[ivtv-users] Is HVR-1600 model 74591 supported by cx18 driver?

[Andy Walls]

On Sun, 2009-05-03 at 17:59 -0700, Matt Beadon wrote:
> >After you've tested it and are happy the settings are good enough
> for 
> >general user use, I can add a patch and issue a PULL request. I
> usually 
> >issue a PULL request on Sunday nights. The v4l-dvb maintainer
> usually 
> >gets to them within a week, unless he's really busy. 
> 
> 
> I'm happy that analog tuning is working now.  Do you have some
> suggestions on what testing I should do beyond watching it?  :)

Test all the channels.  Especially ones near the VHF-Low/VHF-High
boundary and the VHF-High/UHF boundary.  The channel/frequency tables in
the ivtv-tune source can tell you the mapping of cable channels to
frequency.

The file

linux/drivers/media/common/tuners/tuner-types.c

shows that for the FM1236 MK3 tuner, the VHF-Low/VHF-High boundary is
around 160 MHz and the VHF-High/UHF boundary is 442 MHz.

There is only one other analog/only NTSC tuner in the tuner-types.c file
with a TDA9887: tuner type 46, the TUNER_PANASONIC_VP27.  It likely
won't work.  Please test tuner type 46 (I suspect it won't work or work
as well).




> As a follow up I'm having some issues with the ATSC channels on this
> card (beyond the listings problem I still have posted on the
> mythtv-users list).  Occasionally the signal breaks up and/or stutters
> along with audio glitches and pops.
> I have a Core2 E6600 and when I'm playing live ATSC the cpu usage is
> around 44% but it's actually about 2% higher when I'm playing live
> NTSC so I don't think the system is too slow.

That seems high for NTSC - you (MythTV) must be doing some software
scaling somewhere.  mplayer doesn't do software scaling unless you tell
it to.

You can load the cx18 module with the debug=15 module parameter and look
for "Possibly falling behind" messages to see how respinsive you system
is to CX23418 interrupts.  If you get a lot of those messages in the
logs that come with sequence numbers that are close together, you've got
some system level inefficiencies.


>   I thought it might be signal strength so I've cut out as many
> splitters as possible and this card is getting the 2nd cleanest cable
> I have (best goes to cable modem).

You whole cable plant in your home affects the S/N ratio (e.g. voltage
wave reflections due to impedenace mismatches come back up from the far
end of the cable and can look like noise).

Please review:

http://www.ivtvdriver.org/index.php/Howto:Improve_signal_quality





> 
> When I tune an ATSC channel with mythtv it says "Signal 0% | SNR 2.5dB
> | BEXXX | LAM(lock)".  The 0% part is what has me worried that I still
> don't have good enough SNR but I haven't poked around enough to figure
> what other people are getting for signal % and SNR?

Meh.  The signal 0% is a known deficiency.  I can't remember if it's the
mxl5005s driver or the s5h1409 driver that's reporting junk.  The SNR of
about 2.3 dB is what I get for OTA ATSC.  LAM(lock) is good.  BE (block
errors) should not be increasing, but a fixed non-zero number is OK.


Regards,
Andy

> There seem to be a ton of cx18 threads. Is there a guide for
> optimizing settings for cx18?  Or some general tips that might help?
> 

>