On 1/29/2019 1:16 PM, Eric Wilde wrote:
My understanding of at least one VHS protection scheme was to record
the video with the horizontal/vertical sync pulses set very low to the
threshold for detection. The idea was that, if you made a copy, which
was lossy, the copy would not have detectable sync pulses and the
picture would appear scrambled.
That fits my memory, too. There was also macrovision, which IIRC added extra
analog pulses to mess with the recorder's AGC circuits. Been a long time
since I've thought about this.
I'm not sure how a DVD recorder would detect this, as opposed to a
VHS recording that was just of poor quality. But, if you suspect that
to be the case, you could certainly confirm it with a scope on the
output of the VHS player.
Digital capture of any analog tape source, especially VHS, without at least
a proc-amp (TBC would be better) in line will give rather-less-than-optimal
results. Capturing the composite signal just compounds the problems (as
opposed to using Y/C or component).
z!
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