[linux-dvb] Re: Channel switching

[Ralph Metzler <rjkm@convergence.de>]

Dave Chapman writes:
 > Klaus,
 > 
 > I haven't tried your channel switching test yet, but I agree with your patch.
 > 
 > In my opinion, the driver should do what is requested from it - it is up to 
 > the application to decide whether a tuning action needs to take place or not. 
 >  An application can check the current status of the frontend by using the 
 > QPSK_GET_STATUS command to find the currently tuned frequency and SR.
 > 
 > I'm curious to know the driver developers' opinions on this.  Is there a good 
 > reason why the driver doesn't accept a request tune to the current frequency?


If you did not try the patch, at least read what it does.
The driver does not reject any tuning request. It only does not 
reset the FEC and symbol rate if they are the same as before.
It also does not retune if the last requested frequency was the same
and the demodulator still has a lock.
All this was done to make tuning faster (not having to wait for a new
demodulator lock). I never had a problem with it with my setup.

If it does not work with every card I expect feedback and patches
(like Klaus now provided). It is open source after all.
I will of course apply the patches if this helps make the driver 
work more reliably for more people. 
I still could not recreate those tuning problems myself. I had
"ctest" running for hours without problems.
Yesterday it was only with a Rev. 2.1 card which seems to have less
problems but I also tested a Rev. 1.3 card before.


I would also like to announce that the tuning API will change soon.
QPSK, QAM, OFDM, etc. will use the same command set. This will
make things a lot easier in the driver and in applications to
handle different kinds of cards with the same code.
So, be prepared to change your applications. I'll make a last snapshot
this weekend. Everything in CVS afterwards will be using the new
tuning API. This should not create more work than the addition
of DVB-T support would anyway.


Ralph







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