Free Warp

Warp tabs are a kind of marker or anchor that can be attached to musically relevant time positions in an audio event, e.g. the first beat of every bar. Warp tabs can be dragged to the corresponding time positions in the project, and the audio will be stretched accordingly.

A typical application of warp tabs is to use them to synchronize audio to video, i.e. manipulate audio that is not musical.

You can also use warp tabs for further tweaking after having applied Straighten Up (see “About the Straighten Up mode” on page 275).

When you change the Straighten Up mode, select another Quantize value or move the Swing slider, all your warp edits will be lost.

Using the Free warp tool

Warp tabs are created using the Free Warp tool on the Playback tab of the Sample Editor, but can also be created from hitpoints (see “Creating warp tabs from hitpoints” on page 287). In this example, we will show how a file with a slightly varying tempo can be locked to a steady tempo by using warp tabs.

1.Open the audio file you wish to process in the Sample Editor.

2.Activate the “Use snap” button in the Sample Editor toolbar.

When you activate this button, warp tabs will snap to zero crossings and hitpoints (if shown).

3.Determine the original tempo (if this is non-varying) or the length of the file (see “Determining the audio tempo automatically and time-stretching your audio” on page 272).

4.Click the Auto Adjust button so that the audio event is stretched to the project tempo.

The Straighten Up mode is automatically activated.

5.Select the Free Warp tool by clicking on it.

For aligning the tempo, you should use Bars and Beats as the ruler resolution. When you place the mouse pointer in the waveform display, it changes to a clock with arrows on either side, and a vertical line in the middle which represents the pointer. When you move the pointer in the waveform window, it shows the position in bars, beats and ticks as well as in seconds.

6. Line up the audio file so that the first beat of the first bar (in the audio event) starts on the first beat of a bar in the project.

• If the audio file doesn’t start on a downbeat, you can use the Event Start handle in the Sample Editor and adjust the position in the Project window so that the first downbeat in the sample is aligned with the first beat of a bar in the grid.

Now the musical first downbeat should be aligned with the first beat of a bar in the project. The next step is to see where the first warp tab needs to be added. It may be useful to hear the metronome click to determine when the tempo of the audio clip drifts from the project tempo. To hear the metronome, activate the Click button on the Transport panel and play back using the transport controls.

7. Play back the audio file, either by auditioning in the Sample Editor or from the Transport panel, and determine where the first beat of a bar in the audio event does not match the corresponding ruler position in the project.

If you find it difficult to pinpoint an exact position in the audio event, you can switch to the Scrub tool and/or zoom in the view. Switch back to the Free Warp tool when you have found the position.

8. In our example, the first beat of the third bar in the audio event is slightly offset from the corresponding grid position and thus needs to be moved back a bit.

11. Release the mouse button.

Now the first beat in the audio event is perfectly aligned with the corresponding position in the project!

The third downbeat in the audio event.

9.Place the pointer at the position of the first beat of the third bar in the audio event and click and hold.

When you click, a warp tab is added. If the position where you clicked was off, you can adjust it by dragging the tab in the ruler.

10.With the mouse button still pressed, drag the warp tab so that the position lines up with the first beat of the bar in the ruler.

• You can also first add warp tabs at the relevant musical positions and change their positions later, see “Editing warp tabs” on page 287.

Next to the warp tab handle in the ruler, a number is shown. This number indicates the warp factor, i.e. the amount of stretch. Warp factor numbers higher than 1.0 indicate that the audio region preceding the warp tab is expanded and will play back slower. Warp factor numbers lower than 1.0 indicate that the audio region preceding the warp tab is compressed and will play back faster.

Ö Note that this ratio is limited to a range between 0.1 and 10. This factor is updated when you change the project tempo with Straighten Up mode enabled or apply the timestretch tool in the project.

12. Continue to use the same method to align the first beat in each bar to the corresponding ruler position.

You only have to add warp tabs where the downbeat in the audio file drifts from the ruler position and/or if you want to lock a warp tab so that it is not moved when editing other points.

When you are done, the previously varying tempo of the audio event will be metronome-steady and will adapt to any tempo in Nuendo.

This example illustrates the general methods of using warp tabs and the Free Warp tool. But you can of course use warp tabs for other operations than aligning downbeats to grid positions. With the Free Warp tool, you can literally stretch any region within a sample to any position!

Editing warp tabs

Moving the destination position of existing warp tabs

To move a destination position of a warp tab (and thus stretch the audio), select the Free Warp tool and position the pointer on the Warp line in the waveform so that the line in the middle of the pointer becomes blue. Then click and drag to move the position of the warp tab.

Moving the source position of existing warp tabs

If you simply wish to change the position of a warp tab regarding the audio, click and drag the warp tab header in the ruler. However, this will change the warping.

Unstretching audio files

By selecting “Unstretch Audio” from the Realtime Processing submenu of the Audio menu, all realtime time-stretching (by sizing or by warp tabs) can be removed.

Ö Note that realtime transpose (in the infoline) and Straighten Up mode will not be removed by this.

Whether the “Unstretch Audio” menu item is available depends on whether the time-stretching was applied on the event or clip level:

•If you sized an audio event in the Project window using “Sizing Applies Time Stretch” (see “Resizing events using time stretch” on page 49), you can undo the time-stretch- ing by selecting the event in the Project window and then applying “Unstretch Audio”.

This will remove all time-stretching and warp tabs.

•When you have entered a tempo and/or length using the Definition tab, this information is saved for the source clip and all events that use it.

Creating warp tabs from hitpoints

You can also create warp tabs from hitpoints selecting “Create Warp Tabs from Hitpoints” on the Realtime Processing submenu of the Audio menu.

For descriptions of how hitpoints are created and edited please see “Using hitpoints” on page 278.

Realtime pitch-shifting of audio events

Audio events can be pitch-shifted in realtime just like MIDI events. The process is very simple:

1.Open the audio event in the Sample Editor and open the Playback tab.

2.Set a value in the corresponding field in the Transpose section.

The value range is up/down two octaves in semitone steps.

3. Press [Enter].

The audio event is now transposed to the set value using pitch-shift.

4. If a root key is specified or if the Transpose track has been added, you can click the Follow Global mode to activate/deactivate Global Transpose.

Event transpose will be added to the Global transpose value.

For more information on the transpose functions and the Transpose track, see the chapter “The Transpose functions” on page 114.

• You can also select the audio event in the Project window and change the Transpose value on the infoline. In this case, you can also fine-tune selected audio events in cent steps (100ths of a semitone) by entering a value in the Finetune field to the right.

Audio and MIDI events cannot be transposed simultaneously.

Flattening the realtime processing

You can “flatten” any realtime processing at any time. This can be done to serve two purposes; to conserve CPU power and to optimize the sound quality of the processing.

• Select the audio event(s) you wish to process and select “Flatten Timestretch and Transpose” from the Realtime Processing submenu of the Audio menu.

You should also use this function before applying any offline processing. When the flatten processing is applied, a copy of the original file is automatically created in the Pool so that the original audio clip remains intact.

Selecting an algorithm for the flattening

When you flatten the realtime processing, you can use the MPEX 3 algorithm to process the audio, which may produce better sound quality than the realtime processing.

This is also the only way to achieve polyphonic formant conserving pitch-shifting, apart from offline processing. Proceed as follows:

1.Select the audio event(s) you wish to process.

2.Click the Flatten button on the Playback tab of the Sample Editor Inspector, or select “Flatten Timestretch and Transpose” from the Realtime Processing submenu of the Audio menu.

A dialog appears where you can select an algorithm for the processing. You can either select the MPEX 3 algorithm, which will produce the highest sound quality, or the Realtime algorithm which is much quicker but will not improve the audio quality of the processing (although it will lessen the CPU load).