avfilter/af_aiir: add support for alternative coefficients format

Support for zeros/poles syntax on Z-plane.

Signed-off-by: Paul B Mahol <onemda@gmail.com>

1 files changed, 20 insertions, 3 deletions

diff --git a/doc/filters.texi b/doc/filters.texi
index 1a2a93b..69c59d7 100644
--- a/doc/filters.texi
+++ b/doc/filters.texi
@@ -1071,16 +1071,27 @@ It accepts the following parameters:
 Set denominator/poles coefficients.
 
 @item b
-Set nominator/zeros coefficients.
+Set numerator/zeros coefficients.
 
 @item dry_gain
 Set input gain.
 
 @item wet_gain
 Set output gain.
+
+@item f
+Set coefficients format.
+Can be @code{tf} - transfer function or @code{zp} - Z-plane zeros/poles.
 @end table
 
-Coefficients are separated by spaces and are in ascending order.
+Coefficients in @code{tf} format are separated by spaces and are in ascending
+order.
+
+Coefficients in @code{zp} format are separated by spaces and order of coefficients
+doesn't matter. Coefficients in @code{zp} format are complex numbers with @var{i}
+imaginary unit, also first number in numerator, option @var{b}, is not complex but
+real number and sets overall gain for channel.
+
 Different coefficients can be provided for every channel, in such case
 use '|' to separate coefficients. Last provided coefficients will be
 used for all remaining channels.
@@ -1091,7 +1102,13 @@ used for all remaining channels.
 @item
 Apply 2 pole elliptic notch at arround 5000Hz for 48000 Hz sample rate:
 @example
-aiir=b=7.957584807809675810E-1 -2.575128568908332300 3.674839853930788710 -2.57512875289799137 7.957586296317130880E-1:a=1 -2.86950072432325953 3.63022088054647218 -2.28075678147272232 6.361362326477423500E-1
+aiir=b=7.957584807809675810E-1 -2.575128568908332300 3.674839853930788710 -2.57512875289799137 7.957586296317130880E-1:a=1 -2.86950072432325953 3.63022088054647218 -2.28075678147272232 6.361362326477423500E-1:f=tf
+@end example
+
+@item
+Same as above but in @code{zp} format:
+@example
+aiir=b=0.79575848078096756 0.80918701+0.58773007i 0.80918701-0.58773007i 0.80884700+0.58784055i 0.80884700-0.58784055i:a=0.63892345+0.59951235i 0.63892345-0.59951235i 0.79582691+0.44198673i 0.79582691-0.44198673i:f=zp
 @end example
 @end itemize