[PATCH] Add detail to the documentation for ffmpeg -map.

[Mike Scheutzow]

Signed-off-by: Mike Scheutzow <mjs973 at optonline.net>
---
 doc/ffmpeg.texi |   22 +++++++++++++++++-----
 1 files changed, 17 insertions(+), 5 deletions(-)

diff --git a/doc/ffmpeg.texi b/doc/ffmpeg.texi
index 047444a..f807799 100644
--- a/doc/ffmpeg.texi
+++ b/doc/ffmpeg.texi
@@ -622,11 +622,23 @@ Synchronize read on input.
 @section Advanced options
 
 @table @option
- at item -map @var{input_stream_id}[:@var{sync_stream_id}]
-Set stream mapping from input streams to output streams.
-Just enumerate the input streams in the order you want them in the output.
- at var{sync_stream_id} if specified sets the input stream to sync
-against.
+ at item -map @var{input_file_id}:@var{input_stream_id}[:@var{sync_file_id}:@var{sync_stream_id}]
+Specify an input stream to be a source for the output file. An input
+stream is identified by two numbers: an input file index and an input 
+stream index within that file.  Both start counting from 0.
+If any -map options are used, the number of -map options on the command 
+line must match the number of streams in the output file.  The first -map 
+option on the command line specifies the source for output stream 0, 
+the second -map option specifies the source for output stream 1, etc.
+
+If used, @var{sync_file_id}:@var{sync_stream_id} specifies which input 
+stream is used as a presentation sync reference.
+
+For example, to select stream 2 from input file A.mov, and stream 6 from 
+input file B.mov:
+ at example
+ffmpeg -i A.mov -i B.mov -vcodec copy -acodec copy out.mov -map 0:2 -map 1:6
+ at end example
 @item -map_meta_data @var{outfile}[, at var{metadata}]:@var{infile}[, at var{metadata}]
 Set meta data information of @var{outfile} from @var{infile}. Note that those
 are file indices (zero-based), not filenames.
-- 
1.7.4


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