Posted by Richard Crowley on 04/18/07 03:04

"jazu" wrote ...
> If you encode mpg that was encoded previously from avi, does it lower
> picture quality?

"AVI" is not a file type. It is a container. You must know
what kind of file is inside (i.e. the "codec") in order to
answer your question properly.

For example, if you are asking whether an AVI file with a
DV video in it will lose quality when encoded into MPEG,
it depends on how much the MPEG is compressed. It is
possible that a very low-compression MPEG is just as good
as a DV-AVI quality. But the kind of MPEG required to
make DVD video discs is sigificantly lower quality than
DV.

> Does every next step lower quality too?

Unclear whether you are asking about all transcoding/
compression, or *subsequent* transcoding and re-
compression. If you are talking about serial steps then,
yes, subsequent transcodings will likely reduce quality
even if not additionally compressed. (Just from the
artifacts of the decoding and re-encoding.)

It would be very helpful to know WHY you are asking
this question. It doesn't hold up very well as a generic
question. If you had a specific scenario in mind it would
be easier to offer a definitive answer.

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