[linux-dvb] Re: Frontend IP based

[wolfgang@leila.ping.de]

Ralph Metzler schrieb:
> sf writes:
>  > Ralph Metzler wrote:
>  > ...
>  > > Of course most cards do not deliver time stamps for the incoming TS
>  > > packets (but some do). So, most RTP servers programs derive the 
>  > > time from the PCR and interpolation which kind of defeats their purpose.
>  > 
>  > Which cards do deliver time stamps? How can I get at them from user space? 
>
> The newer DVB chips by ST do deliver a TS with timestamps. But those
> are only used in STBs.
Do they really deliver timestamps? I did not know something like this exists 
yet. nice to hear
I suppose DVB-ASI boards (like those from DekTec or Computermodules) also 
deliver timestamps, but have to admit I did not have a look at the driver 
yet. 
IMHO it depends on the application which kind of timestamps you need. For 
our RTP/UDP streaming, we had a software PLL synchronized by the incoming 
PCR of a simple DVB-Nova, and this was very reliable as long as we did not 
have extreme interrupt latency. 
What we needed was an accuracy in the range of few microseconds (IIRC we 
achieved around 5-10 microseconds at the node with the DVB-Nova and approx. 
four times these values at the receiving node), though, so not enough for a 
real measurement or DVB-conforming TS playback... But we did have 
considerable interupt latency because of the network hardware used, 
unfortunately. 
Regards,
Wolfgang