lavfi/aevalsrc: add option channel_layout

Allow to explicitly specify the channel layout to select.

1 files changed, 14 insertions, 2 deletions

diff --git a/doc/filters.texi b/doc/filters.texi
index bdb9fe23f9..06374fc5d5 100644
--- a/doc/filters.texi
+++ b/doc/filters.texi
@@ -606,8 +606,9 @@ audio signal.
 
 It accepts the syntax: @var{exprs}[::@var{options}].
 @var{exprs} is a list of expressions separated by ":", one for each
-separate channel. The output channel layout depends on the number of
-provided expressions, up to 8 channels are supported.
+separate channel. In case the @var{channel_layout} is not
+specified, the selected channel layout depends on the number of
+provided expressions.
 
 @var{options} is an optional sequence of @var{key}=@var{value} pairs,
 separated by ":".
@@ -616,6 +617,10 @@ The description of the accepted options follows.
 
 @table @option
 
+@item channel_layout, c
+Set the channel layout. The number of channels in the specified layout
+must be equal to the number of specified expressions.
+
 @item duration, d
 Set the minimum duration of the sourced audio. See the function
 @code{av_parse_time()} for the accepted format.
@@ -667,6 +672,13 @@ aevalsrc="sin(440*2*PI*t)::s=8000"
 @end example
 
 @item
+Generate a two channels signal, specify the channel layout (Front
+Center + Back Center) explicitly:
+@example
+aevalsrc="sin(420*2*PI*t):cos(430*2*PI*t)::c=FC|BC"
+@end example
+
+@item
 Generate white noise:
 @example
 aevalsrc="-2+random(0)"