Calculate accurate Image capture time for Axis H.264

[VinothkumarEkambaram]

Hi,
As discussed in the following ticket https://github.com/orgs/AxisCommunications/discussions/806,

We are observing the latency of 100 to 120milliseconds for Axis F9114 camera. That means the image captured at the time 12:00:00 100ms will be displayed at 12:00:00 200ms due to latency. we want to calculate the actual image capture time for the image. That means we want the timestamp as 12:00:00 100ms for the image clicked at 12:00:00 100ms. Ideally we want the eliminate the latency of 100 to 120ms from the image received timestamp.
As discussed in the following ticket https://github.com/orgs/AxisCommunications/discussions/655, we can calculate the latency of 30 to 40 milliseconds using the RTCP and RTP protocols. We need a mechanism to calculate the exact latency of 100 to 120ms.

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[Cacsjep]

I do a lot of latency Tests around this, we use acap and vdo timestamps to get the moast accurate timestamp. But this Would imply you do packing the stream by your self. The timestamp that comes from VDO is still a little Bit off i think its 20-30 MS

@VinothkumarEkambaram See Here https://github.com/orgs/AxisCommunications/discussions/157#discussioncomment-11436217

[VinothkumarEkambaram]

Hi @Cacsjep,
We are ok with current latency of 100 to 120ms. We are not requesting the steps to reduce the latency. Our question is how to calculate the latency programmatically. By using the timestamp referred in the RTCP and RTP protocols we can calculate the latency of 20 to 30 ms. But the actual latency is 100 to 120ms.
We are getting the Axis H.264 video using RTP/RTCP protocol through VAPIX API and displaying the video on our customized viewer. Our customized video viewer will also display the actual time of image captured in the camera. We are focusing the timer with microseconds in front of the axis camera. we are observing the 100 to 120ms difference between time in the timer and the time in our customized video viewer. If the axis camera captures the image at 24.12.2024 14:05:15 300ms and displays the image at 24.12.2024 14:05:15 400ms. We are ok with displaying the time with 100ms latency. But the problem is, the time in the video is 24.12.2024 14:05:15 300ms. But image capture time calculated using the RTP/RTCP protocol is 24.12.2024 14:05:15 370ms. We are getting this 70 to 90ms deviation of image displayed in the video and the timestamp printed (image capture time printed by us) in the video. Is there any way to get the actual latency of 100ms.

Note:
Our preference is using the Axis with the default settings and get the actual latency with the default setting with high resolution image. Not by reducing the latency with low resolution image.

[Cacsjep]

@VinothkumarEkambaram i understand my idea was to use vdo frame timestamp as the reference Point. Of course you subtract your decoding time and Rendering time and Display refresh time, right ?

[VinothkumarEkambaram]

Hi @Cacsjep, we are using the Axis VAPIX APIs for our Axis H.264 implementation. We are getting only the RTP reference timestamp in each RTP packet and RTP reference time and NTP time in each RTCP packets. Apart from that we are not getting any other timestamps. Whether your suggestion applicable for VAPIX APIs?

[Cacsjep]

@VinothkumarEkambaram If you Want we could discuss this in discord https://discord.gg/jNeCsGZX