Proposal: opt-in continuous camera capture API

[SolveSoul]

The current ps2cam API is caller-driven: applications read packets or assemble a frame when they need one.

That's useful for snapshots and intermittent capture. For real-time camera applications, it may also be useful to offer an opt-in continuous-capture mode where the IOP keeps receiving and assembling frames, while the EE retrieves the newest complete frame when ready.

I am experimenting with this in a homebrew project and would be happy to contribute an implementation, but I would like feedback on the API and architecture before preparing a PR. For the homebrew project, I needed local SDK patches to support continuous video capture. This could open up more EyeToy-style homebrew possibilities.

Initial shape:

int PS2CamStartFrameCapture(int handle);
int PS2CamReadLatestFrame(int handle, void *buffer, int buffer_size);
int PS2CamStopFrameCapture(int handle);

Key compatibility goals:

• Existing packet and single-frame APIs retain their current behaviour.
• Continuous capture is an additional opt-in mode. It is mutually exclusive with caller-driven reads on the same handle.
• Capture state and buffers are per handle.
• Stopping or closing a device cleanly terminates its capture worker.
• New RPC commands are version/capability-gated.

I’m also looking for input on implementation placement: should this be a small adjacent capture module, or remain in ps2cam.c?

[Florin9doi]

For an EyeToy-style app, you'll probably need to switch the camera from jpeg mode to ipu/mpeg mode and uncompress the frames using the ipu to free some resources.

[SolveSoul]

@Florin9doi I've been working on some homebrew with EyeToy and I'm indeed letting the IPU do the heavy lifting to get a proper videofeed rather than jpeg decoding on the EE which is really bad performance-wise (tried picojpeg too, which was better but still not usable).

I've got it working on a local fork of the ps2sdk but I'm unsure what exactly would be usable for the SDK (include IPU decoding or not, separate file or all in ps2cam.c, etc).

I can push my work on a branch for review if you just want to check it out as-is.

I based the implementation on reverse engineering the EyeToy Play game which shipped with debug symbols back in the day.

Disclaimer: it works in pcsx2 but haven't been able to verify on real hardware as I'm short on actual hardware...