I was wondering if say you took 3 avi files
put them on a timeline, then rendered to avi.
Will there be degridation (encode/re-encode)
or an exact copy with no degridation

TIA!

<here@now.com> wrote ...
"AVI" is not a type of video ("codec"), it is a container
file type. The answer to your question depends significantly
on two things:

1) What codec was used to encode the three source files
2) What editing software are you asking about.

I use primarily AVI files encoded with "DV" (from my
DV camcorders). I use Adobe Premiere for most of
my video editing. When I use DV-AVI source files in
Adobe Premiere and the project is configured for DV-
AVI output, then there is no "transcoding" or "recoding"
because frames are copied straight across from source
to output (unless you do some processing like titles or
transitions, etc.)

You can use a free utility like "Gspot" to peek inside
your AVI files to determine what codec they were
encoded with: http://www.headbands.com/gspot/

It is likely that most mainstream editing applications
pass video through from source to output without
recoding assuming the input and output codec is
the same. However, note that temporally-compressed
codecs (MPEG, etc.) may require re-coding even with
no special effects.

"Richard Crowley" <rcrowley@xp7rt.net> wrote in message
news:13kvdmvaor7anc6@corp.supernews.com...

You must know better, by now. Why do you keep making
these foolish prejudicial statements about MPEG? MPEG
Editors use a "Smart Rendering" process, just a little more
advanced than the "Smart Rendering" process your DV
Editors use. You know this.

There is no more effect on the overall video quality when
outputting to the same format and parameters, whether it is
MPEG or DV. Both suffer next to no, overall or perceivable
quality loss.

Luck;
Ken

"Ken Maltby" wrote ...
A temporally-compressed video stream cannot be cut
in the middle of a GOP without re-rendering. This is
not necessary for formats which are not temporally-
compressed.

MPEG is what it is. DV is what it is. Dunno why it is
such an emotional and religeous experience.

DV does not require "rendering", (smart or stupid) because
each frame is a separate block of data which does not
need to be touched when doing straight-cuts editing.

If you are satisfied with MPEG, then I am happy for you.
Have a nice day.

<here@now.com> wrote in message
news:b5avk394ruvairqhnfil207di33st18h1d@4ax.com...
Get virtual dub
Load first avi
append the other 2
choose direct stream copy for the video
full processing for the audio
save

"Richard Crowley" <rcrowley@xp7rt.net> wrote in message
news:13kvh4lsudk1928@corp.supernews.com...
Which could theoretically have a small effect on a
very few frames, (with your "middle of a GOP"
example, and assuming you are keeping both sides
of the cut; then 3 to 8 of the 1/30th of a second
frames could require re-encoding - all the rest
would be simply copied frame by frame.)


So your editing programs don't render DV, and all you do
is "straight-cuts editing"? (That explains a lot!) You must
be using only free programs. Funny, how most who edit
DV find the "render time" of their setup to be of such great
importance, if, as you say "DV does not require "rendering"".
It's also my understanding that there was "Smart Rendering"
for DV25 in editing programs, long before affordable MPEG
editing programs appeared.


The Point is, Dickey; that when "Smart Rendering" DV or
MPEG there is no significant quality impact, compared to the
video you started with.

You don't want a fair comparison or a real world comparison
between MPEG2 and your DV. [There is no point comparing
your 25 Mbps DV with <10Mbps MPEG.]

"DV uses DCT intraframe compression at a fixed bitrate of 25
megabits per second (25.146 Mbit/s), which, when added to
the sound data (1.536 Mbit/s), the subcode data, error detection,
and error correction (approx 8.7 Mbit/s) amounts in all to roughly
36 megabits per second (approx 35.382 Mbit/s) or one Gigabit
every four minutes. At equal bitrates, DV performs somewhat
better than the older MJPEG codec, and is comparable to
intraframe MPEG-2. (Note that many MPEG-2 encoders for
real-time acquisition applications only use intraframe compression
[I-frames only], but not interframe compression [P and B frames].)
DCT compression is lossy, and sometimes suffers from artifacting
around small or complex objects such as text."

(MPEG is also a DCT (Discrete Cosine Transform) compression
algorithm format.)

Your DV25 is little different from [I-frames only] MPEG-2 encoded
at the same bitrate. As you know, HDV is not "[I-frames only]" but
is MPEG-2 at the same bitrate, as your DV25. BUT, you can't accept
a comparison based on DV vs. HDV, NO it has to be DV vs. MP/ML
MPEG (DVD compatible).

But you and PT know all this, so this is just for those less experienced
who might be misled by your comments.

Luck;
Ken

"Ken Maltby" <kmaltby@sbcglobal.net> wrote in message
news:VO-dnX82EuR2c9LanZ2dnUVZ_remnZ2d@giganews.com...
Thanks for the technical stuff, but your personal attacks stamp you as an
immature twit. Calm down.

Steve King

"Steve King" wrote ...
[to Ken Maltby]
Mr. Maltby apparently didn't read (or reply to) the OP,
but he sure seems enjoy these silly DV vs. MPEG rants.
Whattever makes him happy. The facts are the facts.