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miifox
miifox
According to the document I shared earlier (and other info I found online), the main role of the equalizing pulses is to make sure the vertical sync pulse of odd-line fields trigger at the same time as the even-line fields, despite the horizontal triggers being half a phase late.
The problem is that with the horizontal and vertical syncs embedded in one signal, the TV detects a vertical sync when the horizontal sync's vsync integrator goes beyond a thrashhold. Hence, it's imperative that that thrashhold gets hit at exactly the same time both fields, which requires both to be discharged at the same time despite the capacitor in odd fields holding half a charge.
According to this logic, one would need 6 short blanks to discharge a half-charge capacitor fully.
Of course, the reason this peeked my interest is the potential to replace the 0-½ interlace pattern of traditional television with a 0-⅓-⅔ pattern, potentially increasing vertical resolution by 33%.
If my logic is correct this would require to increase the amount of short blanks from 6 to 8. This is assuming that one full syncless line accumulates 12 units of charge, and the maximum retardement we'd face would be 8/12th of a line.
The way to accomplish this would be to sacrifice one scanline for creating an extra half-line sync pulse. Yes, this would imply 287 and not 288 active scanlines, and would mean that our effective active resolution would be 1440x861 and not 1440x864. Details, details!
Then we can just shift the first blanking line post-equalizing pulse ⅓ and ⅔ instead of ½, and we'd get a 3-field interlacing sequence instead of a 2-field interlacing.
Interestingly, the implication is that if a digital system ain't aware of what the heck's going on, it'll show the first field correctly and then interpret both of the second fields as one odd-line field.
One small note on my research: i have no heck the idea what i'm talking about. The role of the equalizing pulses is ill-explained on wikipedia and the internet in general. But the clue of their role I found actually on the wikipedia page for the old British 405-line system which *lacked* them. It said they needed to be synthesized for integrator-type sync seperation systems (by the broadcaster or by the set) and was not needed for other types of sync seperation. So I googled "integrator+equalizing pulses analog video" and got what I needed.
I find in general info on non-525/625 video systems lacking, I'd love to know more about 35p, 180p, 441i, and other early video standards even if I'm never gonna find signals to test them with. Also did you know France had a monochrome 819i50 system at some point?
Oh well...
An image of the role of the syn…
The same image with some modifi…
The problem is that with the horizontal and vertical syncs embedded in one signal, the TV detects a vertical sync when the horizontal sync's vsync integrator goes beyond a thrashhold. Hence, it's imperative that that thrashhold gets hit at exactly the same time both fields, which requires both to be discharged at the same time despite the capacitor in odd fields holding half a charge.
According to this logic, one would need 6 short blanks to discharge a half-charge capacitor fully.
Of course, the reason this peeked my interest is the potential to replace the 0-½ interlace pattern of traditional television with a 0-⅓-⅔ pattern, potentially increasing vertical resolution by 33%.
If my logic is correct this would require to increase the amount of short blanks from 6 to 8. This is assuming that one full syncless line accumulates 12 units of charge, and the maximum retardement we'd face would be 8/12th of a line.
The way to accomplish this would be to sacrifice one scanline for creating an extra half-line sync pulse. Yes, this would imply 287 and not 288 active scanlines, and would mean that our effective active resolution would be 1440x861 and not 1440x864. Details, details!
Then we can just shift the first blanking line post-equalizing pulse ⅓ and ⅔ instead of ½, and we'd get a 3-field interlacing sequence instead of a 2-field interlacing.
Interestingly, the implication is that if a digital system ain't aware of what the heck's going on, it'll show the first field correctly and then interpret both of the second fields as one odd-line field.
One small note on my research: i have no heck the idea what i'm talking about. The role of the equalizing pulses is ill-explained on wikipedia and the internet in general. But the clue of their role I found actually on the wikipedia page for the old British 405-line system which *lacked* them. It said they needed to be synthesized for integrator-type sync seperation systems (by the broadcaster or by the set) and was not needed for other types of sync seperation. So I googled "integrator+equalizing pulses analog video" and got what I needed.
I find in general info on non-525/625 video systems lacking, I'd love to know more about 35p, 180p, 441i, and other early video standards even if I'm never gonna find signals to test them with. Also did you know France had a monochrome 819i50 system at some point?
Oh well...
An image of the role of the syn…
The same image with some modifi…
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