libavfilter/ebur128: add gauge option

Allow to show short-term instead of momentary in gauge. Useful for monitoring
whilst live mixing.
Signed-off-by: Daniel Molkentin <daniel@molkentin.de>
Signed-off-by: Conrad Zelck <c.zelck@imail.de>

doc/filters.texi

@@ -19281,7 +19281,8 @@ time graph to observe the loudness evolution. The graphic contains the logged
 message mentioned above, so it is not printed anymore when this option is set,
 unless the verbose logging is set. The main graphing area contains the
 short-term loudness (3 seconds of analysis), and the gauge on the right is for
-the momentary loudness (400 milliseconds).
+the momentary loudness (400 milliseconds), but can optionally be configured
+to instead display short-term loudness (see @var{gauge}).
 
 More information about the Loudness Recommendation EBU R128 on
 @url{http://tech.ebu.ch/loudness}.
@@ -19364,6 +19365,12 @@ Set a specific target level (in LUFS) used as relative zero in the visualization
 This parameter is optional and has a default value of -23LUFS as specified
 by EBU R128. However, material published online may prefer a level of -16LUFS
 (e.g. for use with podcasts or video platforms).
+
+@item gauge
+Set the value displayed by the gauge. Valid values are @code{momentary} and s
+@code{shortterm}. By default the momentary value will be used, but in certain
+scenarios it may be more useful to observe the short term value instead (e.g.
+live mixing).
 @end table
 
 @subsection Examples

libavfilter/f_ebur128.c

@@ -143,6 +143,7 @@ typedef struct EBUR128Context {
     int dual_mono;                  ///< whether or not to treat single channel input files as dual-mono
     double pan_law;                 ///< pan law value used to calculate dual-mono measurements
     int target;                     ///< target level in LUFS used to set relative zero LU in visualization
+    int gauge_type;                 ///< whether gauge shows momentary or short
 } EBUR128Context;
 
 enum {
@@ -151,6 +152,12 @@ enum {
     PEAK_MODE_TRUE_PEAKS    = 1<<2,
 };
 
+enum {
+    GAUGE_TYPE_MOMENTARY = 0,
+    GAUGE_TYPE_SHORTTERM = 1,
+};
+
+
 #define OFFSET(x) offsetof(EBUR128Context, x)
 #define A AV_OPT_FLAG_AUDIO_PARAM
 #define V AV_OPT_FLAG_VIDEO_PARAM
@@ -170,6 +177,11 @@ static const AVOption ebur128_options[] = {
     { "dualmono", "treat mono input files as dual-mono", OFFSET(dual_mono), AV_OPT_TYPE_BOOL, {.i64 = 0}, 0, 1, A|F },
     { "panlaw", "set a specific pan law for dual-mono files", OFFSET(pan_law), AV_OPT_TYPE_DOUBLE, {.dbl = -3.01029995663978}, -10.0, 0.0, A|F },
     { "target", "set a specific target level in LUFS (-23 to 0)", OFFSET(target), AV_OPT_TYPE_INT, {.i64 = -23}, -23, 0, V|F },
+    { "gauge", "set gauge display type", OFFSET(gauge_type), AV_OPT_TYPE_INT, {.i64 = 0 }, GAUGE_TYPE_MOMENTARY, GAUGE_TYPE_SHORTTERM, V|F, "gaugetype" },
+        { "momentary",   "display momentary value",   0, AV_OPT_TYPE_CONST, {.i64 = GAUGE_TYPE_MOMENTARY}, INT_MIN, INT_MAX, V|F, "gaugetype" },
+        { "m",           "display momentary value",   0, AV_OPT_TYPE_CONST, {.i64 = GAUGE_TYPE_MOMENTARY}, INT_MIN, INT_MAX, V|F, "gaugetype" },
+        { "shortterm",   "display short-term value",  0, AV_OPT_TYPE_CONST, {.i64 = GAUGE_TYPE_SHORTTERM}, INT_MIN, INT_MAX, V|F, "gaugetype" },
+        { "s",           "display short-term value",  0, AV_OPT_TYPE_CONST, {.i64 = GAUGE_TYPE_SHORTTERM}, INT_MIN, INT_MAX, V|F, "gaugetype" },
     { NULL },
 };
 
@@ -741,9 +753,16 @@ static int filter_frame(AVFilterLink *inlink, AVFrame *insamples)
             if (ebur128->do_video) {
                 int x, y, ret;
                 uint8_t *p;
+                double gauge_value;
+
+                if (ebur128->gauge_type == GAUGE_TYPE_MOMENTARY) {
+                    gauge_value = loudness_400 - ebur128->target;
+                } else {
+                    gauge_value = loudness_3000 - ebur128->target;
+                }
 
                 const int y_loudness_lu_graph = lu_to_y(ebur128, loudness_3000 - ebur128->target);
-                const int y_loudness_lu_gauge = lu_to_y(ebur128, loudness_400  - ebur128->target);
+                const int y_loudness_lu_gauge = lu_to_y(ebur128, gauge_value);
 
                 /* draw the graph using the short-term loudness */
                 p = pic->data[0] + ebur128->graph.y*pic->linesize[0] + ebur128->graph.x*3;
@@ -755,7 +774,7 @@ static int filter_frame(AVFilterLink *inlink, AVFrame *insamples)
                     p += pic->linesize[0];
                 }
 
-                /* draw the gauge using the momentary loudness */
+                /* draw the gauge using either momentary or short-term loudness */
                 p = pic->data[0] + ebur128->gauge.y*pic->linesize[0] + ebur128->gauge.x*3;
                 for (y = 0; y < ebur128->gauge.h; y++) {
                     const uint8_t *c = get_graph_color(ebur128, y_loudness_lu_gauge, y);