avfilter: new multimedia filter avf_showcqt.c

this filter is the same as showspectrum but with constant Q transform,
so frequency is spaced logarithmically

Changelog

@@ -26,6 +26,7 @@ version <next>:
 - native Opus decoder
 - display matrix export and rotation api
 - WebVTT encoder
+- showcqt multimedia filter
 
 
 version 2.2:

MAINTAINERS

@@ -341,6 +341,7 @@ Filters:
   af_ladspa.c                           Paul B Mahol
   af_pan.c                              Nicolas George
   avf_avectorscope.c                    Paul B Mahol
+  avf_showcqt.c                         Muhammad Faiz
   vf_blend.c                            Paul B Mahol
   vf_colorbalance.c                     Paul B Mahol
   vf_dejudder.c                         Nicholas Robbins

doc/filters.texi

@@ -10133,6 +10133,76 @@ settb=AVTB
 @end example
 @end itemize
 
+@section showcqt
+Convert input audio to a video output (at full HD resolution), representing
+frequency spectrum logarithmically (using constant Q transform with
+Brown-Puckette algorithm), with musical tone scale, from E0 to D#10 (10 octaves).
+
+The filter accepts the following options:
+
+@table @option
+@item volume
+Specify the transform volume (multiplier). Acceptable value is [1.0, 100.0].
+Default value is @code{16.0}.
+
+@item timeclamp
+Specify the transform timeclamp. At low frequency, there is trade-off between
+accuracy in time domain and frequency domain. If timeclamp is lower,
+event in time domain is represented more accurately (such as fast bass drum),
+otherwise event in frequency domain is represented more accurately
+(such as bass guitar). Acceptable value is [0.1, 1.0]. Default value is @code{0.17}.
+
+@item coeffclamp
+Specify the transform coeffclamp. If coeffclamp is lower, transform is
+more accurate, otherwise transform is faster. Acceptable value is [0.1, 10.0].
+Default value is @code{1.0}.
+
+@item gamma
+Specify gamma. Lower gamma makes the spectrum more contrast, higher gamma
+makes the spectrum having more range. Acceptable value is [1.0, 7.0].
+Default value is @code{3.0}.
+
+@item fps
+Specify video fps. Default value is @code{25}.
+
+@item count
+Specify number of transform per frame, so there are fps*count transforms
+per second. Note tha audio data rate must be divisible by fps*count.
+Default value is @code{6}.
+
+@end table
+
+@subsection Examples
+
+@itemize
+@item
+Playing audio while showing the spectrum:
+@example
+ffplay -f lavfi 'amovie=a.mp3, asplit [a][out1]; [a] showcqt [out0]'
+@end example
+
+@item
+Same as above, but with frame rate 30 fps:
+@example
+ffplay -f lavfi 'amovie=a.mp3, asplit [a][out1]; [a] showcqt=fps=30:count=5 [out0]'
+@end example
+
+@item
+A1 and its harmonics: A1, A2, (near)E3, A3:
+@example
+ffplay -f lavfi 'aevalsrc=0.1*sin(2*PI*55*t)+0.1*sin(4*PI*55*t)+0.1*sin(6*PI*55*t)+0.1*sin(8*PI*55*t),
+                 asplit[a][out1]; [a] showcqt [out0]'
+@end example
+
+@item
+Same as above, but with more accuracy in frequency domain (and slower):
+@example
+ffplay -f lavfi 'aevalsrc=0.1*sin(2*PI*55*t)+0.1*sin(4*PI*55*t)+0.1*sin(6*PI*55*t)+0.1*sin(8*PI*55*t),
+                 asplit[a][out1]; [a] showcqt=timeclamp=0.5 [out0]'
+@end example
+
+@end itemize
+
 @section showspectrum
 
 Convert input audio to a video output, representing the audio frequency

libavfilter/Makefile

@@ -224,6 +224,7 @@ OBJS-$(CONFIG_MP_FILTER) += libmpcodecs/vf_uspp.o
 # multimedia filters
 OBJS-$(CONFIG_AVECTORSCOPE_FILTER)           += avf_avectorscope.o
 OBJS-$(CONFIG_CONCAT_FILTER)                 += avf_concat.o
+OBJS-$(CONFIG_SHOWCQT_FILTER)                += avf_showcqt.o
 OBJS-$(CONFIG_SHOWSPECTRUM_FILTER)           += avf_showspectrum.o
 OBJS-$(CONFIG_SHOWWAVES_FILTER)              += avf_showwaves.o
 

libavfilter/allfilters.c

@@ -231,6 +231,7 @@ void avfilter_register_all(void)
     /* multimedia filters */
     REGISTER_FILTER(AVECTORSCOPE,   avectorscope,   avf);
     REGISTER_FILTER(CONCAT,         concat,         avf);
+    REGISTER_FILTER(SHOWCQT,        showcqt,        avf);
     REGISTER_FILTER(SHOWSPECTRUM,   showspectrum,   avf);
     REGISTER_FILTER(SHOWWAVES,      showwaves,      avf);
 

libavfilter/version.h

@@ -30,7 +30,7 @@
 #include "libavutil/version.h"
 
 #define LIBAVFILTER_VERSION_MAJOR   4
-#define LIBAVFILTER_VERSION_MINOR   5
+#define LIBAVFILTER_VERSION_MINOR   6
 #define LIBAVFILTER_VERSION_MICRO 100
 
 #define LIBAVFILTER_VERSION_INT AV_VERSION_INT(LIBAVFILTER_VERSION_MAJOR, \