[opendtv] MPEG2 system clock recovery

The MPEG2 system spec 13818-1 (H.222), Appendix D, describes a process 
whereby the decoder time clock get synchronized with the encoder time 
clock.  This is done by comparing SCR values in the transport stream 
with the decoders local clock and taking appropriate action.  There were 
many papers written on various ways to do this quite a few years ago.
I am told some (hardware) decoder implementations don't do this 
anymore.   I was wondering if anyone could shed some light on this?  
Presumably the PTS time stamps provide enough information to accurately 
decode and present the content....isn't this all PC decoders use?   Are 
modern day STB designs foregoing this "SCR clock sync" at the input to 
the decoder?   Is there any resulting inaccuracy in the output?  Maybe 
the when the spec was put in place, system designers thought it was 
needed.  Then as technology and people got better/smarter, we figured 
out how to eliminate that step?  Anyone have first hand knowledge they 
can share?? or comment?

Also, I dont think this step applies in MPEG over IP.....
 
 
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