Merge commit 'd7b3ee9a3a03ab88d61a5895fbdbc6689f4dd671'

[ffmpeg] / doc / filters.texi

diff --git a/doc/filters.texi b/doc/filters.texi
index 8329bf0c0700c0afee546af323e3e1efddd8b50a..8bcfd8270833ca89485badbe12c6c89a9328e3c3 100644 (file)
--- a/doc/filters.texi
+++ b/doc/filters.texi
@@ -371,7 +371,7 @@ smaller than number of channels all remaining channels will not be delayed.
 Delay first channel by 1.5 seconds, the third channel by 0.5 seconds and leave
 the second channel (and any other channels that may be present) unchanged.
 @example
-adelay=1500:0:500
+adelay=1500|0|500
 @end example
 @end itemize
 
@@ -435,6 +435,70 @@ aecho=0.8:0.9:1000|1800:0.3|0.25
 @end example
 @end itemize
 
+@section aeval
+
+Modify an audio signal according to the specified expressions.
+
+This filter accepts one or more expressions (one for each channel),
+which are evaluated and used to modify a corresponding audio signal.
+
+This filter accepts the following options:
+
+@table @option
+@item exprs
+Set the '|'-separated expressions list for each separate channel. If
+the number of input channels is greater than the number of
+expressions, the last specified expression is used for the remaining
+output channels.
+
+@item channel_layout, c
+Set output channel layout. If not specified, the channel layout is
+specified by the number of expressions. If set to @samp{same}, it will
+use by default the same input channel layout.
+@end table
+
+Each expression in @var{exprs} can contain the following constants and functions:
+
+@table @option
+@item ch
+channel number of the current expression
+
+@item n
+number of the evaluated sample, starting from 0
+
+@item s
+sample rate
+
+@item t
+time of the evaluated sample expressed in seconds
+
+@item nb_in_channels
+@item nb_out_channels
+input and output number of channels
+
+@item val(CH)
+the value of input channel with number @var{CH}
+@end table
+
+Note: this filter is slow. For faster processing you should use a
+dedicated filter.
+
+@subsection Examples
+
+@itemize
+@item
+Half volume:
+@example
+aeval=val(ch)/2:c=same
+@end example
+
+@item
+Invert phase of the second channel:
+@example
+eval=val(0)|-val(1)
+@end example
+@end itemize
+
 @section afade
 
 Apply fade-in/out effect to input audio.
@@ -1896,7 +1960,8 @@ This source accepts the following options:
 @item exprs
 Set the '|'-separated expressions list for each separate channel. In case the
 @option{channel_layout} option is not specified, the selected channel layout
-depends on the number of provided expressions.
+depends on the number of provided expressions. Otherwise the last
+specified expression is applied to the remaining output channels.
 
 @item channel_layout, c
 Set the channel layout. The number of channels in the specified layout