Syntax and call forms

Use supported call form that best fits your script. Paired examples in same section are alternate syntax for same operation.

Generic filter calls

output = filter(source("input.mkv"), "resize", #{ width: 1280, height: 720 })

output = source("input.mkv").resize(#{ width: 1280, height: 720 })

Zero-input filters can also use the function form directly:

output = filter("blank_clip", #{ width: 1280, height: 720 })

Built-in std namespace

output = std.resize(source("input.mkv"), #{ width: 1280, height: 720 })

output = source("input.mkv").std.resize(#{ width: 1280, height: 720 })

Zero-input built-ins use the namespace form without a clip argument:

output = std.blank_clip(#{ width: 1280, height: 720 })

Third-party plugin namespace

output = plugin.acme.blur(source("input.mkv"), #{ radius: 2 })

output = source("input.mkv").plugin.acme.blur(#{ radius: 2 })

Multi-input filters

Use array input form when filter consumes more than one clip:

y = source("input.mkv").std.split_plane(#{ plane: 0 })
u = source("input.mkv").std.split_plane(#{ plane: 1 })
v = source("input.mkv").std.split_plane(#{ plane: 2 })
output = std.merge_planes([y, u, v], #{ format: "yuv420p8" })

Metadata property reads

Use prop(clip, key) to read a metadata property from frame 0, or prop(clip, frame, key) to read a specific zero-based frame.

clip = source("input.mkv")
output = clip

if prop(clip, 0, "core:matrix") == "bt709" {
    output = clip.std.convert_colorspace(#{ matrix: "bt2020_ncl" })
}

The method form is equivalent:

clip = source("input.mkv")
frame_number = clip.prop(10, "core:frame_number")
output = clip

None metadata values return none(). Use is_none(value) before comparing or passing optional metadata into filters.

Top-level frame metadata reads

Use these accessors to read structural frame fields from frame 0, or pass a zero-based frame number to inspect another frame. They are runtime-backed like prop(...): the script host may index sources and render the requested frame while evaluating the script.

clip = source("input.mkv")

width = clip.width()
height = clip.height()
format = clip.format()
family = clip.format_family()
subsampling = clip.chroma_subsampling()
bits = clip.bit_depth()
planes = clip.plane_count()

output = clip.std.resize(#{ width: width / 2, height: height / 2 })

Function forms are also supported:

clip = source("input.mkv")
width_10 = width(clip, 10)
format_10 = format(clip, 10)
output = clip

Accessors return these values:

• width, height, bit_depth, and plane_count return integers.
• format returns PixelFlow’s canonical pixel format string, such as yuv420p10.
• format_family returns gray, yuv, or planar_rgb.
• chroma_subsampling returns 4:4:4, 4:2:2, 4:2:0, or none() for non-YUV formats.

Negative frame numbers are rejected. Frame numbers outside the rendered clip range fail during runtime resolution.