Audio Sync and Multicam Editing¶

Oak provides audio-sync tools based on timecode and waveforms, as well as basic multicam editing support.

Audio Sync¶

Synchronize by Source Time¶

• Use case: different cameras or recorders share the same source timecode / BWF time reference.

• Operation: select multiple clips on the timeline → right-click → Synchronize by Source Time.

• Oak reads each footage item’s source_start_time, calculates the time offset, and moves the clips to the corresponding positions.

Synchronize by Waveform¶

• Use case: no reliable timecode, but the audio content is the same across sources.

• Operation: select two or more clips with cached waveforms on the timeline → right-click → Synchronize by Waveform (shortcut Ctrl+Shift+W).

• The algorithm extracts an RMS envelope and estimates the offset using normalized cross-correlation.

• Uncached waveform regions are not treated as silence: envelope extraction marks uncached windows as invalid and the correlation skips them, so partially cached clips still align accurately.

• Window size is 50 ms; maximum supported offset is 10 minutes.

• Synchronize by Waveform (Adjust Speed) is a variant for sources running at slightly different speeds (e.g. 24 fps vs 25 fps pull-down). When plain offset alignment is inconclusive, it searches a playback-rate range of 0.75–1.34 and applies the estimated rate as a clip speed change together with the offset placement, as a single undoable operation.

Timecode / BWF Auto-Detection¶

• When footage is imported, FFmpegDecoder automatically probes:

  • timecode: LTC / VITC timecode strings.

  • time_reference: the BWF bext chunk sample reference.

• Detected source start times are written to the footage’s FootageDescription and saved with the project.

• If a file does not contain these metadata fields, Synchronize by Source Time cannot be used unless a source start time is set manually (see below).

Manually Setting the Source Start Time¶

• Right-click a footage item → Properties opens the Footage Properties dialog, which contains a Source Start Time field: an enable checkbox plus a value in seconds.

• Use it for footage whose metadata lacks timecode / BWF information, or where auto-detection produced a wrong value.

• The dialog also indicates whether the current value was auto-detected (and from which metadata) or set manually.

• The value is used by Synchronize by Source Time and is saved with the project.

Multicam Editing¶

Oak’s basic multicam feature treats the tracks inside a nested Sequence as different camera angles.

Creating a Multicam Clip¶

1. Place each camera’s footage on a different track of the same Sequence and align them using the methods above.

2. On the timeline, select the nested Sequence clip (its connected_viewer must be a Sequence).

3. Right-click → check Multi-Cam.

4. Oak creates a MultiCamNode, rewires the Sequence output into it, and connects each track to kSourcesInput.

Switching Angles¶

• Open the Multicam panel (hidden by default; open it from the Window menu) to see a grid of angle thumbnails.

• Shortcuts:

  • 1–9: switch to the corresponding angle and split the clip at the playhead.

  • Ctrl+1–Ctrl+9: switch angle without splitting.

• Clicking a thumbnail in the Multicam panel also switches and splits.

• Switching creates an undo command; press Ctrl+Z to undo.

Multicam Output¶

• MultiCamNode’s kCurrentInput determines which angle is currently output.

• In preview mode, RenderProcessor generates a multicam_output attribute for MulticamDisplay to show all angles; final output is still controlled by the currently selected angle.

Limitations¶

• There is no dedicated multicam sync wizard; you must first align the tracks inside a Sequence manually.

• Only the simple Sequence → MultiCamNode structure is supported.

• There is no cut-list export.

• The README roadmap lists “full multicam angle switching” as a 0.5 milestone, so the current implementation is still early.