Easing and extensions for FFmpeg Xfade filter

Standard easings • CSS easings • transpiled GLSL transitions • custom expressions

Summary

This project is a port of standard easing equations, CSS easings and many GLSL transitions for use in tandem with easing or alone. The easing expressions can be used for other filters besides xfade.

There are 2 variants:

custom ffmpeg build with xfade easing and reverse options
custom expressions for use with standard ffmpeg build

Xfade is a FFmpeg video transition filter with many built-in transitions and an expression evaluator for custom transitions. However the progress rate is linear, starting and stopping abruptly and proceeding at constant speed, therefore transitions lack interest. Easing inserts a progress envelope to smooth transitions in a natural way.

Example usage:

custom ffmpeg: set the new easing option to the easing name, with optional CSS-easing arguments, and the transition option to the transition name, with optional customisation arguments.
Example (quartic-out,radial):
xfade=duration=3:offset=10:easing=quartic-out:transition=radial
Example (CSS,GL,reversed):
xfade=duration=3:offset=10:easing='cubic-bezier(0.12,0.57,0.63,0.21)'
:transition='gl_cube(floating=5,unzoom=0.8)':reverse=1
custom expression: set the xfade transition option to custom and the expr option to the concatenation of a standard easing expression and a transition expression (this variant does not support CSS easings).
Example (quartic-out,radial):
xfade=duration=3:offset=10:transition=custom:expr='st(0,P^4);
st(1,atan2(X-W/2,Y-H/2)-(ld(0)-0.5)*PI*2.5);st(1,st(1,clip(ld(1),0,1))*ld(1)*(3-2*ld(1)));B*ld(1)+A*(1-ld(1))'
Pre-generated expressions can be copied verbatim from supplied files.

A CLI wrapper script is provided to generate custom expressions, test videos, visual media sequences and more. It also facilitates generic ffmpeg filter easing – see Easing other filters.

The custom ffmpeg variant is fast with a simple API and no restrictions. Installation involves a few patches to a single ffmpeg C source file, with no dependencies. The custom expression variant is convenient but clunky – see Performance – and runs on plain vanilla ffmpeg but with restrictions: it doesn’t support CSS easings, certain transitions, or the reverse feature.

At present extended transitions are limited to ported GLSL transitions but more effects may be added downstream.

Example

wipedown with cubic easing

CLI command (for custom ffmpeg use)

ffmpeg -i first.mp4 -i second.mp4 -filter_complex "
    xfade=duration=3:offset=1:easing=cubic-in-out:transition=wipedown
    " output.mp4

Easing mode in-out is the default mode; the above is equivalent to easing=cubic.
The default easing is linear (none).

CLI command (for custom expression use)

ffmpeg -i first.mp4 -i second.mp4 -filter_complex_threads 1 -filter_complex "
    xfade=duration=3:offset=1:transition=custom:expr='
        st(0, if(lt(P, 0.5), 4 * P^3, 1 - 4 * (1-P)^3)) ;
        if(gt(Y, H*(1-ld(0))), A, B)
    '" output.mp4

Here, the expr parameter is shown on two lines for clarity.
The first line is the easing expression $e(P)$ (cubic in-out) which stores its calculated progress value in st(0).
The second line is the transition expression $t(e(P))$ (wipedown) which loads its eased progress value from ld(0) instead of P. The semicolon token combines expressions.

Caution

ffmpeg option -filter_complex_threads 1 is required because xfade expression variables (the st() & ld() functions) are shared between slice processing jobs and therefore not thread-safe, consequently processing is much slower

Getting the expressions

In this example you can copy the easing expression from file easings-inline.txt and the transition expression from transitions-rgb24-inline.txt or transitions-yuv420p-inline.txt. Those contain inline expressions for CLI use.

Alternatively use the CLI script:

xfade-easing.sh -t wipedown -e cubic -x -

dumps the xfade expr parameter:

'st(0,if(lt(P,0.5),4*P^3,1-4*(1-P)^3));if(gt(Y,H*(1-ld(0))),A,B)'

Using a script

Some expressions are very long, so using a filtergraph script keeps things manageable and readable.

For this same example you can copy the easing expression from file easings-script.txt and the transition expression from transitions-rgb24-script.txt or transitions-yuv420p-script.txt. Those contain multiline expressions for script use (but the inline expressions work too).

Alternatively use xfade-easing.sh with expansion specifiers expr='%n%X' (see Usage):

xfade-easing.sh -t wipedown -e cubic -s "xfade=offset=10:duration=5:transition=custom:expr='%n%X'" -x script.txt

writes the complete xfade filter description to file script.txt:

xfade=offset=10:duration=5:transition=custom:expr='
st(0, if(lt(P, 0.5), 4 * P^3, 1 - 4 * (1-P)^3))
;
if(gt(Y, H * (1 - ld(0))), A, B)'

and the command becomes

ffmpeg -i first.mp4 -i second.mp4 -filter_complex_threads 1 -/filter_complex script.txt output.mp4`

Note

this option syntax has changed and is not documented:

for ffmpeg version 7+ use -/filter_complex filename
for earlier versions use -filter_complex_script filename

Custom FFmpeg

Building ffmpeg

This is easy:

check the FFmpeg Compilation Guide for any prerequisites, e.g. macOS requires Xcode
get the ffmpeg source tree:
use latest stable release at Download Source Code then extract the .xz archive:
tar -xJf ffmpeg-x.x.x.tar.xz or use xz/gunzip/etc.
cd ffmpeg and patch libavfilter/vf_xfade.c:
- download vf_xfade.patch and run git apply vf_xfade.patch
- or download patched vf_xfade.c (for ffmpeg v7.0.2)
- or patch manually, see vf_xfade diff – only 9 small changes
download xfade-easing.h to libavfilter/
run ./configure with any --prefix and other options (drawtext requires --enable-libfreetype --enable-libharfbuzz --enable-libfontconfig); to replicate an existing configuration run ffmpeg -hide_banner -buildconf and copy-paste the options
run make, it takes a while
the C99 code mixes declarations and statements so may produce profuse compiler warnings
the fix for ld: warning: text-based stub file are out of sync warnings is here
if required run make install or use ffmpeg from the root source directory
test using ffmpeg -hide_banner --help filter=xfade: there should be easing and reverse options under xfade AVOptions

For simplicity, xfade-easing is implemented as static functions in the header file xfade-easing.h and included into vf_xfade.c at an optimal place. As those functions have no external linkage and completely implement an interface that is only visible to the vf_xfade.c compilation unit, this approach is justified IMO, even if unusual, and obviates changing the Makefile. Implementation within header files is not uncommon.

Testing

The custom FFmpeg version has been built and tested on Mac with Clang and Ubuntu Linux with GCC, not Windows. It uses C99 features so expect some warnings.

Custom expressions

Pre-generated easing and transition expressions are in the expr/ subdirectory for mix and match use. The CLI script can produce combined expressions in any syntax using expansion specifiers (like printf).

Inline, for -filter_complex

This format is condensed into a single line stripped of whitespace.

Example: elastic out easing (leaves progress in st(0))

st(0,cos(20*(1-P)*PI/3)/2^(10*(1-P)))

Script, for -/filter_complex

This format is best for expressions that are too unwieldy for inline ffmpeg commands.

Example: gl_rotate_scale_fade transition (expects progress in ld(0) (cf. rotate_scale_fade.glsl)

st(1, 0.5);
st(2, 0.5);
st(3, 1);
st(4, 8);
st(5, X / W - ld(1));
st(6, 1 - Y / H - ld(2));
st(7, hypot(ld(5), ld(6)));
st(5, ld(5) / ld(7));
st(6, ld(6) / ld(7));
st(3, 2 * PI * ld(3) * (1 - ld(0)));
st(8, 2 * abs(ld(0) - 0.5));
st(8, ld(4) * (1 - ld(8)) + 1 * ld(8));
st(4, ld(5) * cos(ld(3)) - ld(6) * sin(ld(3)));
st(6, ld(5) * sin(ld(3)) + ld(6) * cos(ld(3)));
st(1, ld(1) + ld(4) * ld(7) / ld(8));
st(2, ld(2) + ld(6) * ld(7) / ld(8));
if(between(ld(1), 0, 1) * between(ld(2), 0, 1),
 st(1, ld(1) * W);
 st(2, (1 - ld(2)) * H);
 st(3, ifnot(PLANE, a0(ld(1),ld(2)), if(eq(PLANE,1), a1(ld(1),ld(2)), if(eq(PLANE,2), a2(ld(1),ld(2)), a3(ld(1),ld(2))))));
 st(4, ifnot(PLANE, b0(ld(1),ld(2)), if(eq(PLANE,1), b1(ld(1),ld(2)), if(eq(PLANE,2), b2(ld(1),ld(2)), b3(ld(1),ld(2))))));
 st(5, 1 - ld(0));
 ld(3) * (1 - ld(5)) + ld(4) * ld(5),
 st(1, 0.15);
 if(eq(PLANE,3), 255, ld(1)*255)
)

Uneased, for transitions without easing

These use P directly for progress instead of ld(0). They are especially useful for non-xfade transitions where custom expressions are always needed.

Example: gl_WaterDrop transition (cf. WaterDrop.glsl)

st(1, 30);
st(2, 30);
st(3, 1 - P);
st(4, X / W - 0.5);
st(5, 0.5 - Y / H);
st(6, hypot(ld(4), ld(5)));
st(7, if(lte(ld(6), ld(3)),
 st(1, sin(ld(6) * ld(1) - ld(3) * ld(2)));
 st(4, ld(4) * ld(1));
 st(5, ld(5) * ld(1));
 st(4, X + ld(4) * W);
 st(5, Y - ld(5) * H);
 ifnot(PLANE, a0(ld(4),ld(5)), if(eq(PLANE,1), a1(ld(4),ld(5)), if(eq(PLANE,2), a2(ld(4),ld(5)), a3(ld(4),ld(5))))),
 A
));
ld(7) * (1 - ld(3)) + B * ld(3)

Generic, for easing other filters

These ease ld(0) instead od P - see Easing other filters.

Easing

Standard easings (Robert Penner)

This implementation derives from Michael Pohoreski’s single argument version of Robert Penner’s easing functions, further optimised by me for the peculiarities of xfade.

quadratic
cubic
quartic
quintic
sinusoidal
exponential
circular
elastic
back
bounce

Supplementary easings

squareroot
cuberoot

The squareroot and cuberoot easings focus more on the middle regions and less on the extremes, opposite to quadratic and cubic respectively:

All standard and supplementary easings

Here are all the above easings superimposed using the Desmos Graphing Calculator:

CSS easings

The custom ffmpeg variant supports CSS Easing Functions Level 2 which are too complex for custom expressions:

linear linear()
ease ease-in ease-out ease-in-out cubic-bezier()
step-start step-end steps()

Linear easing

The new CSS linear() function can approximate any progress contour by interpolating between adjacent points, documented at W3C here. There’s a CSS Linear() Generator online by its pioneer Jake Archibald to convert easings expressed in JavaScript or SVG to linear().

Cubic Bézier easing

There are 4 fixed CSS smoothing curves and a general cubic-bezier() easing function documented at W3C here. See also the CSS Cubic Bezier Generator to craft your own. The implementation used here is transpiled from Apple’s open-source Webkit.

Step easing

The CSS steps() staircase function is for transitions that jump a constant amount, documented at W3C here.

Reversed CSS easing

Standard easings have ease-in and ease-out modes but not CSS easings. See Reversing xfade effects to achieve this with the custom ffmpeg build.

Overshoots

The elastic and back easings overshoot and undershoot, causing many transitions to clip and others to show colour distortion. Therefore they are quite useless for xfade (but see Easing other filters). CSS easings linear() and cubic-bezier() can also overshoot.

Rendering expressions can only access the two frames of data available. A wrapping overshoot strategy might work for simple horizontal/vertical effects whereby fetching X & Y pixel data is intercepted but at present eased progress outside the range 0 to 1 yields unpredictable results.

Easing other filters

The easing expressions are useful for filters other than xfade, e.g. blend, drawtext, geq, overlay, rotate, zoompan, etc. – anywhere an ffmpeg expr is used to calculate filter options.

For this purpose the CLI script includes text expansion codes %g & %G to generate generic easing expressions for the value in ld(0) (instead of P for xfade), leaving the result in ld(0). You can also copy generic easing expressions from file generic-easings-inline.txt for inline -filter_complex use, or generic-easings-script.txt for -/filter_complex scripts.

To ease other filters, store a normalised input value in st(0,…), append the easing expression, then scale the eased result left in ld(0).

Example: zoompan filter with elastic-out zooming

Here’s the zoom option expression for the zoompan filter:

zoom='st(0, clip((time - 1) / 3, 0, 1));
        st(0, 1 - cos(20 * ld(0) * PI / 3) / 2^(10 * ld(0)));
      lerp(1, 3, ld(0))'

The first line stores a 3 second duration delayed by 1 second normalised to a value between 0 and 1.
The last line scales the result to zoom between 1x and 3x.
The middle line performs elastic-out easing, obtained from generic-easings-script.txt, or
xfade-easing.sh -e elastic-out -s %G -x -

The zoompan filter can produce impressive Ken Burns effects when zoom, x & y are all dynamic. Adding easing can take the illusion of motion even further. I have another FFmpeg project on the go that does just that.

Example: zoompan with back zooming and drawtext with squareroot scrolling

The initial zoom here is 1.2x to accommodate the 10% undershoot that back easing produces. So the zoompan zoom expression, with back expr from generic-easings-inline.txt, is:

z='st(0, clip((time - 1) / 3, 0, 1));
     st(0,if(lt(ld(0),0.5),2*ld(0)*ld(0)*(2*ld(0)*3.59491-2.59491),1-2*(1-ld(0))^2*(4.59491-2*ld(0)*3.59491)));
   lerp(1.2, 3.1, ld(0))'

And the drawtext y expression with squareroot easing is:

y='st(0, clip((t - 1) / 3, 0, 1));
     st(0, if(lt(ld(0), 0.5), sqrt(2 * ld(0)), 2 - sqrt(2 * (1 - ld(0)))) / 2);
   lerp(line_h + 3, h - line_h * 2 + 5, ld(0))'

Transitions

Xfade transitions

The custom ffmpeg variant eases the built-in xfade transitions; these are provided for custom expression use. They are converted from C-code in vf_xfade.c to custom expressions for use with easing. Omitted transitions are distance and hblur which perform aggregation, so cannot be computed efficiently on a per plane-pixel basis.

fade fadefast fadeslow
fadeblack fadewhite fadegrays
wipeleft wiperight wipeup wipedown
wipetl wipetr wipebl wipebr
slideleft slideright slideup slidedown
smoothleft smoothright smoothup smoothdown
circlecrop rectcrop
circleopen circleclose
vertopen vertclose horzopen horzclose
diagtl diagtr diagbl diagbr
hlslice hrslice vuslice vdslice
radial zoomin
dissolve pixelize
squeezeh squeezev
hlwind hrwind vuwind vdwind
coverleft coverright coverup coverdown
revealleft revealright revealup revealdown

Gallery

Here are the xfade transitions processed using custom expressions instead of the built-in transitions (for testing), without easing – see also the FFmpeg Wiki Xfade page:

GLSL transitions

The open collection of GL Transitions initiative lead by Gaëtan Renaudeau (gre) “aims to establish an universal collection of transitions that various softwares can use” released under a Free License.

Other GLSL transition sources were found on shadertoy and the Vegas Forum. All GLSL transitions adapted to the GL Transition Specification are at glsl/.

Many of the transitions at gl-transitions and elsewhere have been transpiled to native C transitions (for custom ffmpeg variant) and custom expressions (for custom expression variant) for use with or without easing. The list shows the names, authors, and customisation parameters and defaults:

gl_angular [args: startingAngle,clockwise; default: (90,0)] (by: Fernando Kuteken)
gl_BookFlip (by: hong)
gl_Bounce [args: shadowAlpha,shadowHeight,bounces,direction; default: (0.6,0.075,3,0)] (by: Adrian Purser)
gl_BowTie [args: vertical; default: (0)] (by: huynx)
gl_cannabisleaf (by: Flexi23)
gl_CornerVanish (by: Mark Craig)
gl_CrazyParametricFun [args: a,b,amplitude,smoothness; default: (4,1,120,0.1)] (by: mandubian)
gl_crosshatch [args: center.x,center.y,threshold,fadeEdge; default: (0.5,0.5,3,0.1)] (by: pthrasher)
gl_CrossOut [args: smoothness; default: (0.05)] (by: Mark Craig)
gl_crosswarp (by: Eke Péter)
gl_cube [args: persp,unzoom,reflection,floating,bgBkWhTr; default: (0.7,0.3,0.4,3,0)] (by: gre)
gl_Diamond [args: smoothness; default: (0.05)] (by: Mark Craig)
gl_DirectionalScaled [args: direction.x,direction.y,scale,bgBkWhTr; default: (0,1,0.7,0)] (by: Thibaut Foussard)
gl_directionalwarp [args: smoothness,direction.x,direction.y; default: (0.1,-1,1)] (by: pschroen)
gl_doorway [args: reflection,perspective,depth,bgBkWhTr; default: (0.4,0.4,3,0)] (by: gre)
gl_DoubleDiamond [args: smoothness; default: (0.05)] (by: Mark Craig)
gl_Dreamy (by: mikolalysenko)
gl_Exponential_Swish [args: zoom,angle,offset,exponent,wrap.x,wrap.y,blur,bgBkWhTr; default: (0.8,0,0,4,2,2,0,0)] (by: Boundless)
gl_FanIn [args: smoothness; default: (0.05)] (by: Mark Craig)
gl_FanOut [args: smoothness; default: (0.05)] (by: Mark Craig)
gl_FanUp [args: smoothness; default: (0.05)] (by: Mark Craig)
gl_Flower [args: smoothness,rotation; default: (0.05,360)] (by: Mark Craig)
gl_GridFlip [args: size.x,size.y,pause,dividerWidth,randomness,bgBkWhTr; default: (4,4,0.1,0.05,0.1,0)] (by: TimDonselaar)
gl_heart (by: gre)
gl_hexagonalize [args: steps,horizontalHexagons; default: (50,20)] (by: Fernando Kuteken)
gl_InvertedPageCurl [args: angle,radius,reverseEffect; default: (100,0.159,0)] (by: Hewlett-Packard)
gl_kaleidoscope [args: speed,angle,power; default: (1,1,1.5)] (by: nwoeanhinnogaehr)
gl_Lissajous_Tiles [args: grid.x,grid.y,speed,freq.x,freq.y,offset,zoom,fade,backColor; default: (10,10,0.5,2,3,2,0.8,3,0)] (by: Boundless)
gl_Mosaic [args: endx,endy; default: (2,-1)] (by: Xaychru)
gl_perlin [args: scale,smoothness; default: (4,0.01)] (by: Rich Harris)
gl_pinwheel [args: speed; default: (2)] (by: Mr Speaker)
gl_polar_function [args: segments; default: (5)] (by: Fernando Kuteken)
gl_PolkaDotsCurtain [args: dots,centre.x,centre.y; default: (20,0,0)] (by: bobylito)
gl_powerKaleido [args: scale,z,speed; default: (2,1.5,5)] (by: Boundless)
gl_randomNoisex (by: towrabbit)
gl_randomsquares [args: size.x,size.y,smoothness; default: (10,10,0.5)] (by: gre)
gl_ripple [args: amplitude,speed; default: (100,50)] (by: gre)
gl_Rolls [args: type,rotDown; default: (0,0)] (by: Mark Craig)
gl_RotateScaleVanish [args: fadeInSecond,reverseEffect,reverseRotation,bgBkWhTr; default: (1,0,0,0)] (by: Mark Craig)
gl_rotateTransition (by: haiyoucuv)
gl_rotate_scale_fade [args: centre.x,centre.y,rotations,scale,backColor; default: (0.5,0.5,1,8,0.15)] (by: Fernando Kuteken)
gl_SimpleBookCurl [args: angle,radius,shadow; default: (150,0.1,0.2)] (by: Raymond Luckhurst)
gl_SimplePageCurl [args: angle,radius,roll,reverseEffect,greyBack,opacity,shadow; default: (80,0.15,0,0,0,0.8,0.2)] (by: Andrew Hung)
gl_Slides [args: type,slideIn; default: (0,0)] (by: Mark Craig)
gl_squareswire [args: squares.h,squares.v,direction.x,direction.y,smoothness; default: (10,10,1.0,-0.5,1.6)] (by: gre)
gl_StarWipe [args: border_thickness,star_rotation,border_color; default: (0.01,0.75,1)] (by: Ben Lucas)
gl_static_wipe [args: upToDown,maxSpan; default: (1,0.5)] (by: Ben Lucas)
gl_Stripe_Wipe [args: nlayers,layerSpread,color1,color2,shadowIntensity,shadowSpread,angle; default: (3,0.5,0x3319CCFF,0x66CCFFFF,0.7,0,0)] (by: Boundless)
gl_swap [args: reflection,perspective,depth,bgBkWhTr; default: (0.4,0.2,3,0)] (by: gre)
gl_Swirl (by: Sergey Kosarevsky)
gl_WaterDrop [args: amplitude,speed; default: (30,30)] (by: Paweł Płóciennik)
gl_windowblinds (by: Fabien Benetou)

Gallery

Here are the ported GLSL transitions with default parameters and no easing. See also the GL Transitions Gallery which lacks many recent contributor transitions plus even more stacking up as Pull requests – which is why I have not added my bundle.

With easing

GLSL transitions can also be eased, although easing is integral with some:

Example: Swirl transition with bounce easing

Customisation parameters

Many GLSL transitions accept parameters to customise the transition effect. The parameters and default values are shown above.

Example: two pinwheel speeds: 'gl_pinwheel(0.5)' and 'gl_pinwheel(10)'

Parameters are appended to the transition name as CSVs within parenthesis.

For the custom ffmpeg variant the parameters may be name=value pairs in any order, e.g. gl_WaterDrop(speed=20,amplitude=50), or they may be indexed values, as follows.

For the custom expression variant the parameters must be indexed values only but empty values assume defaults, e.g. gl_GridFlip(5,3,,0.1,,1) arguments are size.x=5,size.y=3,dividerWidth=0.1,bgBkWhTr=1 with default values for other parameters.

Custom expressions can also be amended directly: parameters are specified using store functions st(p,v) where p is the parameter number and v its value. So for gl_pinwheel with a speed value 10, change the first line of its expr below to st(1, 10);.

st(1, 2);
st(2, 1 - ld(0));
st(1, atan2(0.5 - Y / H, X / W - 0.5) + ld(2) * ld(1));
st(1, mod(ld(1), PI / 4));
if(lte(ld(2), ld(1)), A, B)

Similarly, gl_directionalwarp takes 3 parameters: smoothness, direction.x, direction.y (from xfade-easing.sh -L) and its expr starts with 3 corresponding st() (store) functions which may be changed from their default values:

st(1, 0.1);
st(2, -1);
st(3, 1);
st(4, hypot(ld(2), ld(3)));
etc.

Altered GL Transitions

gl_angular has an additional clockwise parameter
gl_Bounce has an additional direction parameter to control bounce direction: 0=south, 1=west, 2=north, 3=east
gl_BowTie combines BowTieHorizontal and BowTieVertical using parameter vertical
gl_Exponential_Swish option blur default was originally 0.5 but blurring makes it unacceptably slow
gl_InvertedPageCurl omits anti-aliased edges and takes 3 parameters:
- angle may be 100 (default) or 30 degrees from horizontal east
- radius is the cylinder radius
- reverseEffect produces an uncurl effect (custom ffmpeg only)
gl_RotateScaleVanish has an additional trkMat parameter (track matte, custom ffmpeg only) which treats the moving image/video as a variable-transparency overlay – see Dr Who example under Transparency (I might add this feature to other transitions)
gl_rotate_scale_fade option backColor is restricted to greyscale for the custom expression variant
several GL Transitions show a black background during their transition, e.g. gl_cube and gl_doorway, but this implementation provides an additional bgBkWhTr parameter to control the background: 0=black (default), 1=white, -1=transparent

Example: gl_InvertedPageCurl 30° with uncurl (useful for sheet music with repeats)
'gl_InvertedPageCurl(30,0.15,0)' and 'gl_InvertedPageCurl(30,0.15,1)' concatenated

Porting

GLSL shader code runs on the GPU in real time. However GL Transition and Xfade APIs are broadly similar and non-complex algorithms are easily ported using vector resolution.

context	GL Transitions	Xfade filter	notes
progress	`uniform float progress` moves from 0 to 1	`P` moves from 1 to 0	`progress ≡ 1 - P`
ratio	`uniform float ratio`	`W / H`	GL width and height are normalised
coordinates	`vec2 uv` `uv.y == 0` is bottom `uv == vec2(1.0)` is top-right	`X`, `Y` `Y == 0` is top `(X,Y) == (W,H)` is bottom-right	`uv.x ≡ X / W` `uv.y ≡ 1 - Y / H`
texture	`vec4 getFromColor(vec2 uv)` `vec4 getToColor(vec2 uv)`	`a0(x,y)` to `a3(x,y)` or `A` for first input `b0(x,y)` to `b3(x,y)` or `B` for second input	`vec4 transition(vec2 uv) {...}` runs for every pixel position xfade `expr` is evaluated for every texture component (plane) and pixel position
plane data	normalised RGBA	GBRA or YUVA unsigned integer	xfade bit depth depends on pixel format

To make the transpiled code easier to follow, original variable names from the GLSL and xfade source code are replicated in xfade-easing.sh and xfade-easing.h. The script uses pseudo functions to emulate real functions, expanding them inline later.

Example: porting transition gl_randomsquares

randomsquares.glsl:

uniform ivec2 size; // = ivec2(10, 10)
uniform float smoothness; // = 0.5

float rand (vec2 co) {
    return fract(sin(dot(co.xy ,vec2(12.9898,78.233))) * 43758.5453);
}

vec4 transition(vec2 p) {
    float r = rand(floor(vec2(size) * p));
    float m = smoothstep(0.0, -smoothness, r - (progress * (1.0 + smoothness)));
    return mix(getFromColor(p), getToColor(p), m);
}

xfade-easing.sh (custom expression variant):

gl_randomsquares) # (case)
    _make "st(1, ${a[0]-10});" # size.x
    _make "st(2, ${a[1]-10});" # size.y
    _make "st(3, ${a[2]-0.5});" # smoothness
    _make 'st(1, floor(ld(1) * X / W));'
    _make 'st(2, floor(ld(2) * (1 - Y / H)));'
    _make 'st(4, frand(ld(1), ld(2), 4));' # r
    _make 'st(4, ld(4) - ((1 - P) * (1 + ld(3))));'
    _make 'st(4, smoothstep(0, -ld(3), ld(4), 4));' # m
    _make 'mix(A, B, ld(4))'
    ;;

Here, frand(), smoothstep() and mix() are pseudo functions. Customizable parameters are generally stored first. _make is just an expression string builder function.

xfade-easing.h (custom ffmpeg variant):

static vec4 gl_randomsquares(const XTransition *e)
{
    PARAM_BEGIN
    PARAM_2(ivec2, size, 10, 10)
    PARAM_1(float, smoothness, 0.5)
    PARAM_END
    float r = frand2(floor2(mul2(vec2i(size), e->p)));
    float m = smoothstep(0, -smoothness, r - e->progress * (1 + smoothness));
    return mix4(e->a, e->b, m);
}

Here, vec4 and ivec2 simulate GLSL vector types and XTransition encapsulates all data pertaining to a transition:

typedef struct { // modelled on GL Transition Specification v1
    const float progress; // transition progress, moves from 0.0 to 1.0 (cf. P)
    const float ratio; // viewport width / height (cf. W / H)
    vec2 p; // pixel position in slice, .y==0 is bottom (cf. X, Y)
    vec4 a, b; // plane data at p (cf. A, B)
    ...
} XTransition;

Curls and Rolls

Transition `gl_InvertedPageCurl`

This is transpiled from the InvertedPageCurl GL transition which originated from the WebVfx WebGL pagecurl shader which is itself based on code by Calyptus Life AB which seems no longer available. The Hewlett-Packard accreditation by Sergey Kosarevsky is obscure but preserved here.

Transition `gl_SimplePageCurl`

This is adapted from the elegant simple page curl effect by Andrew Hung who also provides an excellent shader breakdown to demystify the deformation effect.
It is more versatile than gl_InvertedPageCurl and takes the following parameters:

angle may be any 360° angle (horizontal east is 0°, curl direction is angle - 90° anticlockwise); in effect, 1–89° curls from bottom-right; 91–179° top-right; 181–269° (or -91–-179°) top-left; 271–359° (or -1–-89°) bottom-left; 0° curls upwards; 90° left; ±180° down; 270° (or -90°) right
radius sets the cylinder radius
roll to roll the turning page into a cylinder (gl_InvertedPageCurl only rolls)
reverseEffect to uncurl or unroll
greyBack to render overleaf greyscale instead of colour
opacity the underside opacity
shadow the shadow intensity

The main differences from gl_InvertedPageCurl are:

curling in any direction, not just right-to-left at 30° or 100°
takes aspect ratio into account, ensuring accurate angle
can render back of turning page either rolling or just curled over
back of turning page rendered in colour or greyscale with variable opacity
smaller default radius of 0.15, not 1/2π

Example: using gl_SimplePageCurl to emulate gl_InvertedPageCurl
'gl_InvertedPageCurl(30)' vs 'gl_SimplePageCurl(24.8,0.159,1,0,1,0.8,0.1)'
these parameters factor in the disregarded aspect ratio (5:4 here), 1/2π radius, roll effect, greyscale overleaf, and shadowing.

There is barely any noticeable difference, which confirms Mr Hung’s observation that complex mathematics is unjustified: scalar product projections and simple trigonometry are sufficient.

Example: gl_SimplePageCurl with various angle and roll options (Abstract and Renaissance art by Kandinsky and Titian)

A by-product effect is a wipe transition in any direction, achieved by setting radius=0,roll=1.

Example: 'gl_SimplePageCurl(160,0,1)' 160° wipe

Transition `gl_SimpleBookCurl`

(custom ffmpeg only)

This is adapted from gl_SimplePageCurl to clamp the curl to the virtual ‘spine’ at the horizontal centre, then to flatten the radius to zero, using built-in easing to appear more realistic.
It takes the following parameters:

angle may be any 360° angle (horizontal east is 0°, curl direction is angle - π/2 anticlockwise); in effect, angles from 180° to 359° (or -1° to -180°) page backwards
radius sets the cylinder radius
shadow the shadow intensity

Example: gl_SimpleBookCurl with various angle and radius values paging forwards and backwards, rotated and overlaid onto a desk texture (credit: Ethical Corporation Magazine)

Pixel format

Transitions that affect colour components work differently for RGB than non-RGB colour spaces and for different bit depths. For the custom expression variant, xfade-easing.sh emulates vf_xfade.c function config_output() logic, deducing the RGB signal type AV_PIX_FMT_FLAG_RGB from the -f option format name (rgb/bgr/etc. see pixdesc.c) and the bit depth from ffmpeg -pix_fmts data. It can then set the black, white and mid plane values correctly. See How does FFmpeg identify color spaces? for details.

The expression files in expr/ cater for RGB and YUV formats with 8-bit component depth. For faster processing of greyscale media use xfade-easing.sh -f gray. Greyscale is not RGB therefore it is processed as a luma plane.

If in doubt, check with ffmpeg -pix_fmts or use the xfade-easing.sh -f option.

Transparency

The expression files in expr/ also cater for RGBA and YUVA formats with 4 planes.

For lossless intermediate video content with alpha channel support use the xfade-easing.sh -f -v options with an alpha format, e.g. rgba/yuva420p, and .mkv filename extension. For lossy video with alpha use an alpha format and the .webm extension.

Example: overlaid transparent gl_RotateScaleVanish transition with quadratic-in easing

xfade-easing.sh -f rgba -e quadratic-in -t 'gl_RotateScaleVanish(FadeInSecond=0,ReverseEffect=1,trkMat=1)' -v alpha.mkv -z 250x skaro.png tardis.png
ffmpeg -i gallifrey.png -i alpha.mkv -filter_complex '[0]scale=250:-2[b]; [b][1]overlay' drwho.mp4

This demonstrates the additional trkMat option which tracks the Tardis alpha value to expose Skaro behind, then Gallifrey’s Citadel when the transition ends, both planets being opaque images.
(trkMat is only availble in the custom ffmpeg variant)

See also the example under Transition gl_SimpleBookCurl.

Colour parameters

For the custom expression variant, which does not support colour, values are specified as a decimal proportion of maximum and rendered as greyscale.
e.g. gl_rotate_scale_fade(backColor=0.75)

For the custom ffmpeg variant, decimal values from 0 to 1 are rendered as greyscale, as above, but all other values are treated as RGBA colour, specified using the ffmpeg syntax described at Color.
e.g. gl_Stripe_Wipe(color1=DeepSkyBlue,color2=ffd700)
Consequently. a value of exactly 1 is rendered white but 2 (RGB #000002) is nearly black.
Colour examples:

random (a random colour)
DarkGoldenRod (a standard X11 colour name, see FFmpeg colour names)
0x56789A or #56789A (packed RGB hex digits)
0.75 (75% grey)

Custom expression performance

FFmpeg expr strings initially get parsed into an expression tree of AVExpr nodes in libavutil/eval.c. That expression is then executed for every pixel in each plane, which obviously incurs a performance hit, considerably exacerbated by disabling slice threading in order to use the st() and ld() functions. So custom transition expressions are not fast.

The following times are based on empirical timings scaled by benchmark scores (the Geekbench Mac Benchmark Chart). They are rough estimates in seconds to process a 3-second transition of HD720 (1280x720) 3-plane media (rgb24) through a null muxer at Mac benchmark midpoints. For greyscale (single plane), subtract two thirds. For an alpha plane, add a third. Mac model performance varies enormously so the Mac vintage dates are only approximate. Windows performance has not been measured.

benchmark → transition ↓	2335‑3120 M1,M2,M3 Macs	1150‑1655 2017‑19 Macs	700‑1150 2013‑16 Macs	195‑700 2008‑12 Macs
`fade` `wipeleft` `wipeup`	2	4	6	12
`wiperight` `wipedown`	3	6	9	18
`wipetl` `wipetr` `wipebl` `wipebr`	5	10	14	30
`squeezeh` `squeezev`	8	16	24	48
`gl_CornerVanish`	9	18	26	54
`fadefast` `fadeslow` `rectcrop`	10	20	30	60
`dissolve`	12	24	36	72
`gl_Diamond` `gl_DoubleDiamond` `gl_FanUp` `gl_randomNoisex`	14	28	42	84
`smoothleft` `smoothup` `coverleft` `revealleft` `coverup` `revealup`	16	32	48	100
`slideleft` `slideup` `slidedown` `circlecrop` `vertopen` `vertclose` `horzopen` `horzclose` `coverright` `revealright` `coverdown` `revealdown` `gl_FanIn` `gl_FanOut` `gl_pinwheel`	18	36	54	110
`slideright` `smoothright` `smoothdown` `diagtl` `diagtr` `diagbl` `diagbr`	20	40	60	120
`radial` `gl_CrossOut`	22	42	66	133
`gl_BookFlip` `gl_heart` `gl_polar_function`	24	46	72	147
`hlslice` `hrslice` `vdslice` `vuslice`	28	54	84	171
`circleopen` `circleclose` `gl_angular` `gl_Slides`	30	60	88	180
`hlwind` `hrwind` `vdwind` `vuwind` `gl_PolkaDotsCurtain`	32	63	95	200
`gl_WaterDrop`	36	72	105	220
`fadeblack` `fadewhite` `gl_windowblinds`	38	76	114	228
`gl_Bounce` `pixelize` `gl_cannabisleaf` `gl_randomsquares` `zoomin`	42	84	126	260
`gl_Dreamy` `gl_Flower`	48	95	140	300
`fadegrays` `gl_rotateTransition`	51	100	152	304
`gl_crosswarp` `gl_ripple`	54	105	160	336
`gl_DirectionalScaled`	57	114	168	340
`gl_Rolls`	60	120	180	360
`gl_doorway`	63	126	189	380
`gl_RotateScaleVanish`	66	126	200	400
`gl_Swirl`	69	133	200	420
`gl_InvertedPageCurl` `gl_squareswire`	80	160	240	480
`gl_CrazyParametricFun`	84	168	252	520
`gl_crosshatch` `gl_static_wipe`	88	171	260	540
`gl_directionalwarp` `gl_rotate_scale_fade`	95	189	280	580
`gl_cube` `gl_hexagonalize`	105	210	304	640
`gl_Mosaic` `gl_swap`	110	220	320	680
`gl_perlin`	132	260	400	800
`gl_kaleidoscope`	247	480	720	1500
`gl_powerKaleido`	1000	1960	2960	6100

The slowest supported transition gl_powerKaleido is clearly impractical for most purposes! The most complex transition is gl_InvertedPageCurl which involved considerable refactoring; it omits anti-aliasing for simplicity.

See xfade-easing.h for the C code transpiled from GLSL that helped to optimize the custom expressions. See the files in glsl/ refactored from other GLSL transition sources that were used for intermediate testing in the GL Transition Editor.

Using the custom ffmpeg build on M2 Macs, the slowest transition takes just 4 seconds for the same task. However gl_Exponential_Swish with blurring can take 3 minutes! While much slower than a GPU, CPU processing is at least tolerable. Unlike built-in xfade transitions the custom ffmpeg C code in xfade-easing.h deploys a single pixel iterator for all extended transition functions which in turn operate on all planes at once. And it does not require -filter_complex_threads 1.

Performance-wise, custom expressions are slower by a factor of 41 (median), 47 (mean) with a huge standard deviation of 26!

Other faster ways to use GL Transitions with FFmpeg are:

gl-transition-scripts includes a Node.js CLI script gl-transition-render which can render multiple GL Transitions and images for FFmpeg processing
ffmpeg-concat is a Node.js package which requires installation and a lot of temporary storage
ffmpeg-gl-transition is a native FFmpeg filter which requires building ffmpeg from source

Reversing xfade effects

(custom ffmpeg only)

This is a generic xfade reverse option that has been added to reverse transition and/or easing effects. It takes a single digit:

0 no reverse (default)
1 swap the inputs and reverse the transition effect
2 reverse the easing effect
3 swap the inputs and reverse the transition and easing effects

It is necessary to swap the inputs during the reversed transition to match the inputs before and after the transition, i.e. during the offset time and after the offset+duration time. This is tricky but not impossible to implement in the xfade-easing.sh script for custom expressions. The script has a -b option to pass reverse values through to xfade for the custom ffmpeg variant.

Most standard xfade transitions have reversed equivalents, e.g. wipeleft and wiperight but few GLSL transitions have. Unlike standard easings, CSS easings also have no mirror-image reversal mode.

Example: using the same CSS Linear coefficients as above
easing: 'linear(0, 0.5 30%, 0.2 60% 80%, 1)' transition: gl_FanUp reverse: 0–3

There is no gl_FanDown transition but reversing gl_FanUp provides one.

CLI script

xfade-easing.sh is a Bash 4 shell wrapper for ffmpeg. It can:

generate custom easing and transition expressions for the xfade expr parameter
generate easing graphs via gnuplot (especially useful for CSS easings)
create demo videos for testing
concenate visual media with eased transitions for presentations and slideshows.

Usage

FFmpeg XFade easing and extensions version 3.0.2 by Raymond Luckhurst, https://scriptit.uk
Generates custom expressions for rendering eased transitions and easing in other filters,
also creates easing graphs, demo videos, presentations and slideshows
See https://github.com/scriptituk/xfade-easing
Usage: xfade-easing.sh [options] [image/video inputs]
Options:
    -f pixel format (default: rgb24): use ffmpeg -pix_fmts for list
    -t transition name and arguments, if any (default: fade); use -L for list
       args in parenthesis as CSV, e.g.: 'gl_perlin(5,0.1)' (both variants)
       or key=value pairs, e.g.: 'gl_perlin(smoothness=0.1, scale=5)' (custom ffmpeg only)
    -e easing function and arguments, if any (default: linear)
       CSS args in parenthesis as CSV, e.g.: 'cubic-bezier(0.17,0.67,0.83,0.67)'
    -b reverse transition and/or easing effect (custom ffmpeg only) (default: 0)
       1 reverses the inputs and transition effect; 2 reverses the easing; 3 reverses both
    -x expr output filename (default: no expr), accepts expansions, - for stdout
    -a append to expr output file
    -s expr output format string with text expansion (default: '%x')
       %f expands to pixel format, %F to format in upper case
       %e expands to the easing name
       %t expands to the transition name
       %E, %T upper case expansions of %e, %t
       %c expands to the CSS easing arguments
       %a expands to the GL transition arguments; %A to the default arguments (if any)
       %x expands to the generated expr, condensed, intended for inline filterchains
       %X uncondensed version of %x, intended for -/filter_complex script files
       %p expands to the progress easing expression, condensed, for inline filterchains
       %g expands to the generic easing expression (for other filters), condensed
       %z expands to the eased transition expression only, condensed
          for the uneased transition expression only, omit -e option and use %x or %X
       %P, %G, %Z, uncondensed versions of %p, %g, %z, for -/filter_complex script files
       %n inserts a newline
    -p easing plot filename (default: no plot), accepts expansions
       formats: gif, jpg, png, svg, pdf, eps, html <canvas>, from file extension
    -m multiple easings to plot on one graph (default: the -e easing)
       CSV easings with optional legend prefix, e.g. in=cubic-in,out=cubic-out,in-out=cubic
    -q plot title (default: easing name, or Easings for multiple plots)
    -c canvas size for easing plot (default: 640x480, scaled to inches for PDF/EPS)
       format: WxH; omitting W or H keeps aspect ratio, e.g. -z x300 scales W
    -v video output filename (default: no video), accepts expansions
       formats: animated gif, mp4 (x264), webm, mkv (FFV1 lossless), from file extension
       if - then format is the null muxer (no output)
       if -f format has alpha then webm and mkv generate transparent video output
       if gifsicle is available then gifs will be optimised
    -z video size (default: input 1 size)
       format: WxH; omitting W or H keeps aspect ratio, e.g. -z 400x scales H
    -d video transition duration (default: 3s, minimum: 0) (see note after -l)
    -i time between video transitions (default: 1s, minimum: 0) (see note after -l)
    -l video length (default: 5s)
       note: options -d, -i, -l are interdependent: l=ni+(n-1)d for n inputs
       given -t & -l, d is calculated; else given -l, t is calculated; else l is calculated
    -j allow input videos to play within transitions (default: no)
       normally videos only play during the -i time but this sets them playing throughout
    -r video framerate (default: 25fps)
    -n show effect name on video as text (requires the libfreetype library)
    -u video text font size multiplier (default: 1.0)
    -k video stack orientation,gap,colour,padding (default: ,0,white,0), e.g. h,2,red,1
       stacks uneased and eased videos horizontally (h), vertically (v) or auto (a)
       auto selects the orientation that displays easing to best effect
       also stacks transitions with default and custom parameters, eased or not
       videos are only stacked if they are different (nonlinear-eased or customised)
       unstacked videos can be padded using orientation=1, e.g. 1,0,blue,5
    -L list all transitions and easings
    -H show this usage text
    -V show this script version
    -X use custom expressions, not the xfade API that supports xfade-easing natively
       by default native support is detected automatically using ffmpeg --help filter=xfade
       the native API adds an easing option and runs much faster
       e.g. xfade=duration=4:offset=1:easing=quintic-out:transition=wiperight
       e.g. xfade=duration=5:offset=2.5:easing='cubic-bezier(.17,.67,.83,.67)' \
            transition='gl_swap(depth=5,reflection=0.7,perspective=0.6)' (see repo README)
    -I set ffmpeg loglevel to info for -v (default: warning)
    -D dump debug messages to stderr and set ffmpeg loglevel to debug for -v
    -P log xfade progress percentage using custom expression print() function (implies -I)
    -T temporary file directory (default: /tmp)
    -K keep temporary files if temporary directory is not /tmp
Notes:
    1. point the shebang path to a bash4 location (defaults to MacPorts install)
    2. this script requires Bash 4 (2009), ffmpeg, gawk, gsed, seq, also gnuplot for plots
    3. use ffmpeg option -filter_complex_threads 1 (slower!) because xfade expression
       vars used by st() & ld() are shared across slices, therefore not thread-safe
       (the custom ffmpeg build works without -filter_complex_threads 1)
    4. CSS easings are supported in the custom ffmpeg build but not as custom expressions
    4. certain xfade transitions are not implemented as custom expressions because
       they perform aggregation (distance, hblur)
    5. many GLSL transitions are also ported, some of which take customisation parameters
       to override defaults append parameters in parenthesis (see -X above)
    6. certain GLSL transitions are only available in the custom ffmpeg build
    7. many transitions do not lend themselves well to easing, others have easing built in
       easings that overshoot (back & elastic) may cause weird effects!

Generating expr code

Expr code is generated using the -x option and customised with the -s,-a options.

xfade-easing.sh -t slideright -e quadratic -x -
prints expr for slideright transition with quadratic-in-out easing to stdout
xfade-easing.sh -t coverup -e quartic-in -x coverup_quartic-in.txt
prints expr for coverup transition with quartic-in easing to file coverup_quartic-in.txt
xfade-easing.sh -t coverup -e quartic-in -x %t_%e.txt
ditto, using expansion specifiers in file name
xfade-easing.sh -t rectcrop -e exponential-out -s "\$expr['%t_%e'] = '%n%X';" -x exprs.php -a
appends the following to file exprs.php:

$expr['rectcrop_exponential-out'] = '
st(0, if(eq(P, 0), 0, 2^(-10 * (1 - P))))
;
st(1, abs(ld(0) - 0.5));
if(lt(abs(X - W / 2), ld(1) * W) * lt(abs(Y - H / 2), ld(1) * H),
 if(lt(ld(0), 0.5), B, A),
 if(lt(PLANE,3), 0, 255)
)';

xfade-easing.sh -t gl_polar_function -s "expr='%n%X'" -x fc-script.txt
This is not eased, therefore the expr written to fc-script.txt uses progress P directly:

expr='
st(1, 5);
st(2, X / W - 0.5);
st(3, 0.5 - Y / H);
st(4, atan2(ld(3), ld(2)) - PI / 2);
st(4, cos(ld(1) * ld(4)) / 4 + 1);
st(1, hypot(ld(2), ld(3)));
if(gt(ld(1), ld(4) * (1 - P)), A, B)'

Generating test plots

Plots are generated using the -p option and customised with the -m,-q,-c options.

Plot data is logged using the print function of the ffmpeg expression evaluator for the first plane and first pixel as xfade progress P goes from 1 to 0 at 100fps.

xfade-easing.sh -e elastic -p plot-%e.pdf
creates a PDF file plot-elastic.pdf of elastic easing
xfade-easing.sh -q 'Bounce Easing' -m in=bounce-in,out=bounce-out,in-out=bounce -p %e.png -c 500x
creates image file bounce.png of the bounce easing scaled to 500px wide with title and legends:

The plots above in Standard easings show test plots for all standard easings and all three modes (in, out and in-out).

Generating demo videos

Videos are generated using the -v option and customised with the -z,-d,-i,-l,-j,-r,-n,-u,-k options.

Note

all transition effect demos on this page are animated GIFs regardless of the commands shown

Timing

Input media is serialised according to the expression $L=NI+(N-1)D$ where L is the total video length (option -l); I is the individual display time (option -i); D is the transition duration (option -d); N is the number of inputs. Transition offsets are spaced accordingly. Depending on option -j and the input media length, pre and post padding is added by frame cloning to ensure enough frames are available for transition processing. See Usage for the precedence of options -l, -i, -d.

Examples

xfade-easing.sh -t hlwind -e quintic-in -v windy.gif creates an animated GIF image of the hlwind transition with quintic-in easing using default built-in images
xfade-easing.sh -t fadeblack -e circular -v maths.mp4 dot.png cross.png creates a MP4 video of the fadeblack transition with circular easing using specified inputs
xfade-easing.sh -t coverdown -e bounce-out -v %t-%e.mp4 wallace.png shaun.png creates a video of the coverdown transition with bounce-out easing using expansion specifiers for the output file name
xfade-easing.sh -t 'gl_polar_function(25)' -v paradise.mkv -n -u 1.2 islands.png rainbow.png creates a lossless (FFV1) video (e.g. for further processing) of an uneased polar_function GL transition with 25 segments annotated in enlarged text
xfade-easing.sh -t 'gl_Lissajous_Tiles(16,20,0.3,9,3,1,0.8,3,Lavender)' -v lissajous.mp4 titian.png kandinsky.png creates a stunning Lissajous effect against a Lavender background demonstrating extensive use of transition parameters
xfade-easing.sh -t 'gl_angular(270,1)' -e exponential -v multiple.mp4 -n -k h -l 20 street.png road.png flowers.png bird.png barley.png creates a video of the angular GL transition with parameter startingAngle=270 (south) and clockwise=1 (an added parameter) for 5 inputs with fast exponential easing
xfade-easing.sh -t gl_BookFlip -e quartic-out -v book.mp4 -f gray -z 248x -n -k h,2,black,1 alice12.png alice34.png creates a simple greyscale page turn with quartic-out easing for a more realistic effect.
xfade-easing.sh -t circlecrop -e sinusoidal -v home-away.mp4 -l 10 -d 8 -z 246x -k h,4,LightSkyBlue,2 -n phone.png beach.png creates a 10s video with a slow 8s circlecrop xfade transition with sinusoidal easing, horizontally stacked with a 4px LightSkyBlue gap (see Color) and 2px padding
xfade-easing.sh -t gl_InvertedPageCurl -e cubic-in -v score.mp4 -f gray -i 2 -d 3 -z 480x -k 1,0,0xD8D8D8,10 fugue1.png fugue2.png fugue3.png a 3s page curl effect, static for 2s, with cubic-in easing using greyscale format (-k 1,0,colour,padding creates a border)

🎹 I play this Bach fugue on my YouTube channel digitallegro but the GL InvertedPageCurl there was generated by ffmpeg-concat
xfade-easing.sh -t 'gl_PolkaDotsCurtain(10,0.5,0)' -e 'cubic-bezier(0.4,1.2,0.6,-1.1)' -v life.mp4 -l 7 -d 5 -z 500x -f yuv420p -r 30 balloons.png fruits.png a GL transition with arguments and cubic-bezier easing, running at 30fps for 7 seconds, processing in YUV (Y'CbCr) colour space throughout

Files

README.md

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README.md

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Easing and extensions for FFmpeg Xfade filter

Standard easings • CSS easings • transpiled GLSL transitions • custom expressions

Summary

Example

wipedown with cubic easing

CLI command (for custom ffmpeg use)

CLI command (for custom expression use)

Getting the expressions

Using a script

Custom FFmpeg

Building ffmpeg

Testing

Custom expressions

Inline, for -filter_complex

Script, for -/filter_complex

Uneased, for transitions without easing

Generic, for easing other filters

Easing

Standard easings (Robert Penner)

Supplementary easings

All standard and supplementary easings

CSS easings

Linear easing

Cubic Bézier easing

Step easing

Reversed CSS easing

Overshoots

Easing other filters

Transitions

Xfade transitions

Gallery

GLSL transitions

Gallery

With easing

Customisation parameters

Altered GL Transitions

Porting

Curls and Rolls

Transition gl_InvertedPageCurl

Transition gl_SimplePageCurl

Transition gl_SimpleBookCurl

Pixel format

Transparency

Colour parameters

Custom expression performance

Reversing xfade effects

CLI script

Usage

Generating expr code

Generating test plots

Generating demo videos

Timing

Examples

See also

Transition `gl_InvertedPageCurl`

Transition `gl_SimplePageCurl`

Transition `gl_SimpleBookCurl`