[FFmpeg-devel] [PATCH] avfilter: add signalstats filter
Dave Rice
dave at dericed.com
Sat Jun 7 17:23:47 CEST 2014
On Jun 4, 2014, at 4:36 AM, Stefano Sabatini <stefasab at gmail.com> wrote:
> On date Monday 2014-06-02 23:50:27 +0200, Clément Bœsch encoded:
>> Signed-off-by: Mark Heath <mjpeg0 at silicontrip.net>
>> Signed-off-by: Dave Rice <dericed at yahoo.com>
>> Signed-off-by: Clément Bœsch <u at pkh.me>
>> ---
>> TODO: bump lavfi minor
>> ---
>> Changelog | 1 +
>> doc/filters.texi | 168 +++++++++++++++
>> libavfilter/Makefile | 1 +
>> libavfilter/allfilters.c | 1 +
>> libavfilter/vf_signalstats.c | 479 +++++++++++++++++++++++++++++++++++++++++++
>> 5 files changed, 650 insertions(+)
>> create mode 100644 libavfilter/vf_signalstats.c
>>
>> diff --git a/Changelog b/Changelog
>> index 3d416c4..9c366ff 100644
>> --- a/Changelog
>> +++ b/Changelog
>> @@ -26,6 +26,7 @@ version <next>:
>> - native Opus decoder
>> - display matrix export and rotation api
>> - WebVTT encoder
>> +- signalstats filter
>>
>>
>> version 2.2:
>> diff --git a/doc/filters.texi b/doc/filters.texi
>> index e004c44..d30827a 100644
>> --- a/doc/filters.texi
>> +++ b/doc/filters.texi
>> @@ -7532,6 +7532,174 @@ Swap the second and third planes of the input:
>> ffmpeg -i INPUT -vf shuffleplanes=0:2:1:3 OUTPUT
>> @end example
>>
>> + at section signalstats
>> +Evaluate various visual metrics that assist in determining issues associated
>> +with the digitization of analog video media.
>> +
>> +By default the filter will log these metadata values:
>> +
>> + at table @option
>> + at item YMIN
>> +Display the minimal Y value contained within the input frame. Expressed in
>> +range of [0-255].
>> +
>> + at item YLOW
>> +Display the Y value at the 10% percentile within the input frame. Expressed in
>> +range of [0-255].
>> +
>> + at item YAVG
>> +Display the average Y value within the input frame. Expressed in range of
>> +[0-255].
>> +
>> + at item YHIGH
>> +Display the Y value at the 90% percentile within the input frame. Expressed in
>> +range of [0-255].
>> +
>> + at item YMAX
>> +Display the maximum Y value contained within the input frame. Expressed in
>> +range of [0-255].
>> +
>> + at item UMIN
>> +Display the minimal U value contained within the input frame. Expressed in
>> +range of [0-255].
>> +
>> + at item ULOW
>> +Display the U value at the 10% percentile within the input frame. Expressed in
>> +range of [0-255].
>> +
>> + at item UAVG
>> +Display the average U value within the input frame. Expressed in range of
>> +[0-255].
>> +
>> + at item UHIGH
>> +Display the U value at the 90% percentile within the input frame. Expressed in
>> +range of [0-255].
>> +
>> + at item UMAX
>> +Display the maximum U value contained within the input frame. Expressed in
>> +range of [0-255].
>> +
>> + at item VMIN
>> +Display the minimal V value contained within the input frame. Expressed in
>> +range of [0-255].
>> +
>> + at item VLOW
>> +Display the V value at the 10% percentile within the input frame. Expressed in
>> +range of [0-255].
>> +
>> + at item VAVG
>> +Display the average V value within the input frame. Expressed in range of
>> +[0-255].
>> +
>> + at item VHIGH
>> +Display the V value at the 90% percentile within the input frame. Expressed in
>> +range of [0-255].
>> +
>> + at item VMAX
>> +Display the maximum V value contained within the input frame. Expressed in
>> +range of [0-255].
>> +
>> + at item SATMIN
>> +Display the minimal saturation value contained within the input frame.
>> +Expressed in range of [0-~181.02].
>> +
>> + at item SATLOW
>> +Display the saturation value at the 10% percentile within the input frame.
>> +Expressed in range of [0-~181.02].
>> +
>> + at item SATAVG
>> +Display the average saturation value within the input frame. Expressed in range
>> +of [0-~181.02].
>> +
>> + at item SATHIGH
>> +Display the saturation value at the 90% percentile within the input frame.
>> +Expressed in range of [0-~181.02].
>> +
>> + at item SATMAX
>> +Display the maximum saturation value contained within the input frame.
>> +Expressed in range of [0-~181.02].
>> +
>> + at item HUEMED
>> +Display the median value for hue within the input frame. Expressed in range of
>> +[0-360].
>> +
>> + at item HUEAVG
>> +Display the average value for hue within the input frame. Expressed in range of
>> +[0-360].
>> +
>
>> + at item YDIF
>> +Display a quantification of the visual change on the Y plane between the input
>> +frame and the previous input frame.
>> +
>> + at item UDIF
>> +Display a quantification of the visual change on the U plane between the input
>> +frame and the previous input frame.
>> +
>> + at item VDIF
>> +Display a quantification of the visual change on the V plane between the input
>> +frame and the previous input frame.
>> + at end table
>
> "a quantification" is a bit vague.
Reworded for clarity here: http://github.com/bavc/FFmpeg/commits/signalstats
>> +
>> +The filter accepts the following options:
>> +
>
>> + at table @option
>> + at item stat
>> +Specify an additional form of image analysis. It accepts the following values:
>> +
>
> Compression nit:
>
> @item stat
> @item out
>
> @option{stat} specify an additional form of image analysis.
> @option{out} output video with the specified type of pixel highlighted.
>
> Both options accept the following values:
Thanks, updated.
>> + at table @samp
>> + at item tout
>> +Identify @var{temporal outliers} pixels. A @var{temporal outlier} is a pixel
>> +unlike the neighboring pixels of the same field. Examples of temporal outliers
>> +include the results of video dropouts, head clogs, or tape tracking issues.
>> +
>> + at item vrep
>> +Identify @var{vertical line repetition}. Vertical line repetition includes
>> +similar rows of pixels within a frame. In born-digital video vertical line
>> +repetition is common, but this pattern is uncommon in video digitized from an
>> +analog source. When it occurs in video that results from the digitization of an
>> +analog source it can indicate concealment from a dropout compensator.
>> +
>> + at item brng
>> +Identify pixels that fall outside of legal broadcast range.
>> + at end table
>> +
>> + at item out
>> +Output video with the specified type of pixel highlighted. It accepts the
>> +following values:
>> +
>> + at table @samp
>> + at item tout
>> + at item vrep
>> + at item brng
>> + at end table
>> +
>
>> + at item color, c
>> +Set the highlight color for the @option{out} option. The default color is
>> +yellow.
>> + at end table
>> +
>> + at subsection Examples
>> +
>> + at itemize
>> + at item
>> +Output data of various video metrics:
>
>> + at example
>> +ffprobe -f lavfi movie=example.mov,signalstats="stat=tout+vrep+rang" -show_frames
>
> what is "rang"?
Typo. Fixed.
>> + at end example
>> +
>> + at item
>> +Output specific data about the minimum and maximum values of the Y plane per frame:
>> + at example
>> +ffprobe -f lavfi movie=example.mov,signalstats -show_entries frame_tags=lavfi.values.YMAX,lavfi.values.YMIN
>
> Do we have a namespace resolution scheme? What about lavfi.signalstats.VAL?
Typo (earlier version of the filter was called 'values'). Corrected to lavfi.signalstats.VAL.
>> + at end example
>> +
>> + at item
>> +Playback video while highlighting pixels that are outside of broadcast range in red.
>> + at example
>> +ffplay example.mov -vf values="out=brng:color=red"
>> + at end example
>> + at end itemize
>> +
>> @anchor{smartblur}
>> @section smartblur
>>
>> diff --git a/libavfilter/Makefile b/libavfilter/Makefile
>> index f981dfa..142c06e 100644
>> --- a/libavfilter/Makefile
>> +++ b/libavfilter/Makefile
>> @@ -174,6 +174,7 @@ OBJS-$(CONFIG_SETSAR_FILTER) += vf_aspect.o
>> OBJS-$(CONFIG_SETTB_FILTER) += settb.o
>> OBJS-$(CONFIG_SHOWINFO_FILTER) += vf_showinfo.o
>> OBJS-$(CONFIG_SHUFFLEPLANES_FILTER) += vf_shuffleplanes.o
>> +OBJS-$(CONFIG_SIGNALSTATS_FILTER) += vf_signalstats.o
>> OBJS-$(CONFIG_SMARTBLUR_FILTER) += vf_smartblur.o
>> OBJS-$(CONFIG_SPLIT_FILTER) += split.o
>> OBJS-$(CONFIG_SPP_FILTER) += vf_spp.o
>> diff --git a/libavfilter/allfilters.c b/libavfilter/allfilters.c
>> index 22d643d..4b9db9e 100644
>> --- a/libavfilter/allfilters.c
>> +++ b/libavfilter/allfilters.c
>> @@ -191,6 +191,7 @@ void avfilter_register_all(void)
>> REGISTER_FILTER(SETTB, settb, vf);
>> REGISTER_FILTER(SHOWINFO, showinfo, vf);
>> REGISTER_FILTER(SHUFFLEPLANES, shuffleplanes, vf);
>> + REGISTER_FILTER(SIGNALSTATS, signalstats, vf);
>> REGISTER_FILTER(SMARTBLUR, smartblur, vf);
>> REGISTER_FILTER(SPLIT, split, vf);
>> REGISTER_FILTER(SPP, spp, vf);
>> diff --git a/libavfilter/vf_signalstats.c b/libavfilter/vf_signalstats.c
>> new file mode 100644
>> index 0000000..e06bfe1
>> --- /dev/null
>> +++ b/libavfilter/vf_signalstats.c
>> @@ -0,0 +1,479 @@
>> +/*
>> + * Copyright (c) 2010 Mark Heath mjpeg0 @ silicontrip dot org
>> + * Copyright (c) 2014 Clément Bœsch
>> + * Copyright (c) 2014 Dave Rice @dericed
>> + *
>> + * 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
>> + */
>> +
>> +#include "libavutil/opt.h"
>> +#include "libavutil/pixdesc.h"
>> +#include "libavcodec/mathops.h"
>> +#include "internal.h"
>> +
>> +enum FilterMode {
>> + FILTER_NONE = -1,
>> + FILTER_TOUT,
>> + FILTER_VREP,
>> + FILTER_BRNG,
>> + FILT_NUMB
>> +};
>> +
>> +typedef struct {
>> + const AVClass *class;
>> + int chromah;
>> + int chromaw;
>> + int hsub;
>> + int vsub;
>
>> + int fs;
>> + int cfs;
>
> nit: add comments
Added.
>> + enum FilterMode outfilter;
>> + int filters;
>> + AVFrame *frame_prev;
>> + char *vrep_line;
>> + uint8_t rgba_color[4];
>> + int yuv_color[3];
>> +} SignalstatsContext;
>> +
>> +#define OFFSET(x) offsetof(SignalstatsContext, x)
>> +#define FLAGS AV_OPT_FLAG_FILTERING_PARAM|AV_OPT_FLAG_VIDEO_PARAM
>> +
>> +static const AVOption signalstats_options[] = {
>> + {"stat", "set statistics filters", OFFSET(filters), AV_OPT_TYPE_FLAGS, {.i64=0}, 0, INT_MAX, FLAGS, "filters"},
>> + {"tout", "analyze pixels for temporal outliers", 0, AV_OPT_TYPE_CONST, {.i64=1<<FILTER_TOUT}, 0, 0, FLAGS, "filters"},
>> + {"vrep", "analyze video lines for vertical line repitition", 0, AV_OPT_TYPE_CONST, {.i64=1<<FILTER_VREP}, 0, 0, FLAGS, "filters"},
>> + {"brng", "analyze for pixels outside of broadcast range", 0, AV_OPT_TYPE_CONST, {.i64=1<<FILTER_BRNG}, 0, 0, FLAGS, "filters"},
>> + {"out", "set video filter", OFFSET(outfilter), AV_OPT_TYPE_INT, {.i64=FILTER_NONE}, -1, FILT_NUMB-1, FLAGS, "out"},
>> + {"tout", "highlight pixels that depict temporal outliers", 0, AV_OPT_TYPE_CONST, {.i64=FILTER_TOUT}, 0, 0, FLAGS, "out"},
>> + {"vrep", "highlight video lines that depict vertical line repitition", 0, AV_OPT_TYPE_CONST, {.i64=FILTER_VREP}, 0, 0, FLAGS, "out"},
>> + {"brng", "highlight pixels that are outside of broadcast range", 0, AV_OPT_TYPE_CONST, {.i64=FILTER_BRNG}, 0, 0, FLAGS, "out"},
>> + {"c", "set highlight color", OFFSET(rgba_color), AV_OPT_TYPE_COLOR, {.str="yellow"}, .flags=FLAGS},
>> + {"color", "set highlight color", OFFSET(rgba_color), AV_OPT_TYPE_COLOR, {.str="yellow"}, .flags=FLAGS},
>> + {NULL}
>> +};
>> +
>> +AVFILTER_DEFINE_CLASS(signalstats);
>> +
>> +static av_cold int init(AVFilterContext *ctx)
>> +{
>> + uint8_t r, g, b;
>> + SignalstatsContext *s = ctx->priv;
>> +
>> + if (s->outfilter != FILTER_NONE)
>> + s->filters |= 1 << s->outfilter;
>> +
>> + r = s->rgba_color[0];
>> + g = s->rgba_color[1];
>> + b = s->rgba_color[2];
>
>> + s->yuv_color[0] = (( 66*r + 129*g + 25*b + (1<<7)) >> 8) + 16;
>> + s->yuv_color[1] = ((-38*r + -74*g + 112*b + (1<<7)) >> 8) + 128;
>> + s->yuv_color[2] = ((112*r + -94*g + -18*b + (1<<7)) >> 8) + 128;
>
> Unrelated note: having an API for this transform would be useful in
> several places.
>
>> + return 0;
>> +}
>> +
>> +static av_cold void uninit(AVFilterContext *ctx)
>> +{
>> + SignalstatsContext *s = ctx->priv;
>> + av_frame_free(&s->frame_prev);
>> + av_freep(&s->vrep_line);
>> +}
>> +
>> +static int query_formats(AVFilterContext *ctx)
>> +{
>> + // TODO: add more
>> + enum AVPixelFormat pix_fmts[] = {
>> + AV_PIX_FMT_YUV444P, AV_PIX_FMT_YUV422P, AV_PIX_FMT_YUV420P, AV_PIX_FMT_YUV411P,
>> + AV_PIX_FMT_NONE
>> + };
>> +
>> + ff_set_common_formats(ctx, ff_make_format_list(pix_fmts));
>> + return 0;
>> +}
>> +
>> +static int config_props(AVFilterLink *outlink)
>> +{
>> + AVFilterContext *ctx = outlink->src;
>> + SignalstatsContext *s = ctx->priv;
>> + AVFilterLink *inlink = outlink->src->inputs[0];
>> + const AVPixFmtDescriptor *desc = av_pix_fmt_desc_get(outlink->format);
>> + s->hsub = desc->log2_chroma_w;
>> + s->vsub = desc->log2_chroma_h;
>> +
>> + outlink->w = inlink->w;
>> + outlink->h = inlink->h;
>> +
>> + s->chromaw = FF_CEIL_RSHIFT(inlink->w, s->hsub);
>> + s->chromah = FF_CEIL_RSHIFT(inlink->h, s->vsub);
>> +
>> + s->fs = inlink->w * inlink->h;
>> + s->cfs = s->chromaw * s->chromah;
>> +
>> + if (s->filters & 1<<FILTER_VREP) {
>> + s->vrep_line = av_malloc(inlink->h * sizeof(*s->vrep_line));
>> + if (!s->vrep_line)
>> + return AVERROR(ENOMEM);
>> + }
>> +
>> + return 0;
>> +}
>> +
>> +static void burn_frame(SignalstatsContext *s, AVFrame *f, int x, int y)
>> +{
>> + const int chromax = x >> s->hsub;
>> + const int chromay = y >> s->vsub;
>> + f->data[0][y * f->linesize[0] + x] = s->yuv_color[0];
>> + f->data[1][chromay * f->linesize[1] + chromax] = s->yuv_color[1];
>> + f->data[2][chromay * f->linesize[2] + chromax] = s->yuv_color[2];
>> +}
>> +
>> +static int filter_brng(SignalstatsContext *s, const AVFrame *in, AVFrame *out, int y, int w, int h)
>> +{
>> + int x, score = 0;
>> + const int yc = y >> s->vsub;
>> + const uint8_t *pluma = &in->data[0][y * in->linesize[0]];
>> + const uint8_t *pchromau = &in->data[1][yc * in->linesize[1]];
>> + const uint8_t *pchromav = &in->data[2][yc * in->linesize[2]];
>> +
>> + for (x = 0; x < w; x++) {
>> + const int xc = x >> s->hsub;
>> + const int luma = pluma[x];
>> + const int chromau = pchromau[xc];
>> + const int chromav = pchromav[xc];
>> + const int filt = luma < 16 || luma > 235 ||
>> + chromau < 16 || chromau > 240 ||
>> + chromav < 16 || chromav > 240;
>> + score += filt;
>> + if (out && filt)
>> + burn_frame(s, out, x, y);
>> + }
>> + return score;
>> +}
>> +
>> +static int filter_tout_outlier(uint8_t x, uint8_t y, uint8_t z)
>> +{
>> + return ((abs(x - y) + abs (z - y)) / 2) - abs(z - x) > 4; // make 4 configurable?
>> +}
>> +
>> +static int filter_tout(SignalstatsContext *s, const AVFrame *in, AVFrame *out, int y, int w, int h)
>> +{
>> + const uint8_t *p = in->data[0];
>> + int lw = in->linesize[0];
>> + int x, score = 0, filt;
>> +
>> + if (y - 1 < 0 || y + 1 >= h)
>> + return 0;
>> +
>> + // detect two pixels above and below (to eliminate interlace artefacts)
>
>> + // should check that video format is infact interlace.
>
> typo: interlaced?
Fixed.
>> +#define FILTER(i, j) \
>> +filter_tout_outlier(p[(y-j) * lw + x + i], \
>> + p[ y * lw + x + i], \
>> + p[(y+j) * lw + x + i])
>> +
>> +#define FILTER3(j) (FILTER(-1, j) && FILTER(0, j) && FILTER(1, j))
>> +
>> + if (y - 2 >= 0 && y + 2 < h) {
>> + for (x = 1; x < w - 1; x++) {
>> + filt = FILTER3(2) && FILTER3(1);
>> + score += filt;
>> + if (filt && out)
>> + burn_frame(s, out, x, y);
>> + }
>> + } else {
>> + for (x = 1; x < w - 1; x++) {
>> + filt = FILTER3(1);
>> + score += filt;
>> + if (filt && out)
>> + burn_frame(s, out, x, y);
>> + }
>> + }
>> + return score;
>> +}
>> +
>> +#define VREP_START 4
>> +
>> +static void filter_init_vrep(SignalstatsContext *s, const AVFrame *p, int w, int h)
>> +{
>> + int i, y;
>> + int lw = p->linesize[0];
>> +
>> + for (y = VREP_START; y < h; y++) {
>> + int totdiff = 0;
>> + int y2lw = (y - VREP_START) * lw;
>> + int ylw = y * lw;
>> +
>> + for (i = 0; i < w; i++)
>> + totdiff += abs(p->data[0][y2lw + i] - p->data[0][ylw + i]);
>> +
>> + /* this value should be definable */
>> + s->vrep_line[y] = totdiff < w;
>> + }
>> +}
>> +
>> +static int filter_vrep(SignalstatsContext *s, const AVFrame *in, AVFrame *out, int y, int w, int h)
>> +{
>> + int x, score = 0;
>> +
>> + if (y < VREP_START)
>> + return 0;
>> +
>> + for (x = 0; x < w; x++) {
>> + if (s->vrep_line[y]) {
>> + score++;
>> + if (out)
>> + burn_frame(s, out, x, y);
>> + }
>> + }
>> + return score;
>> +}
>> +
>> +static const struct {
>> + const char *name;
>> + void (*init)(SignalstatsContext *s, const AVFrame *p, int w, int h);
>> + int (*process)(SignalstatsContext *s, const AVFrame *in, AVFrame *out, int y, int w, int h);
>> +} filters_def[] = {
>> + {"TOUT", NULL, filter_tout},
>> + {"VREP", filter_init_vrep, filter_vrep},
>> + {"BRNG", NULL, filter_brng},
>> + {NULL}
>> +};
>> +
>> +#define DEPTH 256
>> +
>> +static int filter_frame(AVFilterLink *link, AVFrame *in)
>> +{
>> + SignalstatsContext *s = link->dst->priv;
>> + AVFilterLink *outlink = link->dst->outputs[0];
>> + AVFrame *out = in;
>> + int i, j;
>> + int w = 0, cw = 0, // in
>> + pw = 0, cpw = 0; // prev
>> + int yuv, yuvu, yuvv;
>> + int fil;
>> + char metabuf[128];
>> + unsigned int histy[DEPTH] = {0},
>> + histu[DEPTH] = {0},
>> + histv[DEPTH] = {0},
>> + histhue[360] = {0},
>> + histsat[DEPTH] = {0}; // limited to 8 bit data.
>> + int miny = -1, minu = -1, minv = -1;
>> + int maxy = -1, maxu = -1, maxv = -1;
>> + int lowy = -1, lowu = -1, lowv = -1;
>> + int highy = -1, highu = -1, highv = -1;
>> + int minsat = -1, maxsat = -1, lowsat = -1, highsat = -1;
>> + int lowp, highp, clowp, chighp;
>> + int accy, accu, accv;
>
>> + int accsat, acchue=0;
>
> nit+++: acchue = 0;
Fixed.
>> + int medhue, maxhue;
>> + int toty = 0, totu = 0, totv = 0, totsat=0;
>> + int tothue = 0;
>> + int dify = 0, difu = 0, difv = 0;
>> +
>> + int filtot[FILT_NUMB] = {0};
>> + AVFrame *prev;
>> +
>> + if (!s->frame_prev)
>> + s->frame_prev = av_frame_clone(in);
>> +
>> + prev = s->frame_prev;
>> +
>> + if (s->outfilter != FILTER_NONE)
>> + out = av_frame_clone(in);
>> +
>> + for (fil = 0; fil < FILT_NUMB; fil ++)
>> + if ((s->filters & 1<<fil) && filters_def[fil].init)
>> + filters_def[fil].init(s, in, link->w, link->h);
>> +
>> + // Calculate luma histogram and difference with previous frame or field.
>> + for (j = 0; j < link->h; j++) {
>> + for (i = 0; i < link->w; i++) {
>> + yuv = in->data[0][w + i];
>> + histy[yuv]++;
>> + dify += abs(in->data[0][w + i] - prev->data[0][pw + i]);
>> + }
>> + w += in->linesize[0];
>> + pw += prev->linesize[0];
>> + }
>> +
>> + // Calculate chroma histogram and difference with previous frame or field.
>> + for (j = 0; j < s->chromah; j++) {
>> + for (i = 0; i < s->chromaw; i++) {
>> + int sat, hue;
>> +
>> + yuvu = in->data[1][cw+i];
>> + yuvv = in->data[2][cw+i];
>> + histu[yuvu]++;
>> + difu += abs(in->data[1][cw+i] - prev->data[1][cpw+i]);
>> + histv[yuvv]++;
>> + difv += abs(in->data[2][cw+i] - prev->data[2][cpw+i]);
>> +
>> + // int or round?
>> + sat = ff_sqrt((yuvu-128) * (yuvu-128) + (yuvv-128) * (yuvv-128));
>> + histsat[sat]++;
>> + hue = floor((180 / M_PI) * atan2f(yuvu-128, yuvv-128) + 180);
>> + histhue[hue]++;
>> + }
>> + cw += in->linesize[1];
>> + cpw += prev->linesize[1];
>> + }
>> +
>> + for (j = 0; j < link->h; j++) {
>> + for (fil = 0; fil < FILT_NUMB; fil ++) {
>> + if (s->filters & 1<<fil) {
>> + AVFrame *dbg = out != in && s->outfilter == fil ? out : NULL;
>> + filtot[fil] += filters_def[fil].process(s, in, dbg, j, link->w, link->h);
>> + }
>> + }
>> + }
>> +
>> + // find low / high based on histogram percentile
>> + // these only need to be calculated once.
>> +
>> + lowp = s->fs * 10 / 100;
>> + highp = s->fs * 90 / 100;
>> + clowp = s->cfs * 10 / 100;
>> + chighp = s->cfs * 90 / 100;
>
> I wonder if we should make the percentile value parametric (for
> example setting the percentile margin M and then computing 1-M and M
> values).
I was using ebur128 for inspiration where volume is computed at values at the 10% and 95% percentiles to exclude the major outliers. Feasibly M could be a parameter though the metadata output so then contain the value of M to put the high and low values into context.
Thanks for your comments,
Dave Rice
> [...]
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