[linux-dvb] [RFC/PATCH] moving commonly used frontend configs to separate drivers

Hartmut Hackmann hartmut.hackmann at t-online.de
Sat Jul 23 23:32:02 CEST 2005


Hi,

> Many analog tuners are used by ATSC decoders too. The FCC 
> allocates the same channel frequency and bandwidth to both 
> services so the same tuner can be used for either one. 
> These tuners have their own i2c address. They are not a 
> part of the decoder chip.
> 
That's similar with DVB-T
They use the same frequencies and bandwidths. The classic PLLs
even have a similar programming model but:
- IF frequency is different
- Tuning is controlled more carefully. The bands are divided in
   subbands with different setups for the charge current and
   something else i don't know. The simple scheme VHF low, VHF high
   and UHF no longer is sufficient.
- RF AGC setup is different.
- Many of the current tuners are hybrid versions. They reqire
   switching between analog and digital mode.

> Currently these tuners have separate code in video4linux CVS 
> and dvb CVS that does exactly the same thing. The code in 
> video4linux CVS is configured by tables and supports a 
> large number of the analog tuners. It would be nice if the 
> code in video4linux was shared instead of having to 
> maintain code that does the same thing in dvb CVS for 
> tuners that are used by both analog TV and ATSC.
> 
So for ATSC this might be possible, but for DVB-T bigger
changes are necessary to get i.e the modes and the subbands
implemented. I am in doubt that this is a good idea.

Hartmut




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