avfilter/showcqt: add and extend tlength and volume options

Add a tlength option with frequency and timeclamp variable

Add to the volume option support for frequency and timeclamp variable,
   a_weighting, b_weighting and c_weighting functions

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

1 files changed, 40 insertions, 2 deletions

diff --git a/doc/filters.texi b/doc/filters.texi
index f59926a05e..e0759fccfd 100644
--- a/doc/filters.texi
+++ b/doc/filters.texi
@@ -10515,8 +10515,34 @@ 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}.
+Specify transform volume (multiplier) expression. The expression can contain
+variables:
+@table @option
+@item frequency, freq, f
+the frequency where transform is evaluated
+@item timeclamp, tc
+value of timeclamp option
+@end table
+and functions:
+@table @option
+@item a_weighting(f)
+A-weighting of equal loudness
+@item b_weighting(f)
+B-weighting of equal loudness
+@item c_weighting(f)
+C-weighting of equal loudness
+@end table
+Default value is @code{16}.
+
+@item tlength
+Specify transform length expression. The expression can contain variables:
+@table @option
+@item frequency, freq, f
+the frequency where transform is evaluated
+@item timeclamp, tc
+value of timeclamp option
+@end table
+Default value is @code{384/f*tc/(384/f+tc)}.
 
 @item timeclamp
 Specify the transform timeclamp. At low frequency, there is trade-off between
@@ -10587,6 +10613,18 @@ ffplay -f lavfi 'aevalsrc=0.1*sin(2*PI*55*t)+0.1*sin(4*PI*55*t)+0.1*sin(6*PI*55*
                  asplit[a][out1]; [a] showcqt=timeclamp=0.5 [out0]'
 @end example
 
+@item
+B-weighting of equal loudness
+@example
+volume=16*b_weighting(f)
+@end example
+
+@item
+Lower Q factor
+@example
+tlength=100/f*tc/(100/f+tc)
+@end example
+
 @end itemize
 
 @section showspectrum