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avfilter/vf_blackdetect: add alpha option

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Check the alpha plane for (almost) transparent frames, instead of checking
the luma channel for almost black frames.

Signed-off-by: Niklas Haas <git@haasn.dev>
Sponsored-by: nxtedition
This commit is contained in:
Niklas Haas
2025-02-27 19:21:20 +01:00
parent 02f45a7f3f
commit 7e783fac5b
2 changed files with 44 additions and 13 deletions
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6
doc/filters.texi
View File

@@ -8687,6 +8687,12 @@ the input video format, the range is [0-255] for YUV full-range
formats and [16-235] for YUV non full-range formats.
Default value is 0.10.
@item alpha
If true, check the alpha channel instead of the luma channel. Detects frames
which are (almost) transparent, instead of frames which are almost black.
Default value is disabled.
@end table
The following example sets the maximum pixel threshold to the minimum

51
libavfilter/vf_blackdetect.c
View File

@@ -31,6 +31,7 @@
#include "libavutil/timestamp.h"
#include "avfilter.h"
#include "filters.h"
#include "formats.h"
#include "video.h"
typedef struct BlackDetectContext {
@@ -45,6 +46,7 @@ typedef struct BlackDetectContext {
double picture_black_ratio_th;
double pixel_black_th;
unsigned int pixel_black_th_i;
int alpha;
unsigned int nb_black_pixels; ///< number of black pixels counted so far
AVRational time_base;
@@ -63,6 +65,7 @@ static const AVOption blackdetect_options[] = {
{ "pic_th", "set the picture black ratio threshold", OFFSET(picture_black_ratio_th), AV_OPT_TYPE_DOUBLE, {.dbl=.98}, 0, 1, FLAGS },
{ "pixel_black_th", "set the pixel black threshold", OFFSET(pixel_black_th), AV_OPT_TYPE_DOUBLE, {.dbl=.10}, 0, 1, FLAGS },
{ "pix_th", "set the pixel black threshold", OFFSET(pixel_black_th), AV_OPT_TYPE_DOUBLE, {.dbl=.10}, 0, 1, FLAGS },
{ "alpha", "check alpha instead of luma", OFFSET(alpha), AV_OPT_TYPE_BOOL, {.i64=0}, 0, 1, FLAGS },
{ NULL }
};
@@ -71,11 +74,21 @@ AVFILTER_DEFINE_CLASS(blackdetect);
#define YUVJ_FORMATS \
AV_PIX_FMT_YUVJ411P, AV_PIX_FMT_YUVJ420P, AV_PIX_FMT_YUVJ422P, AV_PIX_FMT_YUVJ444P, AV_PIX_FMT_YUVJ440P
#define YUVA_FORMATS \
AV_PIX_FMT_YUVA420P, AV_PIX_FMT_YUVA422P, AV_PIX_FMT_YUVA444P, \
AV_PIX_FMT_YUVA444P9, AV_PIX_FMT_YUVA444P10, AV_PIX_FMT_YUVA444P12, AV_PIX_FMT_YUVA444P16, \
AV_PIX_FMT_YUVA422P9, AV_PIX_FMT_YUVA422P10, AV_PIX_FMT_YUVA422P12, AV_PIX_FMT_YUVA422P16, \
AV_PIX_FMT_YUVA420P9, AV_PIX_FMT_YUVA420P10, AV_PIX_FMT_YUVA420P16
static const enum AVPixelFormat yuvj_formats[] = {
YUVJ_FORMATS, AV_PIX_FMT_NONE
};
static const enum AVPixelFormat pix_fmts[] = {
static const enum AVPixelFormat yuva_formats[] = {
YUVA_FORMATS, AV_PIX_FMT_NONE
};
static const enum AVPixelFormat yuv_formats[] = {
AV_PIX_FMT_GRAY8,
AV_PIX_FMT_YUV410P, AV_PIX_FMT_YUV411P,
AV_PIX_FMT_YUV420P, AV_PIX_FMT_YUV422P,
@@ -91,13 +104,23 @@ static const enum AVPixelFormat pix_fmts[] = {
AV_PIX_FMT_YUV440P12,
AV_PIX_FMT_YUV444P14, AV_PIX_FMT_YUV422P14, AV_PIX_FMT_YUV420P14,
AV_PIX_FMT_YUV420P16, AV_PIX_FMT_YUV422P16, AV_PIX_FMT_YUV444P16,
AV_PIX_FMT_YUVA420P, AV_PIX_FMT_YUVA422P, AV_PIX_FMT_YUVA444P,
AV_PIX_FMT_YUVA444P9, AV_PIX_FMT_YUVA444P10, AV_PIX_FMT_YUVA444P12, AV_PIX_FMT_YUVA444P16,
AV_PIX_FMT_YUVA422P9, AV_PIX_FMT_YUVA422P10, AV_PIX_FMT_YUVA422P12, AV_PIX_FMT_YUVA422P16,
AV_PIX_FMT_YUVA420P9, AV_PIX_FMT_YUVA420P10, AV_PIX_FMT_YUVA420P16,
AV_PIX_FMT_NONE
YUVA_FORMATS, AV_PIX_FMT_NONE
};
static int query_format(const AVFilterContext *ctx,
AVFilterFormatsConfig **cfg_in,
AVFilterFormatsConfig **cfg_out)
{
const BlackDetectContext *s = ctx->priv;
AVFilterFormats *formats;
if (s->alpha)
formats = ff_make_format_list(yuva_formats);
else
formats = ff_make_format_list(yuv_formats);
return ff_set_common_formats2(ctx, cfg_in, cfg_out, formats);
}
static int config_input(AVFilterLink *inlink)
{
AVFilterContext *ctx = inlink->dst;
@@ -114,9 +137,9 @@ static int config_input(AVFilterLink *inlink)
return AVERROR(ENOMEM);
av_log(s, AV_LOG_VERBOSE,
"black_min_duration:%s pixel_black_th:%f picture_black_ratio_th:%f\n",
"black_min_duration:%s pixel_black_th:%f picture_black_ratio_th:%f alpha:%d\n",
av_ts2timestr(s->black_min_duration, &s->time_base),
s->pixel_black_th, s->picture_black_ratio_th);
s->pixel_black_th, s->picture_black_ratio_th, s->alpha);
return 0;
}
@@ -140,7 +163,8 @@ static int black_counter(AVFilterContext *ctx, void *arg,
const unsigned int threshold = s->pixel_black_th_i;
unsigned int *counterp = &s->counter[jobnr];
AVFrame *in = arg;
const int linesize = in->linesize[0];
const int plane = s->alpha ? 3 : 0;
const int linesize = in->linesize[plane];
const int w = in->width;
const int h = in->height;
const int start = (h * jobnr) / nb_jobs;
@@ -149,7 +173,7 @@ static int black_counter(AVFilterContext *ctx, void *arg,
unsigned int counter = 0;
if (s->depth == 8) {
const uint8_t *p = in->data[0] + start * linesize;
const uint8_t *p = in->data[plane] + start * linesize;
for (int i = 0; i < size; i++) {
for (int x = 0; x < w; x++)
@@ -157,7 +181,7 @@ static int black_counter(AVFilterContext *ctx, void *arg,
p += linesize;
}
} else {
const uint16_t *p = (const uint16_t *)(in->data[0] + start * linesize);
const uint16_t *p = (const uint16_t *)(in->data[plane] + start * linesize);
for (int i = 0; i < size; i++) {
for (int x = 0; x < w; x++)
@@ -180,7 +204,8 @@ static int filter_frame(AVFilterLink *inlink, AVFrame *picref)
const int max = (1 << s->depth) - 1;
const int factor = (1 << (s->depth - 8));
const int full = picref->color_range == AVCOL_RANGE_JPEG ||
ff_fmt_is_in(picref->format, yuvj_formats);
ff_fmt_is_in(picref->format, yuvj_formats) ||
s->alpha;
s->pixel_black_th_i = full ? s->pixel_black_th * max :
// luminance_minimum_value + pixel_black_th * luminance_range_size
@@ -252,6 +277,6 @@ const FFFilter ff_vf_blackdetect = {
.priv_size = sizeof(BlackDetectContext),
FILTER_INPUTS(blackdetect_inputs),
FILTER_OUTPUTS(ff_video_default_filterpad),
FILTER_PIXFMTS_ARRAY(pix_fmts),
FILTER_QUERY_FUNC2(query_format),
.uninit = uninit,
};