Filter reference

The FFmpeg filters compiled into the default build, with examples, key parameters, and a clear split between the ones that work in wasmpeg's single-frame pipeline and the ones that don't.

These are the filters compiled into the default LGPL build (the filters list in the lgpl preset). They are passed as a filtergraph string to wasmpeg.scale(input, w, h, graph) or wasmpeg.run(input, ['-vf', graph]).

Each filter below lists the parameters you’ll actually reach for — not the full FFmpeg option set. For every option, every default, and every edge case, the FFmpeg filter documentation is the source of truth; each heading links to its exact section there. What you won’t find on that page is which of these filters actually do anything when driven through wasmpeg’s pipeline — that’s what this page is for.

When a filter changes the frame’s dimensions, end the graph with an explicit integer scale=W:H so the returned buffer is sized correctly — see output sizing.

At a glance

Every filter below is compiled into the build. What varies is whether the single-frame pipeline can actually drive it:

The “Yes” rows are documented with examples in the sections that follow; the “No” rows are explained under Multi-input, Temporal, and Audio.

Geometry and transform

scale

Resize to a target size. The output dimensions of a graph are read from this filter.

Parameters: w, h (size, -1 keeps aspect) · flags (scaling algorithm — bilinear default, lanczos/spline for quality) · force_original_aspect_ratio

await wasmpeg.scale(file, 1280, 720);                 // implicit scale=1280:720
await wasmpeg.run(file, ['-vf', 'scale=1280:720']);
await wasmpeg.run(file, ['-vf', 'scale=1280:720:flags=lanczos']);   // sharper downscale

crop

Cut a w×h region at offset x,y. Follow with scale to the cropped size.

Parameters: w, h, x, y — x/y default to centered if omitted.

await wasmpeg.scale(file, 640, 480, 'crop=640:480:0:0,scale=640:480');
await wasmpeg.scale(file, 640, 480, 'crop=640:480,scale=640:480');   // centered crop

pad

Add borders to reach a larger canvas, optionally with a background color.

Parameters: width, height, x, y (offset of the original frame within the new canvas), color (CSS-style name or 0xRRGGBB).

await wasmpeg.scale(file, 1280, 720, 'pad=1280:720:80:0:black,scale=1280:720');

transpose

Rotate by 90° and swap width/height. Scale to the swapped dimensions.

Parameters: dir — 0 (90° CCW + vflip), 1 (90° CW), 2 (90° CCW), 3 (90° CW + vflip).

// transpose=1 → 90° clockwise
await wasmpeg.scale(file, 720, 1280, 'transpose=1,scale=720:1280');

rotate

Rotate by an arbitrary angle in radians (output keeps the source size unless ow/oh are given).

Parameters: angle (radians, or an expression like PI/6) · ow, oh (output size) · fillcolor (area exposed outside the source frame).

await wasmpeg.scale(file, 1280, 720, 'scale=1280:720,rotate=PI/6');
await wasmpeg.run(file, ['-vf', 'rotate=PI/6:fillcolor=black']);

hflip / vflip

Mirror horizontally or vertically. Dimensions are unchanged, so no trailing scale is required. Neither takes parameters.

await wasmpeg.run(file, ['-vf', 'hflip']);
await wasmpeg.run(file, ['-vf', 'vflip']);

Pixel format

format

Force an intermediate pixel format. Useful to coerce a processing format; convert back to rgba at the end if needed.

Parameters: pix_fmts — a |-separated list of acceptable formats (e.g. gray, yuv420p, rgba).

await wasmpeg.scale(file, 1280, 720, 'scale=1280:720,format=gray,format=rgba');

colorspace

Convert between colorspaces (BT.601/709/2020, range, primaries).

Parameters: all (set every colorspace property from one preset) · space, range, primaries, trc (set individually) · iall/ispace/etc. (declare the input’s properties when the source doesn’t signal them).

await wasmpeg.scale(file, 1280, 720, 'scale=1280:720,colorspace=bt709:iall=bt601-6-625');

Color and tone

eq

Adjust brightness, contrast, saturation, and gamma.

Parameters: contrast (default 1) · brightness (default 0) · saturation (default 1) · gamma (default 1) · gamma_r/gamma_g/gamma_b (per-channel gamma).

await wasmpeg.scale(file, 1280, 720, 'scale=1280:720,eq=contrast=1.2:brightness=0.04:saturation=1.1');

hue

Rotate hue and scale saturation.

Parameters: h (degrees) · s (saturation multiplier) · b (brightness).

await wasmpeg.scale(file, 1280, 720, 'scale=1280:720,hue=h=90:s=1.2');

curves

Apply tone curves, including built-in presets.

Parameters: preset — one of color_negative, cross_process, darker, increase_contrast, lighter, linear_contrast, medium_contrast, negative, strong_contrast, vintage · or master/red/green/blue with explicit control points (0/0 0.5/0.58 1/1).

await wasmpeg.scale(file, 1280, 720, 'scale=1280:720,curves=preset=increase_contrast');
await wasmpeg.run(file, ['-vf', "curves=master='0/0 0.5/0.4 1/1'"]);   // custom curve

colorbalance

Shift shadows, midtones, and highlights per RGB channel.

Parameters: rs/gs/bs (shadows), rm/gm/bm (midtones), rh/gh/bh (highlights) — each in [-1, 1].

await wasmpeg.scale(file, 1280, 720, 'scale=1280:720,colorbalance=rs=0.1:gm=-0.05');

colorchannelmixer

Mix channels with a 4×4 matrix — e.g. a sepia tone or a channel swap.

Parameters: rr/rg/rb/ra … ar/ag/ab/aa (16 coefficients, one row per output channel) — the example below sets only RGB, leaving alpha at its default.

await wasmpeg.scale(file, 1280, 720,
  'scale=1280:720,colorchannelmixer=.393:.769:.189:0:.349:.686:.168:0:.272:.534:.131');

Blur, sharpen, and noise

boxblur

Fast box blur by radius.

Parameters: luma_radius/chroma_radius/alpha_radius (or the short forms lr/cr/ar) · luma_power (repeat count for a smoother falloff).

await wasmpeg.scale(file, 1280, 720, 'scale=1280:720,boxblur=2');
await wasmpeg.run(file, ['-vf', 'boxblur=luma_radius=4:luma_power=2']);

gblur

Gaussian blur by sigma — smoother falloff than boxblur, more expensive.

Parameters: sigma (blur strength) · steps (quality vs. speed) · sigmaV (vertical sigma, if different from horizontal).

await wasmpeg.scale(file, 1280, 720, 'scale=1280:720,gblur=sigma=3');

unsharp

Sharpen (or blur) with an unsharp mask.

Parameters: luma_msize_x/luma_msize_y (matrix size, odd, 3–23) · luma_amount (positive sharpens, negative blurs) — the positional form below is lx:ly:la.

await wasmpeg.scale(file, 1280, 720, 'scale=1280:720,unsharp=5:5:1.0');

noise

Add noise — useful for dithering or film-grain effects.

Parameters: alls (strength, all components) · allf (flags — t temporal, u uniform, p mix with original, c per-component).

await wasmpeg.scale(file, 1280, 720, 'scale=1280:720,noise=alls=20:allf=t');

GPU

scale_webgpu

wasmpeg’s own filter — not part of upstream FFmpeg, so there’s no FFmpeg doc page for it. It’s the GPU-accelerated scale on the WebGPU build. wasmpeg.scale() selects it automatically when WebGPU is active; pass it explicitly to force it.

Parameters: w, h — same positional size arguments as scale.

await wasmpeg.run(file, ['-vf', 'scale_webgpu=1280:720']);

See WebGPU for what’s actually wired up versus scaffolded.

Multi-input filters

These are compiled in but cannot be driven through wasmpeg today: the pipeline has a single buffer source, so a filtergraph that needs two inputs has nothing to feed its second pad.

overlay · hstack · vstack · amerge · amix · concat

split is similarly not useful in a single-frame, single-output operation.

Temporal filters

These need a stream of frames. A single-frame operation can’t produce meaningful output from them, even though they’re present in the build.

fps · trim · setpts · yadif · bwdif · deinterlace

To deinterlace or change frame timing, you would need a multi-frame pipeline, which the current dispatcher does not expose.

Audio filters

Audio filters are compiled in, but the dispatcher’s audio path returns decoded PCM without applying the graph (see the audio routing caveat). They are listed here for completeness:

aresample · volume · atrim · asetpts · aecho · highpass · lowpass · equalizer · anull

Process audio in the Web Audio graph after decoding to PCM instead.

Passthrough

null (video) and anull (audio) pass frames through unchanged, no parameters — occasionally useful as explicit no-ops in a graph.

Adding a filter

The filter set is defined by the filters array in the active preset. To enable one that isn’t listed, add it and rebuild — see Configuration. Enabling a filter only makes it available to the filtergraph parser; whether it produces useful output through the single-frame dispatcher is the separate question the sections above answer.