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Re: Apple II+ 80-col video conversion

On Sunday, March 24, 2013 1:21:51 AM UTC, Michael J. Mahon wrote:
> Curtis Schroeder wrote:
> > Again, what I am most interested in is recommendations for a PCIe 1x
> > video capture solution or more detailed ][+ 80-col video information that
> > might allow me to make an educated selection, i.e. do I need NTSC 4.43
> > support, advanced de-interlacing, or both?  What feature(s) made the 15K RGB successful?
>
> The fundamental problem for any video sampling solution (any non-analog 
> solution) is the coherence of the video sampler with the Apple's video dot
> clock--14.3MHz for most modes and 16MHz for IIgs SHR mode. 
>
> If the converter dot sync range accommodates these frequencies, the output 
> can be sharp and alias-free. 
> 
> For good 80-column text, 14.3MHz is the critical frequency. Sampling at any
> integral multiple of 14.3MHz will result in crisp, non-aliased text. 

I found some more detailed Apple II video information (40-col, 80-col, HIRES, DHIRES, and IIgs) in this presentation:
http://www.kansasfest.org/wp-content/uploads/2009-ferdinand-video.pdf

As I seek a better understanding of the ][+ 80-col video, I think there is more to it than just the 14.3MHz frequency.  The NTSC standard crystal frequency is 14.31818, which is a 4x multiple of the NTSC M color subcarrier, so the ][+ is on spec in this regard.  Of more importance may be a converter or capture card that can handle the Apple II's non-interlaced video and higher line bandwidth required by 80-col or DHIRES video (even though the bandwidth is technically still within NTSC 3.58 display spec)?

Is it possible the better converters treat the Apple II +/e/c video as PAL-M?
https://en.wikipedia.org/wiki/NTSC#PAL-M_.28Brazil.29

Kind regards,

Curt