Argus: first images dropped

[MarkusHess]

Hi, I have a camera which is triggered externally by an electrical signal. Because, the time between two triggers is unknown, I set enableCamInfiniteTimeout=1 which helps against timeouts. Nevertheless there is still an issue with the setup. It needs a number of triggers until the first image is received in my application. The first 7 images are dropped somewhere in the image pipeline. With the 8th trigger, the first image arrives. Then the next image again gets dropped. Starting with the 10th trigger, all following images are received.
I had a similar issue also in another project on a Jetson Nano with Video4Linux before. There I could solve it by enabling the “Low Latency Mode” in the v4l controls. I tried this also on the Xavier NX but it seems that this setting is not used when using Argus. Is there any other option to change this behavior? Or can it be changed by some driver modification in the kernel?

Thanks

[JerryChang]

hello MarkusHess,

it’s two threads approaches to capture camera frames as low latency mode.
Xavier series using VI-5 which already work on two threads approaches, that’s why low-latency mode control is unavailable.

@MarkusHess

It needs a number of triggers until the first image is received in my application.

it’s due to Argus FIFOs.
it takes 2 internal captures to align sensor settings and ISP programming. these 2 capture frames were ignored at driver level, and not sending to Argus or client.
Argus pipeline it uses queue, it needs 3 buffers for Argus to setup a capture pipeline.
besides, capture buffers should be queue depth add 1 since a capture request were based-on frame-start, not frame-end.