Overview

Engine Loop Creator Overview

The Engine Loop Creator by Tazman Audio allows you to create fixed pitch loops from harmonic content. The tool is mainly aimed at creating vehicle loops from engine acceleration/deceleration sweeps.

Workflow Summary

Source Analysis

  • Import audio into the tool by clicking ‘Load a New Audio Source’.
  • Set the engine and FFT settings, then click ‘Analyse’ to produce a spectrum of the imported audio.
  • Choose a track (harmonic) on the spectrogram by clicking on one. The tool will use this track as a reference to flatten the pitch in the ‘Create Loops’ screen.

Create Loops

  • Click and drag regions, then click ‘Create loop from selection’ to create loops. These regions can be previewed, edited and moved around after creation, and multiple regions can be created.

Export Loops

  • Choose a folder to export the flattened loops to, then click ‘Export’.

Source Analysis

Importing Audio into the Tool

You can import audio into the tool by clicking ‘Load a New Audio Source’, and selecting the audio file you wish to import.

  • The tool can import files of varying sample rate and channel count. However, the tool only supports exporting in mono.

Once imported, you can preview the original source in the transport panel.

  • Play, stop, pause, and adjust the preview gain via the transport control.
  • You can scrub through the file by clicking on the audio file preview.

Spectral Analysis

The next step is to perform a spectral analysis of the imported audio. The tool uses harmonics from this spectrum to flatten the pitch of the loops in the ‘Create Loops’ stage.

Analysis Settings

You can edit several settings that affect the output of the analysis stage.

Engine Properties

The engine properties affect the calculation of RPM in the tool, along with the positioning of grain markers in the ‘Create Loops’ section.

  • Engine Cylinders: the number of cylinders in the engine.
    • This value will affect the positioning of grain markers in the 'Create Loops' panel. Setting this to the number of cylinders found in the engine you are referencing will reduce the chance of phasing when the loop is cross-fading.
  • Engine Strokes: the number of strokes output by the engine.
    • This value will affect the calculation of RPM from Hz in the tool.
  • Sweep Type: whether the engine sweep is rising, falling, or at a steady pitch.
    • This setting will alter the polarity of the some GUI elements in the 'Create Loops' screen.
Peak Detection

These settings affect the thresholds at which harmonics are detected and defined as ‘tracks’ in the tool.

  • Magnitude Threshold: the volume threshold above which a harmonic will be detected as a track.
    • Try reducing this if the tool does not detect many harmonics, or if there are gaps in a harmonic that you wish to connect.
    • Try increasing this if the analysis produces a noisy spectrum with too many harmonics.
  • Maximum Frequency: The maximum frequency that harmonics will be detected at.
    • If working with content with extremely high frequencies, this threshold can be increased.
FFT Settings

Use these settings to tweak the FFT analysis. In general, larger FFT frame sizes are better at detecting harmonics in most engine sources.

  • FFT Frame Overlap: the proportion of the FFT Frame size that overlaps as a percentage. A larger value may reduce the gaps within a harmonic, but will cause the Analysis process to run slower.
  • FFT Order: The size of the FFT window as a proportion of 2 ^ FFT Order. In general, a larger window size (and FFT order) will produce a spectrum with a better resolution.

Spectrum Panel

Once you are happy with the Analysis settings, click ‘Analyse’ to create a spectrum from the input audio.

Generated Tracks

The tool will draw yellow lines on harmonics it detected during the analysis stage. You can then click on a harmonic to select it as the “reference track” that the tool will use during the “Create Loops” stage to flatten pitch.

  • Selected tracks will be coloured in orange, and will be thicker.
  • Any harmonic can be used. However, for the best results, it is recommended to use the fundamental frequency. This will ensure RPM calculations are accurate.
User tracks

The tool allows you to draw your own tracks on the spectrogram, rather than use the harmonics output by the Analysis stage. Reasons to do this may include:

  • When the auto peak detection has missed a section in a harmonic track due to lower peak values, in what is otherwise a clearly defined track 
  • When a harmonic track starts earlier than the point that the auto peak detection picked it up

To create a User track:

  • Click the ‘Draw New Track’ button.
  • Hold CTRL/CMD and click on the spectrogram to place points.
  • Reposition the points by dragging with the mouse.
  • Once you are happy with the shape of your user track, click the ‘Write Track’ button

The track will then appear on the spectrogram. To select it, click ‘User Tracks’ in the left hand panel, and then select the custom track.

Create Loops

Once a track (harmonic) has been selected in the analysis spectrogram, you can navigate to the loop editor in the bottom panel.

The loop editor allows you to draw regions and create loops from the original audio source whose pitch has been flattened. The pitch flattening algorithm uses the track (harmonic) selected in the first stage as a reference.

Top transport Panel

The transport panel at the top shows the waveform of the original audio file. Note that the audio loaded into the ‘Create Loops’ panel is a subsection of the original audio file. This subsection is defined by the length and position of the harmonic track selected in the Analysis stage.

  • Play, stop, pause, and adjust the preview gain via the transport control.
  • You can scrub through the file by clicking on the audio file preview.
  • Loop regions will show up in this transport panel in light grey. You can double click on a region to snap the viewport to that position.

Central Transport Panel

In the centre of the ‘Create Loops’ panel is another larger preview of the original audio file. This panel also includes Grain Markers, which are positioned at zero crossings and at regular cycles of the engine, as defined by the engine settings in the Analysis stage.

In this panel, you can create loop regions by dragging the mouse, and clicking ‘Create loop from selection’. The loop’s position, size, fade length, etc. can be edited after the loop region has been created in this panel. The boundaries of the loop will automatically snap to the grain markers.

  • Note: you can switch between using mouse hotspots or modifier keys to edit loop region properties in the Settings menu.

Loop Region Overview

At the bottom of the ‘Create Loops’ panel, you will find an overview of all the created loops. Here you can pick the playback type, decide to override the RPM/pitch with a custom value, as well as preview the flattened loop. Settings (such as region name, start time, fade length, etc.) can be edited directly by double clicking the text box and typing in a value.

You can also delete or duplicate Loop Regions by right clicking on the row you wish to delete/duplicate.

Loop RPM and Override

By default, the tool will use the central point of the loop to define the base RPM/pitch that the region is flattened to. By moving the region around, or changing its size, the base RPM/pitch will automatically update.

You can override the auto-detection by clicking the ‘override’ toggle. Doing this will disable the auto detection, and enable the RPM slider for customising. You may use this to tweak the base RPM/pitch of the loop to a custom value.

Playback Style

The tool currently offers two playback styles.

  • Simple loop (no fades): The loop region will export and playback with no additional fades. The start and end points of the loop will be located at zero crossings in the flattened audio file. Unless the source is steady, it is recommended to use the crossfade option instead.
  • Crossfade regions (fade outside region): This will add crossfades to the front and back of the loop region. The length of these crossfades can be edited in the Central Transport Panel.

The tool will support editing these settings while previewing the loop, so you can tweak them in real time.

Export Loops

Once you have created all of your loop regions, you can export them in the Export Loops panel.

  • The tool currently supports exporting mono .wavs.
  • The tool currently supports exporting at 44.1kHz, 48kHz, or 96kHz.
  • Set the export directory via the 'Browse for directory' button.
  • When ready, click 'Export' to render out the loop regions.

Additional Settings

Saving and loading a project

You can save and load projects in the File Menu. This will save any spectrograms, analysis settings and loop regions you have created.

  • If you have moved/deleted the source audio file since the project was last saved, you will be directed to locate the file on disk.
  • You can change the default project folder in the Settings menu.

When loading a project, navigate to the project folder location and click 'Open'.

Settings Menu

General

  • Default New Project Start Directory: Sets the default directory the project files are saved to.
  • Mouse interactions with loop regions: Choose between Hotspots and Modifier Keys.
    • Hotspots: Edit loop regions by hovering your mouse over 'Hotspots'. For example, to change the loop length on the right, click and drag the right-most boundary.
    • Modifier Keys: Edit loop regions by holding down a Modifier Key when clicking and dragging the loop. See the Keyboard Shortcuts section for a list of Modifier Keys.

Audio Settings

  • Audio Device Type: Change the audio driver for playback in the tool.
  • Output: Change the output for playback in the tool.
  • Sample Rate: Change the sample rate of playback in the tool (currently fixed at 48kHz).
  • Audio Buffer Size: Change the buffer size for playback in the tool.

Export Flattened Sweep to Desktop

You can find this option in the Tools menu. Once you have imported and analysed an audio file in the tool, you can flatten and export the entire file via this option.

  • The reference pitch for this export is taken from the middle point of the file.
  • The file will export directly to your Desktop.

Find the Online Documentation

You can navigate to the online documentation directly within the Help menu.

Keyboard Shortcuts

Spectrogram Action / Shortcut
Scroll vertically Mouse wheel
Scroll horizontally  SHIFT + mouse wheel
Zoom in vertically LMB at point you want to zoom, then CTRL + mouse wheel
Zoom out vertically  CTRL + mouse wheel
Zoom in horizontally  LMB at point you want to zoom, then CTRL + SHIFT + mouse wheel
Zoom out horizontally  CTRL + SHIFT + mouse wheel
Select track  LMB on track
De-select track  LMB off track
Delete track  del/backspace
Add point on new track CTRL + LMB
Delete point on new track
SHIFT + LMB



Loop Editor Waveform View
Action / Shortcut
Scroll horizontally
Mouse wheel
Zoom in horizontally
LMB at point you want to zoom, then CTRL + mouse wheel
Zoom out horizontally
CTRL + mouse wheel
Make selection
LMB + hold/drag
Clear selection
LMB outside selection
"Zoom" view to loop region

1. Double click on loop region in the top thumbnail, or 

2. Press the play button to preview the loop

Move RPM marker
LMB + mouse on marker 
Move loop region
LMB + mouse on region header
Trim loop region bounds
LMB + mouse on loop bound
Trim loop region bounds (Modifier Keys enabled)
LMB + CTRL
Trim fade length
LMB + mouse on fade area

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