Does buffer data carry a tag or a sequence number while flowing through a pipeline?

[jeyp4]

Hello
v4l2src -> timeoverlay -> vaapih265enc -> vaapidecode -> appsink

Does data flowing through above(e.g.) pipeline carry any tag or any kind of
sequence number?

So that the final element(appsink) pad can match data tag with first element
pad(v4l2src).

My ultimate purpose is to provide a time-stamp to appsink data. Where the
time-stamp can represent to image shot time as close as possible. I am
flexible to use any time reference, e.g. ros::Time::now()



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[Nicolas Dufresne-5]

Le ven. 11 oct. 2019 06 h 55, jeyp4 <[hidden email]> a écrit :

Hello
v4l2src -> timeoverlay -> vaapih265enc -> vaapidecode -> appsink

Does data flowing through above(e.g.) pipeline carry any tag or any kind of
sequence number?

So that the final element(appsink) pad can match data tag with first element
pad(v4l2src).

My ultimate purpose is to provide a time-stamp to appsink data. Where the
time-stamp can represent to image shot time as close as possible. I am
flexible to use any time reference, e.g. ros::Time::now()

The timestamp is from v4l2src, which is in turn derived from whatever the Linux/BSD kernel provided. It's a bit of a round trip, but here the conversion flow.

v4l2src

Monotonic -> pipeline clock -> stream time

Pts = t + delta - base_time

So when you receive buffer in appasrc, to find back the monotonic time you do the opposite.

T = pts - delta + base_time

Delta is the distance between pipeline clock now and time now. This is were precision is lost, as there is no atomic way to retrieve this.

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[scottca]

There is the PTS time.
which would be maintained...
wish there was a better answer, I was looking for something "nice" as well.




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