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PostPosted: Tue Jan 10, 2017 8:34 pm 
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Joined: Thu May 19, 2005 11:30 am
Posts: 170
Quote:
Do you have a flashcart?
Nope. I don't really have an overview of which one to get for a 60-pin system.


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PostPosted: Tue Jan 10, 2017 8:57 pm 
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Location: NE Indiana, USA (NTSC)
For a 60-pin system, the EverDrive N8 should be good enough.


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PostPosted: Tue Jan 10, 2017 9:32 pm 
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Location: Seattle
NewRisingSun wrote:
color $31 at 319.9 degrees (nominal: 330)
color $36 at 113.1 degrees (nominal: 120)
Since I bothered to play around with the Pac-Land image and write down some numbers:
Blue $31 at 316-323° (nom: 330)
Blue $11 at 323-335° (nom: 330)
Magenta $15 at 84-90° (nom: 90)
Peach $36 at 109-117° (nom: 120)
Brown $07 at 150-158° (nom: 150)
Orange $27 at 140-146° (nom: 150)
Green $1B at 268-274° (nom: 270)

I clearly need to put more effort into filter design to reduce those ranges.


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PostPosted: Wed Jan 11, 2017 7:57 am 
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I don't use Matlab, but I can post the C source to my NTSC decoder that takes the .raw captured file and outputs a .rawraw RGB file, if that helps you.


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PostPosted: Wed Jan 11, 2017 2:55 pm 
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Joined: Sun Jan 22, 2012 12:03 pm
Posts: 4584
Location: Canada
NewRisingSun wrote:
Quote:
Do you have a flashcart?
Nope. I don't really have an overview of which one to get for a 60-pin system.

The Everdrive N8 has a Famicom 60-pin option, though I can also confirm that the PowerPak and Everdrive N8 72-pin both work on a Famicom using simple 72-60 pin converters.


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PostPosted: Wed Jan 11, 2017 6:37 pm 
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Joined: Tue Nov 23, 2004 9:35 pm
Posts: 540
You need to perform two simple soldering mods to get the most out of your PowerPak with just about all 72-to-60 pin converters and it the stacked PowerPak and converter can get a bit wobbly, but otherwise you will be good.

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Nerdly Pleasures - My Vintage Video Game & Computing Blog


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PostPosted: Wed Jan 11, 2017 8:05 pm 
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Joined: Sun Apr 13, 2008 11:12 am
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Location: Seattle
NewRisingSun wrote:
I don't use Matlab, but I can post the C source to my NTSC decoder that takes the .raw captured file and outputs a .rawraw RGB file, if that helps you.
Eh, the matlab/octave fragment was more for proving to myself that your methodology is correct. It clearly is, and now I think the only remaining parameter to be explored is just how much variation we should anticipate across all the hardware variants.

Is there an easy way to calculate how "non-ideal" either not a square wave or not a sine wave this is? Is the "skewness" test the right one?

Skewness of 10000 points of a sampled ideal sine wave appears to be approximately 0, but skewness of the huge patch of color $31 is 0.126 and the mean is very slightly higher than the median (Δ=0.336).


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PostPosted: Thu Jan 12, 2017 5:27 pm 
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Skewness is a measure of asymmetry. A square wave with non-equal duty cycles is indeed asymmetrical, though I am not sure how this translates to the phase of the fundamental frequency. Tepples suggested hue-specific phase shifts resulting from hue-specific duty cycles. If non-equal duty cycles of a square wave translate into phase shifts at the subcarrier (fundamental) frequency, then the phase shift amount should be correlated with skewness in sign and magnitude.

For the record, I have used the same setup to measure the composite video output of a Tandy 1000 computer. It can output six hues at two luminance levels. The two levels are different for each of the hues. I measure no level-specific phase shift beyond the noise level between the two luminance levels of each hue:
Code:
Color 1: 0.008638 (blue, nominal: 0)
Color 2: 223.742996 (green, nominal: 225)
Color 3: 269.025116 (cyan, nominal: 270)
Color 4: 92.503235 (red, nominal: 90)
Color 5: 46.509937 (magenta, nominal: 45)
Color 6: 180.940750 (yellow, nominal: 180)
Color 9: 359.858380 (blue, nominal: 0)
Color A: 223.127350 (green, nominal: 225)
Color B: 268.470940 (cyan, nominal: 270)
Color C: 91.619957 (red, nominal: 90)
Color D: 46.090595 (magenta, nominal: 45)
Color E: 179.678253 (yellow, nominal: 180)
This tells me that whatever I am measuring from the Famicom is not an artifact introduced by my capturing hardware, otherwise I would be measuring level-specific phase shifts in the the Tandy 1000's composite video output as well. I have attached that capture as well, in case you want to try your skewness test on that file.


Attachments:
RGBI16.zip [162.59 KiB]
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