Algorithms and rendering

When you stretch an audio clip, AudioSnap uses a particular formula, or algorithm, to stretch the audio. The best algorithms take the most computing time and power to complete, so if AudioSnap always used the best available algorithms (the iZotope Radius algorithms), you would not be able to play back your clip in a reasonable amount of time to listen to the timing. That’s why you can choose a quick algorithm for “online” rendering (real-time playback), and a different algorithm for “offline” or non-real-time rendering. Offline rendering in an AudioSnap context usually means bouncing to track, but it also refers to other offline processes such as freezing tracks and applying effects. When you do any of these mixdown operations such as bouncing, exporting, or freezing, audio clips use the offline rendering algorithm you have chosen for them.

Note: The Online render mode is for preview purposes only during playback. The final audio quality will be greatly improved after the Offline render mode is applied during mixdown/export.

Typical algorithm choices for an AudioSnap session work like this:

Do your AudioSnap time stretching, error correction, etc., with a quick algorithm: choose either Percussion or GrooveClip.

After your AudioSnap editing is finished, bounce to track with a better algorithm: choose one of the Radius choices, or for drum tracks, Percussion is usually the best choice.

Note: You should avoid rendering AudioSnap clips more than once. Applying stretch algorithms multiple times in succession can degrade the audio quality (similar to transcoding an MP3 file). Until your project is mixed and finalized, it is recommended that you use the Freeze function instead of Bounce to Track(s) or Bounce to Clip(s) if you need to temporarily off-load CPU processing power. For details, see To freeze an AudioSnap-enabled clip.

The following table describes the available algorithms.

Table 118.  

Algorithm	Description
GrooveClip	Good all-around algorithm to use while stretching audio
Percussion	Gives a better sound on percussion clips while stretching audio
iZotope Radius Mix	Best all-around choice when bouncing to track with audio clips that contain a mix of different sounds
iZotope Radius Mix Advanced	This choice is similar to iZotope Radius Mix, but exposes two parameters: Pitch coherence. Pitch coherence preserves naturalness of timbre for pitched solo voices, such as human speech, saxophone or vocals. The default value for this control is 50%. Higher values of pitch coherence will increase phase accuracy but may sound more modulated. Phase coherence. When processing stereo or surround audio, Phase coherence helps to preserve the phase relationships between channels. The default value for this control is 50%. Higher values of phase coherence will preserve the phase between multiple audio channels at the expense of slight distortion. The Pitch coherence and Phase coherence parameters can be adjusted in Edit > Preferences > Project - AudioSnap.
iZotope Radius Solo	Best choice when bouncing to track with audio clips of a solo instrument. Although a guitar is a “solo” instrument, if you play chords instead of single notes you may want to select “Radius Mix” instead. Tip: if a clip/track contains a mixture of polyphonic and monophonic parts, you may want to split the parts into separate clips and experiment with different algorithms for each clip.
iZotope Radius Solo (Bass)	Best choice when bouncing to track with audio clips of a bass instrument
iZotope Radius Solo (Vocal)	Best choice when bouncing to track with audio clips of a solo voice

To choose default algorithms

1.	Press A to open the AudioSnap palette.

2.	In the Applies To list, select Default Settings.

3.	Under Render Mode, select the desired Online and Offline render modes.

Every AudioSnap-enabled clip that you stretch or bounce uses the settings you choose for default stretch algorithms, except clips that you choose individual settings for.

To choose render algorithms for an individual clip

1.	Select the clip or clips you want to edit.

2.	Press A to open the AudioSnap palette.

The AudioSnap palette displays the current render mode of the selected clip. If you select multiple clips that have different render modes, the Online and Offline lists display (Multi).

3.	In the Applies To list, select Clips.

4.	Under Render Mode, select the desired Online and Offline render modes.

To choose render algorithms for all current and future clips on a track

1.	Select the track or tracks you want to edit.

2.	Press A to open the AudioSnap palette.

3.	In the Applies To list, select Tracks.

4.	Under Render Mode, select the desired Online and Offline render modes.

All current and future clips in the selected tracks will inherit the selected render modes.

To freeze an AudioSnap-enabled clip

1.	Do one of the following to open the Freeze Options dialog:

In the Track view, right-click any track’s Freeze button .

Right-click an audio track, and select Freeze > Freeze Options from the pop-up menu.

2.	Make sure the Track FX check box is cleared.

3.	Click OK to close the Freeze Options dialog box.

4.	Do one of the following:

In the Track view, click the desired track’s Freeze button .

Right-click the track and select Freeze > Freeze Track from the pop-up menu.

SONAR bounces the audio in the track to a new audio clip or clips.

To bounce an AudioSnap-enabled clip

1.	Select the clip you want to bounce.

2.	Click the Track view Tracks menu and choose Bounce to Track(s) to open the Bounce to Track(s) dialog box.

3.	In the Destination field, choose the track where you want your new audio clip to go.

4.	In the Source Category field, choose Tracks.

5.	Choose the Channel Format and Dithering options you want.

6.	Enable all the options in the Mix Enables section.

7.

Click OK.

 

See:

Freeze tracks and synths

To bounce multiple audio clips to a new track

To bounce to clips

Using global tools on AudioSnap transient markers

Editing transient markers

Using the AudioSnap palette

Synchronizing audio and the project tempo

Fixing timing problems in audio clips

Extracting MIDI timing information from audio

General editing

Using the Pool