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Topic:		Audio syncing nightmares
Author:		Mayonaise
Posted:		 2001-03-12 06:32
I've been tinkering with Divx3.11, AngelPotion and now OpenDIVX for
almost a year.
Both Divx3.11 alpha & OpenDivx (Divx3Win4 and both codecs have sound
syncing problems, whereas Angelpotion does not. I'm surprised that
no-one seems to be having these problems in this forum - I use
Flask0.594 & 0.6beta with all my codec experiments. The Divx audio
problems are truly bizarre - sometimes the video goes at half speed even
though properties says that the video rate is correct - most of the time
the audio is just ahead of the video by about a second. About 1 in 10
times the syncing is correct.

A side note to several forum entries about comparisons of codecs, I've
always preferred AngelPotion's video quality. (Note that I say 'prefer',
never say 'better' unless you've done some heavy testing) - in areas
where blocks are clearly evident, AngelPotion uses smaller blocks which
I like better, a sort of finer 'dither' if you like.

cheers all.

Topic:		Audio syncing nightmares
Author:		eagle
Posted:		 2001-03-12 07:16
Sync should be independent of the codec you use.  In the AVI/Windows
architecture, all the codec does is convert between compressed and
non-compressed representations of each frame.

The only way I can think that changing codec would affect sync is the
CPU usage of the codec - in your case, the amount of time the codec
takes to decompress a frame.  Frequency of key-frames could be a factor
in this.

I thought the Angel Potion codec was a binary hack of the obscelescent
DivX ;-) 3.11.  Can anyone explain why it might have produced different
video quality? (I know it made pictures go purple, so something odd was
going on there!)


Topic:		yes i AM a dumbass, help me
Author:		abligandor
Posted:		 2001-03-12 08:49
ok, just downloaded the codec, opened virtual dub

set the bitrate, left  the rest, let my vid encode, then played it

the movie is in like 4 parts (at once) and is all green

is it because of the width/height (not devisable by 16 but i'm using a
resize filter to fix it while encoding)

.... i've been encoding for a while now, just need a little help

Topic:		Audio syncing nightmares
Author:		Flare
Posted:		 2001-03-12 10:10
I've run some brief tests with the above combination (DivX 3.11 &
Flask0.6beta) and also experienced AV-Sync problems.  I had the opposite
problem though - the video was always ahead of the audio by half second
or so, so a visual event would happen and the 'accompanying' audio
follow shortly afterwards.  Pausing and restarting playback part way
through didn't make any difference.  It was so consistent with every
clip I tried that I suspected the files were being encoded out of sync -
rather than a playback problem (?).

Topic:		OpenDivX Variable Bitrate Encoding
Author:		Flare
Posted:		 2001-03-12 10:34

Yes I performed tests at various settings - at one point I had both min
and max quanitizers set to Max (31 I think it was) ...I wanted to try
higher settings but that seemed to be the limit.  

I find with 3.11 I can balance out image size (resolution) against
requested data rate to ensure it never drops frames when encoding - I
usually want 25fps for smooth motion.  Also, knowing the limitations, if
I plan carefully at the storyboard stage, I can make sure there's not
too much rapid motion across the whole frame (that definitely trips up
the encoder at low data rates).  Think I'll stick with DivX 3.11 for now
since it does what I want, and keep my eye on OpenDivX (for features
that improve image quality at low data rates) as it develops...

Topic:		Audio syncing nightmares
Author:		Mayonaise
Posted:		 2001-03-12 20:15
Eagle & Flare....I'll clarify a couple of things.

The audio & video playing at 1/2 speed has only appeared for me in
opendivx, i can't recall it ever happening with divx3.11 Also, I made a
mistake - my audio is behind the video, not the other way around as I
stated in my first posting (sorry about that - interrupted halfway
through the sentence).

Also, my comments about angelpotion can be attributed to the
post-processing that divx does. I'd forgotten to put the postprocessing
back down to the lowest setting, which is where I like it more often
than not.

I took a sneak look at Acidlabs codec as well...it appears to be very
similar to angelpotion, which you're saying is a earlier hack of divx,
so its all getting a bit incentuous. Angelpotion encodes about twice as
fast as divx though, so maybe its not from divx ? Anyone know for sure ?
Angelpotion appears to be no-more, as the site is kaput.

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