MPEG TS PCR and PTS

[krzysztof.konopko at konagma.eu]

Hi, 

To my understanding, `buffer->get_pts()` makes little sense in case of
MPEG-TS as each GStreamer buffer will typically hold a number of TS
packets which in turn can be part of different PES packets and
elementary streams and relate to different access units (frames). So I
do not find it particularly useful to indicate with GStreamer PTS when
to "present" such ambiguous chunk of stream before demuxing it. 

Also to my understanding information like TOT/TDT is more useful when
presenting programme events (EIT) for example in a guide and to
synchronise intended start date and time of the events with the local
time (for presentation or recording purposes). I can't see how it could
be useful to relate it to the actual media time where it's not really
useful to care about absolute values especially when timestamps can
wrap. 

Kris 

On Fri, 2018-05-04 at 07:13 +0000, Adams, Bruce (KMLWG) wrote: 

> Hi, 
> 
> I am trying to work out how to get absolute time-stamps from an incoming MPEG transport stream. 
> 
> The basics seem to be that we get a presentation time-stamp via buffer->get_pts(). This is relative to the program clock reference PCR which is dictated by one of the elementary streams - typically the video. How do I get that base time out of gstreamer? 
> 
> I note that if I use a tsparse element it can decode TOT and TDT sections for DVB inputs. However, I also notice that one of my inputs is a TSIP input which does not include these sections. 
> 
> How can I tell if an absolute time reference is available and when it is what is the epoch? Is it the standard unix epoch 1970-01-01T00:00:00Z? 
> 
> Regards, 
> 
> Bruce. 
> 
> Kantar Disclaimer [2] 
> 
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