Handling iming and Exposure Information in Video Mode

antoinec

Hello,

I'm currently working with the ZWO ASI SDK in C++ to control multiple ASI cameras simultaneously, each with potentially different exposure times. I’m using video mode and would like to start all cameras synchronously.
Below is an overview of my setup and the challenges I’m facing with timing and exposure information.

My Setup

I use ASIStartVideoCapture() to begin video capture for each camera.
Each camera has its own thread, which retrieves frames using ASIGetVideoData() in a loop.
Exposure times are set individually for each camera using ASISetControlValue() with ASI_EXPOSURE.

My Questions

Synchronous Start : Since each camera has a different exposure time, I want to ensure that all cameras start their captures as synchronously as possible, despite using separate threads for each.
Are there any recommended techniques for achieving synchronous capture across multiple cameras in this kind of setup?
Timestamping Frames : Is there a way to get precise information about when a frame exposure started and ended? Currently, I timestamp the frames when they are retrieved from the buffer using ASIGetVideoData(), but this only gives me the time the frame was pulled, not the actual exposure period.
Exposure Timing for Each Frame : Does ASIGetControlValue(ASI_EXPOSURE)provide the exact exposure time for the frame I just retrieved, or is it just the last set value? Is there any way to get the precise exposure time for each individual frame?
Best Practices for Timings: Since ASIGetVideoData() can block while waiting for frames, are there best practices for managing and synchronizing timing information (e.g., exposure start and end times) when controlling multiple cameras with separate threads? I want to avoid losing frames or introducing timing inaccuracies, especially given the different exposure durations across cameras.

Thank you in advance !

Antoine

Tech@ZWO

antoinec
1 Sorry, it does not support that, only some OEM trigger cameras can realize this.
2 The same as above, only OEM GPS camera supports to access the exposure started and ended time.
3 It is the time you set, not the exact exposure time
4 Every cameras has its separate thread to handle, no need to worry that.