avconv: extend -r to work on any input stream.

This is done by automatically inserting a setpts filter.

1 files changed, 9 insertions, 2 deletions

diff --git a/doc/avconv.texi b/doc/avconv.texi
index 693c45e429..2ebfe9fe44 100644
--- a/doc/avconv.texi
+++ b/doc/avconv.texi
@@ -257,8 +257,15 @@ attachments.
 @item -vframes @var{number} (@emph{output})
 Set the number of video frames to record. This is an alias for @code{-frames:v}.
 @item -r[:@var{stream_specifier}] @var{fps} (@emph{input/output,per-stream})
-Set frame rate (Hz value, fraction or abbreviation), (default = 25). For output
-streams implies @code{-vsync cfr}.
+Set frame rate (Hz value, fraction or abbreviation).
+
+As an input option, ignore any timestamps stored in the file and instead
+generate timestamps assuming constant frame rate @var{fps}.
+
+As an output option, duplicate or drop input frames to achieve constant output
+frame rate @var{fps} (note that this actually causes the @code{fps} filter to be
+inserted to the end of the corresponding filtergraph).
+
 @item -s[:@var{stream_specifier}] @var{size} (@emph{input/output,per-stream})
 Set frame size.