[linux-dvb] Re: Channel switching

[Klaus Schmidinger <Klaus.Schmidinger@cadsoft.de>]

I had the patched DVB driver running over night now with the EPG scanner
enabled. The result looks pretty good. I have extracted the "channel not
sync'ed" messages and uploaded them to

   ftp://ftp.cadsoft.de/pub/people/kls/vdr/dvb-no-patch.txt
   ftp://ftp.cadsoft.de/pub/people/kls/vdr/dvb-patched.txt

Both files contain the messages collected over the same period of time
(from 00:00 to around 10:30 - although on two different days, but that
shouldn't make any difference).

In the dvb-no-patch.txt file there is a total of 315 entries, most of which
are triples that belong to the same channel switching attempt (i.e. the switching
did not succeed, even after two retries).

The dvb-patched.txt file, on the other hand, contains only 56 entries, amoung which
(as far as I could see) is only _one_ case where the channel switching did not work
even after two retries. In all other cases the one retry that was performed led
to success.

So the bottom line from my experiments and other comments on the list seems to be
that apparently the channel switching problem only occurs on DVB cards of
rev. 1.3 (2.1 cards don't have this problem), and that for 1.3 cards my driver
patch leads to a _much_ better channel syncing.

I don't know if there is a way to dynamically detect the card revision, so that
the patched behaviour could be performed only for such cards, or if there is a
totally different way of fixing the underlying problem (maybe in the firmware,
which I don't have access to).

For me I am going to apply this patch to future driver versions - unless the
driver developers can come up with a better solution.

I am aware that the checks I have patched out have been done in order to make
channel switching faster (which, of course, is a good thing), but if I have to
chose between "fast" and "safe", the decision is easy...

Klaus
-- 
_______________________________________________________________

Klaus Schmidinger                       Phone: +49-8635-6989-10
CadSoft Computer GmbH                   Fax:   +49-8635-6989-40
Hofmark 2                               Email:   kls@cadsoft.de
D-84568 Pleiskirchen, Germany           URL:     www.cadsoft.de
_______________________________________________________________


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