encoding.md

Encoding Parameters

Reference for all encoding options exposed by FastEdit. These map directly to the underlying codec configurations.

Animated WebP (libwebp)

FastEdit exposes the complete WebPConfig struct from libwebp via a custom WebAssembly build.

Parameter	Range	Default	Description
quality	0–100	80	Lossy compression quality. Higher = better quality, larger file.
lossless	bool	false	Lossless encoding. Ignores quality when enabled.
method	0–6	4	Compression method. 0 = fastest, 6 = best compression.
pass	1–10	1	Number of entropy analysis passes. More passes = better compression, slower.
sharpYuv	bool	true	Use sharp RGB→YUV conversion. Better color accuracy at edges.
preprocessing	0–2	0	0 = none, 1 = segment-smooth, 2 = pseudo-random dithering.
snsStrength	0–100	50	Spatial noise shaping. Higher = more adaptive quantization.
filterStrength	0–100	60	Deblocking filter strength.
filterSharpness	0–7	0	Filter sharpness. 0 = sharpest, 7 = least sharp.
filterType	bool	true	true = strong filter, false = simple filter.
autofilter	bool	false	Auto-adjust filter strength per segment.
alphaQuality	0–100	100	Alpha channel compression quality.
alphaCompression	bool	true	Compress alpha channel (vs. raw).
alphaFiltering	0–2	1	Alpha pre-filtering. 0 = none, 1 = fast, 2 = best.
nearLossless	60–100	100	Near-lossless preprocessing. 100 = no preprocessing (true lossless).
exact	bool	false	Preserve RGB values in transparent areas.
segments	1–4	4	Number of macroblock segments for lossy encoding.
partitions	0–3	0	Log2 of the number of token partitions.
partitionLimit	0–2	0	Quality degradation limit for partitions.
emulateJpegSize	bool	false	Try to match JPEG output size at equivalent quality.
keyframeInterval	0+	17	Maximum frames between keyframes. 0 = encoder decides.
loopCount	0+	0	Number of loops. 0 = infinite.
targetSize	bytes	0	Target file size. 0 = disabled. Overrides quality when set.

Video (MP4 / WebM / MKV)

Parameter	Options	Default	Description
codec	avc (H.264), hevc (H.265), vp8, vp9, av1	avc	Video codec. Available codecs depend on output format.
bitrate	bps	2000000	Target bitrate in bits per second.
bitrateMode	variable, constant	variable	VBR adapts quality per frame. CBR maintains fixed rate.
hardwareAcceleration	no-preference, prefer, deny	no-preference	GPU encoding when available.
keyFrameInterval	seconds	5	Seconds between keyframes. Lower = better seeking, larger file.
contentHint	"", "detail", "motion", "text"	""	Hints to the encoder. "text" for screen recordings, "motion" for action.
fastStart	bool	true	Move MP4 metadata to file start for progressive playback.

Codec Availability by Format

Format	H.264	H.265	VP8	VP9	AV1
MP4	Yes	Yes	No	No	Yes
WebM	No	No	Yes	Yes	Yes
MKV	Yes	Yes	Yes	Yes	Yes

GIF

Parameter	Range	Default	Description
quality	0–100	80	Color quantization quality. Lower = fewer colors, smaller file.
loopCount	0+	0	Number of loops. 0 = infinite.

APNG

Parameter	Range	Default	Description
quality	0–100	80	Quantization quality for color reduction.

Timeline Effects

These apply to all animated output formats.

Effect	Parameters	Description
Trim	start, end (seconds)	Set playback range
Cut	Multiple {start, end} regions	Remove sections from timeline
Fade in	Duration (seconds)	Opacity ramp from 0→1 at start
Fade out	Duration (seconds)	Opacity ramp from 1→0 at end
Mid-fade	center, width (seconds)	Dip opacity at a point in the timeline
Speed	{start, end, speed} regions	Variable speed 0.25×–4× over time ranges
Zoom	{start, end, from, to, easeIn, easeOut}	Animated pan + scale between keyframes
Blur	{start, end, rect, strength}	Blur a rectangular region during a time range

Resize Methods

Method	Algorithm	Best For
lanczos3	Lanczos windowed sinc (3 lobes)	General purpose, sharp results
catrom	Catmull-Rom bicubic	Moderate sharpness, fewer artifacts
mitchell	Mitchell-Netravali bicubic	Balanced sharpness and smoothness
triangle	Bilinear interpolation	Fast, smooth, slightly soft