How am I going to be able to use my VHS recorders when digital is forced on us?

Discussion in 'Video Cameras' started by Alan Holmes, Jun 9, 2005.

  1. Alan Holmes

    :::Jerry:::: Guest

    Read what is said Tony <g>, I didn't say he was a broadcast engineer
    (and I don't think he has either), IIRC his brother in-law works for
    (again IIRC) for one of the ITV companies. The fact he *isn't* a
    broadcast engineer is exactly why he seems to be a bit mixed up...
    :~)
     
    :::Jerry::::, Aug 7, 2005
    1. Advertisements

  2. Alan Holmes

    Tony Morgan Guest

    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.

    I think that you'll find it to be very close to 3.4Mb/s. And *very* far
    removed from 25Mb/s. As Jerry suggested, the 25Mb/s figure is perhaps
    DVPro, and not miniDV. Apples and oranges are *not* the same.
     
    Tony Morgan, Aug 8, 2005
    1. Advertisements

  3. Alan Holmes

    :::Jerry:::: Guest

    <big snip
    You are of course quite correct.
     
    :::Jerry::::, Aug 8, 2005
  4. Alan Holmes

    G Hardy Guest

    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.
     
    G Hardy, Aug 9, 2005
    1. Advertisements

Ask a Question

Want to reply to this thread or ask your own question?

You'll need to choose a username for the site, which only take a couple of moments (here). After that, you can post your question and our members will help you out.