avconv: add -attach option.

It allows attaching arbitrary files, e.g. fonts to Matroska files.

1 files changed, 15 insertions, 0 deletions

diff --git a/doc/avconv.texi b/doc/avconv.texi
index c298dc5710..e14ab857f4 100644
--- a/doc/avconv.texi
+++ b/doc/avconv.texi
@@ -192,6 +192,21 @@ Specify the preset for matching stream(s).
 @item -stats (@emph{global})
 Print encoding progress/statistics. On by default.
 
+@item -attach @var{filename} (@emph{output})
+Add an attachment to the output file. This is supported by a few formats
+like Matroska for e.g. fonts used in rendering subtitles. Attachments
+are implemented as a specific type of stream, so this option will add
+a new stream to the file. It is then possible to use per-stream options
+on this stream in the usual way. Attachment streams created with this
+option will be created after all the other streams (i.e. those created
+with @code{-map} or automatic mappings).
+
+Note that for Matroska you also have to set the mimetype metadata tag:
+@example
+avconv -i INPUT -attach DejaVuSans.ttf -metadata:s:2 mimetype=application/x-truetype-font out.mkv
+@end example
+(assuming that the attachment stream will be third in the output file).
+
 @end table
 
 @section Video Options