[ddots-l] Re: Quantizing audio

  • From: "Greg Brayton" <Greg@xxxxxxxxxxxx>
  • To: <ddots-l@xxxxxxxxxxxxx>
  • Date: Mon, 2 Jan 2012 05:58:14 -0500

Thanks Bryan but when I turn on audio snap I don't see anything that says sensitivity as I tab through. Is that unusual or could it be called something else? I see something for presets, and no list or nothing that says how to open a list. ----- Original Message ----- From: "Bryan Smart" <bryansmart@xxxxxxxxxxxxxx> 

To: <ddots-l@xxxxxxxxxxxxx>
Sent: Sunday, January 01, 2012 3:19 PM
Subject: [ddots-l] Re: Quantizing audio
A transient is a place in audio where Sonar has detected a strong/loud sound. The threshold/sensitivity control in the AudioSnap dialog is where you set how loud a sound must be before it is considered to be a transient. Setting that control is a little like setting the threshold on a noise gate. If you're working with drums or bass, you want the threshold to be set high enough so that only the sound of the drum being struck, or the bass being picked, would be strong enough to register as a transient. You don't want the relatively quiet sound of the sustaining note to be loud enough to qualify.
When AudioSnap is off, then pressing tab on a track just moves to the next sound on the track. If AudioSnap is on for the clips on the track, then pressing tab in the track view only moves to AudioSnap transients.
Once AudioSnap is on for a clip, you adjust the threshold/sensitivity settings in the AudioSnap window so that transients are registering at places where notes are struck/picked. Transients aren't permanent things. They're only markers where Sonar has found sound that meets the criteria that you've set. You can set the sensitivity, close AudioSnap, and try tabbing in the track view to move between transients. If you think to many, or not enough, are being detected, you just re-open the AudioSnap window, change the settings, close it, and try again. Due to the variability of audio and how people play, you'll almost never find settings that catch every last note strike/pick. The idea is to just get as close as you can. If you could see, you could get fairly close with the automatic settings, then use the mouse to manually drag the transient markers that weren't able to automatically find their beats. There isn't a way for screen reader users to do that, though, so just do as well as you can with the auto settings.
Once the transient markers are in the right place, then you just use the control+q dialog, as always. Make sure that the audio beats check box is checked, though.
If it helps, you can think about this process in two parts. Working with all of the detection settings in the AudioSnap dialog is what you do to help Sonar figure out/track the existing beat/rhythm in the audio. At this stage, you aren't telling Sonar what you'd like the rhythm to become, but are trying to help it figure out what it is listening to. If it hears a mish mash of sound, it helps if you can tell it to try to only catch 16th notes, quarter notes, etc. The sensitivity control is there so that you can help it figure out if it is incorrectly registering faint sounds as beats, when it should ignore them. When the settings are correct, Sonar will be tracking the rhythm of the sound, and will have transient markers at most of the places in the audio where strong individual beats occurred.
Once it is tracking/understands the rhythm in the audio, you can tell it to do something with that rhythm. The obvious thing is to quantize the track, but you can do other stuff.
Sonar can save the discovered rhythm to a groove file, the same sort of groove file that is used by Groove Quantize. So, after you've helped Sonar figure out how to track the rhythm of a drummer with great timing, you can save that to a groove file, then use Groove Quantize to quantize other MIDI or audio tracks to the feel of that drummer.
Another use for this sort of thing is drum replacement. You can have Sonar generate a MIDI note on a new track with the same timing as the transients in the audio. If you used AudioSnap on the track with the kick drum mic, and got all of its transients to register, then you can have Sonar create a pattern of notes on a MIDI track to trigger a kick drum on a softsynth or MIDI module with the exact same timing. You can then mute out the original kick drum audio track. That would leave just the synth kick drum, although it would have the timing of the kick that was originally played in the acoustic kit. Instead of muting out the original, you could mix the real and synth kicks together. There are lots of possibilities. 

Bryan

On Jan 1, 2012, at 12:24 PM, Greg Brayton wrote:
I sorta thought it was strange you signing your namme Bryan at the end, but 
I couldn't be sure.
----- Original Message -----
From: "Jack Conti" <jackconti@xxxxxxx>
To: <ddots-l@xxxxxxxxxxxxx>
Sent: Sunday, January 01, 2012 12:06 PM
Subject: [ddots-l] Re: Quantizing audio
Not saying anything, that was Bryan Smart's message. <smile> At 06:40 AM 
1/1/2012, you wrote:

so it sounds like I need to find out what a transient is as opposed to
just a note. If my first note strarts on 41 .1, and my phrase gos to 43.1, 
do I go to that measure and tab to find the first transient occuring on
the spot? Are you saying that it will need to be nudged to the start then select that 2 measures then open audio snap find the sensitivity and play 
around with that? Do we even use control Q  As we do  with the midi or
soft synths?

----- Original Message ----- From: "Jack Conti" <jackconti@xxxxxxx>
To: <ddots-l@xxxxxxxxxxxxx>
Sent: Saturday, December 31, 2011 9:30 PM
Subject: [ddots-l] Re: Quantizing audio



Greg maybe this will help.

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
At 05:00 PM 12/31/2011, you wrote:

Bryan mentioned that on his demo, but not really how to go about doing
it.
What section of the tutorial could I find that in? Talks about midi
quantize but I couldn't find audio. I just happen to be working on a
song where the rhythm guitar could be just a bit cleaner if quantized in 
a section to 16ths.


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