Overlay image render delay

Hi,

What are the minimum and maximum delays for rendering an overlay image with alpha blending (once it's uploaded to the playback card) onto a video frame on a DeckLink SDI 4K card? Is it always less than or equal to 1 frame delay?
I realize this is probably a hardware question, but I thought I'd ask here first.

Thanks!

[Cameron Nichols]

Hi Ed,

If you are referring to delay from Input signal to output, the internal keying occurs directly onto the incoming signal in hardware, so consider this delay to be sub-microsecond.

If you are referring to delay from key frame to output, I recommend measuring timestamps between IDeckLinkOutput::ScheduleVideoFrame and the IDeckLinkVideoOutputCallback::ScheduledFrameCompleted callback. You may want to refer to the InputLoopThrough SDK sample for reference on how to measure the output latency.

Regards
Cameron

Hi Cameron,

Thanks for the very helpful information!

Best,
Ed