Calculate Image capture time for Axis H.264

[VinothkumarEkambaram]

Hi,
We are using in Axis H.264 codec in our implementation. We captured the running timer console in Axis H.264 camera and compared the time difference between the current time in console and the captured image.

we are observing around 250 milli seconds difference between the Axis H.264 captured image and the running timer. Is there any way to calculate the actual image capture time. Current time is 2024-10-07 10:16:42 868 milliseconds. But the capture image contains the 2024-10-07 10:16:42 618 milliseconds. So I want the calculate the image capture time 10-07 10:16:42 618 milliseconds for the captured image?
Also whether Axis doing any image buffering? why we are getting around 250 milliseconds delay between the current time and captured image?

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[vivekatoffice]

Hi @VinothkumarEkambaram ,

Please check this Latency in live network video surveillance document which may help you find the way to calculate the latency.

There is one overlay modifier available for epoch time too:

You can also activate the Low latency mode enable and try if that helps:

[rocky-ji]

I am afraid F34 is too old to support low latency mode,

https://github.com/orgs/AxisCommunications/discussions/655

[VinothkumarEkambaram]

Hi @rocky-ji ,
We are using the same logic mentioned in the https://github.com/orgs/AxisCommunications/discussions/655 discussion, but not getting the actual image capture time. The Actual delay between the current timer and time in the captured image is 250ms. That means the image displayed in browser is taken 250 milli seconds back. But we are not getting capture time of 250ms old. Instead, we are getting 120ms old. For example, Imaged captured at 2024-10-07 10:16:42 618 milliseconds displayed at 2024-10-07 10:16:42 868 milliseconds. Ideally we should get image capture time is 2024-10-07 10:16:42 618 . But we are getting around 2024-10-07 10:16:42 740. Any suggestion?

[rocky-ji]

Not sure whether your own code adding some bufer, Have you tried to test with gstreamer to set latency to 0 to see the latency? if it is the same as your result. That should be the real latency of F34.

gst-launch-1.0 rtspsrc location= rtsp://root:[email protected]/axis-media/media.amp latency=0 ! decodebin ! autovideosink

I can't understand why you are using F34， since it is too old and already discontinued, in my experice, test with F9114 should have 100-120 ms latency when enable low latency mode:

[VinothkumarEkambaram]

hi @rocky-ji ,
Why is low latency mode not the default option? Is it advisable to enable it in a production environment? Will it impact any other functionality?

[rocky-ji]

Depending on the use case, for basic video surveillance and recording, video latency is not important, maybe smooth is much appreciated. For some quality detection or time critical use case, you may need enable that mode.
This function is added by some use cases, for old camera or camera with lower OS version, it is not supported. So it is default to disable.

[VinothkumarEkambaram]

Hi Rocky,
Will it be any impact smoothness if we enable the low latency mode for F9114 camera? Also I am observing the 2seconds time difference, in your previously attached timestamp capturing. you have mentioned 100 to 120ms deviation for F9114 camera. Whether its taken with F9114 camera?

[rocky-ji]

If you need low latency, smooth should not be a problem, also it is not obvious by human eyes.
Normally, if you connect camera and your PC to same switch, if only get one video stream, for most artpec 7/8 1080P camera the latency should still be less than 200 ms even you don't enable low latency mode.
Just remember if you want to get the lowest latency, don't use any buffer in your decoding and display side. For most player, there will some buffer to make it smooth.

In my test, gstreamer can get the lowest latency
gst-launch-1.0 rtspsrc location= rtsp://root:[email protected]/axis-media/media.amp latency=0 ! decodebin ! autovideosink