[linux-dvb] Re: Suggestion for channel tuning

["Yu, Jacob" <jyu@opentv.com>]

In a typical Settop or IRD environment, viewers select program number or
service number where service number is the DVB's equivalence of program
number and the internal software will figure out the actual PIDs for video,
audio and others and intruct demultiplexer for desired PID selection.


Jacob
-----Original Message-----
From: Dave Chapman [mailto:dave@dchapman.com]
Sent: Saturday, April 21, 2001 2:20 AM
To: linux-dvb@linuxtv.org
Subject: [linux-dvb] Suggestion for channel tuning


After reading ISO-13818-1 (the MPEG-2 standards document that defines the 
structure of a Transport Stream), I've been experimenting with tuning 
channels without knowing their video and audio pids - just the service_id / 
program_number.

I've written a small program that tunes a channel based on only the 
frequency, polarity, symbol rate and program number.  This works well, and 
the scanning of the PAT (to get the PID of the PMT), PMT (to get the ES
PIDs) 
and SDT (to get the name of the channel and broadcaster - possibly 
unneccesary) adds between 0.1 and 0.5 seconds to the tuning time.  This 
depends on luck and how many channels are on the transponder.

Has anyone else had any experience of tuning like this?  It seems to me that

ISO-13818 is implying that the only parameters needed to tune a channel is 
the service_id.  This makes sense to me - at least on Astra 28, the channels

change PIDs quite frequently.

Regards,

Dave.


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