How does CoDec get invoked for movie clips

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Guest

I've been reading through some of the threads on this forum and there is
mention that CoDecs need to match up on each end (i.e. the presentation
creation computer and presentation playing computer). How is the CoDec
invoked?

If you are simply copying all files in a presentation from one computer to
another, or onto a memory stick or CD, is CoDec at work here? If so, does
Power Point give you a clue it's invoking the CoDec?
 
I'll try to use an analogy and see if it makes sense to you.

Have you ever used a "Zip" file? If so then you know that you must have a
program to zip the file together and the person you send it to must also
have a program to un-zip it. A codec works in much the same way, it
compresses the file on one machine and in order to uncompress it on another
machine you must have the same codec installed.

The issue is that there are many, many codecs out there (I have 180 codecs
and filters installed on one XP box.) and you have no idea what the next PC
may or may not have. In fact about the only codec you can be reasonably
certain is on all Windows PCs is wmv. (Be aware though, there are several
versions of wmv.)

As for PowerPoint, it is completely unaware of the codec being used. In
fact it knows very little about the video itself. PowerPoint doesn't really
play the video at all, instead it calls upon the Windows MCI player to do
all the work. It simply passes the name of the video and it's path to the
MCI player and asks it to play it at a specified time. The MCI player
examines the file, determines what codec is required to play it, and then
uses that codec if it is present on the PC. It is not present, the file
doesn't play or doesn't play properly.



Austin Myers
MS PowerPoint MVP Team

Provider of PFCMedia, PFCPro, PFCExpress
http://www.pfcmedia.com
 
thanks Austin. But my question isn't that the CoDec compresses, as your Zip
anology discusses; I get that. Rather, what invokes the CoDec becoming
involved in the 1st place?

In other words, if you are simply copying all the files in a presentation,
including the supporting movie clip files, from one media to another (ie from
a network location to a hard drive on a laptop or memory stick, has CoDec
become involved? If so, what invoked/launched it?
 
cayce said:
thanks Austin. But my question isn't that the CoDec compresses, as your
Zip
anology discusses; I get that. Rather, what invokes the CoDec becoming
involved in the 1st place?
Click to expand...

The creation of the video file. If we look at say a video that is 640 x 480
and is ten seconds long it would be several tens of megabytes in size if it
wasn't compressed. The same file can be compressed to 1/10 of that (or
less) if done properly. Very few applications create uncompressed video
files today. (Most will allow it if you make the proper changes in the
settings.) This has storage advantages as well as requiring less time when
transfered. (Say over the internet.)

In other words, if you are simply copying all the files in a presentation,
including the supporting movie clip files, from one media to another (ie
from
a network location to a hard drive on a laptop or memory stick, has CoDec
become involved? If so, what invoked/launched it?
Click to expand...

I think you are missing the key part here. The video files are almost
always built using a codec so they will require the same codec to uncompress
them. So yes, in almost all cases (except an uncompressed video) the codec
will become a requirement to play the video.

Now, as to your question about moving it to another medium on the same PC I
think you may be seeing a different problem. If I create a presentation
with a video it is always "linked". That is, it is NOT part of the
presentation. So lets say your presentation and video file is stored on say
C:\MyDocuments\Mypresentation. If you move the presentation and the video
to a memstick (say E:\) when the presentation is ran the "link" to the video
is still pointing at C:\MyDocuments\MyPresentation. When the presentation
tries to run the video it can't find it (you moved it) or if you left a copy
in it's original location then it can find and run it. Obviously if you
transfer it to another machine it will never work because the path is
different.

If you are having problems with this, you might want to check out some of
our add ins that greatly simplify the entire process of using a standard
codec and transfering the presentation and media.

http://www.pfcmedia.com



Austin Myers
MS PowerPoint MVP Team

Provider of PFCMedia, PFCPro, PFCExpress
http://www.pfcmedia.com
 
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