This patch extends aphasemeter to detect out of phase or mono sequences in
stereo streams, with its associated documentation.
From 7e2846ac3b4b79a2e9beca845d0f2be7ae6abcdb Mon Sep 17 00:00:00 2001
From: Romane Lafon
Date: Mon, 8 Jul 2019 13:51:05 +0200
Subject: [PATCH] avfilter/avf_aphasemeter: Add out of phase and mono detection
Signed-off-by: Romane Lafon
---
doc/filters.texi | 33 +++
libavfilter/avf_aphasemeter.c | 127 --
2 files changed, 156 insertions(+), 4 deletions(-)
diff --git a/doc/filters.texi b/doc/filters.texi
index ee6a93ffbf..46d19826d0 100644
--- a/doc/filters.texi
+++ b/doc/filters.texi
@@ -20672,6 +20672,39 @@ Set color which will be used for drawing median phase. If color is
Enable video output. Default is enabled.
@end table
+@subsection phasing detection
+
+The filter also detects out of phase and mono sequences in stereo streams.
+It logs the sequence start, end and duration when it lasts longer or as long as the minimum set.
+
+The filter accepts the following options for this detection:
+
+@table @option
+@item phasing
+Enable mono and out of phase detection. Default is disabled.
+
+@item tolerance
+Set phase tolerance for mono detection, in amplitude ratio. Default is @code{0}.
+Allowed range is @code{[0, 1]}.
+
+@item angle
+Set angle threshold for out of phase detection, in degree. Default is @code{170}.
+Allowed range is @code{[0, 180]}.
+
+@item duration
+Set mono or out of phase duration until notification, expressed in seconds. Default is @code{2}.
+@end table
+
+@subsection Examples
+
+@itemize
+@item
+Complete example with @command{ffmpeg} to detect 1 second of mono with 0.001 phase tolerance:
+@example
+ffmpeg -i stereo.wav -af aphasemeter=video=0:phasing=1:duration=1:tolerance=0.001 -f null -
+@end example
+@end itemize
+
@section avectorscope
Convert input audio to a video output, representing the audio vector
diff --git a/libavfilter/avf_aphasemeter.c b/libavfilter/avf_aphasemeter.c
index f497bc9969..77701e5cde 100644
--- a/libavfilter/avf_aphasemeter.c
+++ b/libavfilter/avf_aphasemeter.c
@@ -28,26 +28,41 @@
#include "libavutil/intreadwrite.h"
#include "libavutil/opt.h"
#include "libavutil/parseutils.h"
+#include "libavutil/timestamp.h"
#include "avfilter.h"
#include "formats.h"
#include "audio.h"
#include "video.h"
#include "internal.h"
+#include "stdbool.h"
+#include "float.h"
typedef struct AudioPhaseMeterContext {
const AVClass *class;
AVFrame *out;
int do_video;
+int do_phasing_detection;
int w, h;
AVRational frame_rate;
int contrast[4];
uint8_t *mpc_str;
uint8_t mpc[4];
int draw_median_phase;
+int is_mono;
+int is_out_phase;
+int start_mono_presence;
+int start_out_phase_presence;
+float tolerance;
+float angle;
+float phase;
+float mono_idx[2];
+float out_phase_idx[2];
+double duration;
} AudioPhaseMeterContext;
#define OFFSET(x) offsetof(AudioPhaseMeterContext, x)
#define FLAGS AV_OPT_FLAG_FILTERING_PARAM|AV_OPT_FLAG_VIDEO_PARAM
+#define get_duration(index) (index[1] - index[0])
static const AVOption aphasemeter_options[] = {
{ "rate", "set video rate", OFFSET(frame_rate), AV_OPT_TYPE_VIDEO_RATE, {.str="25"}, 0, INT_MAX, FLAGS },
@@ -59,6 +74,10 @@ static const AVOption aphasemeter_options[] = {
{ "bc", "set blue contrast", OFFSET(contrast[2]), AV_OPT_TYPE_INT, {.i64=1}, 0, 255, FLAGS },
{ "mpc", "set median phase color", OFFSET(mpc_str), AV_OPT_TYPE_STRING, {.str = "none"}, 0, 0, FLAGS },
{ "video", "set video output", OFFSET(do_video), AV_OPT_TYPE_BOOL, {.i64 = 1}, 0, 1, FLAGS },
+{ "phasing", "set mono and out-of-phase detection output", OFFSET(do_phasing_detection), AV_OPT_TYPE_BOOL, {.i64 = 0}, 0, 1, FLAGS },
+{ "tolerance", "set phase tolerance for mono detection", OFFSET(tolerance), AV_OPT_TYPE_FLOAT, {.dbl = 0.}, 0, 1, FLAGS },
+{ "angle", "set angle threshold for out-of-phase detection", OFFSET(angle), AV_OPT_TYPE_FLOAT, {.dbl = 170.}, 90, 180, FLAGS },
+{ "duration", "set minimum mono or out-of-phase duration in seconds", OFFSET(duration), AV_OPT_TYPE_DOUBLE, {.dbl=2.}, 0, 24*60*60, FLAGS },
{ NULL }
};
@@ -140,6 +159,22 @@ static inline int get_x(float phase, int w)
return (phase + 1.) / 2. * (w - 1);
}
+static inline float get_index(AVFilterLink *inlink, AVFrame *in)
+{
+char *index_str = av_ts2timestr(in->pts, >time_base);
+return atof(index_str);
+}
+
+static inline void add_metadata(AVFrame *insamples, const char *key, float value)
+{
+char buf[128];
+char str[128];
+
+snprintf(str, sizeof(str), "%f", value);
+snprintf(buf, sizeof(buf), "lavfi.aphasemeter.%s", key);
+av_dict_set(>metadata, buf, str, 0);
+}
+
static int filter_frame(AVFilterLink *inlink, AVFrame *in)
{
AVFilterContext *ctx = inlink->dst;
@@ -154,6 +189,10 @@ static int filter_frame(AVFilterLink *inlink, AVFrame
