Re: size of DV/1394 video stream

On Mon, 27 Jun 2005 09:52:02 -0700 Richard Crowley <rcrowley7@xxxxxxxx> wrote:
| phil-news-nospam wrote ...
|> Richard Crowley wrote:
|> | All you need to do is have some external method of identifying
|> | the file as a DV bitstream. That is why RIFF, AVI, MOV, etc.
|> | formats were invented. They use a miniscule part of the file to
|> | internally identify the file encoding (aka. "codec')
|>
|> Why would the extension on the file name, such as ".dv" not be
|> enough?
|
| Because it can be changed (or even removed) by the user. But then
| we have no idea what the application/situation is so only you know
| whether this is an issue or not.

Why would someone do that?


| You will get lots of irrelevant info when you have such an unstructured
| and context-free question. If you want to play 20 questions maybe
| you can find a fun-n-games newsgroup somewhere.

As long as I don't know what is actually in the AVI format, I'm not
going to be able to phrase very good questions for it. Aside from
being able to share with NLEs, I see no reason to add any more to
the DV stream than what comes over the wire. But if I do use a file
format that is different than DV, it would have to be something that
I can use as well as at least one major NLE.


|> Still, knowing how these other formats embed DV would be useful to
|> exchange these files with an NLE on another computer.
|
| That is precicesely the job of the codec.

I think we are not using the term "codec" consistently here. Are you
talking about the classes of codecs or the individual implementations?
A class would be "DV" in general, whereas a specific implementation
might be the particular chip in the ADVC-110. Will the plain DV stream
that comes from the ADVC-110 play just fine when output to some other
brand of converter? If yes, then we are talking about general codecs.
If no, then we have to be talking about specific codecs. I think the
answer has to be yes, but the way you have been referencing it, I cannot
rule out that the answer could be no.

It would be easier to discuss AVI if there was more info on details of
how it works. How much of it do you know and have documented? At the
very least, can you say what bytes (number or string?) are in the AVI
file to identify the "DV" codec? Is it "DV" or 17494 or 22084?

Do you have a PDF of the AVI format specification?

--
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| Phil Howard KA9WGN | http://linuxhomepage.com/ http://ham.org/ |
| (first name) at ipal.net | http://phil.ipal.org/ http://ka9wgn.ham.org/ |
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.

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