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Topic: Adobe Audition Stretching (Read 26708 times) previous topic - next topic
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Adobe Audition Stretching

Reply #25
Someone mentioned the speed difference between PAL and NTSC. That peed difference is 25/23.976 - about 4.17% - more than 2/3 of a semitone. Your amount of change is 13900/13899 - less than 1/10 of the difference between NTSC B/W and NTSC color. Before pitch correction was practical the Europeans simply listened to American video 4% fast.
No, we listen to films fast: 24p sped up to 25p-in-50i. This is almost universal on TV and DVD (sometimes with pitch correction, especially on DVD, but often without), but not on BluRay (which is almost always native 24p). However, video converted from NTSC to PAL (60i to 50i) keeps its duration exactly.

Film transferred to NTSC video and then converted to PAL in the normal way also keeps its duration exactly (and has its picture quality wrecked!). This isn't common in the UK (if they show an excerpt from a new movie trailer on the news you'll sometimes see this, but otherwise I've never seen it), but in some markets and with some content types (especially anime), it's very common that a film is telecined to NTSC 24p-in-60i, field blend converted to PAL 50i, and then watched in that format - this gives you the correct audio duration and pitch, but lousy picture quality.

Cheers,
David.

Adobe Audition Stretching

Reply #26
Someone mentioned the speed difference between PAL and NTSC. That peed difference is 25/23.976 - about 4.17% - more than 2/3 of a semitone. Your amount of change is 13900/13899 - less than 1/10 of the difference between NTSC B/W and NTSC color. Before pitch correction was practical the Europeans simply listened to American video 4% fast.
No, we listen to films fast: 24p sped up to 25p-in-50i. This is almost universal on TV and DVD (sometimes with pitch correction, especially on DVD, but often without), but not on BluRay (which is almost always native 24p). However, video converted from NTSC to PAL (60i to 50i) keeps its duration exactly.

Film transferred to NTSC video and then converted to PAL in the normal way also keeps its duration exactly (and has its picture quality wrecked!). This isn't common in the UK (if they show an excerpt from a new movie trailer on the news you'll sometimes see this, but otherwise I've never seen it), but in some markets and with some content types (especially anime), it's very common that a film is telecined to NTSC 24p-in-60i, field blend converted to PAL 50i, and then watched in that format - this gives you the correct audio duration and pitch, but lousy picture quality.

Cheers,
David.



Aren´t all NTSC movies sped up to? (24 to 23.976), but that´s pretty negligible though.

But so, if a movie is 60i, and converted to 50i, we keep the same, either skipping or blending frames?

Quite funny how PAL is either to fast, or to slow compared to NTSC depending on material.

And when you say NTSC film, do you mean 29.97?, cause when that´s used in PAL, we either change it to 23.976 and speed it up, or we skip blend frames, making it "identical" to the NTSC version.

And as you say, TV are pretty much never pitch corrected, at least Analogue, i don´t think it ever was (may be wrong), and DVD is as you say, very rare, But it does exist.

The sad fact is though, that when dubbing is done in PAL for normal movies and series, we dub with 25fps, meaning we are dubbing to the sped up version, so we always get the background music etc, wrong, and it can´t be fixed.
However, for movies that have been shown at Cinema (24fps) we dub at that speed. So only material that have been shown at the Cinema has been dubbed correctly, which is very sad really.

Adobe Audition Stretching

Reply #27
Can someone point me to the highest quality settings when using SOX and speed (for example, speed 0.96)?

Cause i noticed i get some noise currently, and i have been using

-rate -v speed 0.96

So it seems i must add dither, but if i just add dither, there is still noise
If i add dither -a it goes away, at least on silent parts.

It also goes away if i use -p 24.

So i am a bit confused.

The sound i am working with is 16bit and should end at 16bit after the conversion.

Adobe Audition Stretching

Reply #28
I'm a bit confused. I think there's a

rate

and a

--rate

but not a

-rate

option. I presume you're specifying rate to choose maximum quality (rate -v), though for 16-bit, it appears that rate -h is recommended, with -v intended for 24-bit. You could try rate -h instead to modify the quality of resampling that speed itself will default to.
Dynamic – the artist formerly known as DickD

Adobe Audition Stretching

Reply #29
The default rate parameters (giving –120dB) should be fine for 16-bit.

One possible source of noise is dither. Here's 3 different dither options: default (TPDF), none, and shaped:

Code: [Select]
sox -D -n -b 16 in.wav synth 8 sine 0:24k gain -1
sox    in.wav out1.wav speed .96
sox -D in.wav out2.wav speed .96
sox    in.wav out3.wav speed .96 dither -s

sox -M in.wav out[123].wav -n spectrogram -wk
display spectrogram.png &

(using linux syntax in the last two commands).

The other is clipping, so e.g.
Code: [Select]
sox -G in.wav out.wav speed .96

Adobe Audition Stretching

Reply #30
The default rate parameters (giving –120dB) should be fine for 16-bit.

One possible source of noise is dither. Here's 3 different dither options: default (TPDF), none, and shaped:

Code: [Select]
sox -D -n -b 16 in.wav synth 8 sine 0:24k gain -1
sox    in.wav out1.wav speed .96
sox -D in.wav out2.wav speed .96
sox    in.wav out3.wav speed .96 dither -s

sox -M in.wav out[123].wav -n spectrogram -wk
display spectrogram.png &

(using linux syntax in the last two commands).

The other is clipping, so e.g.
Code: [Select]
sox -G in.wav out.wav speed .96


From my tests, Disabling Dither (-D) removes the noise. But i don´t really understand, why is it enabled if it adds noise, i thought dither was there to prevent the noise?

Adobe Audition Stretching

Reply #31
I'm a bit confused. I think there's a

rate

and a

--rate

but not a

-rate

option. I presume you're specifying rate to choose maximum quality (rate -v), though for 16-bit, it appears that rate -h is recommended, with -v intended for 24-bit. You could try rate -h instead to modify the quality of resampling that speed itself will default to.


Well that makes me confused as well. I thought, rate was rate, no matter if it is --rate or -rate etc.

But as you say, i am only using it to increase the quality of the resampling (as i guess that´s used when changing speed).
It doesn´t make any difference if i change it, to the noise that is, the noise comes from Dithering which is a bit confusing for me.

But there shouldn´t be anything bad with choosing -v even if it´s 16 bit. I think they recommend it for 24bit, as it´s overkill, pretty much like placebo settings on stuff. But as it goes very fast anyway, i don´t see any reason to not use the best settings possible.

Adobe Audition Stretching

Reply #32
Actualy dither IS noise. Do we talk about some noise you see in some zoomed spectral view and get annoyed or can you hear it? If so please provide a sample where we can hear the noise Sox adds.
Is troll-adiposity coming from feederism?
With 24bit music you can listen to silence much louder!

Adobe Audition Stretching

Reply #33
From my tests, Disabling Dither (-D) removes the noise. But i don´t really understand, why is it enabled if it adds noise, i thought dither was there to prevent the noise?

No, dither adds noise to prevent distortion.

Adobe Audition Stretching

Reply #34
Actualy dither IS noise. Do we talk about some noise you see in some zoomed spectral view and get annoyed or can you hear it? If so please provide a sample where we can hear the noise Sox adds.


Ah now that you mention it, it´s there to hide more apparent noise and stuff like that. But i still think it´s wierd that it only adds noise in this case.

And haven´t looked at it in a spectral view so can´t speak for that. But it´s hearable, you can´t hear it, at least not well, if there is normal music or sound, as the noise get´s swallowed.
But if it´s very low sound, or silence, the noise is very apparent.

So the noise floor is pretty high, but not That high.

But if i disable dither, there is no noise at all (at least not audible).

Adobe Audition Stretching

Reply #35
From my tests, Disabling Dither (-D) removes the noise. But i don´t really understand, why is it enabled if it adds noise, i thought dither was there to prevent the noise?

No, dither adds noise to prevent distortion.


Oh, well, am i supposed to use dithering for what i am doing or what;S?
I was on the impression that using dithering, is often a good thing, and shaped dithering is often better to hide noise at certain hertz.

I only want to change the speed at the highest quality possible with sox.

Adobe Audition Stretching

Reply #36
Still i wonder how silent your music is to be able to hear the sox dither noise. It must be so silent you better go with 24bit or try to maximize its volume. Upping the volume on silent parts only to hear the noise makes no sense. Dither is designed to be not audibke at normal listening levels.
Is troll-adiposity coming from feederism?
With 24bit music you can listen to silence much louder!

Adobe Audition Stretching

Reply #37
Still i wonder how silent your music is to be able to hear the sox dither noise. It must be so silent you better go with 24bit or try to maximize its volume. Upping the volume on silent parts only to hear the noise makes no sense. Dither is designed to be not audibke at normal listening levels.


Not like that, the thing is. It´s not pure music, it´s a Movie.

But the noise is clearly hearable if there is silence. I hear it very clearly at normal volume, the same volume i have to listen to the Movie itself.

But if there is a Movie Sound, that will swallow the noise, but it should still be there. Not really a problem as it´s not audible. But it shouldn´t be there, i mean, no dither makes silence, well silent.
With dithering, silence becomes noise, or well the nosie is everywhere, so the noise floor is at a normal range, but not that high that it overcomes other sounds.

Hope you get what i mean.

Adobe Audition Stretching

Reply #38
Still i wonder. Flat dither can add a maximum of 6dB noise to your so called silence, leave alone noise shaped dither. If that is a problem you should have already problems without any dither.
Is troll-adiposity coming from feederism?
With 24bit music you can listen to silence much louder!

Adobe Audition Stretching

Reply #39
Still i wonder. Flat dither can add a maximum of 6dB noise to your so called silence, leave alone noise shaped dither. If that is a problem you should have already problems without any dither.


Well that´s weird, not that good with Decibels, but should i be able to hear 6db normally, or would i need to increase the volume very high?

Cause i am not using shaped (have tried that, sounds the same i think), and i have no problems before, silence is silent.

Adobe Audition Stretching

Reply #40
I doubt a movie audio stream has silence with absolute zero. It should have its own noisefloor you simply increase a bit with dither. If this paticular movie has not you should at least have problems with other movies' noise. It makes no sense to me otherwise, good luck.
Is troll-adiposity coming from feederism?
With 24bit music you can listen to silence much louder!

Adobe Audition Stretching

Reply #41
I doubt a movie audio stream has silence with absolute zero. It should have its own noisefloor you simply increase a bit with dither. If this paticular movie has not you should at least have problems with other movies' noise. It makes no sense to me otherwise, good luck.


Well probably, i don´t think it´s completely silent, but it´s not audible, even with increased volume, so it´s extremely low then.

But i still don´t know. Am i supposed to use Dither or Not?
Didn´t think it would be this problematic;S

Adobe Audition Stretching

Reply #42
I'm sorry. I was going off on a tangent about video standards conversion. How can I delete a post?


Adobe Audition Stretching

Reply #43
@zerowalker:

In your scenario, shaped dither will make a difference, because you most probably are hearing the noise between 1...4Khz, while shaping it would move it up to 10Khz+.

Movies are usually of lower volume (less dynamic compression, and more regulated), so we could perfectly be in a scenario equivalent to 12 or 13bits.
Also, I don't know what you use to playback, but there could be some DRC or envelope follower in your equipment that in fact, increases slightly the volume on parts with less volume.
Also, you don't mention if you listen with headphones, or in a 5.1 setup. Headphones are definitely going to make noise more audible, because they would soften other noises around.


Very quick (but I hope, "to the point") explanation of dither:

1)Scenario:
-Integer digital formats have a finite number of values and cannot describe points inbetween.
-Signals are continuous, so a value at a specific time, can take any value.
-Sampling implies getting a value at periodic intervals (sample rate), and quantize that value (bit depth).
-Quantizing by truncation (round to zero) causes the so-called quantization distortion. Concretely, since the value is different than the original, the process is in fact adding a new signal into the original one. This signal is correlated to the original one, and changes according to the first. This makes it clearly visible in spectograms and audibly more annoying than simple noise.

2) Dither:
-Quantizing by dithering (rounding by adding a defined type of noise, white, triangular pdf, Gueiss...) causes dither noise. Again, the value is different than the original, and this also implies adding  a new signal into the original one. But in this case, the signal is both, not correlated, and rather constant (in terms of variation during time).  It is also very visible in spectograms, given enough bit depth, but being just noise, it is more pleasant that a distortion that matches the signal frequencies.
- Noise shaping is conceptually an equalizer that softens some frequencies to boost others. Noise shaping the dither noise previous to adding it to the original signal is implemented so that frequencies that humans are more sensible with have less noise, and those that were are less sensitive have more noise. When this shaped noise signal is added to the original, we still get the benefits of dithering (i.e. the added signal is not correlated), and we remove part of the problems of dithering (the added noise).


Edit:
Mmm.. that made me think... could we ride the dither noise by an envelope follower? So as to apply less noise on low volume (lower than maybe -40dBFS). Of course then we would have both, noise and quantization distortion, but it is a scenario to test what would be more pleasant.

Adobe Audition Stretching

Reply #44

@zerowalker:

In your scenario, shaped dither will make a difference, because you most probably are hearing the noise between 1...4Khz, while shaping it would move it up to 10Khz+.

Movies are usually of lower volume (less dynamic compression, and more regulated), so we could perfectly be in a scenario equivalent to 12 or 13bits.
Also, I don't know what you use to playback, but there could be some DRC or envelope follower in your equipment that in fact, increases slightly the volume on parts with less volume.
Also, you don't mention if you listen with headphones, or in a 5.1 setup. Headphones are definitely going to make noise more audible, because they would soften other noises around.


Very quick (but I hope, "to the point") explanation of dither:

1)Scenario:
-Integer digital formats have a finite number of values and cannot describe points inbetween.
-Signals are continuous, so a value at a specific time, can take any value.
-Sampling implies getting a value at periodic intervals (sample rate), and quantize that value (bit depth).
-Quantizing by truncation (round to zero) causes the so-called quantization distortion. Concretely, since the value is different than the original, the process is in fact adding a new signal into the original one. This signal is correlated to the original one, and changes according to the first. This makes it clearly visible in spectograms and audibly more annoying than simple noise.

2) Dither:
-Quantizing by dithering (rounding by adding a defined type of noise, white, triangular pdf, Gueiss...) causes dither noise. Again, the value is different than the original, and this also implies adding  a new signal into the original one. But in this case, the signal is both, not correlated, and rather constant (in terms of variation during time).  It is also very visible in spectograms, given enough bit depth, but being just noise, it is more pleasant that a distortion that matches the signal frequencies.
- Noise shaping is conceptually an equalizer that softens some frequencies to boost others. Noise shaping the dither noise previous to adding it to the original signal is implemented so that frequencies that humans are more sensible with have less noise, and those that were are less sensitive have more noise. When this shaped noise signal is added to the original, we still get the benefits of dithering (i.e. the added signal is not correlated), and we remove part of the problems of dithering (the added noise).


Edit:
Mmm.. that made me think... could we ride the dither noise by an envelope follower? So as to apply less noise on low volume (lower than maybe -40dBFS). Of course then we would have both, noise and quantization distortion, but it is a scenario to test what would be more pleasant.


Very true, Shaped should be more pleasant, though when i tried it didn´t seem any different.

I don´t think any Dynamic Compression is going on, there shouldn´t be any, as i am working with Flac from AC3, and i never use DRC with AC3 for that matter.

I am also using Headphones (HD 280Pro), a Sound Card (ZxR Creative) and a Headphone Amp (O2).

I have uploaded 2 clips , one with the dither noise, one without.

I am letting you guess which is which (please only listen, do not check with Spectral etc).

Both are identical, except for one difference. "input" -D "output" trim 0 5 rate -v speed 0.96 , one uses this, and the other uses the same but Not with "-D".
So, both are identical except for the dithering part.

I clearly hear the noise of one of them.

There is silence at the beginning, then the intro starts slowly.

Adobe Audition Stretching

Reply #45
errm.. uploaded where?

And please, do not full quote. (you can edit your post within one hour of your initial post time. else, i guess a moderator will do it, and maybe warn you )


Adobe Audition Stretching

Reply #47
Is it possible to stretch audio by a very precise amount in Adobe Audition?

Currently, i am talking about 500ms over the entire duration.
so for example.

1:55:50:000
will become: 1:55:50:500.


OK I tried a little experiment with Audition 3. First I made a file of 6950 seconds of 1KHz tone of length 1:55.50.000. Then I 'stretched' it at a ratio of 100.0071948 (13900/13899). The resulting file is now 1:55.50.500.

Does that help?


Adobe Audition Stretching

Reply #48
Hi.
Sorry, i missed your reply.

I checked both files (listened in foobar2000 and checked spectra in Audacity).
With (stereo) headphones, playing at a moderate volume, i wasn't able to hear the noise.
Then i started to test, and I was able to start hearing the noise when adding +10dB to the test.flac file. But still, that noise was not as high as the noise which the signal already has starting at second 1.8.


So, i wouldn't consider the noise added by dithering a bigger problem than what it really is.
It might be interesting to do what I suggested above, about applying less noise when the peak volume is low, but in this file, the problem really is the use of 16bit integer for a quiet signal.

Adobe Audition Stretching

Reply #49

Hi.
Sorry, i missed your reply.

I checked both files (listened in foobar2000 and checked spectra in Audacity).
With (stereo) headphones, playing at a moderate volume, i wasn't able to hear the noise.
Then i started to test, and I was able to start hearing the noise when adding +10dB to the test.flac file. But still, that noise was not as high as the noise which the signal already has starting at second 1.8.


So, i wouldn't consider the noise added by dithering a bigger problem than what it really is.
It might be interesting to do what I suggested above, about applying less noise when the peak volume is low, but in this file, the problem really is the use of 16bit integer for a quiet signal.


Ah good, well it´s precisely as you say, the noise doesn´t really bother the rest of the sound, as it´s to low.

But the thing is, why should i even had dithering on, if i get noise with it and it seems to sound the same?
Or will it prevent harmonic distortions, cause i haven´t really done any depth analysis of that.

Not sure how to make it apply different depending on the peak. But i would prefer not to use, Adaptive solutions, they usually have some problematics , as they aren´t bulletproof.

And it´s probably as you say, the 16bit that makes the noise. But 16bit itself shouldn´t have that noise, so i guess it´s only working with 16bit.

Shouldn´t Sox be working in Float and then dithering it down to 16bit, making it as good as possible?

As i know that working only as one plane as 16bit, will create much more audible rounding errors, compared to working in float and then truncate it to 16bit.