"Mark Carver" <mark....@invalid.invalid> wrote in message
news:j33l05...@mid.individual.net...
> interval, and you'd so the image 'slice' at the cut point.
I've seen a lot of older TV programmes repeated on Talking Pictures TV,
Drama, Yesterday where the digital TV frame consists of one field from one
source frame and one field from an adjacent frame. This is not apparent for
studio video, but it is very obvious for film if there is movement because
you get two fairly sharp images (sharper because of shorter shutter speed
than 1/25 sec) of adjacent film frames on each DVD frame, when you should
get both fields of the DVD showing different parts of the *same* film frame
and therefore no movement between fields of the same DVD frame.
The first series of Boon (so as late as 1986) had this problem on the DVD
set of the first series. When I later bought a box set of all seven series,
S1's film inserts were fine so someone had corrected the problem.
My analogue TV capture card randomly synchronises either correctly or
wrongly, so when I was copying programmes off VHS or other analogue source I
would check just after starting a recording to MPG, by single-stepping
through movement of a film insert; if it was there was a double image I'd
wind back and start again - rinse and repeat until it gets it right.
I've seen some recordings of very old TV programmes where the cuts between
studio cameras didn't look quite right, and single-stepping showed that the
cut had taken place during a field (not in VBI) so you got image slices.
There was one programme, broadcast from film recording, where I saw a cut
that had occurred during a line, so not even during line flyback. I was
rather surprised to learn that some early vision mixing equipment used
physical switches (relays) rather than transistor switches, so there was
plenty of opportunity for image corruption due to contact bounce, which
would be invisible if the cut occurred during VBI or line flyback but would
be very obvious at any other time.