Leonid Makarovsky wrote:
I have a 2 hour WAV file that I need to make 1 second longer. I was
doing
the video capture and audio was ahead of video by 1 second factor.

So I need to stretch it without losing quality. The effect should be
the
same as if I played an analog cassette tape a bit slower. The reason
I'm asking
is that I had never had problems with squeezing WAV file (i.e. making
them
shorter). But I once tried to stretch the WAV file in GoldWave sound
editor
and artifacts such as clicks and distortion were introduced in sound.
Any way
to do it without artifacts? Thanks.

--Leonid

PS. The WAV file is 16 bit 48kHz.

Hi Leonid.

You specified that the audio is ahead by 1 second. So, are you sure you
need to stretch the audio? Do you mean that the audio starts off
in-sync but that by the end of the playout the audio is ahead by a
second? Otherwise all you need to do is re-align the audio with the
video.

If you, indeed, you need to stretch the audio by 1 second then that
amounts to .013% change (very little for sure). I have used the the
time-stretch facilities in ProTools, Nuendo and Logic. And each should
be able to perform the change inaudibly (as long as you specify the
highest quality setting vs operational speed).

Regards,
Hassan

Hassan Davis wrote:
: You specified that the audio is ahead by 1 second. So, are you sure you
: need to stretch the audio? Do you mean that the audio starts off
: in-sync but that by the end of the playout the audio is ahead by a
: second? Otherwise all you need to do is re-align the audio with the
: video.

I *assume* that the audio starts in-sync. Honestly, there's no way I can check
that. I can, however, check the audio relative to video position at the end of
the whole thing by re-capturing just the very end of the program, then finding
the same video frame and from that point of time copying audio.

--Leonid

In article ,
Leonid Makarovsky wrote:
Hassan Davis wrote:
: You specified that the audio is ahead by 1 second. So, are you sure you
: need to stretch the audio? Do you mean that the audio starts off
: in-sync but that by the end of the playout the audio is ahead by a
: second? Otherwise all you need to do is re-align the audio with the
: video.

I *assume* that the audio starts in-sync. Honestly, there's no way I can check
that. I can, however, check the audio relative to video position at the end of
the whole thing by re-capturing just the very end of the program, then finding
the same video frame and from that point of time copying audio.

If you can't check it, then I assume there is nothing up front that _needs_
to be synched. If that's the case, just shift everything five frames and
let the beginning be out of synch. If there is no dialogue and no synched
effects, it doesn't matter if you're a couple frames off.

If there is dialogue and synched effects up front, then you certainly can tell
if it starts in synch.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

Scott Dorsey wrote:
: If you can't check it, then I assume there is nothing up front that _needs_
: to be synched.

I'm not sure about that. All I know for sure that audio vs video in the
beginning differs from audio vs video at the end. But I can't check precisely.
It looks and sounds ok to me. But the beginning is as important as the end.

By the way, I don't worry about the pitch even if I had adjust it more than
even 10 seconds 'cause theoretically if soundcard's internal clock is really
off, I will get correct pitch by stretching or squeezing the file.

--Leonid

On 14 Oct 2004 13:55:56 GMT, Leonid Makarovsky
wrote:

I *assume* that the audio starts in-sync. Honestly, there's no way I can check
that. I can, however, check the audio relative to video position at the end of
the whole thing by re-capturing just the very end of the program, then finding
the same video frame and from that point of time copying audio.

Where is the first place that you can tell whether audio and video are
in synch? If you drag the audio into alignment here, how far off is
synch at the end (or at the last point where it is an issue)?

CubaseFAQ www.laurencepayne.co.uk/CubaseFAQ.htm
"Possibly the world's least impressive web site": George Perfect

Laurence Payne wrote:
: Where is the first place that you can tell whether audio and video are
: in synch? If you drag the audio into alignment here, how far off is
: synch at the end (or at the last point where it is an issue)?

I'm not sure I understand the question. The audio is out of synch relative
to video.

--Leonid

Leonid Makarovsky wrote:
Laurence Payne wrote:
: Where is the first place that you can tell whether audio and video are
: in synch? If you drag the audio into alignment here, how far off is
: synch at the end (or at the last point where it is an issue)?

I'm not sure I understand the question. The audio is out of synch relative
to video.

At the first shot on the reel, the audio is in synch. At the last shot on
the reel, the audio is out of synch.

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

--
"C'est un Nagra. C'est suisse, et tres, tres precis."

Scott Dorsey wrote:
: At the first shot on the reel, the audio is in synch. At the last shot on
: the reel, the audio is out of synch.

: 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...

--Leonid

Leonid Makarovsky wrote:
Scott Dorsey wrote:
: At the first shot on the reel, the audio is in synch. At the last shot on
: the reel, the audio is out of synch.

: 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...

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

If it's two hours long, there should be PLENTY of places to cut a frame of
audio out here and there to match everything up.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."

Leonid Makarovsky wrote:

Scott Dorsey wrote:
: At the first shot on the reel, the audio is in synch. At the last shot on
: the reel, the audio is out of synch.

: 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...

I suppose a filter/plugin to do this doesn't exist (maybe I should write
one), but I would be awefully tempted to want to solve this problem by
throwing out individual samples instead of resampling. If you're off by
0.0775 seconds per hour, that's only 0.00215%, which is not even one
sample per second at the 44100 Hz sample rate and just over one sample at
48000 Hz. I'm sort of a purist, but I doubt it would be easy to notice
when one sample is removed here and there. It's equivalent to editing
out about 0.02 milliseconds of audio.

The code for a plugin to do this would be very simple. For a little
added flair, the plugin could look for periods of silence or quiet
parts (or parts without much high-frequency content or with lots of
high-frequency noise) and throw out more samples during those periods
and fewer at other times.

I should explain that if none of this makes sense in the context of this
discussion (or it has already been discussed), it might be because I
just got back from vacation and haven't been following the thread.
(By the way, anyone here ever do installed audio for a cruise ship?
This particular one might have had a deal with Yamaha, because everything
from pianos to drums to consoles was all Yamaha.)

- Logan

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.


--
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

In article writes:

I'm not sure I understand the question. The audio is out of synch relative
to video.

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?

Generally synchronization isn't required for every frame, just the
ones where our brain ties visual and sonic events together. Fix those
by editing so they'll be perfect and don't worry about things that you
hear and can't see (or vice versa).

Otherwise you're just doing an exercise in technology which won't
guarantee the results you need.


--
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:
: 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

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