Expanding media capabilities of Win Embedded CE 6.0

Question

I have an embedded device with WinCE 6.0 as OS. The manufacturer provides an IDE for 3rd party development to it. The IDE pretty much allows nothing else than

• .NET 3.5 Compact Framework scripting that's invoked from various events from the main application
• Adding files to the device.

The included mediaplayer seems to be using DirectShow and the OS has media codec only for mpeg-1 encoded video playback. My goal is to to be able to play media encoded with some other codecs as well inside that main application.

I've already managed to use DirectShowNETCF (DirectShow wrapper for .NET Compact Framework) and successfully playback mpeg-1 encoded video.

I'm totally new with this stuff and I have tons of (stupid) questions. I'll try to narrow them down:

• The OS is based on WinCE, but as far as I've understood, it's actually always some customized version of it (via Platform Builder). Only "correct way" of developing anything for it afterwards is to use the SDK the manufacturer usually provides. Right? In my case, the SDK is extremely limited and tightly integrated into IDE as noted above. However, .NET CF 3.5 is capable for interop so its possible to call native libraries -as long as they are compiled for correct platform.

• Compiled code is pretty much just instructions for the processor (assembler code) and the compiler chooses the correct instructions based on the target processor setting. Also there's the PE-header that defines under which platform the program is meant to be run. If I target my "helloworld.exe" (does nothing but returns specific exit code) to x86 and compile it with VC, should it work?

• If the PE-header is in fact the problem, is it possible to setup for WINCE without the SDK? Do I REALLY need the whole SDK for creating a simple executable that uses only base types? I'm using VS2010, which doesn't even support smart device dev anymore and I'd hate to downgrade just for testing purposes.

• Above questions are prequel to my actual idea: Porting ffmpeg/ffdshow for WinCE. This actually already exists, but not targeted nor built for Intel Atom. Comments?

• If the native implementation is not possible and I would end up implementing some specific codec with C#...well that would probably be quite a massive task. But having to choose C# over native, could I run into problems with codec performance? I mean.. is C# THAT much slower?

Thank you.

Answer 1

I've not seen an OEM that shipped their own IDE, but it's certainly possible. That shouldn't change how apps can created, however. It's possible that they've done a lot of work to make sure only things from their IDE work, but that would be a serious amount of work for not that much benefit, so I'd think it's unlikely.

As for your specific questions:

• The OS is Windows CE, not "based on" it. The OS is, however, componentized, so not all pieces are going to be available. An SDK generally provides a mechanism to filter out what isn't available. You can actually use any SDK that targets the right processor architecture, but if your app calls into a library for something that isn't in the OS, then you'll get at the very least an error. For managed code this is all not relevant because the CF isn't componentized. If it's there, and CF app can run (and if it's not, you can often install it after the fact). This means that if the platform supports the CF, then you can write a CF app and run it. That app can then call native stuff via P/Invoke (unless, of course, the OS creator decided to add security to prevent that. This is possible in the OS, though I've never seen it implemented).
• Yes, compiled code is just "instructions". For native, yes, they are processor instructions. For managed, they are MSIL instructions that the managed runtime in turn converts to processor instructions at JIT time. If your target is an ARM platform, you cannot use an x86 compiler. Broadly speaking, you need to use the correct Microsoft compiler that support Windows CE, and call that compiler with the proper switches to tell it not only the processor architecture, but also the target OS because the linking that needs to be done will be different for OS-level APIs and even the C runtimes. The short of this is that for your platform, you need to use Visual Studio 2008 Pro.
• For native apps, you need some SDK that targets the same OS version (CE 6.0) and processor architecture (e.g. ARMv4I). Having it match the OS feature set is also useful but not a requirement. For managed code, you can just use the SDKs that ship with Studio because managed code is not processor-dependent. Still, you have to go back to Studio 2008 because 2010 doesn't have any WinCE compilers.
• If you've found an existing library, then you can try to use it. Things that might impede your progress are A) it's unlikely to use an SDK you have so you probably have to create new project files (painful, but workable) and B) if it uses features not available in your OS, then you'd have to work around those. If you're missing OS features, you're probably out of luck but if it already has a media player and codec, I suspect you'll be ok.
• Don't implement this in managed code. Seriously, just don't do it. Could you? Yes. Performance could probably be made to be nearly the same except to avoid GC stuttering you're going to have to basically create your own memory manager. The amount of work involved in this path is very, very large.