[mythtv-users] Any hope for 1080i content at 1080i with nVidia?

Doug Larrick doug at parkercat.org
Fri Aug 24 00:35:00 UTC 2007


Seth Daniel wrote:
> On Thu, Aug 23, 2007 at 07:56:12PM -0400, Doug Larrick wrote:
>> Seth Daniel wrote:
>>
>>> I don't know if it's the TV, the driver, or just my incompetence, but I
>>> cannot get 1920x540 (the 540pw mode described in the above link) to
>>> work.  My custom 1080i mode is:
>>>
>>>   Mode "1080i"
>>>     DotClock 74.25
>>>     HTimings   1920 2008 2052 2200
>>>     VTimings   1080 1084 1089 1124
>>>     Flags      "Interlace" "+HSync" "+VSync"
>>>   EndMode
>>>
>>> For the 540pw mode I changed it to:
>>>
>>>   Mode "540pw"
>>>     DotClock   79.912
>>>     HTimings   1920 2008 2052 2200
>>>     VTimings   540   542  544  562
>>>     Flags      "+HSync" "+VSync"
>>>   EndMode
>> If you have a working 1080i mode, you want the 540pw vertical timings to
>> be *exactly* half of the corresponding numbers in the 1080i mode.
>> Everything else should be identical.  You want the TV to think it's
>> still receiving a 1080i mode.
> 
> They are exactly half.  Hmmm.  Except for 544...what's exactly half of
> 1089?  Can you place fractional values in the vtimings section?

Yeah, sorry, read '562' as '652' and got carried away.

So your problem is likely to be the dot clock then.
79.921 MHz / 2200 dots is 36.3 kHz horizontal frequency, divided by 1124
lines is 32.3 Hz vertical frequency.
74.25 MHz / 2200 dots is 33.75 kHz, / 562 is 60.05 Hz.

I think the former mode is too far from the ATSC standard for the set to
sync.  In my experience the most important value is the horizontal
frequency.

-Doug

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