[FFmpeg-cvslog] avfilter/af_astats: add entropy stat
Paul B Mahol
git at videolan.org
Sat Sep 11 11:55:18 EEST 2021
ffmpeg | branch: master | Paul B Mahol <onemda at gmail.com> | Sat Sep 11 10:45:09 2021 +0200| [966fc3c070c1e5143537007fb26340c179cc02c5] | committer: Paul B Mahol
avfilter/af_astats: add entropy stat
> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=966fc3c070c1e5143537007fb26340c179cc02c5
---
doc/filters.texi | 5 +++++
libavfilter/af_astats.c | 35 +++++++++++++++++++++++++++++++++++
2 files changed, 40 insertions(+)
diff --git a/doc/filters.texi b/doc/filters.texi
index 94804ca32b..aabfaccfc3 100644
--- a/doc/filters.texi
+++ b/doc/filters.texi
@@ -2693,6 +2693,7 @@ Flat_factor
Peak_count
Noise_floor
Noise_floor_count
+Entropy
Bit_depth
Dynamic_range
Zero_crossings
@@ -2717,6 +2718,7 @@ Flat_factor
Peak_count
Noise_floor
Noise_floor_count
+Entropy
Bit_depth
Number_of_samples
Number_of_NaNs
@@ -2795,6 +2797,9 @@ Minimum local peak measured in dBFS over a short window.
Number of occasions (not the number of samples) that the signal attained
@var{Noise floor}.
+ at item Entropy
+Entropy measured across whole audio. Entropy of value near 1.0 is typically measured for white noise.
+
@item Bit depth
Overall bit depth of audio. Number of bits used for each sample.
diff --git a/libavfilter/af_astats.c b/libavfilter/af_astats.c
index 9577468c81..899746864d 100644
--- a/libavfilter/af_astats.c
+++ b/libavfilter/af_astats.c
@@ -57,6 +57,7 @@
#define MEASURE_NUMBER_OF_DENORMALS (1 << 21)
#define MEASURE_NOISE_FLOOR (1 << 22)
#define MEASURE_NOISE_FLOOR_COUNT (1 << 23)
+#define MEASURE_ENTROPY (1 << 24)
#define MEASURE_MINMAXPEAK (MEASURE_MIN_LEVEL | MEASURE_MAX_LEVEL | MEASURE_PEAK_LEVEL)
@@ -83,9 +84,11 @@ typedef struct ChannelStats {
uint64_t nb_denormals;
double *win_samples;
uint64_t histogram[HISTOGRAM_SIZE];
+ uint64_t ehistogram[HISTOGRAM_SIZE];
int win_pos;
int max_index;
double noise_floor;
+ double entropy;
} ChannelStats;
typedef struct AudioStatsContext {
@@ -135,6 +138,7 @@ static const AVOption astats_options[] = {
{ "Zero_crossings_rate" , "", 0, AV_OPT_TYPE_CONST, {.i64=MEASURE_ZERO_CROSSINGS_RATE }, 0, 0, FLAGS, "measure" },
{ "Noise_floor" , "", 0, AV_OPT_TYPE_CONST, {.i64=MEASURE_NOISE_FLOOR }, 0, 0, FLAGS, "measure" },
{ "Noise_floor_count" , "", 0, AV_OPT_TYPE_CONST, {.i64=MEASURE_NOISE_FLOOR_COUNT }, 0, 0, FLAGS, "measure" },
+ { "Entropy" , "", 0, AV_OPT_TYPE_CONST, {.i64=MEASURE_ENTROPY }, 0, 0, FLAGS, "measure" },
{ "Number_of_samples" , "", 0, AV_OPT_TYPE_CONST, {.i64=MEASURE_NUMBER_OF_SAMPLES }, 0, 0, FLAGS, "measure" },
{ "Number_of_NaNs" , "", 0, AV_OPT_TYPE_CONST, {.i64=MEASURE_NUMBER_OF_NANS }, 0, 0, FLAGS, "measure" },
{ "Number_of_Infs" , "", 0, AV_OPT_TYPE_CONST, {.i64=MEASURE_NUMBER_OF_INFS }, 0, 0, FLAGS, "measure" },
@@ -199,9 +203,11 @@ static void reset_stats(AudioStatsContext *s)
p->last = NAN;
p->noise_floor = NAN;
p->noise_floor_count = 0;
+ p->entropy = 0;
p->win_pos = 0;
memset(p->win_samples, 0, s->tc_samples * sizeof(*p->win_samples));
memset(p->histogram, 0, sizeof(p->histogram));
+ memset(p->ehistogram, 0, sizeof(p->ehistogram));
}
}
@@ -254,6 +260,20 @@ static void bit_depth(AudioStatsContext *s, uint64_t mask, uint64_t imask, AVRat
depth->num++;
}
+static double calc_entropy(AudioStatsContext *s, ChannelStats *p)
+{
+ double entropy = 0.;
+
+ for (int i = 0; i < HISTOGRAM_SIZE; i++) {
+ double entry = p->ehistogram[i] / ((double)p->nb_samples);
+
+ if (entry > 1e-8)
+ entropy += entry * log2(entry);
+ }
+
+ return -entropy / log2(HISTOGRAM_SIZE);
+}
+
static inline void update_minmax(AudioStatsContext *s, ChannelStats *p, double d)
{
if (d < p->min)
@@ -319,6 +339,7 @@ static inline void update_stat(AudioStatsContext *s, ChannelStats *p, double d,
index = av_clip(lrint(av_clipd(FFABS(nd), 0.0, 1.0) * HISTOGRAM_MAX), 0, HISTOGRAM_MAX);
p->max_index = FFMAX(p->max_index, index);
p->histogram[index]++;
+ p->ehistogram[index]++;
if (!isnan(p->noise_floor))
p->histogram[av_clip(lrint(av_clipd(FFABS(drop), 0.0, 1.0) * HISTOGRAM_MAX), 0, HISTOGRAM_MAX)]--;
p->win_pos++;
@@ -406,6 +427,7 @@ static void set_metadata(AudioStatsContext *s, AVDictionary **metadata)
sigma_x = 0,
sigma_x2 = 0,
noise_floor = 0,
+ entropy = 0,
min_sigma_x2 = DBL_MAX,
max_sigma_x2 =-DBL_MAX;
AVRational depth;
@@ -431,6 +453,8 @@ static void set_metadata(AudioStatsContext *s, AVDictionary **metadata)
sigma_x2 += p->sigma_x2;
noise_floor = FFMAX(noise_floor, p->noise_floor);
noise_floor_count += p->noise_floor_count;
+ p->entropy = calc_entropy(s, p);
+ entropy += p->entropy;
min_count += p->min_count;
max_count += p->max_count;
min_runs += p->min_runs;
@@ -476,6 +500,8 @@ static void set_metadata(AudioStatsContext *s, AVDictionary **metadata)
set_meta(metadata, c + 1, "Noise_floor", "%f", LINEAR_TO_DB(p->noise_floor));
if (s->measure_perchannel & MEASURE_NOISE_FLOOR_COUNT)
set_meta(metadata, c + 1, "Noise_floor_count", "%f", p->noise_floor_count);
+ if (s->measure_perchannel & MEASURE_ENTROPY)
+ set_meta(metadata, c + 1, "Entropy", "%f", p->entropy);
if (s->measure_perchannel & MEASURE_BIT_DEPTH) {
bit_depth(s, p->mask, p->imask, &depth);
set_meta(metadata, c + 1, "Bit_depth", "%f", depth.num);
@@ -525,6 +551,8 @@ static void set_metadata(AudioStatsContext *s, AVDictionary **metadata)
set_meta(metadata, 0, "Overall.Noise_floor", "%f", LINEAR_TO_DB(noise_floor));
if (s->measure_overall & MEASURE_NOISE_FLOOR_COUNT)
set_meta(metadata, 0, "Overall.Noise_floor_count", "%f", noise_floor_count / (double)s->nb_channels);
+ if (s->measure_overall & MEASURE_ENTROPY)
+ set_meta(metadata, 0, "Overall.Entropy", "%f", entropy / (double)s->nb_channels);
if (s->measure_overall & MEASURE_BIT_DEPTH) {
bit_depth(s, mask, imask, &depth);
set_meta(metadata, 0, "Overall.Bit_depth", "%f", depth.num);
@@ -655,6 +683,7 @@ static void print_stats(AVFilterContext *ctx)
sigma_x = 0,
sigma_x2 = 0,
noise_floor = 0,
+ entropy = 0,
min_sigma_x2 = DBL_MAX,
max_sigma_x2 =-DBL_MAX;
AVRational depth;
@@ -679,6 +708,8 @@ static void print_stats(AVFilterContext *ctx)
sigma_x += p->sigma_x;
sigma_x2 += p->sigma_x2;
noise_floor = FFMAX(noise_floor, p->noise_floor);
+ p->entropy = calc_entropy(s, p);
+ entropy += p->entropy;
min_count += p->min_count;
max_count += p->max_count;
noise_floor_count += p->noise_floor_count;
@@ -728,6 +759,8 @@ static void print_stats(AVFilterContext *ctx)
av_log(ctx, AV_LOG_INFO, "Noise floor dB: %f\n", LINEAR_TO_DB(p->noise_floor));
if (s->measure_perchannel & MEASURE_NOISE_FLOOR_COUNT)
av_log(ctx, AV_LOG_INFO, "Noise floor count: %"PRId64"\n", p->noise_floor_count);
+ if (s->measure_perchannel & MEASURE_ENTROPY)
+ av_log(ctx, AV_LOG_INFO, "Entropy: %f\n", p->entropy);
if (s->measure_perchannel & MEASURE_BIT_DEPTH) {
bit_depth(s, p->mask, p->imask, &depth);
av_log(ctx, AV_LOG_INFO, "Bit depth: %u/%u\n", depth.num, depth.den);
@@ -779,6 +812,8 @@ static void print_stats(AVFilterContext *ctx)
av_log(ctx, AV_LOG_INFO, "Noise floor dB: %f\n", LINEAR_TO_DB(noise_floor));
if (s->measure_overall & MEASURE_NOISE_FLOOR_COUNT)
av_log(ctx, AV_LOG_INFO, "Noise floor count: %f\n", noise_floor_count / (double)s->nb_channels);
+ if (s->measure_overall & MEASURE_ENTROPY)
+ av_log(ctx, AV_LOG_INFO, "Entropy: %f\n", entropy / (double)s->nb_channels);
if (s->measure_overall & MEASURE_BIT_DEPTH) {
bit_depth(s, mask, imask, &depth);
av_log(ctx, AV_LOG_INFO, "Bit depth: %u/%u\n", depth.num, depth.den);
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