avconv: add -dump_attachment option.

1 files changed, 18 insertions, 0 deletions

diff --git a/doc/avconv.texi b/doc/avconv.texi
index e14ab857f4..1075cc7c56 100644
--- a/doc/avconv.texi
+++ b/doc/avconv.texi
@@ -207,6 +207,24 @@ avconv -i INPUT -attach DejaVuSans.ttf -metadata:s:2 mimetype=application/x-true
 @end example
 (assuming that the attachment stream will be third in the output file).
 
+@item -dump_attachment[:@var{stream_specifier}] @var{filename} (@emph{input,per-stream})
+Extract the matching attachment stream into a file named @var{filename}. If
+@var{filename} is empty, then the value of the @code{filename} metadata tag
+will be used.
+
+E.g. to extract the first attachment to a file named 'out.ttf':
+@example
+avconv -dump_attachment:t:0 out.ttf INPUT
+@end example
+To extract all attachments to files determined by the @code{filename} tag:
+@example
+avconv -dump_attachment:t "" INPUT
+@end example
+
+Technical note -- attachments are implemented as codec extradata, so this
+option can actually be used to extract extradata from any stream, not just
+attachments.
+
 @end table
 
 @section Video Options