avfilter/af_apad: do not add infinite silence for zero pad_dur or whole_dur

Unfortunately pad_len and pad_dur behaviour was different if 0 was specified,
pad_dur handled 0 duration as infinity, for pad_len, infinity was -1.

Let's make the behaviour consistent by handling 0 duration for pad_dur and
whole_dur as indeed 0 duration. This somewhat changes the behaviour of the
filter if 0 was explicitly specified, but deprecating the old option and adding
a new for the corrected behaviour seemed a bit overkill. So let's document the
change instead.

Signed-off-by: Marton Balint <cus@passwd.hu>

1 files changed, 5 insertions, 2 deletions

diff --git a/doc/filters.texi b/doc/filters.texi
index 6ab41706e5..1fced203b6 100644
--- a/doc/filters.texi
+++ b/doc/filters.texi
@@ -2291,12 +2291,12 @@ with @option{pad_len}.
 @item pad_dur
 Specify the duration of samples of silence to add. See
 @ref{time duration syntax,,the Time duration section in the ffmpeg-utils(1) manual,ffmpeg-utils}
-for the accepted syntax. Used only if set to non-zero value.
+for the accepted syntax. Used only if set to non-negative value.
 
 @item whole_dur
 Specify the minimum total duration in the output audio stream. See
 @ref{time duration syntax,,the Time duration section in the ffmpeg-utils(1) manual,ffmpeg-utils}
-for the accepted syntax. Used only if set to non-zero value. If the value is longer than
+for the accepted syntax. Used only if set to non-negative value. If the value is longer than
 the input audio length, silence is added to the end, until the value is reached.
 This option is mutually exclusive with @option{pad_dur}
 @end table
@@ -2305,6 +2305,9 @@ If neither the @option{pad_len} nor the @option{whole_len} nor @option{pad_dur}
 nor @option{whole_dur} option is set, the filter will add silence to the end of
 the input stream indefinitely.
 
+Note that for ffmpeg 4.4 and earlier a zero @option{pad_dur} or
+@option{whole_dur} also caused the filter to add silence indefinitely.
+
 @subsection Examples
 
 @itemize