[Openchrome-users] CN700 NoScale

[Xavier Bachelot]

Udo van den Heuvel wrote:
> Xavier Bachelot wrote:
> 
>>Udo van den Heuvel wrote:
>>
>>>What would it take to make a 720x576NoScale for CN700?
>>>Can I make the mode/modeline myself? How?
>>>(I like the mode on my SP8000 but I will install the EN12000 soon
>>>because TranquilPC appears to have a heatsink/pipe setup that fits the
>>>EN boards. EN has CN700 which has no NoScale for PAL yet.)
>>>Any ideas?
>>>
>>
>>The TV modes are unrelated to the actual chipset, they obviously depend
>>on the TV encoder. 
> 
> 
> Ah, of course.
> 
> 
>>All modes are hardcoded, no way to override them with
>>a modedeline.  There is a page in the wiki which list all the defined
>>modes. In your case, I believe you have a VT1625 TV encoder, 
> 
> 
> The EN boards have one, yes.
> 
> 
>>which is not well supported at the moment. 
> 
> 
> I know, but I can start without the NoScale mode and upgrade later... :-)
> 
No idea which mode are working properly on a VT1625. There was some 
threads some weeks/monthes ago, search the archives. There's even some 
patches to add/fix some modes. Also I've dumped all currently supported 
modes for all supported TV encoders in the wiki. Now ppl with the 
hardware just have to report status for everyone of  them.

> 
>>Ivor may come with something sooner or
>>later now that he owns a board with a VT1625 TV encoder.
> 
> 
> Is there some usable information online that explains how to program the
> vt162x and how a mode is set up that is NoScale?
> (so I can understand how it is done...)
>
No, there's no spec. The modes are set by setting some registers, which 
usage are very often not clear, so it involves a lot of trial and errors.

> Because of the separation of TV-encoder and the rest MPEG is limited to
> 1024*1024 but TV can do more (2048*2048) on CN700?
>
A CRT TV is not able to do anything else than the standard Pal or NTSC 
resolution (720*576 for Pal, don't remember for NTSC). LCD TVs are using 
higher resolution, but I think they are only able to properly display 
either 720p or 1080i, and they'll have to scale any lower or higher res, 
giving the same image quality scaling artifact as a CRT TV. Still on old 
school low-res TV, so I may be wrong. May be TV encoders also have a 
hardware limitation on the max res video input.

The MPEG engine being able to decode up to some resolution doesn't mean 
you won't be able to decode higher res videos, just that it won't be 
hardware assisted. But then, with a low-horsepower processor, you're stuck.

Regards,
Xavier