avi is a file extension that implies the type of file created ( it was invented by microsoft years ago ). like many extensions it is basically called a " wrapper' , in the sense that it has certain things INSIDE it.
CODEC ( COmpression DECompression ) algorthym (sp? ) type stuff fits INSIDE the wrappers.
Soooo, mov can have many codecs, AVI can have many codecs , and so on...
In your case you are asking the difference between whether a codec is used or NOT when the avi file is created. So the answer is compression or no compression.
In most conversations I've heard about this subject it becomes a matter of what your product ( export ) is going to be used for... whether or not you want compression or not.. and which codec you choose.
hope this gets the gist of this post on the right track...
The Uncompressed AVI option uses the V210 codec, which is for use with AJA hardware. If you don't have that hardware, use the AVI option and choose None for the codec instead.
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