[mythtv] Re: Re: [mythtv-commits] Re: Ticket #339: SimplifyTuning process

John Jurrius jjurrius at bbti.us
Thu Sep 22 16:44:53 UTC 2005

The Signal Strength data for the lgdt330x is intended to be calculated from
AGC RF/IF Loop Filter Accumulator Values.  The SNR is calculated from the
Equalizer Mean Square Error.  The routines for calculating both have already
been provided to Taylor.  If you cannot return the SNR in dB perhaps you can
do what is done in Windows driver for the HD5000 which is convert the SNR to
a percentage of its value over a the usable range of the SNR which is then
referred to as Signal Quality.


-----Original Message-----
From: mythtv-dev-bounces at mythtv.org [mailto:mythtv-dev-bounces at mythtv.org]On
Behalf Of Mac Michaels
Sent: Thursday, September 22, 2005 9:08 AM
To: mythtv-dev at mythtv.org
Subject: Re: [mythtv] Re: Re: [mythtv-commits] Re: Ticket #339:
SimplifyTuning process

The lgdt330x chips do not provide signal strength data. It
might be possible to compute signal strength from the
automatic gain control (AGC) data, but the spec sheet does
not provide a formula. As a result the signal strength is
always set to 0.

Data is available from which the signal to noise ratio (snr)
can be calculated. The driver currently returns raw data
since the unsigned 16 bit return value it not appropriate
for returning the actual snr in db. Snr must be signed
because it is negative when the signal is less than the
noise and positive when the signal is greater than the


On Thursday 22 September 2005 09:53 am, David Engel wrote:
> On Thu, Sep 22, 2005 at 10:42:16AM -0400, Taylor Jacob
> > Many drivers just report arbitrary vaules that have no
> > unit because the author did not have the datasheet, and
> > this will not change.. Not even if all manufacturers of
> > demodulators decide to support linux for some reason..
> FWIW, my Fusion HDTV5 always reports 0 for signal level.
> David
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