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Google Summer of Code 2011
What?Rockbox has been accepted to participate in GSoC 2011Accepted projects for GSoC 2011
Information for studentsIf 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 GSoCApplicationTemplate2011 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. 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.Project ideasNOTE: This is not a general wish list for Rockbox features. Don't add a project here without discussing it with the Rockbox developers first. These are only ideas and suggestions, students are free to make up and describe their own project when they apply.Audio codec optimisation (multiple possible projects listed)OverviewRockbox'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 (among many other things):AAC Codec OptimizationRockbox 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. 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.Improving the MDCT libraryRockbox has a single MDCT function used in AAC, WMA, WMA Pro, Vorbis, AC3, Cook and ATRAC3. The performance of this library thus impacts a number of formats. While the current implementation is algorithmically efficient (close to minimum total instruction count) it is not well optimized for many CPUs because it aims to have minimum possible memory use for low memory targets. It could be greatly improved on newer ARM devices at the cost of some memory. Additionally, most ASM is heavily biased in favor of ARMv4. ARMv5/6 or Coldfire implementations would greatly improve performance on other targets.Optimization for MIPS CPUsSome 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.MP3 Codec OptimizationRockbox 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. Note: this project involves comparing highly optimized libraries and identifying small improvements. Several of the proposals below involve much less well optimized libraries that will be substantially easier to optimize, are likely to be better suited to less experienced students.General ARM OptimizationRockbox has a large amount of ARM assembly code written primarily for ARM7TDMI cores. Newer ARM cores based on ARMv5E, ARMv6 or NEON offer a range of new features that could be used to improve rockbox on high end devices or Android based cell phones. In this project a student would propose to improve existing assembly code (or write new assembly from scratch) for newer ARM processors.Codec Library and OptimizationCreate 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.Completing the WMA Voice portDuring last year's GSoC, a port of the WMA Voice codec was started but it was never finished due to time constraints. Currently, the decoder works in the simulator only, and it's still in floating point. The project would aim mainly at completing the decoder port, and - according to progress - the encoder too. Work is basically divided into fixed-point conversion and optimisation for the different CPUs.Skills needed
Suggested goalsDue to the open scope of this project idea we would rely on the student to provide project goals.Potential mentorsPort buflib from the pluginlib over to the core and use it to allocate big buffers in a more dynamic way.OverviewRockbox 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.Skills involved
Suggested goalsThe 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.Potential mentorsStandalone playback core/libraryOverviewRockbox' core function is audio playback. Making it more robust and easier for developers to work in this area is desirable. Currently the playback core has some flaws and is quite enrooted into Rockbox. A project could extract the playback engine into a standalone library that can e.g. be built into an application to run on a PC so that it can be debugged more easily, enables us to run test suites on it, and that generally modularizes it so that it can evolve independently of Rockbox. A further goal could be to make it more Rockbox-agnostic in that it doesn't need Rockbox-specific function calls and data structures (e.g. functional with host kernel primitives or preemptive threads). Ideally, other parts of the Rockbox codebase (such as the metadata parser) would also be split out to libraries.Skills needed
Suggested goals
Potential mentorsImproved video playback (multiple possible projects listed)OverviewRockbox 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:
Skills involved
Suggested goalsThe 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.Potential mentorsMultiple/Relocatable PluginsOverviewRockbox 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:
Skills involved
Suggested goalsThe 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.Potential mentorsUSB CD emulationOverviewRockbox has had support for USB mass storage for a while now, on devices that have software-driven USB controllers (as opposed to the hardware USB-ATA bridge chips that were usual in older players). This project would add support for exporting a disk image file over USB instead of the usual raw disk, and would extend the SCSI handling to present a CDROM device instead of a hard disk. This would allow users to store iso images on a rockbox player, and use the player as a virtual CDROM drive to present those images to a PC, for e.g. recovery or installation purposes. If time permits, implementing all this as a plugin (and therefore allowing USB drivers in rockbox to be implemented as plugins) would be a worthwhile addition.Skills involved
Suggested goalsThe first step would probably be to provide hard disk image exporting, i.e. modifying the existing SCSI code to use a file as a backing store instead of a disk. After that, the SCSI code should be modified and extended to present an MMC device such as a CDROM or DVD drive. Of course the necessary settings and configuration code to control the feature must also be added.Potential mentorsText To SpeechOverviewRockbox 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 Rockbox to overcome these problems. This will make more parts of Rockbox accessible to people that can't use the usual, graphical interface. An engine that might be suited is espeak (the last version that is GPLv2+ is 1.26). There is proof-of-concept rockbox plugin utilizing eSpeak on the tracker which suffers licensing problems. Look at FS#7660 for futhter reference. Another possiblity could be flite. During SummerOfCode2010 there was efford taken to port flite to rb and it was proven non doable. The problem was massive small sized allocation which comes from the very nature of this type of TTS. Memory fragmentation issue seems to be nonsolvable in this case. Look at this ML thread for further reference.Skills involved
Suggested goals
Potential mentorsRockbox Playback Test DriverOverviewRockbox 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 easier reproduction of 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.Skills involved
Suggested goals
Potential mentorsClean up the radio codeOverviewThe 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. FS#9573 might be a good starting point.Skills involved
Suggested goalsThe 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.Potential MentorsMake multi-volume targets look like a single volume (like unionfs on linux)OverviewMany 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 written 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:
Skills involved
Suggested goalsA 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).Potential mentorsARM EmulatorOverviewSince virtually all new DAPs coming to market contain an ARM core, a well working ARM emulator would be extremely useful for 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.Skills involved
Suggested goalsAn 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.Potential mentorsApple/Sandisk/etc Various Docks, Remotes, AccessoriesOverviewSandisk and Apple have a number of accessories that allow control over devices remotely. In the case of Sandisk, these include the Sandisk Sansa Docking Station, Timex Clock Radio for Sansa, and Altec-Lansing inMotion im413. For Apple, this includes a very large number of devices and several different protocols. The simplest and earliest protocol communicates over RS232 and was reverse engineered many years ago. It is now fairly well supported. Newer devices use more advanced communication protocols, or even USB based communications. The goal of this project would be to expand the range of devices rockbox works with by some combination of:
Skills involved
Suggested goalsBy mid-term, it would be good to understand at least a basic communication protocol. At the end of the summer, rockbox should be controllable using some new device over a new protocol.Potential mentorsRockbox web/online servicesOverviewThere 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:
Skills involvedCurrent rockbox webservices are written with php, but other languages are also possible for new services.
Suggested goalsA 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.Potential mentorsCandidate MentorsCandidate Backup mentors
r45 - 02 Apr 2021 - 20:46:07 - UnknownUser
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