Re: Am I wise to convert all my AVIs?
- From: Andy <nomail@xxxxxxxxxx>
- Date: Sun, 23 Apr 2006 13:35:41 +0100
On 22 Apr 2006, Willem<willem@xxxxxxxx> wrote:
Andy wrote:
) I had *assumed* that the extraction process performed by my Blaze
Media ) Pro would remove the AVI wrapper and therefore I thought
that the ) quality of the un-wrappered "underlying MPEG" (which I
would receive as ) a file from the extraction process) would not
be of a different quality ) than the MPEG inside the AVI.
Highly unlikely, given that most AVIs do not use MPEG-1
compression. Usually, they use MPEG-4 (you know, divx etc.),
sometimes something else.
) I would make a guess that the additional losses you refer to come
from ) the extractor utility effectively 'playing' the AVI and then
re-encoding ) that played output into a new MPEG. Presumably the
extra losses come ) from the compression of the video images into
that new MPEG. )
) Is my understanding now correct or am I getting hopelessly
tangled?
Exactly. Furthermore, MPEG-1 is usually of worse quality (per
bitrate) than AVI (with MPEG-4), because it's an older codec, and
less CPU-intensive.
Hello Willem, I do not know a whole lot about AVI and MPEG but my
understanding of what you are saying does not line up with the
explanation given on web pages such as the one I quote below.
You seem to be saying that MPEG-4 is often seen as the format inside an
AVI and that may well be true. However GSpot shows that my AVI contains
an MPEG-1 encoded video.
The question I ask is if it is better to have the internal video on its
own or in an AVI wrapper. So in my case it would be an MPEG-1 video
with or without AVI.
And in your case I *think* you would be referring to an MPEG-4 video
with or without AVI.
However AFAICT (and i am a noobie) you and I are referring to MPEG-1 and
MPEG-4 respectively and that is not the same thing as considering the
impact of embedding either in AVI.
If you see what I mean!
Andy
----------------- START WEB PAGE INFO --------------------
http://www.gromkov.com/faq/faq2004-0041.html
-- snipped --
"QUESTION: I am looking for a document or an article that clears up once
and for all what is MPEG4 and what is AVI???"
"ANSWER: The "difference" is that AVI is a container. It's not a
coder/decoder.
AVI contains only information that describes how the data is included in
file and how to decompress video and audio (which codec to use).
MPEG4 - is a compressor. Video data can be compressed with MPEG-4.
AVI can have any type of codec (or no codec even) for compression,
CinePak, Indeo, Huffyuv, etc whilst a "MPEG4 'file'" specifically
denotes any AVI file that uses an MPEG4 codec (i.e,, DivX)
For ex.: AVI may have MPEG-4 as Video, and MP3 as Audio.
AVI may have Cinepak as Video, and WAV PCM as Audio.
----------------- END WEB PAGE INFO --------------------
.
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