teletext
 

How come I can get the date and time from teletext when I play back a
videotape? Obviously it's a bit garbled but it's good enough to remind me what
channel I've recorded and when. I would have thought VHS would have stopped
teletext dead.

Puzzled

Rotherham

"Bill" wrote in message
...
How come I can get the date and time from teletext when I play back a
videotape? Obviously it's a bit garbled but it's good enough to remind me
what
channel I've recorded and when. I would have thought VHS would have
stopped
teletext dead.

Puzzled

Rotherham

It depends on the video bandwidth of the VHS machine. Some do it, some
don't. It's more likely to work in SP than LP because they tend to use a
wider bandwidth low pass filter. It's also more likely to work with S-VHS
because of the wider bandwidth. The timing error at the top of frame (skew
error) also upsets teletext, so it's more likely to work on a machine that's
playing back it's own recording. The teletext data clock is about 7 MHz, so
in theory the minimum bandwidth needed to record it is 3.5 MHz.

"Bill" wrote in message
...
How come I can get the date and time from teletext when I play back a
videotape? Obviously it's a bit garbled but it's good enough to remind me
what
channel I've recorded and when. I would have thought VHS would have
stopped
teletext dead.

Puzzled

Rotherham

It depends on the video bandwidth of the VHS machine. Some do it, some
don't. It's more likely to work in SP than LP because they tend to use a
wider bandwidth low pass filter. It's also more likely to work with S-VHS
because of the wider bandwidth. The timing error at the top of frame (skew
error) also upsets teletext, so it's more likely to work on a machine that's
playing back it's own recording. The teletext data clock is about 7 MHz, so
in theory the minimum bandwidth needed to record it is 3.5 MHz.

Stephen wrote:
"Bill" wrote in message
...
How come I can get the date and time from teletext when I play back a
videotape? Obviously it's a bit garbled but it's good enough to
remind me what channel I've recorded and when. I would have thought
VHS would have stopped teletext dead.

Puzzled

Rotherham

It depends on the video bandwidth of the VHS machine. Some do it, some
don't. It's more likely to work in SP than LP because they tend to
use a wider bandwidth low pass filter. It's also more likely to work
with S-VHS because of the wider bandwidth. The timing error at the
top of frame (skew error) also upsets teletext, so it's more likely
to work on a machine that's playing back it's own recording. The
teletext data clock is about 7 MHz, so in theory the minimum
bandwidth needed to record it is 3.5 MHz.

Indeed. Also something that helps is that the time/date data is
refreshed (obviously) every second. So your Teletext decoder
stands a good chance of building up the whole header row.
It does work surprisingly well. I've used it to determine which
date I've recorded a particular programme. Useful when you've got
a pile of tapes of a six part series :-)

Stephen wrote:
"Bill" wrote in message
...
How come I can get the date and time from teletext when I play back a
videotape? Obviously it's a bit garbled but it's good enough to
remind me what channel I've recorded and when. I would have thought
VHS would have stopped teletext dead.

Puzzled

Rotherham

It depends on the video bandwidth of the VHS machine. Some do it, some
don't. It's more likely to work in SP than LP because they tend to
use a wider bandwidth low pass filter. It's also more likely to work
with S-VHS because of the wider bandwidth. The timing error at the
top of frame (skew error) also upsets teletext, so it's more likely
to work on a machine that's playing back it's own recording. The
teletext data clock is about 7 MHz, so in theory the minimum
bandwidth needed to record it is 3.5 MHz.

Indeed. Also something that helps is that the time/date data is
refreshed (obviously) every second. So your Teletext decoder
stands a good chance of building up the whole header row.
It does work surprisingly well. I've used it to determine which
date I've recorded a particular programme. Useful when you've got
a pile of tapes of a six part series :-)

"Bill" wrote in message
...
How come I can get the date and time from teletext when I play back a
videotape? Obviously it's a bit garbled but it's good enough to remind me
what
channel I've recorded and when. I would have thought VHS would have
stopped
teletext dead.

Puzzled

Rotherham

It works because the teletext signal is recorded along with the programme.
The ability to access this depends on the quality of the recording equipment
and the quality of the tape used. I have used this method for many years to
date recordings. I have noticed over the years that increasing the
sharpness of the picture improves the decoding of the teletext (If your VCR
has the feature).

Tony

"Bill" wrote in message
...
How come I can get the date and time from teletext when I play back a
videotape? Obviously it's a bit garbled but it's good enough to remind me
what
channel I've recorded and when. I would have thought VHS would have
stopped
teletext dead.

Puzzled

Rotherham

It works because the teletext signal is recorded along with the programme.
The ability to access this depends on the quality of the recording equipment
and the quality of the tape used. I have used this method for many years to
date recordings. I have noticed over the years that increasing the
sharpness of the picture improves the decoding of the teletext (If your VCR
has the feature).

Tony

Mark Carver wrote:
Stephen wrote:

"Bill" wrote in message
...

How come I can get the date and time from teletext when I play back a
videotape? Obviously it's a bit garbled but it's good enough to
remind me what channel I've recorded and when. I would have thought
VHS would have stopped teletext dead.

Puzzled

Rotherham

It depends on the video bandwidth of the VHS machine. Some do it, some
don't. It's more likely to work in SP than LP because they tend to
use a wider bandwidth low pass filter. It's also more likely to work
with S-VHS because of the wider bandwidth. The timing error at the
top of frame (skew error) also upsets teletext, so it's more likely
to work on a machine that's playing back it's own recording. The
teletext data clock is about 7 MHz, so in theory the minimum
bandwidth needed to record it is 3.5 MHz.


Indeed. Also something that helps is that the time/date data is
refreshed (obviously) every second. So your Teletext decoder
stands a good chance of building up the whole header row.
It does work surprisingly well. I've used it to determine which
date I've recorded a particular programme. Useful when you've got
a pile of tapes of a six part series :-)



Aaah, it used to work quite well with our old analogue Betamax...
/nostalgia

Mark Carver wrote:
Stephen wrote:

"Bill" wrote in message
...

How come I can get the date and time from teletext when I play back a
videotape? Obviously it's a bit garbled but it's good enough to
remind me what channel I've recorded and when. I would have thought
VHS would have stopped teletext dead.

Puzzled

Rotherham

It depends on the video bandwidth of the VHS machine. Some do it, some
don't. It's more likely to work in SP than LP because they tend to
use a wider bandwidth low pass filter. It's also more likely to work
with S-VHS because of the wider bandwidth. The timing error at the
top of frame (skew error) also upsets teletext, so it's more likely
to work on a machine that's playing back it's own recording. The
teletext data clock is about 7 MHz, so in theory the minimum
bandwidth needed to record it is 3.5 MHz.


Indeed. Also something that helps is that the time/date data is
refreshed (obviously) every second. So your Teletext decoder
stands a good chance of building up the whole header row.
It does work surprisingly well. I've used it to determine which
date I've recorded a particular programme. Useful when you've got
a pile of tapes of a six part series :-)



Aaah, it used to work quite well with our old analogue Betamax...
/nostalgia

"Bill" wrote in message
...
How come I can get the date and time from teletext when I play back a
videotape? Obviously it's a bit garbled but it's good enough to remind me
what
channel I've recorded and when. I would have thought VHS would have
stopped
teletext dead.

Puzzled

Rotherham



A good VHS deck will give you a bit (teletext is in the flyback lines). An
S-VHS machine will record most of the page.