[FFmpeg-devel] lavfi: add perlin noise generator
Andrew Sayers
ffmpeg-devel at pileofstuff.org
Thu Jun 13 18:45:48 EEST 2024
Some documentation nitpicks. Nothing jumped out about the code, but I don't
know the algorithm well enough to spot anything deep.
> From 9932cfc19500acbd0685eb2cc8fd88e9af3f5dbd Mon Sep 17 00:00:00 2001
> From: Stefano Sabatini <stefasab at gmail.com>
> Date: Mon, 27 May 2024 11:19:08 +0200
> Subject: [PATCH] lavfi: add Perlin noise generator
>
> ---
> Changelog | 1 +
> doc/filters.texi | 100 +++++++++++++++++
> libavfilter/Makefile | 1 +
> libavfilter/allfilters.c | 1 +
> libavfilter/perlin.c | 224 ++++++++++++++++++++++++++++++++++++++
> libavfilter/perlin.h | 101 +++++++++++++++++
> libavfilter/vsrc_perlin.c | 169 ++++++++++++++++++++++++++++
> 7 files changed, 597 insertions(+)
> create mode 100644 libavfilter/perlin.c
> create mode 100644 libavfilter/perlin.h
> create mode 100644 libavfilter/vsrc_perlin.c
>
> diff --git a/Changelog b/Changelog
> index 03d6b29ad8..b8dcf452ac 100644
> --- a/Changelog
> +++ b/Changelog
> @@ -12,6 +12,7 @@ version <next>:
> - qsv_params option added for QSV encoders
> - VVC decoder compatible with DVB test content
> - xHE-AAC decoder
> +- perlin source
>
>
> version 7.0:
> diff --git a/doc/filters.texi b/doc/filters.texi
> index 347103c04f..7af299b2a2 100644
> --- a/doc/filters.texi
> +++ b/doc/filters.texi
> @@ -17290,6 +17290,9 @@ The command accepts the same syntax of the corresponding option.
> If the specified expression is not valid, it is kept at its current
> value.
>
> + at anchor{lutrgb}
> + at anchor{lutyuv}
> + at anchor{lut}
> @section lut, lutrgb, lutyuv
>
> Compute a look-up table for binding each pixel component input value
> @@ -29281,6 +29284,103 @@ ffplay -f lavfi life=s=300x200:mold=10:r=60:ratio=0.1:death_color=#C83232:life_c
> @end example
> @end itemize
>
> + at section perlin
> +Generate Perlin noise.
> +
> +Perlin noise is a kind of noise with local continuity in space. This
> +can be used to generate patterns with continuity in space and time,
> +e.g. to simulate smoke, fluids, or terrain.
> +
> +In case more than one octave is specified through the @option{octaves}
> +option, Perlin noise is generated as a sum of components, each one
> +with doubled frequency. In this case the @option{persistence} option
> +specify the ratio of the amplitude with respect to the previous
> +component. More octave components enable to specify more high
> +frequency details in the generated noise (e.g. small size variations
> +due to bolders in a generated terrain).
Typo: s/bolders/boulders/
> +
> + at subsection Options
> + at table @option
> +
> + at item size, s
> +Specify the size (width and height) of the buffered video frames. For the
> +syntax of this option, check the
> + at ref{video size syntax,,"Video size" section in the ffmpeg-utils manual,ffmpeg-utils}.
> +
> + at item rate, r
> +Specify the frame rate expected for the video stream, expressed as a
> +number of frames per second.
> +
> + at item octaves
> +Specify the total number of components making up the noise, each one
> +with doubled frequency.
> +
> + at item persistence
> +Set the ratio used to compute the amplitude of the next octave
> +component with respect to the previous component amplitude.
> +
> + at item xscale
> + at item yscale
> +Define a scale factor used to multiple the x, y coordinates. This can
> +be useful to define an effect with a pattern stretched along the x or
> +y axis.
> +
> + at item tscale
> +Define a scale factor used to multiple the time coordinate. This can
> +be useful to change the time variation speed.
> +
> + at item random_mode
> +Set random mode used to compute initial pattern.
> +
> +Supported values are:
> + at table @option
> + at item random
> +Compute and use random seed.
> +
> + at item ken
> +Use the predefined initial pattern defined by Ken Perlin in the
> +original article, can be useful to compare the output with other
> +sources.
> +
> + at item seed
> +Use the value specified by @option{random_seed} option.
> + at end table
Nit: "Define a...", "Use the..." etc. is redundant - remove them to
optimise for reading time.
> +
> + at item random_seed, seed
> +Use this value to compute the initial pattern, it is only considered
> +when @option{random_mode} is set to @var{random_seed}.
> + at end table
Nit: the reader needs to read the second clause before the first makes sense.
Consider something like:
When @option{random_mode} is set to @var{random_seed},
this value computes the initial pattern.
> +
> + at subsection Examples
> + at itemize
> + at item
> +Generate single component:
> + at example
> +perlin
> + at end example
> +
> + at item
> +Use Perlin noise with 7 components, each one with a halved contribute
s/contribute/contribution/
> +to total amplitude:
> + at example
> +perlin=octaves=7:persistence=0.5
> + at end example
> +
> + at item
> +Chain Perlin noise with the @ref{lutyuv} to generate a black&white
> +effect:
> + at example
> +perlin:octaves=7:tscale=0.3,lutyuv=y='if(lt(val\,128)\,255\,0)'
> + at end example
> +
> + at item
> +Stretch noise along the y axis, and convert gray level to red-only
I initially thought this was a typo for "read-only" - maybe s/red/blue/?
> +signal:
> + at example
> +perlin=octaves=7:tscale=0.4:yscale=0.3,lutrgb=r=val:b=0:g=0
> + at end example
> + at end itemize
> +
> @section qrencodesrc
>
> Generate a QR code using the libqrencode library (see
> diff --git a/libavfilter/Makefile b/libavfilter/Makefile
> index 5992fd161f..63088e9286 100644
> --- a/libavfilter/Makefile
> +++ b/libavfilter/Makefile
> @@ -603,6 +603,7 @@ OBJS-$(CONFIG_NULLSRC_FILTER) += vsrc_testsrc.o
> OBJS-$(CONFIG_OPENCLSRC_FILTER) += vf_program_opencl.o opencl.o
> OBJS-$(CONFIG_PAL75BARS_FILTER) += vsrc_testsrc.o
> OBJS-$(CONFIG_PAL100BARS_FILTER) += vsrc_testsrc.o
> +OBJS-$(CONFIG_PERLIN_FILTER) += vsrc_perlin.o perlin.o
> OBJS-$(CONFIG_QRENCODE_FILTER) += qrencode.o textutils.o
> OBJS-$(CONFIG_QRENCODESRC_FILTER) += qrencode.o textutils.o
> OBJS-$(CONFIG_RGBTESTSRC_FILTER) += vsrc_testsrc.o
> diff --git a/libavfilter/allfilters.c b/libavfilter/allfilters.c
> index c532682fc2..63600e9b58 100644
> --- a/libavfilter/allfilters.c
> +++ b/libavfilter/allfilters.c
> @@ -569,6 +569,7 @@ extern const AVFilter ff_vsrc_openclsrc;
> extern const AVFilter ff_vsrc_qrencodesrc;
> extern const AVFilter ff_vsrc_pal75bars;
> extern const AVFilter ff_vsrc_pal100bars;
> +extern const AVFilter ff_vsrc_perlin;
> extern const AVFilter ff_vsrc_rgbtestsrc;
> extern const AVFilter ff_vsrc_sierpinski;
> extern const AVFilter ff_vsrc_smptebars;
> diff --git a/libavfilter/perlin.c b/libavfilter/perlin.c
> new file mode 100644
> index 0000000000..f09020bf8f
> --- /dev/null
> +++ b/libavfilter/perlin.c
> @@ -0,0 +1,224 @@
> +/*
> + * This file is part of FFmpeg.
> + *
> + * FFmpeg is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License as published by
> + * the Free Software Foundation; either version 2 of the License, or
> + * (at your option) any later version.
> + *
> + * FFmpeg is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
> + * GNU General Public License for more details.
> + *
> + * You should have received a copy of the GNU General Public License along
> + * with FFmpeg; if not, write to the Free Software Foundation, Inc.,
> + * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
> + */
> +
> +/**
> + * @file
> + * Perlin Noise generator, based on code from:
> + * https://adrianb.io/2014/08/09/perlinnoise.html
> + *
> + * Original article from Ken Perlin:
> + * http://mrl.nyu.edu/~perlin/paper445.pdf
> + */
> +
> +#include <math.h>
> +
> +#include "libavutil/lfg.h"
> +#include "libavutil/random_seed.h"
> +#include "perlin.h"
> +
> +static inline int inc(int num, int period)
> +{
> + num++;
> + if (period > 0)
> + num %= period;
> + return num;
> +}
> +
> +static inline double grad(int hash, double x, double y, double z)
> +{
> + // Take the hashed value and take the first 4 bits of it (15 == 0b1111)
> + int h = hash & 15;
> + // If the most significant bit (MSB) of the hash is 0 then set u = x. Otherwise y.
> + double u = h < 8 /* 0b1000 */ ? x : y;
> + double v;
> +
> + // In Ken Perlin's original implementation this was another
> + // conditional operator (?:), then expanded for readability.
> + if (h < 4 /* 0b0100 */)
> + // If the first and second significant bits are 0 set v = y
> + v = y;
> + // If the first and second significant bits are 1 set v = x
> + else if (h == 12 /* 0b1100 */ || h == 14 /* 0b1110*/)
Nit: add space before final *
> + v = x;
> + else
> + // If the first and second significant bits are not equal (0/1, 1/0) set v = z
> + v = z;
> +
> + // Use the last 2 bits to decide if u and v are positive or negative. Then return their addition.
> + return ((h&1) == 0 ? u : -u)+((h&2) == 0 ? v : -v);
> +}
> +
> +static inline double fade(double t)
> +{
> + // Fade function as defined by Ken Perlin. This eases coordinate values
> + // so that they will "ease" towards integral values. This ends up smoothing
> + // the final output.
Given the verbosity of the comments so far, do you want to explicitly mention
how this is using Horner's method?
https://en.wikipedia.org/wiki/Horner%27s_method
> + return t * t * t * (t * (t * 6 - 15) + 10); // 6t^5 - 15t^4 + 10t^3
> +}
> +
> +static double lerp(double a, double b, double x)
> +{
> + return a + x * (b - a);
> +}
> +
> +// Hash lookup table as defined by Ken Perlin. This is a randomly
> +// arranged array of all numbers from 0-255 inclusive.
> +static uint8_t ken_permutations[] = {
> + 151, 160, 137, 91, 90, 15, 131, 13, 201, 95, 96, 53, 194, 233, 7, 225,
> + 140, 36, 103, 30, 69, 142, 8, 99, 37, 240, 21, 10, 23, 190, 6, 148,
> + 247, 120, 234, 75, 0, 26, 197, 62, 94, 252, 219, 203, 117, 35, 11, 32,
> + 57, 177, 33, 88, 237, 149, 56, 87, 174, 20, 125, 136, 171, 168, 68, 175,
> + 74, 165, 71, 134, 139, 48, 27, 166, 77, 146, 158, 231, 83, 111, 229, 122,
> + 60, 211, 133, 230, 220, 105, 92, 41, 55, 46, 245, 40, 244, 102, 143, 54,
> + 65, 25, 63, 161, 1, 216, 80, 73, 209, 76, 132, 187, 208, 89, 18, 169,
> + 200, 196, 135, 130, 116, 188, 159, 86, 164, 100, 109, 198, 173, 186, 3, 64,
> + 52, 217, 226, 250, 124, 123, 5, 202, 38, 147, 118, 126, 255, 82, 85, 212,
> + 207, 206, 59, 227, 47, 16, 58, 17, 182, 189, 28, 42, 223, 183, 170, 213,
> + 119, 248, 152, 2, 44, 154, 163, 70, 221, 153, 101, 155, 167, 43, 172, 9,
> + 129, 22, 39, 253, 19, 98, 108, 110, 79, 113, 224, 232, 178, 185, 112, 104,
> + 218, 246, 97, 228, 251, 34, 242, 193, 238, 210, 144, 12, 191, 179, 162, 241,
> + 81, 51, 145, 235, 249, 14, 239, 107, 49, 192, 214, 31, 181, 199, 106, 157,
> + 184, 84, 204, 176, 115, 121, 50, 45, 127, 4, 150, 254, 138, 236, 205, 93,
> + 222, 114, 67, 29, 24, 72, 243, 141, 128, 195, 78, 66, 215, 61, 156, 180
> +};
> +
> +int ff_perlin_init(FFPerlin *perlin, double period, int octaves, double persistence,
> + enum FFPerlinRandomMode random_mode, unsigned int random_seed)
> +{
> + int i;
> +
> + /* todo: perform validation? */
Should this line be removed?
> + perlin->period = period;
> + perlin->octaves = octaves;
> + perlin->persistence = persistence;
> + perlin->random_mode = random_mode;
> + perlin->random_seed = random_seed;
> +
> + if (perlin->random_mode == FF_PERLIN_RANDOM_MODE_KEN) {
> + for (i = 0; i < 512; i++) {
> + perlin->permutations[i] = ken_permutations[i % 256];
> + }
> + } else {
> + AVLFG lfg;
> + uint8_t random_permutations[256];
> +
> + if (perlin->random_mode == FF_PERLIN_RANDOM_MODE_RANDOM)
> + perlin->random_seed = av_get_random_seed();
> +
> + av_lfg_init(&lfg, perlin->random_seed);
> +
> + for (i = 0; i < 256; i++) {
> + random_permutations[i] = i;
> + }
> +
> + for (i = 0; i < 256; i++) {
> + unsigned int random_idx = av_lfg_get(&lfg) % (256-i);
> + uint8_t random_val = random_permutations[random_idx];
> + random_permutations[random_idx] = random_permutations[256-i];
> +
> + perlin->permutations[i] = perlin->permutations[i+256] = random_val;
> + }
> + }
> +
> + return 0;
> +}
> +
> +static double perlin_get(FFPerlin *perlin, double x, double y, double z)
> +{
> + int xi, yi, zi;
> + double xf, yf, zf;
> + double u, v, w;
> + const uint8_t *p = perlin->permutations;
> + double period = perlin->period;
> + int aaa, aba, aab, abb, baa, bba, bab, bbb;
> + double x1, x2, y1, y2;
> +
> + if (perlin->period > 0) {
> + // If we have any period on, change the coordinates to their "local" repetitions
> + x = fmod(x, perlin->period);
> + y = fmod(y, perlin->period);
> + z = fmod(z, perlin->period);
> + }
> +
> + // Calculate the "unit cube" that the point asked will be located in
> + // The left bound is ( |_x_|,|_y_|,|_z_| ) and the right bound is that
> + // plus 1. Next we calculate the location (from 0.0 to 1.0) in that cube.
> + xi = (int)x & 255;
> + yi = (int)y & 255;
> + zi = (int)z & 255;
> +
> + xf = x - (int)x;
> + yf = y - (int)y;
> + zf = z - (int)z;
> +
> + // We also fade the location to smooth the result.
> + u = fade(xf);
> + v = fade(yf);
> + w = fade(zf);
> +
> + aaa = p[p[p[ xi ] + yi ] + zi ];
> + aba = p[p[p[ xi ] + inc(yi, period)] + zi ];
> + aab = p[p[p[ xi ] + yi ] + inc(zi, period)];
> + abb = p[p[p[ xi ] + inc(yi, period)] + inc(zi, period)];
> + baa = p[p[p[inc(xi, period)] + yi ] + zi ];
> + bba = p[p[p[inc(xi, period)] + inc(yi, period)] + zi ];
> + bab = p[p[p[inc(xi, period)] + yi ] + inc(zi, period)];
> + bbb = p[p[p[inc(xi, period)] + inc(yi, period)] + inc(zi, period)];
> +
> + // The gradient function calculates the dot product between a pseudorandom
> + // gradient vector and the vector from the input coordinate to the 8
> + // surrounding points in its unit cube.
> + // This is all then lerped together as a sort of weighted average based on the faded (u,v,w)
> + // values we made earlier.
> + x1 = lerp(grad(aaa, xf , yf , zf),
> + grad(baa, xf-1, yf , zf),
> + u);
> + x2 = lerp(grad(aba, xf , yf-1, zf),
> + grad(bba, xf-1, yf-1, zf),
> + u);
> + y1 = lerp(x1, x2, v);
> +
> + x1 = lerp(grad(aab, xf , yf , zf-1),
> + grad(bab, xf-1, yf , zf-1),
> + u);
> + x2 = lerp(grad(abb, xf , yf-1, zf-1),
> + grad(bbb, xf-1, yf-1, zf-1),
> + u);
> + y2 = lerp(x1, x2, v);
> +
> + // For convenience we bound it to 0 - 1 (theoretical min/max before is -1 - 1)
> + return (lerp(y1, y2, w) + 1) / 2;
> +}
> +
> +double ff_perlin_get(FFPerlin *perlin, double x, double y, double z)
> +{
> + double total = 0;
> + double frequency = 1;
> + double amplitude = 1;
> + double max_value = 0; // Used for normalizing result to 0.0 - 1.0
> +
> + for (int i = 0; i < perlin->octaves; i++) {
> + total += perlin_get(perlin, x * frequency, y * frequency, z * frequency) * amplitude;
> + max_value += amplitude;
> + amplitude *= perlin->persistence;
> + frequency *= 2;
> + }
> +
> + return total / max_value;
> +}
> +
> diff --git a/libavfilter/perlin.h b/libavfilter/perlin.h
> new file mode 100644
> index 0000000000..1d2922a587
> --- /dev/null
> +++ b/libavfilter/perlin.h
> @@ -0,0 +1,101 @@
> +/*
> + * Perlin noise generator
> + *
> + * This file is part of FFmpeg.
> + *
> + * FFmpeg is free software; you can redistribute it and/or
> + * modify it under the terms of the GNU Lesser General Public
> + * License as published by the Free Software Foundation; either
> + * version 2.1 of the License, or (at your option) any later version.
> + *
> + * FFmpeg is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
> + * Lesser General Public License for more details.
> + *
> + * You should have received a copy of the GNU Lesser General Public
> + * License along with FFmpeg; if not, write to the Free Software
> + * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
> + */
> +
> +/**
> + * @file
> + * Perlin Noise generator
> + */
> +
> +#ifndef AVFILTER_PERLIN_H
> +#define AVFILTER_PERLIN_H
> +
> +#include <stdint.h>
> +
> +enum FFPerlinRandomMode {
> + FF_PERLIN_RANDOM_MODE_RANDOM,
> + FF_PERLIN_RANDOM_MODE_KEN,
> + FF_PERLIN_RANDOM_MODE_SEED,
> + FF_PERLIN_RANDOM_MODE_NB
> +};
> +
> +/**
> + * Perlin generator context. This needs to be initialized with the
> + * parameters used to generate the Perlin noise.
> + */
> +typedef struct FFPerlin {
> + /**
> + * spatial repeat period, if negative it is ignored
> + */
> + double period;
> +
> + /**
> + * total number of components making up the noise, each one with
> + * doubled frequency
> + */
> + int octaves;
> +
> + /**
> + * ratio used to compute the amplitude of the next octave
> + * component with respect to the previous component
> + */
> + double persistence;
> +
> + /**
> + * permutations array used to compute the Perlin noise hash
> + */
> + uint8_t permutations[512];
> +
> + /**
> + * define how to compute the permutations array
> + */
> + enum FFPerlinRandomMode random_mode;
> +
> + /**
> + * random seed used to compute the permutations array when random_mode is set to
> + * FF_PERLIN_RANDOM_MODE_RANDOM,
Nit: remove trailing comma
> + */
> + unsigned int random_seed;
> +} FFPerlin;
> +
> +/**
> + * Initialize the Perlin noise generator with parameters.
> + *
> + * @param perlin Perlin noise generator context
> + * @param period spatial repeat period, if negative it is ignored
> + * @param octaves total number of components making up the noise, each one with doubled frequency
> + * @param persistence define how to ratio used to compute the amplitude of the next
> + * octave component with respect to the previous component
I think "how to ratio used" should be "how the ratio is used"?
> + * @param random_mode define how to compute the permutations array
> + * @param random_seed random seed used to compute the permutations array when random_mode is set to
> + * FF_PERLIN_RANDOM_MODE_RANDOM,
Nit: trailing comma again
> + * @return a negative AVERROR code in case of error, a non negative value otherwise
> + */
> +int ff_perlin_init(FFPerlin *perlin, double period, int octaves, double persistence,
> + enum FFPerlinRandomMode random_mode, unsigned int random_seed);
> +
> +/**
> + * Compute Perlin noise for the 3D coordinates given the x, y, z coordinates.
Nit: "for the 3D coordinates" and "given the x, y, z coordinates" is redundant -
either is fine, but not both.
> + *
> + * @param perlin Perlin noise generator context
> + * @return normalized value for the perlin noise, in the range [0, 1]
> + */
> +double ff_perlin_get(FFPerlin *perlin, double x, double y, double z);
> +
> +#endif /* AVFILTER_PERLIN_H */
> diff --git a/libavfilter/vsrc_perlin.c b/libavfilter/vsrc_perlin.c
> new file mode 100644
> index 0000000000..27493a1b3b
> --- /dev/null
> +++ b/libavfilter/vsrc_perlin.c
> @@ -0,0 +1,169 @@
> +/*
> + * This file is part of FFmpeg.
> + *
> + * FFmpeg is free software; you can redistribute it and/or
> + * modify it under the terms of the GNU Lesser General Public
> + * License as published by the Free Software Foundation; either
> + * version 2.1 of the License, or (at your option) any later version.
> + *
> + * FFmpeg is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
> + * Lesser General Public License for more details.
> + *
> + * You should have received a copy of the GNU Lesser General Public
> + * License along with FFmpeg; if not, write to the Free Software
> + * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
> + */
> +
> +/**
> + * @file
> + * Perlin noise generator
> + */
> +
> +#include <float.h>
> +
> +#include "perlin.h"
> +#include "libavutil/lfg.h"
> +#include "libavutil/opt.h"
> +#include "avfilter.h"
> +#include "internal.h"
> +#include "formats.h"
> +#include "video.h"
> +
> +typedef struct PerlinContext {
> + const AVClass *class;
> +
> + int w, h;
> + AVRational frame_rate;
> +
> + FFPerlin perlin;
> + int octaves;
> + double persistence;
> + unsigned int random_seed;
> + enum FFPerlinRandomMode random_mode;
> +
> + double xscale, yscale, tscale;
> + uint64_t pts;
> +} PerlinContext;
> +
> +#define OFFSET(x) offsetof(PerlinContext, x)
> +#define FLAGS AV_OPT_FLAG_VIDEO_PARAM|AV_OPT_FLAG_FILTERING_PARAM
> +
> +static const AVOption perlin_options[] = {
> + { "size", "set video size", OFFSET(w), AV_OPT_TYPE_IMAGE_SIZE, {.str = "320x240"}, 0, 0, FLAGS },
> + { "s", "set video size", OFFSET(w), AV_OPT_TYPE_IMAGE_SIZE, {.str = "320x240"}, 0, 0, FLAGS },
> + { "rate", "set video rate", OFFSET(frame_rate), AV_OPT_TYPE_VIDEO_RATE, {.str = "25"}, 0, INT_MAX, FLAGS },
> + { "r", "set video rate", OFFSET(frame_rate), AV_OPT_TYPE_VIDEO_RATE, {.str = "25"}, 0, INT_MAX, FLAGS },
> + { "octaves", "set the number of components to use to generate the noise", OFFSET(octaves), AV_OPT_TYPE_INT, {.i64=1}, 1, INT_MAX, FLAGS },
> + { "persistence", "set the octaves persistence", OFFSET(persistence), AV_OPT_TYPE_DOUBLE, {.dbl=1}, 0.0, DBL_MAX, FLAGS },
> +
> + { "xscale", "set x-scale factor", OFFSET(xscale), AV_OPT_TYPE_DOUBLE, {.dbl=1}, 0.0, DBL_MAX, FLAGS },
> + { "yscale", "set y-scale factor", OFFSET(yscale), AV_OPT_TYPE_DOUBLE, {.dbl=1}, 0.0, DBL_MAX, FLAGS },
> + { "tscale", "set t-scale factor", OFFSET(tscale), AV_OPT_TYPE_DOUBLE, {.dbl=1}, 0.0, DBL_MAX, FLAGS },
> +
> + { "random_mode", "set random mode used to compute initial pattern", OFFSET(random_mode), AV_OPT_TYPE_INT, {.i64=FF_PERLIN_RANDOM_MODE_RANDOM}, 0, FF_PERLIN_RANDOM_MODE_NB-1, FLAGS, .unit = "random_mode" },
> + { "random", "compute and use random seed", 0, AV_OPT_TYPE_CONST, {.i64=FF_PERLIN_RANDOM_MODE_RANDOM}, 0, 0, FLAGS, .unit = "random_mode" },
> + { "ken", "use the predefined initial pattern defined by Ken Perlin in the original article", 0, AV_OPT_TYPE_CONST, {.i64=FF_PERLIN_RANDOM_MODE_KEN}, 0, 0, FLAGS, .unit = "random_mode" },
> + { "seed", "use the value specified by random_seed", 0, AV_OPT_TYPE_CONST, {.i64=FF_PERLIN_RANDOM_MODE_SEED}, 0, 0, FLAGS, .unit = "random_mode" },
> +
> + { "random_seed", "set the seed for filling the initial grid randomly", OFFSET(random_seed), AV_OPT_TYPE_UINT, {.i64=0}, 0, UINT_MAX, FLAGS },
> + { "seed", "set the seed for filling the initial grid randomly", OFFSET(random_seed), AV_OPT_TYPE_UINT, {.i64=0}, 0, UINT_MAX, FLAGS },
Nit: "set the seed for filling the initial grid randomly" is ambiguous.
Do you mean:
a) Set the seed for the RNG to a specified value (value is the seed number)
b) Pick a random number to fill the grid with (value is a boolean yes/no)
I settled on the former after several reads, but would appreciate clearer wording.
> + { NULL }
> +};
> +
> +AVFILTER_DEFINE_CLASS(perlin);
> +
> +static av_cold int init(AVFilterContext *ctx)
> +{
> + PerlinContext *perlin = ctx->priv;
> + int ret;
> +
> + if (ret = ff_perlin_init(&perlin->perlin, -1, perlin->octaves, perlin->persistence,
> + perlin->random_mode, perlin->random_seed)) {
> + return ret;
> + }
> +
> + av_log(ctx, AV_LOG_VERBOSE,
> + "s:%dx%d r:%d/%d octaves:%d persistence:%f xscale:%f yscale:%f tscale:%f\n",
> + perlin->w, perlin->h, perlin->frame_rate.num, perlin->frame_rate.den,
> + perlin->octaves, perlin->persistence,
> + perlin->xscale, perlin->yscale, perlin->tscale);
> + return 0;
> +}
> +
> +static int config_props(AVFilterLink *outlink)
> +{
> + PerlinContext *perlin = outlink->src->priv;
> +
> + outlink->w = perlin->w;
> + outlink->h = perlin->h;
> + outlink->time_base = av_inv_q(perlin->frame_rate);
> + outlink->frame_rate = perlin->frame_rate;
> +
> + return 0;
> +}
> +
> +static int request_frame(AVFilterLink *outlink)
> +{
> + AVFilterContext *ctx = outlink->src;
> + PerlinContext *perlin = ctx->priv;
> + AVFrame *picref = ff_get_video_buffer(outlink, perlin->w, perlin->h);
> + int i, j;
> + uint8_t *data0, *data;
> + double x, y, t;
> +
> + if (!picref)
> + return AVERROR(ENOMEM);
> +
> + picref->sample_aspect_ratio = (AVRational) {1, 1};
> + picref->pts = perlin->pts++;
> + picref->duration = 1;
> +
> + t = perlin->tscale * (perlin->pts * av_q2d(outlink->time_base));
> + data0 = picref->data[0];
> +
> + for (i = 0; i < perlin->h; i++) {
> + y = perlin->yscale * (double)i / perlin->h;
> +
> + data = data0;
> +
> + for (j = 0; j < perlin->w; j++) {
> + double res;
> + x = perlin->xscale * (double)j / perlin->w;
> + res = ff_perlin_get(&perlin->perlin, x, y, t);
> + av_log(ctx, AV_LOG_DEBUG, "x:%f y:%f t:%f => %f\n", x, y, t, res);
> + *data++ = res * 255;
> + }
> + data0 += picref->linesize[0];
> + }
> +
> + return ff_filter_frame(outlink, picref);
> +}
> +
> +static int query_formats(AVFilterContext *ctx)
> +{
> + enum AVPixelFormat pix_fmts[] = { AV_PIX_FMT_GRAY8, AV_PIX_FMT_NONE };
> +
> + return ff_set_common_formats_from_list(ctx, pix_fmts);
> +}
> +
> +static const AVFilterPad perlin_outputs[] = {
> + {
> + .name = "default",
> + .type = AVMEDIA_TYPE_VIDEO,
> + .request_frame = request_frame,
> + .config_props = config_props,
> + },
> +};
> +
> +const AVFilter ff_vsrc_perlin = {
> + .name = "perlin",
> + .description = NULL_IF_CONFIG_SMALL("Generate Perlin noise"),
> + .priv_size = sizeof(PerlinContext),
> + .priv_class = &perlin_class,
> + .init = init,
> + .inputs = NULL,
> + FILTER_OUTPUTS(perlin_outputs),
> + FILTER_QUERY_FUNC(query_formats),
> +};
> --
> 2.34.1
>
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