[mythtv-users] Summery of my problems

Michael T. Dean mtdean at thirdcontact.com
Fri Jan 27 18:25:06 UTC 2006

On 01/27/2006 01:07 AM, Robert Johnston wrote:
> On 1/26/06, Dylan R. Semler <dsemler at macalester.edu> wrote:
>> For analog, the picture quality is pretty bad (noisy) and there are
>> about three or four horizontal lines at the top of the screen that have
>> some random patterns of black and white streaks.  The picture quality is
>> much better using tvtime and those lines do not appear.
> As for the noise, make sure that Myth is tuning into the same
> frequency (EXACTLY the same frequency) as TVTime is. It sounds like
> Myth's off by a few Khz.
Being off by a few KHz shouldn't matter.  Many of the NTSC cable channel 
frequencies are off by 12.5 KHz (and the same goes for IRC, and HRC 
varies by 5-15KHz), but the tuner hardware's fine-tuning mechanism 
should still be able to find the appropriate center frequency.  See 
http://www.gossamer-threads.com/lists/mythtv/dev/164614#164614 (which 
was totally ignored by the guy complaining in Trac that the frequencies 
are off) for an in-depth listing of what frequencies are off and why it 
shouldn't matter.

If you (Dylan) want to try an academically-correct list of frequency 
definitions, I'd be happy to create one for you (against SVN--just let 
me know which frequency list you're using: ntsc_bcast, ntsc_cable, 
ntsc_hrc, ntsc_irc (I'm assuming NTSC based on your e-mail address)), 
but you'll have to do all the testing because I don't have any 
RF-modulated sources.

Or, to find out if it's worth testing a more precise frequency list, 
play with the fine tuning values in Myth for the affected channels.  
And, most importantly, make sure you're using the right tuner 
definition--just because you get a bad picture doesn't mean you've 
chosen the right tuner; often it means you've chosen the wrong one.  ;)  
(And, it's completely possible to get a perfect picture/audio on some 
channels and a bad picture/audio on other channels when choosing the 
wrong tuner definition.)


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