[ddots-l] Re: quantizing audio
- From: Bryan Smart <bryansmart@xxxxxxxxxxxxxx>
- To: "ddots-l@xxxxxxxxxxxxx" <ddots-l@xxxxxxxxxxxxx>
- Date: Tue, 19 Oct 2010 12:54:16 -0400
When quantizing audio, remember that Sonar is identifying beats in the audio by
detecting transients, and then moving those transients to line up with the
quantization grid. If you have a note that begins on 1.2.400, and extends to
2.1, and quantize to quarter notes, then Sonar will pull the start of the
transient at 1.2.400 back to 1.2. It pulls the transient back by stretching the
segment from 1.2.400 and 2.1 so that it now lasts from 1.2 to 2.1. Another way
to think about it is that, like MIDI, Sonar is only moving the start of the
note. In the quantize dialog, you can also set to quantize durations, in which
case the end of the note will also be pulled toward the nearest grid position.
However, unlike MIDI, Sonar really doesn't know what is a discrete note in
audio. Instead, transient detection is used. Transient detection looks for
places in the sound where there is a strong sudden increase in the strength.
This is usually the exact moment where you went from silence to singing a word,
where you strummed the guitar, when you struck a drum, etc. You need to set the
sensitivity setting in the AudioSnap dialog so that it, for the most part, only
picks out real note boundaries. In the same place, you can also set how often
the transients can occur.
There aren't "correct" settings for these. You have to feel them out for each
situation. In general, they're a lot easier to set on a individual
track/instrument than for a stem/mix.
If you're working with something rhythmic, like a rhythm guitar part, bass,
drums, etc, then you really need to set the resolution size to something
appropriate. If it is set to quarter notes for example, then transients will
only be detected at intervals of a quarter note or more, and so quantizing to
16th notes would just round all of the quarter notes to the nearest 16th.
Always selecting 16ths or some other small value isn't appropriate either, as
stretching a fewer larger segments (as happens with quarters or large) results
in smoother sound, particularly for guitars, vocals, pads, etc.
For sensitivity, I usually start with something high, like 90%, and work my way
down. I try with 90, quantize, and listen. If it sounds like there are lots of
pieces that were somehow ignored, then I un-do, lower the sensitivity, and try
again. Be careful. You can't find a perfect sensitivity. If you go too far,
then Sonar will detect transients continuously, not just at the start of
individual notes. A sighted person lowers the sensitivity to a level that
catches most notes, and then can use the mouse to visually include or exclude
additional transients in order to correct Sonar's mistakes. All we have,
though, is the sensitivity slider, so get the best compromise you can, and
leave it alone.
Here are some tips for dealing with false transients when you can't get
sensitivity just right:
If you get several false transient detections, no matter what you do, then
quantize with less strength. True, the correctly detected transients won't be
perfectly quantized, but the falsely detected transients will not be moved
dramatically off their original positions, either. The result is an
improvement, but not a full cleanup. You can also use the window parameter for
quantize to ignore notes that are too far off of the beat. The real recorded
notes might not be that far, but the transient markers might, and this will
help you to exclude them from being incorrectly quantized.
There are some techniques that it would take too long to go in to detail here
that can also help. You can improve transient detection, particularly on drum
tracks, by squishing the crap out of them before running AudioSnap. You only
squish them for purposes of detection. You still apply quantize to the original
uncompressed tracks.
You can also split your track in to multiple clips, and work with audiosnap in
segments.
There is also manual correction. You can find the start of a beat or note with
the tab key, mark that off as the from time, move forward to the end of the
note with the keyboard or your scrub wheel, mark that as the through time.
Then, you split the selection in to a clip, and nudge that clip until the start
time aligns with the time that you'd like for the beat (like 2.1).
Bryan
-----Original Message-----
From: ddots-l-bounce@xxxxxxxxxxxxx [mailto:ddots-l-bounce@xxxxxxxxxxxxx] On
Behalf Of Charles Marston
Sent: Monday, October 18, 2010 11:01 PM
To: ddots-l@xxxxxxxxxxxxx
Subject: [ddots-l] Re: quantizing audio
Neville:
I just used audio snap to quantize three tracks with acoustic guitars.
First, remember that audio snap is a real-time effect, so it usually sounds
messy specially in the parts that need some more help. So, what I did was to
use the bounce to clip command on the track afterwards so that the effect is
applied distructively. After I did that, I was able to listen to the real
results of the quantization with audio snap. It worked perfectly on two of the
three tracks. On the third track, I noticed some degradation of the sound
quality in very small segments of audio, however, this was only noticeable when
I solo the track.
Try it and see if you like the results. Select the track, press shift-A.
Make sure you enable audio snap. Then, go to the quantize value and select the
one you want. Then, after closing audio snap, select the track and do a bounce
to clip with alt-e and then b. Let me know if it works.
--------------------------------------------------
From: "neville" <neville@xxxxxxxxxxxxxxxx>
Sent: Monday, October 18, 2010 9:04 PM
To: <ddots-l@xxxxxxxxxxxxx>
Subject: [ddots-l] Re: quantizing audio
> I guess nobody has any ideas for me? I really could use some help with
> this.
> See message below.
>
> May the peace of God which passes all understanding guard your heart
> and mind in Christ Jesus. God bless you!
>
> Music soft sacred and soulful
>
> Website http://www.nevillepeter.com
>
> email neville@xxxxxxxxxxxxxxxx
>
> phone 407-222-4488
>
>
> -----Original Message-----
> From: ddots-l-bounce@xxxxxxxxxxxxx
> [mailto:ddots-l-bounce@xxxxxxxxxxxxx]
> On
> Behalf Of neville
> Sent: Monday, October 18, 2010 6:11 PM
> To: ddots-l@xxxxxxxxxxxxx
> Subject: [ddots-l] quantizing audio
>
> Is there a way to quantize the audio on a acoustic guitar track with
> out compromising the sound of the track? I have tried the audio
> quantize but I don't like what it does to the audio. I have also tried
> the audio snap, but I'm not sure I'm understanding how to use it and
> the attempts I have made to quantize the audio in the audio snap have
> not been successful. Any ideas?
>
> May the peace of God which passes all understanding guard your heart
> and mind in Christ Jesus. God bless you!
>
> Music soft sacred and soulful
>
> Website http://www.nevillepeter.com
>
> email neville@xxxxxxxxxxxxxxxx
>
> phone 407-222-4488
>
>
>
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