Trying to get a reasonable frame number and timestamp

[pisymbol .]

I know this has been talked about around a thousands times on list. And I
have read most of these threads but I am still getting what I think is
strange behavior.

Here's what I'm trying to do:

I want to intercept every frame of an h.264 30 fps stream (not variable
rate, life is good) and get its frame number and timestamp. So as I
understand the doc, that should be in the GstBuf.dts and GstBuf.offset
fields. I was going down the pad probe route but found that the identity
plugin as per the doc a much easier and better route:

So my first pipeline looked like this:

... ! omxh264enc bitrate=10000000 ! video/x-h264,
stream-format=(string)byte-stream ! h264parse ... ! identity name=nvcamid0
! muxer

Then I connected to the "handoff" signal for my callback and saw the
following:

dts : offset
0 : 816445297
106961 : 839200766
130469 : 849786717
151008 : 876858645
165810 : 909811526

I don't quite understand what the offset is here? I don't see how it can be
a frame number but it is increasing monotonically (but it doesn't look like
a per buffer offset either). Also the offset_end  is also MAXUINT64
(essentially NONE).

Another thread with a similar request as mine can be found here:

http://gstreamer-devel.966125.n4.nabble.com/Getting-Each-h264-Frame-td4664932.html

In this case, the pipeline was augmented to push h264parse into a raw-video
with frame alignment. I tried that via:

... ! omxh264enc bitrate=10000000 ! video/x-h264,
stream-format=(string)byte-stream ! h264parse ... ! tee name=tp tp. ! queue
! muxer.video_0 \
tp. ! queue ! video/x-h264, stream-format=avc ! identity name=nvcamid0

And now of course I see no callback being called and nothing gets recorded.

Anyway, can someone kindly just explain to me what the offset means above?
And do I need to throw my h264parse output back into a video raw format
again to get each frame number?

Again, my goal is to capture the timestamp and frame number (and soon
geotag) as a separate stream to eventually write to disk as a meta file.

Thanks!

-aps
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://lists.freedesktop.org/archives/gstreamer-devel/attachments/20190614/e23b405b/attachment.html>