Scott Dorsey wrote:
: Right. But how far in do you NOTICE it? How far off can it be, before it is
: a problem?


I start notice things when it's off by 2 NTSC frames which is 0.06 of a second.


Would you recommend jumping to zero crossing and keep inserting silences?

--Leonid

Logan Shaw wrote:
: I suppose a filter/plugin to do this doesn't exist (maybe I should write


During the video capture there exists an option to resample audio on the fly.
But I'm not sure it would be a good idea.

There's also an option to shift audio proportionally by number of %. I have
to contact the owner of the software package to find out what he's doing there.
If he just samples audio at say 48001Hz, then I'm good.

--Leonid

Mike Rivers wrote:
: Do you notice that it's .0775 seconds out of sync? Do you have to look
: at a time scale on the computer to know that it's out of sync or is
: there some aural-visual cue that tells you that?


Believe it or not I do notice if I look carefully. I don't notice .03 of a sec.
But .06 is somewhat noticeable.

--Leonid

Mike Rivers wrote:
: It may be difficult to descrbe without us being able to see and hear
: what you have, but the question is really "what's obvious?" Do you see
: lips moving when you hear no speech? Do you see a car crash and hear
: the noise a couple of tenths of a second later? Is the wrong
: background music playing?


I do different types of capture. In some sound is important. And in some it's
not that important. However, synch is important everywhere.

Some of my captures are live conerts. The drum beats are definitely noticeable.

Some other captures are classic hockey games where I care more about synch of
the sound than the quality. When a puck hits the stick or a board and the
sound of it comes late or early, it doesn't feel right.

Unfortunately I'm a purist too.

--Leonid

Leonid Makarovsky wrote:
Scott Dorsey wrote:
: Right. But how far in do you NOTICE it? How far off can it be, before it is
: a problem?

I start notice things when it's off by 2 NTSC frames which is 0.06 of a second.

Would you recommend jumping to zero crossing and keep inserting silences?

No, if the sound is slipping back, I would recommend cutting out video
frames at transitions instead.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

In article writes:

Some of my captures are live conerts. The drum beats are definitely noticeable.

Some other captures are classic hockey games where I care more about synch of
the sound than the quality. When a puck hits the stick or a board and the
sound of it comes late or early, it doesn't feel right.

This is exactly the type of application where you should manually
synchronize. You really can't depend on electronics to be that stable
for two hours. Get the first drum beat of the shot lined up and it
will stay in sync very accurately until the shot is over (unless of
course you're making a two hour movie of a drum stick hitting the
head).

Nothing wrong with getting it right where it matters, but trying to
make one adjustment based on the starting and ending times and hoping
that will make synchronization correct for the full time period is
wishful thinking. Life isn't that easy.


--
I'm really Mike Rivers - )
However, until the spam goes away or Hell freezes over,
lots of IP addresses are blocked from this system. If
you e-mail me and it bounces, use your secret decoder ring
and reach me he double-m-eleven-double-zero at yahoo

"Mike Rivers" wrote in message
news:znr1098130242k@trad...

In article writes:

: If you run the tape, how far in do you first notice that it's out of
synch?

It's proportional. So in 2 hours it's off by .155 of a sec. In 1 hour
it's off
by .0775 of a sec.... Etc...

Do you notice that it's .0775 seconds out of sync? Do you have to look
at a time scale on the computer to know that it's out of sync or is
there some aural-visual cue that tells you that?

Frankly, I think that if you can see that it's 0.0775 seconds out of
sync, you've got a good imagination. What we're trying to get at is
whether you're seeking an exotic solution for a problem that isn't a
problem in practice.

Mr. Makarovsky has been flogging this question now in at
least a couple of newsgroups that I read. Frankly, it has taken
on the tone of a troll. He has ignored at least a dozen suggestions
for the most likely methods of fixing the issue (assuming that it
even exists). if he wants to tweak the length of the sound track
by .002% maybe we should just let him learn for himself.

Scott Dorsey wrote:
: No, if the sound is slipping back, I would recommend cutting out video
: frames at transitions instead.

That's a good idea. I haven't thought about it. I'll try it with my next
capture.

--Leonid

Richard Crowley wrote:
: Mr. Makarovsky has been flogging this question now in at
: least a couple of newsgroups that I read. Frankly, it has taken
: on the tone of a troll. He has ignored at least a dozen suggestions
: for the most likely methods of fixing the issue (assuming that it
: even exists). if he wants to tweak the length of the sound track
: by .002% maybe we should just let him learn for himself.


Mr. Crowley, what went on in your head
Mr. Crowley, did you talk with the dead - Ozzy 1981...

Anyway, I have no time to troll the newsgroups. I posted it to this and
to rec.video.desktop. If you think it's a troll, just ignore the thread.
FYI, I have previously synched audio and video successfully when audio was
longer, but never done it when audio was shorter. Have a nice day.

--Leonid

Mike Rivers wrote:
: Nothing wrong with getting it right where it matters, but trying to
: make one adjustment based on the starting and ending times and hoping
: that will make synchronization correct for the full time period is
: wishful thinking. Life isn't that easy.

Actually, you're wrong. 'cause the synch is proportional the such adjustment
works fine as far as synch goes. With stretching there're side effects though.

--Leonid

On or about 18 Oct 2004 18:56:07 -0400, Scott Dorsey allegedly wrote:

Leonid Makarovsky wrote:
Scott Dorsey wrote:
: Right. But how far in do you NOTICE it? How far off can it be, before it is
: a problem?

I start notice things when it's off by 2 NTSC frames which is 0.06 of a second.

Would you recommend jumping to zero crossing and keep inserting silences?

No, if the sound is slipping back, I would recommend cutting out video
frames at transitions instead.


With the error running at 0.0775 seconds per hour, that would mean only
2.3 frames (asssuming 30fps) in an hour. Find suitable places to remove 4
or 5 frames in the two hour program, and you're done.


Noel Bachelor noelbachelorAT(From:_domain)
Language Recordings Inc (Darwin Australia)

In article writes:

: Nothing wrong with getting it right where it matters, but trying to
: make one adjustment based on the starting and ending times and hoping
: that will make synchronization correct for the full time period is
: wishful thinking. Life isn't that easy.

Actually, you're wrong. 'cause the synch is proportional the such adjustment
works fine as far as synch goes.

Are you absolutely sure that both the video and audio recordings are
running at the same speed throughout? By stretching so that they line
up at the beginning and the end, you're only assuring two points of
perfect synchronization. If something drifts in the middle, it will
still be out of sync. That's why I suggested that you manually line up
everything that's important and let the rest fall where it may.

By the way, what are these video "captures?" I'm not sure I understand
just what it is that you're working with. How did you get the video
into the computer? How did you get the audio into the computer?

--
I'm really Mike Rivers )
However, until the spam goes away or Hell freezes over,
lots of IP addresses are blocked from this system. If
you e-mail me and it bounces, use your secret decoder ring
and reach me he double-m-eleven-double-zero at yahoo

Mike Rivers wrote:
: Are you absolutely sure that both the video and audio recordings are
: running at the same speed throughout? By stretching so that they line
: up at the beginning and the end, you're only assuring two points of
: perfect synchronization. If something drifts in the middle, it will
: still be out of sync. That's why I suggested that you manually line up
: everything that's important and let the rest fall where it may.

Yes. With was previous soundcard it was pretty obvious. In 1 hour the audio was
delayed by .1 of a sec. In 2 hours by .2 of a sec for NTSC video. And all the
DVDRs I watched that I made were perfectly in synch.


: By the way, what are these video "captures?" I'm not sure I understand
: just what it is that you're working with. How did you get the video
: into the computer? How did you get the audio into the computer?

I use a TV Tuner card
(http://www.lifeview.com/html/product...deo3000-w1.htm) to transfer
an analog video from either VHS or LaserDisc to my computer. I connect VCR's
S-Video cable or LaserDisc Player composite cable to this Tuner card. I capture
in AVI file. If I x-fer from VHS, I use an RCA audio cable to run from my VCR
to my soundcard. And of course I sample audio at 48kHz to be DVD compatible.
If I x-fer from LaserDisc player, I use optical digital cable from LD player to
optical digital in of my soundcard. There I set an audio at 44.1kHz that I
later manually resample at 48kHz as postprocessing procedure. Pretty straight
forward, but time consuming if you are shooting for a good quality.

And yeah, I noticed that I screwed up a little. My soundcard was locked at
44.1kHz while my application was set to 48kHz. Besides resampling on the fly,
that may have caused audio alignment to be ahead.

--Leonid

Another way of determining exactly what stretch is required and how well
you've done is to extract the bad audio from the camera and line it up in
multitrack with the good audio. Then you can see where and how much the
time drift is and when you've stretched/shrunk/cut the proper amount.

fwiw, I've found the Wavelab stretch function to sound very good (though
I've never gone more than +/- .02%)