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I've measured the multiburst VITS (Vertical Interval Test Signal) on a few of my PAL LDs and at best the 5 Mhz burst was at -4 dB and quite noisy, so the 5.5 Mhz bandwidth of PAL LD is in practice more like just below 5.0 Mhz.
Does that mean that Laserdiscs have test signals embedded in them (during blanking)?
Yes, on all THX releases and infact it seems many of the rest of them as well, not always with a multiburst line though.
Also, I'm still wondering about Moth3r's statement about DVD's 6.75 MHz translating into 540 lines. Shouldn't it be 720 lines?
No, I believe Moth3r is talking about LINES OF RESOLUTION
For example, since the current DVD format has 720 horizontal pixels (on both NTSC and PAL discs), the true horizontal resolution can be calculated by dividing 720 by 1.33 (for a 4:3 aspect ratio) to get 540 lines. (On a 1.78 [16:9] display, you get 405 lines) In practice, most DVD players provide about 500 lines instead of 540 because of filtering and low-quality digital-to-analog converters.
Although todays DVD players with 108 Mhz DA converters should have no problem reproducing the full 6.75 Mhz bandwidth or 540 lines.