UTC timestamps in v4l2 buffers

[Philippe De Muyter <phdm@macq.eu>]

Hello,

I need to have the v4l2 buffers of my camera sensor timestamped with a
precise (1ms) UTC timestamp, in order to be able to match images from cameras
from several computers (that are of course synchronised with NTP, GPS or PTP).

While I had that some years ago and still have in computers running
freescale's 4.1.15 port for imx6q, I have now discovered that 8 years ago
a decision has been taken by the v4l2 maintainers to switch the timestamp
of the v4l2 buffers to CLOCK_MONOTONIC, which is useless when one needs
to synchronise timestamps of images taken by cameras on different computers,
which of course were not booted at the same time.

At that time a new flag "V4L2_BUF_FLAG_TIMESTAMP_MONOTONIC" was introduced
to tell new users that the timestamp was no more the old and not standardized
behaviour for timestamp, but the new CLOCK_MONOTONIC-based timestamp, but
no other flag for UTC or way to choose which kind of timestamp one wants.

Are there since then new standardized or work-in-progess flag to tell users
that the timestamp is UTC, and way to ask the camera-acquisistion driver to
give that UTC timestamp instead of the CLOCK_MONOTONIC one ?

Best regards.

Philippe

-- 
Philippe De Muyter +32 2 6101532 Macq SA rue de l'Aeronef 2 B-1140 Bruxelles