drivers in Rockbox, one would need to implement the hardware devices they interact with until rockbox (and hopefully the OF) could run as if on real hardware. These would include LCD controller, various internal memories, buttons, and audio hardware.
Additional goals could include emulating the pipeline latencies of various ARM cores, emulating cache to allow memory profiling and introducing a general framework that would allow for easy adaptation to the differing memory maps of various ARM cores.
Another approach would be to have a look at SkyEye to see if we can build upon that. It is designed to emulate various ARM SOCs and could likely be improved to support a SOC used by Rockbox. As an added bonus, it can already run Linux for ARM. Given the advanced state of SkyEye, this may be a better place to start.
An mid-term goal would be for an emulator capable of booting and running one Rockbox target build. By the end of the summer, multiple Rockbox devices would be emulated, proving the multi-SoC capabilities of the emulator.
Sansa has some docks that allow remote control of the device. Some of the higher profile ones that are able to be sourced from your favorite used goods sites are: Sandisk Sansa Docking Station, Timex Clock Radio for Sansa, and Altec-Lansing inMotion im413.
The goal of this project is to allow those docks to be used to control rockbox.
Suggested first steps would be to learn the method and protocol that the dock communicates with the Sansa after receiving remote events (with substeps of possibly figuring out the proper pins to put under a scope). The probable communication methods are Serial, I2C, or USB.
Once the communication method is known, the project would progress onto understanding and implementing the protocol much like the clever folks who did the IPod Accessory Protocol (IAP). There are various details that can be learned from the forum and irc logs about previous research into this and into the IAP.
By mid-term, it would be good to understand at least the basic communication protocol.
At the end of the summer, rockbox should be controllable using one of the docks.
There are already a number of online services on the rockbox webpage to help the community. For example there is the Themepage to host and automatically check all those user generated themes for rockbox various devices. And there is a page to allow people to easily translate rockbox into their own language.
Improving and or adding additional services could greatly help the community. Possible tasks are:
Ofcouse students can also suggest other usefull services.
Current rockbox webservices are written with php, but other languages are also possible for new services.
A possible midterm goal could be to create one service new from scratch.
The remaining part of the summer could be spent developing a second service, or makeing big improvements on existing services.
Rockbox is customizable with themes. Themes are created using a tag-based language and contributed by users (see http://themes.rockbox.org). With these tags a wide variety of aspects can get controlled. The part of Rockbox that's been customizable the longest time is the While Playing Screen (WPS). However, this language is specific to Rockbox -- you might consider it some kind of "compiled markup". This requires artists to learn that language before creating a theme is possible.
A graphical editor for theme files would greatly simplify the process of creating themes. The simplest form of such an editor would be a text editor with syntax hilighting, syntax checking of the input, immediately rendering of the theme file and shortcut buttons to insert available tags.
The current Theme Editor is based on Qt and written in C++. Using a different toolkit and / or programming language can be discussed, though this list assumes keeping the current ones.
r76 - 11 Mar 2011 - 15:52:23 - AustinAppelRevision r76 - 11 Mar 2011 - 15:52 - AustinAppel
Revision r75 - 07 May 2010 - 20:10 - DominikWenger
Copyright © by the contributing authors.