Some issues:
@ppera2,
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Back to resolutions: it's always better to capture in bigger resolutions, because capture itself will be more precise (oversampling).
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I don't understand this. Sampling happens when converting the analog signal to a discrete one. The number of samples is always the same (NTSC: 910, and PAL: 1135; from page 13 data sheet Bt878). After sampling, the clip is resized to the resolution which you used when capturing (with some cards, overscan is included).
In other words: if you capture in bigger resolutions, the capture will be more precise, but not due to oversampling. It is just because you are downsizing to a less smaller resolution.
@Kika,
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Horizontal Lines (VHS has 240, S-VHS up to 400) aren't Pixels and can't be handled like Pixels. To be correct: You have to Capture double the amount of Pixels than the Video-Type provides in (horizontal) Linies.
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I also don't understand this. I guess you are talking about the Nyquist frequency here. This Nyquist frequency stuff doesn't imply you have to double the amount of pixels, wrt the number of active scan lines. Like I said above the number of samples is not related to the capture resolution.
Nyquist sampling means the following: "In order to recover all Fourier components of a periodic waveform, it is necessary to sample more than twice as fast as the highest waveform frequency v." (ref:
www.mathworld.com)
On the same page of the same datasheet, they talk about sampling: "UltraLock^TM operates at CLKx1 although the input waveform is sampled at CLKx2 then low pass filtered and decimated to CLKx1 sample rate".
Where CLKx2 (CLKx1) is the 8*Fsc (4*Fsc) clock signal. This is indeed Nyquist sampling.