🚀 go-pugleaf

In article <56lv0d$9jq$3@uhura.phoenix.net>, cko@tgn.net (C-ko Kotobuki) wrote:

> When the tape is recorded, the VCR produces a signal that is recorded
> on the bottom edge of the tape.  A head in the VCR reads this track
> and adjusts the speed according to it.
> C-ko

True, but incomplete. Yes, all three speeds record all the frames. As each
field (1/2 of a frame, either all the odd or all the even lines) is
recorded, one pulse is recorded at the edge of the tape. The control head
(a non-moving head) reads them when you play the tape. If there are more
than 60 per second, the tape was recorded at a slower speed than it is
playing back, so the machine jumps down a speed, and keeps doing that
until the 60-per-second rate is found. On the other hand, if there are
fewer than 60 per second, the machine jumps up a speed until it finds the
correct rate. And that's how it knows the speed at which the tape was
recorded.

The value of 60 is for NTSC (American) video. Other systems, such as PAL,
used in Europe, use 50. But, the principle is still the same.

Sincerely,
Michael