[Scott Dorsey]

alex wrote:
i found a -20 tone on the 95% of the digital video tapes i saw (more
than 200 in the last few months...).
SO why put that (reference!) tone on tape nowadays, if:
1) there are no relationship with the real level;
2) -20 on digital domain means -20 on every possible player machine, so
we have no need to further describe that level;

In the old days, you put the tone at "nominal level" on the analogue tape,
which was where the meters read zero.

When digital came along, different houses put the "nominal level" at
different digital peak levels. Some folks set the 0dB tone at -15dBFS,
some put it at -20 or -25dBFS.

That level is just there to warn the operator about where the levels
are going to fall.

A tv guy, once, told me that the maximum RMS value should not exceed
-10dB (i was working on a commercial).

-10dB-what? -10dBFS? That would seem a bit high to me... you would
probably have to compress a good bit to get a dialogue track up to
-10dBFS averages without the peak going over 0dBFS. But it's certainly
not out of the question.

In the fact, working for a film festival where most of the material was
issued in form of digital betacam and hdcam, there's no good way to
discover the right playback level setting other than examine the whole
tape. The problem is that there's no indication on where is the loudest
part, so the pojectionist have to discover it using the most time
consuming method! strang that no refernce level is issued!

Okay, stuff delivered to a film festival probably should be AC-3 encoded
and you probably SHOULD follow the Dolby recommendations because many other
people do. If you do it according to the Dolby recommendations, dialogue
will read 85 dBA in the center of the hall.

Unfortunately, lots of people are sloppy and don't, and the only solution
is for the projectionist to ride the gains by hand. Which is, after all,
his job.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."