Quote:
Originally Posted by ARC Tech-109
Has to do with the Nyquist frequency rate at the high end of the carrier frequency, moving the white clip (high end) will give an increase in the resolution (slight) and improve the white dynamic range without clipping or compromising the signal/noise ratio. Take a look at the attached pdf as this may give you some insight.
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I have this document. It was one of the reasons I am asking the question
Regarding VHS, it says: "Two limitations occur due to the frequency and deviation limits selected. The lower frequencies of the luminance signal mix slightly with the down-converted chroma signal."
Ok, I can see that chroma mixes with luma.
Then they say "In addition, the frequency range limits the resolution to 240 lines", is it the same as deviation? Because if deviation defines white to black ratio (S/N, right?), then how both S/N and resolution can be defined by the same parameter?
They say, "Super VHS and Super VHS-C VCRs have higher resolution capabilities by raising the overall frequency of the luminance signal. Thus, the FMed signal is placed farther away from the chroma to reduce luminance and chrominance mixing." So, by moving luma to the right, they have increased the resolution of luma, because it is not smeared with chroma? Chroma resolution remained the same because the chroma bandwidth is not changed? This I can understand.
On the first picture with letters they say A is sync tip. A is at the start of the band. So, is
the left side of the band always the sync tip or not?
Next, they say "In the case of Super VHS and Super VHS-C, the sync tips produce a modulator frequency of 5.4 MHz with 100% white level producing 7.0 MHz. Maximum deviation of the modulated signal equals 1.6 MHz." So, deviation is S/N? Absolute frequency is luma resolution? How exactly absolute frequency and resolution are related? I wish I saw this graph over time to understand how it looks for each line, for each sample.
If the deviation is 1.6 MHz, and sync tip is 5.4 MHz,
what is happening between 1-something... let's say 2 MHz and 5.4 MHz?