[linux-dvb] Re: VDR channel switching more stable!!

[Johannes Stezenbach <js@convergence.de>]

Klaus Schmidinger wrote:
> 
> Somebody here on the list (sorry, can't remember who it was),
> wrote that the problems we are all having with switching channels in
> VDR might have to do with the automatic FEC detection of the driver
> or firmware.

FEC detection is performed in hardware by the QPSK decoder
(VES1893 or stv0299). If FEC is set to AUTO, the hardware will
just try all possible values in succession until one matches.
If you set the FEC manually, signal aquisition will be more
reliable and a few msecs faster, however.

Unfortunately I found that it does not resolve the tuning
issue. I suspect a timing problem in the driver's tuning
functions, or a (possibly heat related) hardware problem.

When the initial tuning operation does not succeed after a few msecs,
the driver conducts a zig-zag scan around the given frequency in
order to achieve a frontend lock.

If you are up to some experiments, I would like to suggest that
you play with the timing constants in dvb.c. Take a look at
qpsk_tune() and mon_tune(), mon_zigzag() etc. and modify the
mon_delay paramters.


Regards,
Johannes


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