[FFmpeg-devel] [PATCH] avfilter: add normalize filter
Nicolas George
george at nsup.org
Thu Sep 14 11:58:17 EEST 2017
L'octidi 28 fructidor, an CCXXV, Richard Ling a écrit :
> This patch adds a filter to normalize (contrast stretch) RGB video.
> Comments welcome.
Thanks for the patch. Unfortunately, your mail software mangled it with
line breaks, it cannot be applied as is. Still, see a few comments
below.
>
> R.
>
> From f08f132ecd79718d0ce6fb07f99c84ab5dd52ee4 Mon Sep 17 00:00:00 2001
> From: Richard Ling <divetec at rling.com>
> Date: Thu, 14 Sep 2017 13:18:50 +1000
> Subject: [PATCH] avfilter: add normalize filter
>
> ---
> doc/filters.texi | 79 +++++++++
> libavfilter/Makefile | 1 +
> libavfilter/allfilters.c | 1 +
> libavfilter/vf_normalize.c | 415
> +++++++++++++++++++++++++++++++++++++++++++++
> 4 files changed, 496 insertions(+)
> create mode 100644 libavfilter/vf_normalize.c
>
> diff --git a/doc/filters.texi b/doc/filters.texi
> index 830de54..1e7712a 100644
> --- a/doc/filters.texi
> +++ b/doc/filters.texi
> @@ -10808,6 +10808,85 @@ Add temporal and uniform noise to input video:
> noise=alls=20:allf=t+u
> @end example
>
> + at section normalize
> +
> +Normalize RGB video (aka histogram stretching, contrast stretching).
> +See: https://en.wikipedia.org/wiki/Normalization_(image_processing)
> +
> +For each channel of each frame, the filter computes the input range and
> maps
> +it linearly to the user-specified output range. The output range defaults
> +to the full dynamic range from pure black to pure white.
> +
> +Temporal smoothing can be used on the input range to reduce flickering
> (rapid
> +changes in brightness) caused when small dark or bright objects enter or
> leave
> +the scene. This is similar to the auto-exposure (automatic gain control)
> on a
> +video camera, and, like a video camera, it may cause a period of over- or
> +under-exposure of the video.
> +
> +The R,G,B channels can be normalized independently, which may cause some
> +color shifting, or linked together as a single channel, which prevents
> +color shifting. Linked normalization preserves hue. Independent
> normalization
> +does not, so it can be used to remove some color casts. Independent and
> linked
> +normalization can be combined in any ratio.
> +
> +The normalize filter accepts the following options:
> +
> + at table @option
> + at item blackpt
> + at item whitept
> +Colors which define the output range. The minimum input value is mapped to
> +the @var{blackpt}. The maximum input value is mapped to the @var{whitept}.
> +The defaults are black and white respectively. Specifying white for
> + at var{blackpt} and black for @var{whitept} will give color-inverted,
> +normalized video. Shades of grey can be used to reduce the dynamic range
> +(contrast). Specifying saturated colors here can create some interesting
> +effects.
> +
> + at item smoothing
> +The amount of temporal smoothing, expressed in seconds. the input range of
> +each channel is smoothed using a rolling average over that many seconds of
> +video. Defaults to 0.0 (no temporal smoothing). The maximum is 60 seconds.
If I read the code correctly, the rolling average is asymmetrical:
the current frame is computed using the n previous frames rather than
the n/2 previous and n/2 next. Which, of course, is the best that can be
done without buffering that many frames.
But the documentation should probably specify it.
> +
> + at item independence
> +Controls the ratio of independent (color shifting) channel normalization to
> +linked (color preserving) normalization. 0.0 is fully linked, 1.0 is fully
> +independent. Defaults to fully independent.
> +
> + at item strength
> +Overall strength of the filter. 1.0 is full strength. 0.0 is a rather
> +expensive no-op.
> +
> + at end table
> +
> + at subsection Examples
> +
> +Stretch video contrast to use the full dynamic range, with no temporal
> +smoothing; may flicker depending on the source content:
> + at example
> +normalize=black:white:0
Better use named options in example. See the drama about that last
summer.
> + at end example
> +
> +As above, but with 2 seconds of temporal smoothing; flicker should be
> +reduced, depending on the source content:
> + at example
> +normalize=black:white:2
> + at end example
> +
> +As above, but with hue-preserving linked channel normalization:
> + at example
> +normalize=black:white:2:1
> + at end example
> +
> +As above, but with half strength:
> + at example
> +normalize=black:white:2:1:0.5
> + at end example
> +
> +Map the darkest input color to red, the brightest input color to cyan:
> + at example
> +normalize=red:cyan
> + at end example
> +
> @section null
>
> Pass the video source unchanged to the output.
> diff --git a/libavfilter/Makefile b/libavfilter/Makefile
> index 8aa974e..31f8170 100644
> --- a/libavfilter/Makefile
> +++ b/libavfilter/Makefile
> @@ -243,6 +243,7 @@ OBJS-$(CONFIG_NLMEANS_FILTER) +=
> vf_nlmeans.o
> OBJS-$(CONFIG_NNEDI_FILTER) += vf_nnedi.o
> OBJS-$(CONFIG_NOFORMAT_FILTER) += vf_format.o
> OBJS-$(CONFIG_NOISE_FILTER) += vf_noise.o
> +OBJS-$(CONFIG_NORMALIZE_FILTER) += vf_normalize.o
> OBJS-$(CONFIG_NULL_FILTER) += vf_null.o
> OBJS-$(CONFIG_OCR_FILTER) += vf_ocr.o
> OBJS-$(CONFIG_OCV_FILTER) += vf_libopencv.o
> diff --git a/libavfilter/allfilters.c b/libavfilter/allfilters.c
> index 63e8672..af2287b 100644
> --- a/libavfilter/allfilters.c
> +++ b/libavfilter/allfilters.c
> @@ -255,6 +255,7 @@ static void register_all(void)
> REGISTER_FILTER(NNEDI, nnedi, vf);
> REGISTER_FILTER(NOFORMAT, noformat, vf);
> REGISTER_FILTER(NOISE, noise, vf);
> + REGISTER_FILTER(NORMALIZE, normalize, vf);
> REGISTER_FILTER(NULL, null, vf);
> REGISTER_FILTER(OCR, ocr, vf);
> REGISTER_FILTER(OCV, ocv, vf);
> diff --git a/libavfilter/vf_normalize.c b/libavfilter/vf_normalize.c
> new file mode 100644
> index 0000000..101651e
> --- /dev/null
> +++ b/libavfilter/vf_normalize.c
> @@ -0,0 +1,415 @@
> +/*
> + * Copyright (c) 2017 Richard Ling
> + *
> + * 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
> + */
> +
> +/*
> + * Normalize RGB video (aka histogram stretching, contrast stretching).
> + * See: https://en.wikipedia.org/wiki/Normalization_(image_processing)
> + *
> + * For each channel of each frame, the filter computes the input range and
> maps
> + * it linearly to the user-specified output range. The output range
> defaults
> + * to the full dynamic range from pure black to pure white.
> + *
> + * Naively maximising the dynamic range of each frame of video in isolation
> + * may cause flickering (rapid changes in brightness of static objects in
> the
> + * scene) when small dark or bright objects enter or leave the scene. This
> + * filter can apply temporal smoothing to the input range to reduce
> flickering.
> + * Temporal smoothing is similar to the auto-exposure (automatic gain
> control)
> + * on a video camera, which performs the same function; and, like a video
> + * camera, it may cause a period of over- or under-exposure of the video.
> + *
> + * The filter can normalize the R,G,B channels independently, which may
> cause
> + * color shifting, or link them together as a single channel, which
> prevents
> + * color shifting. More precisely, linked normalization preserves hue (as
> it's
> + * defined in HSV/HSL color spaces) while independent normalization does
> not.
> + * Independent normalization can be used to remove color casts, such as the
> + * blue cast from underwater video, restoring more natural colors. The
> filter
> + * can also combine independent and linked normalization in any ratio.
> + *
> + * Finally the overall strength of the filter can be adjusted, from no
> effect
> + * to full normalization.
> + *
> + * The 5 AVOptions are:
> + * blackpt, Colors which define the output range. The minimum input
> value
> + * whitept is mapped to the blackpt. The maximum input value is
> mapped to
> + * the whitept. The defaults are black and white respectively.
> + * Specifying white for blackpt and black for whitept will
> give
> + * color-inverted, normalized video. Shades of grey can be
> used
> + * to reduce the dynamic range (contrast). Specifying
> saturated
> + * colors here can create some interesting effects.
> + *
> + * smoothing The amount of temporal smoothing, expressed in seconds
> (0-60).
> + * the minimum and maximum input values of each channel are
> + * smoothed using a rolling average over that many seconds of
> + * video. Defaults to 0.0 (no temporal smoothing).
> + *
> + * independence
> + * Controls the ratio of independent (color shifting) channel
> + * normalization to linked (color preserving) normalization.
> 0.0
> + * is fully linked, 1.0 is fully independent. Defaults to
> fully
> + * independent.
> + *
> + * strength Overall strength of the filter. 1.0 is full strength. 0.0
> is
> + * a rather expensive no-op. Values in between can give a
> gentle
> + * boost to low-contrast video without creating an artificial
> + * over-processed look. The default is full strength.
> + */
> +
> +#include "libavutil/imgutils.h"
> +#include "libavutil/opt.h"
> +#include "libavutil/pixdesc.h"
> +#include "avfilter.h"
> +#include "formats.h"
> +#include "internal.h"
> +#include "video.h"
> +
> +#ifndef MIN
> +#define MIN(x,y) ((x) < (y) ? (x) : (y))
> +#endif
> +#ifndef MAX
> +#define MAX(x,y) ((x) > (y) ? (x) : (y))
> +#endif
FFMIN(), FFMAX()
> +
> +#define MAX_HISTORY_LEN 0x10000
> +
> +typedef struct NormalizeContext {
> + const AVClass *class;
> +
> + // Storage for the corresponding AVOptions
> + uint8_t blackpt[4];
> + uint8_t whitept[4];
> + float smoothing;
> + float independence;
> + float strength;
> +
> + int co[4]; // Offsets to R,G,B,A bytes respectively in each
> pixel
> + int num_components; // Number of components in the pixel format
> + int history_len; // Number of frames to average; based on smoothing
> factor
> + int frame_num; // Increments on each frame, starting from 0.
> +
> + // Per-extremum, per-channel history, for temporal smoothing.
> + struct {
> + uint8_t *history; // History entries.
> + uint32_t history_sum; // Sum of history entries.
> + } min[3], max[3]; // Min and max for each channel in {R,G,B}.
> + uint8_t *history_mem; // Single allocation for above history
> entries
> +
> +} NormalizeContext;
> +
> +#define OFFSET(x) offsetof(NormalizeContext, x)
> +#define FLAGS AV_OPT_FLAG_VIDEO_PARAM|AV_OPT_FLAG_FILTERING_PARAM
> +
> +static const AVOption normalize_options[] = {
> + { "blackpt", "output color to which darkest input color is mapped",
> OFFSET(blackpt), AV_OPT_TYPE_COLOR, { .str = "black" }, CHAR_MIN, CHAR_MAX,
> FLAGS },
> + { "whitept", "output color to which brightest input color is
> mapped", OFFSET(whitept), AV_OPT_TYPE_COLOR, { .str = "white" }, CHAR_MIN,
> CHAR_MAX, FLAGS },
> + { "smoothing", "amount of temporal smoothing of the input range, to
> reduce flicker", OFFSET(smoothing), AV_OPT_TYPE_FLOAT, {.dbl=0.0}, 0.0,
> 60.0, FLAGS },
> + { "independence", "proportion of independent to linked channel
> normalization", OFFSET(independence), AV_OPT_TYPE_FLOAT, {.dbl=1.0}, 0.0,
> 1.0, FLAGS },
> + { "strength", "strength of filter, from no effect to full
> normalization", OFFSET(strength), AV_OPT_TYPE_FLOAT, {.dbl=1.0}, 0.0, 1.0,
> FLAGS },
> + { NULL }
> +};
> +
> +AVFILTER_DEFINE_CLASS(normalize);
> +
> +
> +// This function is the main guts of the filter. Normalizes the input frame
> +// into the output frame. The frames are known to have the same dimensions
> +// and pixel format.
> +static void normalize(NormalizeContext *s, AVFrame *in, AVFrame *out)
> +{
> + // Per-extremum, per-channel local variables.
> + struct {
> + uint8_t in; // Original input byte value for this frame.
> + float smoothed; // Smoothed input value [0,255].
> + float out; // Output value [0,255].
> + } min[3], max[3]; // Min and max for each channel in {R,G,B}.
> +
> + float rgb_min_smoothed; // Min input range for linked normalization
> + float rgb_max_smoothed; // Max input range for linked normalization
> + uint8_t lut[3][256]; // Lookup table
> + int x, y, c;
> +
> + // First, scan the input frame to find, for each channel, the minimum
> + // (min.in) and maximum (max.in) values present in the channel.
> +
> +#define INIT(c) (min[c].in = max[c].in = in->data[0][s->co[c]])
> +#define EXTEND(c) (min[c].in = MIN(min[c].in, inp[s->co[c]])), \
> + (max[c].in = MAX(max[c].in, inp[s->co[c]]))
> +
> + INIT(0);
> + INIT(1);
> + INIT(2);
I think a loop over c, same as below, would be better style.
> + for (y = 0; y < in->height; ++y) {
> + uint8_t *inp = in->data[0] + y * in->linesize[0];
> + uint8_t *outp = out->data[0] + y * out->linesize[0];
> + for (x = 0; x < in->width; ++x) {
> + EXTEND(0);
> + EXTEND(1);
> + EXTEND(2);
> + inp += s->num_components;
> + outp += s->num_components;
> + }
> + }
> +
> + // Next, for each channel, push min.in and max.in into their respective
> + // histories, to determine the min.smoothed and max.smoothed for this
> frame.
> + {
> + int history_idx = s->frame_num % s->history_len;
> + // Assume the history is not yet full; num_history_vals is the
> number
> + // of frames received so far including the current frame.
> + int num_history_vals = s->frame_num + 1;
> + if (s->frame_num >= s->history_len) {
> + //The history is full; drop oldest value and cap
> num_history_vals.
> + for (c = 0; c < 3; c++) {
> + s->min[c].history_sum -= s->min[c].history[history_idx];
> + s->max[c].history_sum -= s->max[c].history[history_idx];
> + }
> + num_history_vals = s->history_len;
> + }
> + // For each extremum, update history_sum and calculate smoothed
> value
> + // as the rolling average of the history entries.
> + for (c = 0; c < 3; c++) {
> + s->min[c].history_sum += (s->min[c].history[history_idx] =
> min[c].in);
> + min[c].smoothed = s->min[c].history_sum /
> (float)num_history_vals;
> + s->max[c].history_sum += (s->max[c].history[history_idx] =
> max[c].in);
> + max[c].smoothed = s->max[c].history_sum /
> (float)num_history_vals;
> + }
> + }
> +
> + // Determine the input range for linked normalization. This is simply
> the
> + // minimum of the per-channel minimums, and the maximum of the
> per-channel
> + // maximums.
> + rgb_min_smoothed = min[0].smoothed;
> + rgb_max_smoothed = max[0].smoothed;
> + rgb_min_smoothed = MIN(rgb_min_smoothed, min[1].smoothed);
> + rgb_max_smoothed = MAX(rgb_max_smoothed, max[1].smoothed);
> + rgb_min_smoothed = MIN(rgb_min_smoothed, min[2].smoothed);
> + rgb_max_smoothed = MAX(rgb_max_smoothed, max[2].smoothed);
> +
> + // Now, process each channel to determine the input and output range
> and
> + // build the lookup tables.
> + for (c = 0; c < 3; c++) {
> + int in_val;
> + // Adjust the input range for this channel
> [min.smoothed,max.smoothed]
> + // by mixing in the correct proportion of the linked normalization
> + // input range [rgb_min_smoothed,rgb_max_smoothed].
> + min[c].smoothed = (min[c].smoothed * s->independence)
> + + (rgb_min_smoothed * (1.0 - s->independence));
> + max[c].smoothed = (max[c].smoothed * s->independence)
> + + (rgb_max_smoothed * (1.0 - s->independence));
> +
> + // Calculate the output range [min.out,max.out] as a ratio of the
> full-
> + // strength output range [blackpt,whitept] and the original input
> range
> + // [min.in,max.in], based on the user-specified filter strength.
> + min[c].out = (s->blackpt[c] * s->strength)
> + + (min[c].in * (1.0 - s->strength));
> + max[c].out = (s->whitept[c] * s->strength)
> + + (max[c].in * (1.0 - s->strength));
> +
> + // Now, build a lookup table which linearly maps the adjusted
> input range
> + // [min.smoothed,max.smoothed] to the output range
> [min.out,max.out].
> + // Perform the linear interpolation for each x:
> + // lut[x] = (int)(float(x - min.smoothed) * scale + max.out +
> 0.5)
> + // where scale = (max.out - min.out) / (max.smoothed -
> min.smoothed)
> + if (min[c].smoothed == max[c].smoothed) {
> + // There is no dynamic range to expand. No mapping for this
> channel.
> + for (in_val = min[c].in; in_val <= max[c].in; in_val++)
> + lut[c][in_val] = min[c].out;
> + } else {
> + // We must set lookup values for all values in the original
> input
> + // range [min.in,max.in]. Since the original input range may be
> + // larger than [min.smoothed,max.smoothed], some output values
> may
> + // fall outside the [0,255] dynamic range. We need to clamp
> them.
> + float scale = (max[c].out - min[c].out) / (max[c].smoothed -
> min[c].smoothed);
> + for (in_val = min[c].in; in_val <= max[c].in; in_val++) {
> + int out_val = (in_val - min[c].smoothed) * scale +
> min[c].out + 0.5;
> + out_val = MAX(out_val, 0);
> + out_val = MIN(out_val, 255);
> + lut[c][in_val] = out_val;
> + }
> + }
> + }
> +
> + // Finally, process the pixels of the input frame using the lookup
> tables.
> + for (y = 0; y < in->height; ++y) {
> + uint8_t *inp = in->data[0] + y * in->linesize[0];
> + uint8_t *outp = out->data[0] + y * out->linesize[0];
> + for (x = 0; x < in->width; ++x) {
> + outp[s->co[0]] = lut[0][inp[s->co[0]]];
> + outp[s->co[1]] = lut[1][inp[s->co[1]]];
> + outp[s->co[2]] = lut[2][inp[s->co[2]]];
> + if (s->num_components == 4)
> + // Copy alpha as-is.
> + outp[s->co[3]] = inp[s->co[3]];
> + inp += s->num_components;
> + outp += s->num_components;
> + }
> + }
> +
> + s->frame_num++;
> +}
> +
> +// Now we define all the functions accessible from the ff_vf_normalize
> class,
> +// which is ffmpeg's interface to our filter. See doc/filter_design.txt
> and
> +// doc/writing_filters.txt for descriptions of what these interface
> functions
> +// are expected to do.
> +
> +// For future use...
> +static av_cold int init(AVFilterContext *ctx)
> +{
> + return 0;
> +}
It can be added when needed.
> +
> +// Set the pixel formats that our filter supports. We should be able to
> process
> +// any 8-bit RGB formats. 16-bit support might be useful one day.
> +static int query_formats(AVFilterContext *ctx)
> +{
> + static const enum AVPixelFormat pixel_fmts[] = {
> + AV_PIX_FMT_RGB24,
> + AV_PIX_FMT_BGR24,
> + AV_PIX_FMT_ARGB,
> + AV_PIX_FMT_RGBA,
> + AV_PIX_FMT_ABGR,
> + AV_PIX_FMT_BGRA,
> + AV_PIX_FMT_0RGB,
> + AV_PIX_FMT_RGB0,
> + AV_PIX_FMT_0BGR,
> + AV_PIX_FMT_BGR0,
> + AV_PIX_FMT_NONE
> + };
> + // According to filter_design.txt, using ff_set_common_formats() this
> way
> + // ensures the pixel formats of the input and output will be the same.
> That
> + // saves a bit of effort possibly needing to handle format conversions.
> + AVFilterFormats *formats = ff_make_format_list(pixel_fmts);
> + if (!formats)
> + return AVERROR(ENOMEM);
> + return ff_set_common_formats(ctx, formats);
> +}
> +
> +// At this point we know the pixel format used for both input and output.
> We
> +// can also access the frame rate of the input video and allocate some
> memory
> +// appropriately
> +static int config_input(AVFilterLink *inlink)
> +{
> + int c;
> + NormalizeContext *s = inlink->dst->priv;
> + // Store offsets to R,G,B,A bytes respectively in each pixel
> + const AVPixFmtDescriptor *desc = av_pix_fmt_desc_get(inlink->format);
> + for (c = 0; c < 4; ++c)
> + s->co[c] = desc->comp[c].offset;
> + s->num_components = desc->nb_components;
> + // Convert smoothing value (seconds) to history_len (a count of frames
> to
> + // average, must be at least 1).
> + s->history_len = (int)(s->smoothing / av_q2d(inlink->time_base)) + 1;
> + // In case the frame rate is unusually high, cap it to MAX_HISTORY_LEN
> + // to avoid allocating stupid amounts of memory.
According to the comments, you are mistaking time_base with the stream's
frame rate. They are not the same, and the streams are not guaranteed to
be constant frame rate anyway.
I think you should consider using an exponential moving average instead:
you can get rid of all the history code. Furthermore, exponential moving
average supports variable frame rate with just a bit of maths: set the
decay coefficient to exp(-dt/T); extra bonus: compute exp(-x) as
1/exp(x) using a short power series to approximate the exponential.
> + if (s->history_len > MAX_HISTORY_LEN) {
> + av_log(s, AV_LOG_WARNING, "history_len capped to %d from %d. "
> + "This could be due to unusually high frame rate.\n",
> + MAX_HISTORY_LEN, s->history_len);
> + s->history_len = MAX_HISTORY_LEN;
> + }
> + // Allocate the history buffers -- there are 6 -- one for each extrema.
> + s->history_mem = av_malloc(s->history_len * 6);
> + if (s->history_mem == NULL)
> + return AVERROR(ENOMEM);
> + for (c = 0; c < 3; c++) {
> + s->min[c].history = s->history_mem + (c*2) * s->history_len;
> + s->max[c].history = s->history_mem + (c*2+1) * s->history_len;
> + }
> + return 0;
> +}
> +
> +// Free any memory allocations here
> +static av_cold void uninit(AVFilterContext *ctx)
> +{
> + NormalizeContext *s = ctx->priv;
> + if (s->history_mem != NULL)
> + av_free(s->history_mem);
> +}
> +
> +// This function is pretty much standard from doc/writing_filters.txt. It
> +// tries to do in-place filtering where possible, only allocating a new
> output
> +// frame when absolutely necessary.
> +static int filter_frame(AVFilterLink *inlink, AVFrame *in)
> +{
> + AVFilterContext *ctx = inlink->dst;
> + AVFilterLink *outlink = ctx->outputs[0];
> + NormalizeContext *s = ctx->priv;
> +
> + AVFrame *out;
> + // Set 'direct' if we can modify the input frame in-place. Otherwise
> we
> + // need to retrieve a new frame from the output link.
> + int direct = av_frame_is_writable(in) && !ctx->is_disabled;
> + if (direct) {
> + 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);
> + }
> +
> + // Now we've got the input and output frames (which may be the same
> frame)
> + // perform the filtering with our custom function.
> + normalize(s, in, out);
> +
> + if (ctx->is_disabled) {
> + av_frame_free(&out);
> + return ff_filter_frame(outlink, in);
> + }
> +
> + if (!direct)
> + av_frame_free(&in);
> +
> + return ff_filter_frame(outlink, out);
> +}
> +
> +// The structures below are standard filter plumbing
> +
> +static const AVFilterPad inputs[] = {
> + {
> + .name = "default",
> + .type = AVMEDIA_TYPE_VIDEO,
> + .filter_frame = filter_frame,
> + .config_props = config_input,
> + },
> + { NULL }
> +};
> +
> +static const AVFilterPad outputs[] = {
> + {
> + .name = "default",
> + .type = AVMEDIA_TYPE_VIDEO,
> + },
> + { NULL }
> +};
> +
> +AVFilter ff_vf_normalize = {
> + .name = "normalize",
> + .description = NULL_IF_CONFIG_SMALL("Normalize RGB video."),
> + .priv_size = sizeof(NormalizeContext),
> + .priv_class = &normalize_class,
> + .init = init,
> + .uninit = uninit,
> + .query_formats = query_formats,
> + .inputs = inputs,
> + .outputs = outputs,
> +};
Regards,
--
Nicolas George
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