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Summer of Code/GSoC2007Summer of Code/GSoC2007

Contents

Introduction

This list contains tasks taken at Google Summer of Code 2007.

Generic infrastructure tasks

Small devices backend

Technical Contact: Eugene Sandulenko, Max Horn

This task was being worked on as part of the Google Summer of Code 2007

Background:

ScummVM has been ported to many platforms, often by simply re-using the SDL backend (which is based on SDL, which by itself has been ported to many platforms, making it fairly easy to port ScummVM to any of these platforms, too).

But for some platforms, dedicated backends are required, either because SDL doesn't support them, or because we can't achieve all our needs by using the SDL port (e.g. because we need more speed, more control, etc.). These backends are typically made for what we call "small systems" -- systems like PDAs or smartphones (PalmOS, Symbian, WinCE), or game consoles (Dreamcast, GP2X/GP32, Nintendo DS, PlayStation 2, PlayStation Portable). These systems share many features. In particular they often have no (full) keyboard and quite limited resources: Little RAM, little permanent storage space, not that much CPU power, or a limited screen resolution.

This makes it often necessary to (re)implement certain functionality, like virtual keyboards, or graphic downscalers.

The Task:

Since the same needs occur again and again, it would be nice to implement such functionality only once in a sufficiently portable and flexible way, making it possible for backends to pick and use whatever they need. Details and further suggestions as to how to achieved this can be found on the Small Devices Backend page.

Besides this, optimizing code for speed and memory usage benefits all our targets, and in particular these "small devices". Hence doing this is a worthy goal on its own.

File system abstraction layer

Technical Contact: Max Horn

This task was being worked on as part of the Google Summer of Code 2007

Background:

ScummVM runs on a great variety of platforms, ranging from full-blown personal computers running Windows, Linux, Mac OS X, etc., to game consoles, smart phones and PDAs (sorry, no support for toasters yet :).

To achieve that, we have to provide abstract APIs for many things, like audio and graphics, user input, and general I/O. One particular area that needs to be covered are filesystems -- great differences exist with regards to this between the platforms we support. In fact, some of them don't even have such a thing as a filesystem.

Still, we need to access files: we have to find and load the game data, GUI themes, save states, config files and more (and also have to store save states, obviously). To compensate for the differences between our target systems, we introduced the FilesystemNode API.

In its present state, it fulfills our absolute minimal requirements. However, the abstraction level it provides is flawed and likely should be overhauled / redesigned. Also, not all parts of ScummVM strictly use this API; there are still many parts of ScummVM which try to work with "paths" to access file data.

The Task:

To work on this, you should be familiar with at least Windows and Unix, ideally more, and be willing to learn about the differences between file systems on many different platforms (our team will be happy to help you with this). You will have to design a revised FilesystemNode API, and implement it, based on the needs of ScummVM engines and infrastructure code (requiring close communication with the rest of the team).

Reference:

This is not a new problem in the computer world. Some links which might serve as helpful inspiration:

Audio related tasks

Mixer improvements

Technical Contact: Max Horn

This task was being worked on as part of the Google Summer of Code 2007

Background:

Most games we supported need to play sampled audio data (PCM encoded). In addition, some code which emulates certain audio devices (like the MT-32 emulator, the FMOPL code or Amiga MOD players) need to do so. To facilitate this, we provide certain APIs: The so-called Mixer object takes a number of AudioStream objects and mixes the audio data it fetches from these together, taking into consideration various external parameters like volume and pan controls. The abstract AudioStream class in turn provides a convenient and flexible way for code which needs to generate and output sampled audio data.

Audiostreams can provide their data with arbitrary sample rates, and the mixer has to convert these to sample rate by the audio output device provided by the backend (which usually means converting to a sample rate of 22050 Hz or 44100 Hz). Currently, we only have a simple linear rate converter.

The Task:

There are much better ways to resample audio data. It should be band pass filtered and other things done to it. Code to do this exists out there. Integrate such code into ScummVM or roll your own. Make sure to keep resource constraints (CPU, memory) in mind. It should be possible to select which resample to use (the low quality but fast linear filter, or your high quality but not quite so fast fancy filter).

Furthermore, on some systems, ScummVM suffers from stutter even though there is plenty CPU power left. The problem here is latency (not throughput). That is, while we can generate data fast, we do so too late. The problem on these system likely could be fixed by using a double buffering approach, i.e. generate audio data slightly before it is requested to avoid latency issues.

Finally, our AudioStreams currently only can have a single fixed sample rate. But for some usages (in particular, Amiga MOD players), it would be convenient to allow streams to change their sample rate on the fly. Adding support for this would be nice, but should not slow down streams which have a constant sample rate.

Reference:

Some links which might be useful if you are interested in this task:

  • The Digital Audio Resampling Home Page describes digital audio sampling-rate conversion and related concepts.
  • Secret Rabbit Code (aka libsamplerate) is a Sample Rate Converter for audio. The SRC quality page contains links to various other sample rate conversion tools.
  • SOX, the swiss army knife of sound processing programs, also contains resampling code.
  • sr-convert is a sample-rate conversion utility for WAV files.

Revive ScummEX (likely from scratch)

Technical Contact: Max Horn

This task was being worked on as part of the Google Summer of Code 2007

Background:

ScummEX (short for "Scumm EXplorer") is a tool which allows browsing the data files of games supported by ScummVM. That's the theory. Current reality is that the ScummEX version in our Subversion repository only supports a subset of SCUMM games (i.e. not even all SCUMM games, not even talking about *all* games supported by ScummVM). It also is based on an old version of wxWidgets, and written in a rather crude way. Hence, starting from a clean new code base likely is the best way to approach this.

The Task:

The goal would be to write a new graphical tool which allows browsing of data files of games supported by ScummVM. Some requirements:

  • It must run on at least Linux, Windows XP, Mac OS X -- more are preferable, of course. You could use wx.
  • Should likely be written in C++ (other languages, like Python or Java, might be acceptable, if the result is sufficiently portable.
  • Browse at least the data of SCUMM v5 till v8 games.
  • Support for older SCUMM versions, and HE SCUMM games, as well for non-SCUMM games, is not necessary, but the code should be written modular/abstract enough to make it possible to add support for more data formats w/o too much trouble
  • Only viewing data is necessary, not being able to edit it (although we won't complain if that's possible :)
  • The interface can be designed in many different ways, but at least SCUMM data tends to suggest a main view with some kind of "data tree", in which one can select specific resources, and view them.
  • Viewing the raw hex data of resources is required.
  • It should be possible to add custom "views" for data (e.g. viewing images as images, not just as hex data; or hooking up a script disassembler; etc.). It is *not* necessary to provide such viewers for all resources types initially, but it must be possible to add them.

Tools

Tools: Game script (bytecode) decompiler

Technical Contact: Max Horn

This task was being worked on as part of the Google Summer of Code 2007

Background:

Most (all?) adventure engines ScummVM supports are driven by bytecode scripts, which control the game behavior. For various reasons (in particular, debugging), it's very useful to be able to take such a script and decompile it into something resembling regular code (with variables, loops, if statements etc.). We have a tool for doing this for the bytecode used by SCUMM games. This tool is called descumm.

Currently, descumm use a relatively crude heuristic to detect "if" statements, loops and so on. In particular, it only supports loops with the condition at the start (think "while(...) { ... }" ), not such with the condition at the end (as in "do { ... } while(...)" and also suffers from various other limitations (like not being able to correctly recognize "continue" and "break" statements.

The whole thing is somewhat complicated by the fact that there are two main versions of this bytecode: V5 and older (register based bytecode), and V6 and newer (stack based).

The Task:

Write an improved bytecode decompiler for SCUMM games, based on the existing "descumm" tool. Initially, support for only one version of the SCUMM bytecode (e.g. plain V5 or V6 or V8) is needed, but everything should be designed and implemented such that it is possible to support all SCUMM versions eventually. Even better would be if the core of the decompiler was so generic that it could be reused to decompile other bytecode dialects (and hence write improved versions of the "dekyra" and "desword2" tools).

A good starting point for this might be the [Jode] Java bytecode decompiler, the author of which used to be on the ScummVM team. The technical contact has several ideas on how to approach this project, too.

The tool should run on at least Windows, Mac OS X and Linux. Acceptable languages include C/C++, Python, Perl, Ruby -- other languages might be OK, but please consult with us first (after all, other developers also will have to use and maintain your code).

Tools: Write a portable GUI for the tools

Technical Contact: Max Horn

This task was being worked on as part of the Google Summer of Code 2007

Background:

We offer a multitude of command line tools in a separate packages (scummvm-tools). Several of these tools are to be used by end users, mainly to (re)compress their data files (good for systems which have not that much storage, like cell phones). But asking end users to use command line tools to perform common tasks is somewhat problematic.

The Task:

We would like to make it easier for users to compress their data files, by offering them a nice graphical user interface (GUI). It should support at least Linux, Windows, Mac OS X, ideally more. This could for example be achieved by using wxWidgets or Qt.

Note that the command line versions of the tools should still be available, for use in shell scripts or on systems where the GUI is not available. This likely requires modularizing the code sufficiently.

Also note that this task meshes well with the previous task (of overhauling the compression tools).

Engine/game specific

Improve AGI engine

Technical Contact: Eugene Sandulenko, Stuart George

This task was being worked on as part of the Google Summer of Code 2007

Background:

We recently added support for many older Sierra games, by adding the AGI engine, by assimilating the Sarien project. Despite the relative age of the code behind this (i.e., Sarien already existed and matured for several years), there are various open tasks:

  • Implement AGI256 and AGI256-2 engine extensions
  • Fix bugs triggered by fan made games
  • Finish implementation of Apple IIgs sound
  • Finish implementation of predictive input
  • Add Amiga style (colored) menus
  • Add a Hercules emulation mode

Some of these tasks will require engine knowledge, but the engine itself is tiny and well documented, so it should be possible to learn enough about it in a relatively brief period of time. Additionally NAGI and DAGII could be used as reference. Particularly, NAGI is known to be more compatible with fan made games

 

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