[FFmpeg-devel] [PATCH] lavfi: add lut3d filter.

Stefano Sabatini stefasab at gmail.com
Wed May 22 10:06:56 CEST 2013


On date Tuesday 2013-05-21 04:49:06 +0200, Clément Bœsch encoded:
> Fixes Ticket #2517.
> 
> TODO: minor bump
> ---
>  Changelog                |   1 +
>  doc/filters.texi         |  32 +++
>  libavfilter/Makefile     |   1 +
>  libavfilter/allfilters.c |   1 +
>  libavfilter/vf_lut3d.c   | 570 +++++++++++++++++++++++++++++++++++++++++++++++
>  5 files changed, 605 insertions(+)
>  create mode 100644 libavfilter/vf_lut3d.c
> 
> diff --git a/Changelog b/Changelog
> index 2ed6c87..91ab2e1 100644
> --- a/Changelog
> +++ b/Changelog
> @@ -52,6 +52,7 @@ version <next>:
>  - Escape 130 video decoder
>  - FTP protocol support
>  - V4L2 output device
> +- 3D LUT filter (lut3d)
>  
>  
>  version 1.2:
> diff --git a/doc/filters.texi b/doc/filters.texi
> index 301887d..325c0ba 100644
> --- a/doc/filters.texi
> +++ b/doc/filters.texi
> @@ -4595,6 +4595,38 @@ kerndeint=map=1
>  @end example
>  @end itemize
>  
> + at section lut3d
> +
> +Apply a 3D LUT to an input video.
> +
> +The filter accepts the following options:
> +
> + at table @option
> + at item file
> +Set the 3D LUT file name.
> +
> +Currently supported formats:

> + at itemize
> + at item 3dl
> + at item cube
> + at item dat
> + at item m3d
> + at end itemize

Adding some notes about these types may help (software used to create
them, reference, etc., so the user is not at the mercy of a search
engine).

Also I think having a tool for generating files in these formats
(e.g. using an ff expression) would be useful. Attaching a sample file
would also help to test it.

> + at item interp
> +Select interpolation mode.
> +
> +Available values are:
> +
> + at table @samp
> + at item nearest
> +Use values from the nearest defined point.
> + at item trilinear
> +Interpolate values using the 8 points defining a cube.
> + at item tetrahedral
> +Interpolate values using a tetrahedron.
> + at end table
> + at end table
> +
>  @section lut, lutrgb, lutyuv
>  
>  Compute a look-up table for binding each pixel component input value
> diff --git a/libavfilter/Makefile b/libavfilter/Makefile
> index d51af94..6cc2930 100644
> --- a/libavfilter/Makefile
> +++ b/libavfilter/Makefile
> @@ -145,6 +145,7 @@ OBJS-$(CONFIG_IL_FILTER)                     += vf_il.o
>  OBJS-$(CONFIG_INTERLACE_FILTER)              += vf_interlace.o
>  OBJS-$(CONFIG_INTERLEAVE_FILTER)             += f_interleave.o
>  OBJS-$(CONFIG_KERNDEINT_FILTER)              += vf_kerndeint.o
> +OBJS-$(CONFIG_LUT3D_FILTER)                  += vf_lut3d.o
>  OBJS-$(CONFIG_LUT_FILTER)                    += vf_lut.o
>  OBJS-$(CONFIG_LUTRGB_FILTER)                 += vf_lut.o
>  OBJS-$(CONFIG_LUTYUV_FILTER)                 += vf_lut.o
> diff --git a/libavfilter/allfilters.c b/libavfilter/allfilters.c
> index 07d7da0..0f2442d 100644
> --- a/libavfilter/allfilters.c
> +++ b/libavfilter/allfilters.c
> @@ -143,6 +143,7 @@ void avfilter_register_all(void)
>      REGISTER_FILTER(INTERLACE,      interlace,      vf);
>      REGISTER_FILTER(INTERLEAVE,     interleave,     vf);
>      REGISTER_FILTER(KERNDEINT,      kerndeint,      vf);
> +    REGISTER_FILTER(LUT3D,          lut3d,          vf);
>      REGISTER_FILTER(LUT,            lut,            vf);
>      REGISTER_FILTER(LUTRGB,         lutrgb,         vf);
>      REGISTER_FILTER(LUTYUV,         lutyuv,         vf);
> diff --git a/libavfilter/vf_lut3d.c b/libavfilter/vf_lut3d.c
> new file mode 100644
> index 0000000..d2cb84f
> --- /dev/null
> +++ b/libavfilter/vf_lut3d.c
> @@ -0,0 +1,570 @@
> +/*
> + * Copyright (c) 2013 Clément Bœsch
> + *
> + * 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
> + */
> +

> +/**
> + * @todo Hald CLUT?

missing @file notice.

"Hald CLUT" sounds like funny nonsense to me.

> + */
> +
> +#include "libavutil/opt.h"
> +#include "libavutil/file.h"
> +#include "libavutil/intreadwrite.h"
> +#include "libavutil/avassert.h"
> +#include "libavutil/pixdesc.h"
> +#include "libavutil/avstring.h"
> +#include "avfilter.h"
> +#include "drawutils.h"
> +#include "formats.h"
> +#include "internal.h"
> +#include "video.h"
> +
> +#define R 0
> +#define G 1
> +#define B 2
> +#define A 3
> +
> +enum interp_mode {
> +    INTERPOLATE_NEAREST,
> +    INTERPOLATE_TRILINEAR,
> +    INTERPOLATE_TETRAHEDRAL,
> +    NB_INTERP_MODE
> +};
> +
> +struct rgbvec {
> +    float r, g, b;
> +};
> +
> +#define MAX_LEVEL 36
> +
> +typedef struct LUT3DContext {
> +    const AVClass *class;
> +    enum interp_mode interpolation;
> +    char *file;
> +    uint8_t rgba_map[4];
> +    int step;
> +    int is16bit;
> +    struct rgbvec (*interp_8) (const struct LUT3DContext*, uint8_t,  uint8_t,  uint8_t);
> +    struct rgbvec (*interp_16)(const struct LUT3DContext*, uint16_t, uint16_t, uint16_t);
> +    struct rgbvec lut[MAX_LEVEL][MAX_LEVEL][MAX_LEVEL];
> +    int lutsize;
> +} LUT3DContext;
> +
> +#define OFFSET(x) offsetof(LUT3DContext, x)
> +#define FLAGS AV_OPT_FLAG_FILTERING_PARAM|AV_OPT_FLAG_VIDEO_PARAM
> +static const AVOption lut3d_options[] = {
> +    { "file",   "set 3D LUT file name", OFFSET(file), AV_OPT_TYPE_STRING, {.str=NULL}, .flags = FLAGS },
> +    { "interp", "select interpolation mode", OFFSET(interpolation), AV_OPT_TYPE_INT, {.i64=INTERPOLATE_TETRAHEDRAL}, 0, NB_INTERP_MODE-1, FLAGS, "interp_mode" },
> +        { "nearest",     "use values from the nearest defined points",            0, AV_OPT_TYPE_CONST, {.i64=INTERPOLATE_NEAREST},     INT_MIN, INT_MAX, FLAGS, "interp_mode" },
> +        { "trilinear",   "interpolate values using the 8 points defining a cube", 0, AV_OPT_TYPE_CONST, {.i64=INTERPOLATE_TRILINEAR},   INT_MIN, INT_MAX, FLAGS, "interp_mode" },
> +        { "tetrahedral", "interpolate values using a tetrahedron",                0, AV_OPT_TYPE_CONST, {.i64=INTERPOLATE_TETRAHEDRAL}, INT_MIN, INT_MAX, FLAGS, "interp_mode" },
> +    { NULL }
> +};
> +
> +AVFILTER_DEFINE_CLASS(lut3d);
> +
> +static inline float lerpf(float v0, float v1, float f)
> +{
> +    return v0 + (v1 - v0) * f;
> +}
> +
> +static inline struct rgbvec lerp(struct rgbvec v0, struct rgbvec v1, float f)
> +{
> +    struct rgbvec v = {
> +        lerpf(v0.r, v1.r, f), lerpf(v0.g, v1.g, f), lerpf(v0.b, v1.b, f)
> +    };
> +    return v;
> +}
> +
> +static inline struct rgbvec interp_nearest(const LUT3DContext *lut3d,
> +                                           const struct rgbvec *s)
> +{
> +#define NEAR(x) ((int)(s->x + .5))
> +    return lut3d->lut[NEAR(r)][NEAR(g)][NEAR(b)];
> +}
> +

> +#define PREV(x) ((int) s->x     )
> +#define NEXT(x) ((int)(s->x + 1))

I'm not fond of this kind of macros which assume the existence of a
variable, please make s a formal parameter and/or move the macro
within the function definition where it is used.

> +
> +static inline struct rgbvec interp_trilinear(const LUT3DContext *lut3d,

> +                                             const struct rgbvec *s)

"s" is a poor name

> +{
> +    const int prev[3] = {PREV(r), PREV(g), PREV(b)};
> +    const int next[3] = {NEXT(r), NEXT(g), NEXT(b)};
> +    const struct rgbvec d = {s->r - prev[0], s->g - prev[1], s->b - prev[2]};
> +    const struct rgbvec c000 = lut3d->lut[prev[0]][prev[1]][prev[2]];
> +    const struct rgbvec c001 = lut3d->lut[prev[0]][prev[1]][next[2]];
> +    const struct rgbvec c010 = lut3d->lut[prev[0]][next[1]][prev[2]];
> +    const struct rgbvec c011 = lut3d->lut[prev[0]][next[1]][next[2]];
> +    const struct rgbvec c100 = lut3d->lut[next[0]][prev[1]][prev[2]];
> +    const struct rgbvec c101 = lut3d->lut[next[0]][prev[1]][next[2]];
> +    const struct rgbvec c110 = lut3d->lut[next[0]][next[1]][prev[2]];
> +    const struct rgbvec c111 = lut3d->lut[next[0]][next[1]][next[2]];
> +    const struct rgbvec c00  = lerp(c000, c100, d.r);
> +    const struct rgbvec c10  = lerp(c010, c110, d.r);
> +    const struct rgbvec c01  = lerp(c001, c101, d.r);
> +    const struct rgbvec c11  = lerp(c011, c111, d.r);
> +    const struct rgbvec c0   = lerp(c00,  c10,  d.g);
> +    const struct rgbvec c1   = lerp(c01,  c11,  d.g);
> +    const struct rgbvec c    = lerp(c0,   c1,   d.b);
> +    return c;
> +}
> +

> +static inline struct rgbvec interp_tetrahedral(const LUT3DContext *lut3d,

> +                                               const struct rgbvec *s)

ditto

> +{
> +    const int prev[3] = {PREV(r), PREV(g), PREV(b)};
> +    const int next[3] = {NEXT(r), NEXT(g), NEXT(b)};
> +    const struct rgbvec d = {s->r - prev[0], s->g - prev[1], s->b - prev[2]};
> +    const struct rgbvec c000 = lut3d->lut[prev[0]][prev[1]][prev[2]];
> +    const struct rgbvec c001 = lut3d->lut[prev[0]][prev[1]][next[2]];
> +    const struct rgbvec c010 = lut3d->lut[prev[0]][next[1]][prev[2]];
> +    const struct rgbvec c011 = lut3d->lut[prev[0]][next[1]][next[2]];
> +    const struct rgbvec c100 = lut3d->lut[next[0]][prev[1]][prev[2]];
> +    const struct rgbvec c101 = lut3d->lut[next[0]][prev[1]][next[2]];
> +    const struct rgbvec c110 = lut3d->lut[next[0]][next[1]][prev[2]];
> +    const struct rgbvec c111 = lut3d->lut[next[0]][next[1]][next[2]];
> +    struct rgbvec c;
> +    if (d.r > d.g) {
> +        if (d.g > d.b) {
> +            c.r = (1-d.r) * c000.r + (d.r-d.g) * c100.r + (d.g-d.b) * c110.r + (d.b) * c111.r;
> +            c.g = (1-d.r) * c000.g + (d.r-d.g) * c100.g + (d.g-d.b) * c110.g + (d.b) * c111.g;
> +            c.b = (1-d.r) * c000.b + (d.r-d.g) * c100.b + (d.g-d.b) * c110.b + (d.b) * c111.b;
> +        } else if (d.r > d.b) {
> +            c.r = (1-d.r) * c000.r + (d.r-d.b) * c100.r + (d.b-d.g) * c101.r + (d.g) * c111.r;
> +            c.g = (1-d.r) * c000.g + (d.r-d.b) * c100.g + (d.b-d.g) * c101.g + (d.g) * c111.g;
> +            c.b = (1-d.r) * c000.b + (d.r-d.b) * c100.b + (d.b-d.g) * c101.b + (d.g) * c111.b;
> +        } else {
> +            c.r = (1-d.b) * c000.r + (d.b-d.r) * c001.r + (d.r-d.g) * c101.r + (d.g) * c111.r;
> +            c.g = (1-d.b) * c000.g + (d.b-d.r) * c001.g + (d.r-d.g) * c101.g + (d.g) * c111.g;
> +            c.b = (1-d.b) * c000.b + (d.b-d.r) * c001.b + (d.r-d.g) * c101.b + (d.g) * c111.b;
> +        }
> +    } else {
> +        if (d.b > d.g) {
> +            c.r = (1-d.b) * c000.r + (d.b-d.g) * c001.r + (d.g-d.r) * c011.r + (d.r) * c111.r;
> +            c.g = (1-d.b) * c000.g + (d.b-d.g) * c001.g + (d.g-d.r) * c011.g + (d.r) * c111.g;
> +            c.b = (1-d.b) * c000.b + (d.b-d.g) * c001.b + (d.g-d.r) * c011.b + (d.r) * c111.b;
> +        } else if (d.b > d.r) {
> +            c.r = (1-d.g) * c000.r + (d.g-d.b) * c010.r + (d.b-d.r) * c011.r + (d.r) * c111.r;
> +            c.g = (1-d.g) * c000.g + (d.g-d.b) * c010.g + (d.b-d.r) * c011.g + (d.r) * c111.g;
> +            c.b = (1-d.g) * c000.b + (d.g-d.b) * c010.b + (d.b-d.r) * c011.b + (d.r) * c111.b;
> +        } else {
> +            c.r = (1-d.g) * c000.r + (d.g-d.r) * c010.r + (d.r-d.b) * c110.r + (d.b) * c111.r;
> +            c.g = (1-d.g) * c000.g + (d.g-d.r) * c010.g + (d.r-d.b) * c110.g + (d.b) * c111.g;
> +            c.b = (1-d.g) * c000.b + (d.g-d.r) * c010.b + (d.r-d.b) * c110.b + (d.b) * c111.b;
> +        }
> +    }
> +    return c;
> +}

For non trivial math a reference to an article/book/resource where you
find the formulas is always good for the reader.

> +
> +#define DEFINE_INTERP_FUNC(name, nbits)                                     \
> +static struct rgbvec interp_##nbits##_##name(const LUT3DContext *lut3d,     \
> +                                             uint##nbits##_t r,             \
> +                                             uint##nbits##_t g,             \
> +                                             uint##nbits##_t b)             \
> +{                                                                           \
> +    const float scale = (1. / ((1<<nbits) - 1)) * (lut3d->lutsize - 1);     \
> +    const struct rgbvec s = {r * scale, g * scale, b * scale};              \
> +    return interp_##name(lut3d, &s);                                        \
> +}
> +
> +DEFINE_INTERP_FUNC(nearest,     8)
> +DEFINE_INTERP_FUNC(trilinear,   8)
> +DEFINE_INTERP_FUNC(tetrahedral, 8)
> +
> +DEFINE_INTERP_FUNC(nearest,     16)
> +DEFINE_INTERP_FUNC(trilinear,   16)
> +DEFINE_INTERP_FUNC(tetrahedral, 16)
> +

> +#define MAX_LINE_SIZE 512
> +
> +static int skip_line(const char *p)
> +{
> +    while (*p && av_isspace(*p))
> +        p++;
> +    return !*p || *p == '#';
> +}
> +
> +#define NEXT_LINE(loop_cond) do {                           \
> +    if (!fgets(line, sizeof(line), f)) {                    \
> +        av_log(ctx, AV_LOG_ERROR, "Unexpected EOF\n");      \
> +        return AVERROR_INVALIDDATA;                         \
> +    }                                                       \
> +} while (loop_cond)
> +
> +/* Basically r g and b float values on each line; seems to be generated by
> + * Davinci */
> +static int parse_dat(AVFilterContext *ctx, FILE *f)
> +{
> +    LUT3DContext *lut3d = ctx->priv;
> +    const int size = lut3d->lutsize;
> +    int i, j, k;
> +
> +    for (k = 0; k < size; k++) {
> +        for (j = 0; j < size; j++) {
> +            for (i = 0; i < size; i++) {
> +                char line[MAX_LINE_SIZE];
> +                struct rgbvec *vec = &lut3d->lut[k][j][i];
> +                NEXT_LINE(skip_line(line));
> +                sscanf(line, "%f %f %f", &vec->r, &vec->g, &vec->b);
> +            }
> +        }
> +    }
> +    return 0;
> +}
> +
> +/* Iridas format */
> +static int parse_cube(AVFilterContext *ctx, FILE *f)
> +{
> +    LUT3DContext *lut3d = ctx->priv;
> +    char line[MAX_LINE_SIZE];
> +    float min[3] = {0.0, 0.0, 0.0};
> +    float max[3] = {1.0, 1.0, 1.0};
> +
> +    while (fgets(line, sizeof(line), f)) {
> +        if (!strncmp(line, "LUT_3D_SIZE ", 12)) {
> +            int i, j, k;
> +            const int size = strtol(line + 12, NULL, 0);
> +
> +            if (size > MAX_LEVEL) {
> +                av_log(ctx, AV_LOG_ERROR, "Too large 3D LUT\n");
> +                return AVERROR(EINVAL);
> +            }
> +            lut3d->lutsize = size;
> +            for (k = 0; k < size; k++) {
> +                for (j = 0; j < size; j++) {
> +                    for (i = 0; i < size; i++) {
> +                        struct rgbvec *vec = &lut3d->lut[k][j][i];
> +
> +                        do {
> +                            NEXT_LINE(0);
> +                            if (!strncmp(line, "DOMAIN_", 7)) {
> +                                float *vals = NULL;
> +                                if      (!strncmp(line + 7, "MIN ", 4)) vals = min;
> +                                else if (!strncmp(line + 7, "MAX ", 4)) vals = max;
> +                                if (!vals)
> +                                    return AVERROR_INVALIDDATA;
> +                                sscanf(line + 11, "%f %f %f", vals, vals + 1, vals + 2);
> +                                av_log(ctx, AV_LOG_DEBUG, "min: %f %f %f | max: %f %f %f\n",
> +                                       min[0], min[1], min[2], max[0], max[1], max[2]);
> +                                continue;
> +                            }
> +                        } while (skip_line(line));
> +                        if (sscanf(line, "%f %f %f", &vec->r, &vec->g, &vec->b) != 3)
> +                            return AVERROR_INVALIDDATA;
> +                        vec->r *= max[0] - min[0];
> +                        vec->g *= max[1] - min[1];
> +                        vec->b *= max[2] - min[2];
> +                    }
> +                }
> +            }
> +            break;
> +        }
> +    }
> +    return 0;
> +}
> +
> +/* Assume 17x17x17 LUT with a 16-bit depth
> + * FIXME: it seems there are various 3dl formats */
> +static int parse_3dl(AVFilterContext *ctx, FILE *f)
> +{
> +    char line[MAX_LINE_SIZE];
> +    LUT3DContext *lut3d = ctx->priv;
> +    int i, j, k;
> +    const int size = 17;
> +    const float scale = 16*16*16;
> +
> +    lut3d->lutsize = size;
> +    if (!fgets(line, sizeof(line), f))
> +        return AVERROR_INVALIDDATA;
> +    for (k = 0; k < size; k++) {
> +        for (j = 0; j < size; j++) {
> +            for (i = 0; i < size; i++) {
> +                int r, g, b;
> +                struct rgbvec *vec = &lut3d->lut[k][j][i];
> +
> +                NEXT_LINE(skip_line(line));
> +                if (sscanf(line, "%d %d %d", &r, &g, &b) != 3)
> +                    return AVERROR_INVALIDDATA;
> +                vec->r = r / scale;
> +                vec->g = g / scale;
> +                vec->b = b / scale;
> +            }
> +        }
> +    }
> +    return 0;
> +}
> +
> +/* Pandora format */
> +static int parse_m3d(AVFilterContext *ctx, FILE *f)
> +{
> +    LUT3DContext *lut3d = ctx->priv;
> +    float scale;
> +    int i, j, k, size, in = -1, out = -1;
> +    char line[MAX_LINE_SIZE];
> +    uint8_t rgb_map[3] = {0, 1, 2};
> +
> +    while (fgets(line, sizeof(line), f)) {
> +        if      (!strncmp(line, "in",  2)) in  = strtol(line + 2, NULL, 0);
> +        else if (!strncmp(line, "out", 3)) out = strtol(line + 3, NULL, 0);
> +        else if (!strncmp(line, "values", 6)) {
> +            const char *p = line + 6;
> +#define SET_COLOR(id) do {                  \
> +    while (av_isspace(*p))                  \
> +        p++;                                \
> +    switch (*p) {                           \
> +    case 'r': rgb_map[id] = 0; break;       \
> +    case 'g': rgb_map[id] = 1; break;       \
> +    case 'b': rgb_map[id] = 2; break;       \
> +    }                                       \
> +    while (*p && !av_isspace(*p))           \
> +        p++;                                \
> +} while (0)
> +            SET_COLOR(0);
> +            SET_COLOR(1);
> +            SET_COLOR(2);
> +            break;
> +        }
> +    }
> +
> +    if (in == -1 || out == -1) {
> +        av_log(ctx, AV_LOG_ERROR, "in and out must be defined\n");
> +        return AVERROR_INVALIDDATA;
> +    }
> +    for (size = 1; size*size*size < in; size++);
> +    lut3d->lutsize = size;
> +    scale = 1. / (out - 1);
> +
> +    for (k = 0; k < size; k++) {
> +        for (j = 0; j < size; j++) {
> +            for (i = 0; i < size; i++) {
> +                struct rgbvec *vec = &lut3d->lut[k][j][i];
> +                float val[3];
> +
> +                NEXT_LINE(0);
> +                if (sscanf(line, "%f %f %f", val, val + 1, val + 2) != 3)
> +                    return AVERROR_INVALIDDATA;
> +                vec->r = val[rgb_map[0]] * scale;
> +                vec->g = val[rgb_map[1]] * scale;
> +                vec->b = val[rgb_map[2]] * scale;
> +            }
> +        }
> +    }
> +    return 0;
> +}
> +
> +static void set_identity_matrix(LUT3DContext *lut3d, int size)
> +{
> +    int i, j, k;
> +    const float c = 1. / (size - 1);
> +
> +    lut3d->lutsize = size;
> +    for (k = 0; k < size; k++) {
> +        for (j = 0; j < size; j++) {
> +            for (i = 0; i < size; i++) {
> +                struct rgbvec *vec = &lut3d->lut[k][j][i];
> +                vec->r = k * c;
> +                vec->g = j * c;
> +                vec->b = i * c;
> +            }
> +        }
> +    }
> +}
> +
> +static av_cold int init(AVFilterContext *ctx)
> +{
> +    int ret;
> +    FILE *f;
> +    const char *ext;
> +    LUT3DContext *lut3d = ctx->priv;
> +
> +    if (!lut3d->file) {
> +        set_identity_matrix(lut3d, 32);
> +        return 0;
> +    }
> +
> +    f = fopen(lut3d->file, "r");
> +    if (!f) {
> +        ret = AVERROR(errno);
> +        av_log(ctx, AV_LOG_ERROR, "%s: %s\n", lut3d->file, av_err2str(ret));
> +        return ret;
> +    }
> +
> +    ext = strrchr(lut3d->file, '.');
> +    if (!ext) {
> +        av_log(ctx, AV_LOG_ERROR, "Unable to guess the format from the extension\n");
> +        ret = AVERROR_INVALIDDATA;
> +        goto end;
> +    }
> +    ext++;
> +
> +    if (!av_strcasecmp(ext, "dat")) {
> +        lut3d->lutsize = 33;
> +        ret = parse_dat(ctx, f);
> +    } else if (!av_strcasecmp(ext, "3dl")) {
> +        ret = parse_3dl(ctx, f);
> +    } else if (!av_strcasecmp(ext, "cube")) {
> +        ret = parse_cube(ctx, f);
> +    } else if (!av_strcasecmp(ext, "m3d")) {
> +        ret = parse_m3d(ctx, f);
> +    } else {
> +        av_log(ctx, AV_LOG_ERROR, "Unrecognized '.%s' file type\n", ext);
> +        ret = AVERROR(EINVAL);
> +    }
> +
> +    if (!ret && !lut3d->lutsize) {
> +        av_log(ctx, AV_LOG_ERROR, "3D LUT is empty\n");
> +        ret = AVERROR_INVALIDDATA;
> +    }
> +
> +end:
> +    fclose(f);
> +    return ret;
> +}
> +
> +static int query_formats(AVFilterContext *ctx)
> +{
> +    static const enum AVPixelFormat pix_fmts[] = {
> +        AV_PIX_FMT_RGB24,  AV_PIX_FMT_BGR24,
> +        AV_PIX_FMT_RGBA,   AV_PIX_FMT_BGRA,
> +        AV_PIX_FMT_ARGB,   AV_PIX_FMT_ABGR,
> +        AV_PIX_FMT_0RGB,   AV_PIX_FMT_0BGR,
> +        AV_PIX_FMT_RGB0,   AV_PIX_FMT_BGR0,
> +        AV_PIX_FMT_RGB48,  AV_PIX_FMT_BGR48,
> +        AV_PIX_FMT_RGBA64, AV_PIX_FMT_BGRA64,
> +        AV_PIX_FMT_NONE
> +    };
> +    ff_set_common_formats(ctx, ff_make_format_list(pix_fmts));
> +    return 0;
> +}
> +
> +static int config_input(AVFilterLink *inlink)
> +{
> +    LUT3DContext *lut3d = inlink->dst->priv;
> +    const AVPixFmtDescriptor *desc = av_pix_fmt_desc_get(inlink->format);
> +
> +    switch (inlink->format) {
> +    case AV_PIX_FMT_RGB48:
> +    case AV_PIX_FMT_BGR48:
> +    case AV_PIX_FMT_RGBA64:
> +    case AV_PIX_FMT_BGRA64:
> +        lut3d->is16bit = 1;
> +    }
> +
> +    ff_fill_rgba_map(lut3d->rgba_map, inlink->format);
> +    lut3d->step = av_get_padded_bits_per_pixel(desc) >> (3 + lut3d->is16bit);
> +
> +#define SET_FUNC(name) do {                                     \
> +    if (lut3d->is16bit) lut3d->interp_16 = interp_16_##name;    \
> +    else                lut3d->interp_8  = interp_8_##name;     \
> +} while (0)
> +
> +    switch (lut3d->interpolation) {
> +    case INTERPOLATE_NEAREST:     SET_FUNC(nearest);        break;
> +    case INTERPOLATE_TRILINEAR:   SET_FUNC(trilinear);      break;
> +    case INTERPOLATE_TETRAHEDRAL: SET_FUNC(tetrahedral);    break;
> +    default:
> +        av_assert0(0);
> +    }
> +
> +    return 0;
> +}
> +
> +#define FILTER(nbits) do {                                                                          \
> +    uint8_t       *dstrow = out->data[0];                                                           \
> +    const uint8_t *srcrow = in ->data[0];                                                           \
> +                                                                                                    \
> +    for (y = 0; y < inlink->h; y++) {                                                               \
> +        uint##nbits##_t *dst = (uint##nbits##_t *)dstrow;                                           \
> +        const uint##nbits##_t *src = (const uint##nbits##_t *)srcrow;                               \
> +        for (x = 0; x < inlink->w * step; x += step) {                                              \
> +            struct rgbvec vec = lut3d->interp_##nbits(lut3d, src[x + r], src[x + g], src[x + b]);   \
> +            dst[x + r] = av_clip_uint##nbits(vec.r * (float)((1<<nbits) - 1));                      \
> +            dst[x + g] = av_clip_uint##nbits(vec.g * (float)((1<<nbits) - 1));                      \
> +            dst[x + b] = av_clip_uint##nbits(vec.b * (float)((1<<nbits) - 1));                      \
> +            if (!direct && step == 4)                                                               \
> +                dst[x + a] = src[x + a];                                                            \
> +        }                                                                                           \
> +        dstrow += out->linesize[0];                                                                 \
> +        srcrow += in ->linesize[0];                                                                 \
> +    }                                                                                               \
> +} while (0)
> +
> +static int filter_frame(AVFilterLink *inlink, AVFrame *in)
> +{
> +    int x, y, direct = 0;
> +    AVFilterContext *ctx = inlink->dst;
> +    LUT3DContext *lut3d = ctx->priv;
> +    AVFilterLink *outlink = inlink->dst->outputs[0];
> +    AVFrame *out;
> +    const int step = lut3d->step;
> +    const uint8_t r = lut3d->rgba_map[R];
> +    const uint8_t g = lut3d->rgba_map[G];
> +    const uint8_t b = lut3d->rgba_map[B];
> +    const uint8_t a = lut3d->rgba_map[A];
> +
> +    if (av_frame_is_writable(in)) {
> +        direct = 1;
> +        out = in;
> +    } else {
> +        out = ff_get_video_buffer(outlink, outlink->w, outlink->h);
> +        if (!out) {
> +            av_frame_free(&in);
> +            return AVERROR(ENOMEM);
> +        }
> +        av_frame_copy_props(out, in);
> +    }
> +
> +    if (lut3d->is16bit) FILTER(16);
> +    else                FILTER(8);
> +
> +    if (!direct)
> +        av_frame_free(&in);
> +
> +    return ff_filter_frame(outlink, out);
> +}

I can't spot apparent mistakes, very nice job.
-- 
FFmpeg = Fast Fast Minimal Proud Enlightened Gem


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