Definition of PX2 image timestamp

[cjluo]

Hi,

Does anyone know details about capture timestamps on PX2?

For example: is NvMediaGlobalTime measured as SOF timestamp or EOF timestamp?

Thanks!
NVIDIA DRIVE OS Linux API Reference: Basic NvMedia Types and Structures

[shayNV]

Hello @cjluo,
please refer to the following documentation :
https://docs.nvidia.com/drive/active/5.0.10.3L/nvvib_docs/index.html#page/NVIDIA%2520DRIVE%2520Linux%2520SDK%2520Development%2520Guide%2FMultimedia%2Fnvmedia_concept_ipp.html

also, consider reading the section “NvMediaIPPManagerSetTimeSource”.

[cjluo]

sorry if I’m missing anything, I didn’t find information about if the NvMediaGlobalTime is measured as SOF or EOF timestamp.

[shayNV]

Hi @cjluo,
following the documentation link on my previous comment, regarding what is the source of NvMediaGlobalTime:

NvMediaIPPManagerSetTimeSource api is used for the client application to establish a callback function to provide an absolute global time. When a frame is received by the capture component, it calls this function to get the absolute global time and stores this timestamp to the image.
If the application does not establish a callback function, NvMedia IPP uses the kernel based timestamp obtained from ktime_get_ts() function to get the clock monotonic time.

also, please consider going through these topics:

Questions about Frame Sync Signal

Hi, I’ve learnt that Frame Sync Signal for cameras are generated by Xavier SoC. My questions are: How Xavier generates the signal? Is it synced with other source like system clock? What’s the frequency of frame sync signal? Can we set that? Thanks.

Question about latency on timestamping

・GMSL Camera Do you have any information about time lag between shooting time and its timestamp time? I am going to use IMX390 as GMSL camera, but other cameras’ information is okay. ・Aurix CAN Do you have any information of processing time from packet reception to time stamp marking? What is the mechanism of the hardware time stamp used on the Aurix CAN? What is the difference between software timestamp and hardware timestamp? Thank you.

if the above does not answer your question, can you elaborate on your challenge that you want to solve?

[cjluo]

Thanks for the additional info. When you mean “a frame is received by the capture component”, do you mean the “frame is fully received” (EOF) or the “starts to receive the first line of the frame”(SOF)?

I want to benchmark the camera latency on PX2 and would like to if the capture time means when the sensor starts to send the new frame or the sensor completed sending the new frame.

E.g. the table 17 of https://www.onsemi.com/pub/Collateral/AR0331-D.PDF shows the diagram about start of frame and end of frame

[VickNV]

Hi @cjluo,

It’s timestamped after EOF. Thanks1