Mask: From File Video Filter

Documentation Documentation - English
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Applies a luminance- or alpha-based mask to a clip using built-in static mask presets or an external image or video file.
The mask determines which areas of the clip are affected, based on brightness or transparency values.

All built-in mask presets are static. Animation requires keyframing, clip motion, or a video file used as the mask.

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NOTE:
This filter operates is not available in GPU processing mode.

Mask source behavior

The mask source can be:

  • A built-in static mask preset
  • Any external media image, video, drawing, or animation media file supported by Shotcut

Mask interpretation rules:

  • Brightness mode
    Dark areas of the mask make the current clip visible.
    Bright areas make the underlying clip visible.
    Gray values produce a gradual transition between the two.

  • Alpha mode
    Transparent areas of the mask make the current clip visible.
    Opaque areas make the underlying clip visible.

When a video file is used as the mask, its values are evaluated per frame.

Parameters

File (preset / file selector)

Selects the mask source.

The dropdown includes:

Built-in geometric masks

  • Bar Horizontal / Bar Vertical
    A single rectangular band across the frame.

  • Barn Door Horizontal / Vertical / Diagonal SW–NE / Diagonal NW–SE
    Four-panel shapes opening from the center, similar to camera barn doors.

  • Diagonal Top Left / Diagonal Top Right
    Half-frame diagonal masks.

  • Barn V Up
    V-shaped opening expanding upward from the bottom.

  • Iris Circle
    Circular opening centered in the frame.

  • Double Iris
    Two mirrored circular openings.

  • Iris Box
    Rectangular opening expanding from the center.

  • Box Bottom Right / Box Bottom Left / Box Right Center
    Rectangular masks anchored to specific edges or corners.

  • Clock Top
    Radial, clock-style sector opening from the top.

Pattern-style masks

  • Matrix Waterfall Horizontal / Vertical
    Repeating rectangular segments arranged in rows or columns.

  • Matrix Snake Horizontal / Vertical
    Sequential block patterns arranged in a snake-like order.

  • Matrix Snake Parallel Horizontal / Vertical
    Multiple parallel snake patterns.

These masks are not animated. Any motion must be created via keyframes or by using a video mask.

Custom…

Opens a file browser to select an external image or video file.

  • Supports common image formats and video files.
  • When a custom file is selected, its filename is displayed below the dropdown list.

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Invert (checkbox)

Inverts the mask interpretation.

  • Revealed areas become blocked
  • Blocked areas become revealed

Applies after Channel selection.

Reverse (checkbox)

Reverses the directional orientation of the mask.

  • Affects directional presets (bars, doors, diagonals)
  • Example: a right-side mask becomes a left-side mask

This does not invert luminance or alpha values.

Channel (radio buttons)

Defines how the mask source is interpreted.

  • Brightness
    Uses the luminance of the mask source.
    Bright areas reveal the effect; dark areas block it.

  • Alpha
    Uses the alpha channel of the mask source.
    Opaque areas reveal the effect; transparent areas block it.

Important notes:

  • Alpha mode requires the mask file to contain an alpha channel.
  • In Alpha mode, RGB color information in the mask is ignored.
  • Most video files do not contain an alpha channel unless explicitly encoded.

Threshold (checkbox + slider, 0.00–100.00%, keyframeable)

Converts the mask into a binary (hard) mask.

  • Unchecked
    Continuous grayscale or alpha values are used.

  • Checked
    Values are clipped to fully on or fully off.

Slider behavior:

  • Lower values
    More of the mask becomes active.

  • Higher values
    Only the brightest or most opaque areas remain active.

Softness (0.00–100.00%)

Controls edge feathering after thresholding.

  • Only active when Threshold is enabled.
  • Low values produce hard edges.
  • Higher values produce smoother transitions.

Softness does not blur the mask image itself.

Keyframes

Only the Threshold slider can be keyframed.

This enables:

  • Animated reveals and wipes using static masks
  • Time-based control when using video masks

Parameter interaction

  • File defines the mask shape or pattern.
  • Channel defines whether luminance or alpha drives the mask.
  • Invert swaps masked and unmasked regions.
  • Reverse flips directional orientation.
  • Threshold forces hard masking.
  • Softness smooths threshold edges.

All operations are applied per frame.

Visual characteristics

  • Clean geometric masking with presets
  • Arbitrary shapes with custom images
  • Animated masking only when using video files or keyframes
  • Mask edge quality depends on source resolution and Softness

Recommended use cases

  • Custom wipes and transitions
  • Layer compositing and selective effects
  • Masks drawn in external image editors
  • Video-driven animated masks
  • Precise, repeatable masking workflows

Limitations

  • CPU-only filter
  • Built-in masks are static
  • No built-in mask animation controls
  • Mask quality depends on source resolution
  • Video masks can increase processing load

Built-in mask presets: quick reference

Linear / band masks

  • Bar Horizontal — Horizontal rectangular band across the frame
  • Bar Vertical — Vertical rectangular band across the frame

Barn door masks

  • Barn Door Horizontal — Four panels opening left and right from the center
  • Barn Door Vertical — Four panels opening up and down from the center
  • Barn Door Diagonal SW–NE — Diagonal barn-door opening from southwest to northeast
  • Barn Door Diagonal NW–SE — Diagonal barn-door opening from northwest to southeast
  • Barn V Up — V-shaped opening expanding upward from the bottom

Diagonal masks

  • Diagonal Top Left — Diagonal half-frame mask anchored to the top-left
  • Diagonal Top Right — Diagonal half-frame mask anchored to the top-right

Iris / aperture masks

  • Iris Circle — Circular opening centered in the frame
  • Double Iris — Two mirrored circular openings
  • Iris Box — Rectangular opening expanding from the center

Box / edge-anchored masks

  • Box Bottom Left — Rectangular mask anchored to the bottom-left
  • Box Bottom Right — Rectangular mask anchored to the bottom-right
  • Box Right Center — Rectangular mask centered vertically on the right edge

Radial masks

  • Clock Top — Radial, clock-style sector opening from the top

Matrix / pattern masks

  • Matrix Waterfall Horizontal — Repeating horizontal rectangular segments
  • Matrix Waterfall Vertical — Repeating vertical rectangular segments
  • Matrix Snake Horizontal — Sequential horizontal block pattern
  • Matrix Snake Vertical — Sequential vertical block pattern
  • Matrix Snake Parallel Horizontal — Multiple parallel horizontal snake patterns
  • Matrix Snake Parallel Vertical — Multiple parallel vertical snake patterns

Notes

  • All built-in presets are static.
  • Directional behavior can be modified using Reverse.
  • Edge hardness is controlled using Threshold and Softness.
  • Animation requires keyframes or a video file used as the mask.

See also: Mask: Draw (Glaxnimate) Video Filter

Mistake in Filter "Mask:from file"
Mask: Apply Video Filter
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