"Tony Morgan" wrote in message
It is my understanding that MiniDV uses 25Mbits per sec for the
video rate. Certainly many docs that I have seen make mention of this
figure. (I believe SMPTE 314 is relevant here.)

Here's how you can discover what it *really* is:

1. Fill a 1 hour miniDV cassette with shot(s) - you can
simply switch to record with a tape and come back
an hour or two later.

2. Capture, using you favourite editor.

3. Move the clip (or clips) into the timeline and note the
number of minutes of video (call that 'X')..

4. Note the size of the AVI file (call that 'Y').

5. Divide 'Y' by (X * 60). This gives you the number of Mb
per second.

Seems like a lot of hard work to me, Tony.

Instead, just stick a five-second colour clip on your timeline and save it
to disk as a AVI (DV type 1).

B = (S - C) / D

Where B is the bitrate for the clip (the value you are trying to work out),
S is the size of the file on disk (in bits), C is a constant (header
information for the disc-based AVI file not present in data on a tape) and D
is the duration of the clip, in seconds.

The larger the clip, the less significant the value of C in calculating the
bitrate.

It's something of an oversimplification, because the value of C changes as
the file gets bigger. I've got an Excel spreadsheet somewhere that (to an
extent) can work out the byte-accurate filesize of a PAL DV AVI if you put
in the duration of the video accurate to 1/25th sec. I ran out of patience
trying to work out when C increases, but there seems to be a pattern to it
in terms of the magnitude of the increase.