In article ,
"Arfa Daily" wrote:
If you are the
telephone company, or a television broadcaster, though, things really do
work a lot better when the digital signals carried by your network all
are at precisely the same bitrate, no matter where they come from.
Right. At one time TV stations etc had their own accurate pulse generator
referenced to the national standard. Here in the UK it was IIRC from the
National Physics Laboratory.
Dave Plowman London SW
To e-mail, change noise into sound.
I reckon that TV companies must now use these laptops with very rough RTCs !
Have you noticed that now programme material is not networked from one
region into some or all of the others, and adverts are no longer 'local',
there is not any need for accurate cueing points around the network, so
advertised starting times are not even nodded at ? I checked the starting
times of about half a dozen programmes tonight, using the teletext clock,
which I believe to be accurate, and not a single one started within 1 minute
of the correct time, and a couple of them were off by several minutes.
That's not the place where television needs precise time; it involves
the generation and dissemination of NTSC or PAL in the past, or MPEG
multiplexes in the present, not the *content* carried by those signals.
There's pretty good reason to suspect that broadcasters purposely offset
the starting times of their programs precisely to make it less desirable
for you to change channels during the interval -- if you can never watch
both the end of one program and the beginning of another, you're less
likely to do it. Note that a lot of contemporary shows start directly
with some dialog and action, while the title and intro follow on a bit
later. You miss the first few seconds, you lose. Same with the ends of
shows.
Isaac