[mythtv] [mythtv-commits] Ticket #3541: Backend Crashes When Recording From Mux A In The UK (Freeview / DVB-T)

Daniel Kristjansson danielk at cuymedia.net
Fri Jul 27 14:33:41 UTC 2007

On Fri, 2007-07-27 at 14:57 +0100, nospam312 wrote:
> Daniel does this fix also change things for the backend as the crashes
> occur just the same as when the frontend is not open - it is the
> backend crashing that makes the frontend either say the backend is not
> running or display an error?  Thanks.

It took me a while to parse this sentence. The frontend we're talking
about here is the DVB driver referred to as the "frontend". This is
the driver that the MythTV backend talks to in order to tune to channels
and record programming. The DVB Linux kernel API is implemented via a
great multitude of drivers for each of the various chips on a digital
television card. There are also a number of drivers that combine various
functional units, one of which is the frontend driver. Each frontend
driver may support a number of different cards with different hardware
modules and different drivers for these modules. But there are many
frontend drivers and each one supports a limited number of actual 
pieces of hardware, so when the MythTV backend sees that we're using
the "lgdt3303" DVB frontend it can guess that we are using either a
DViCO v2, Air2PC v3 or pcHDTV HD-5500 card. Each of these has different
hardware, for instance the DViCO and pcHDTV cards have analog
frame-grabbers and the Air2PC v3 does not. But when we see "or51132"
we know that the card has analog support, and when we see "nxt2002"
we know that the card does not have analog support.

The problem here may be that we flagged a few DVB frontends for
special treatment with respect to PAT & PMT validation, but only
some of the cards using those DVB frontends actually need this
special treatment. Since we can't query for the actual backend
drivers or firmware being used to support any particular card,
we can't apply special treatment to just the one particular 
chip or firmware which is broken.

-- Daniel

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