Are MessageQueues FIFO?

pkyleUPI

I'm trying to minimize latency. I'm calling dai::MessageQueue::get<T>() on a queue initialized with createOutputQueue(
unsigned int maxSize = OUTPUT_QUEUE_DEFAULT_MAX_SIZE,
bool blocking = OUTPUT_QUEUE_DEFAULT_BLOCKING)

I realized that this means i could be 16 frames behind. I'm guessing the solution to this is to set my queue size to 1?
Is there a different/better way to guarantee the lowest latency from image capture -> image display?

OskarSonc

Hey pkyleUPI - Yes, in DepthAI v3 MessageQueue is FIFO.
With createOutputQueue() defaults (maxSize=16, blocking=false), you can lag behind if processing is slower than input rate. For lowest latency, use:
createOutputQueue(1, false)
That gives latest-frame behavior (older frame is dropped when a new one arrives), which is usually best for live display latency.

Thanks,
Oskar

pkyleUPI

Awesome, thanks Oskar!