[FFmpeg-devel] [PATCH] doc/ffmpeg: add notes about timestamp handling

Stefano Sabatini stefasab at gmail.com
Thu Jan 23 17:52:29 CET 2014

 doc/ffmpeg.texi | 22 ++++++++++++++++++++++
 1 file changed, 22 insertions(+)

diff --git a/doc/ffmpeg.texi b/doc/ffmpeg.texi
index fa5f8b5..be9f206 100644
--- a/doc/ffmpeg.texi
+++ b/doc/ffmpeg.texi
@@ -211,6 +211,28 @@ described.
+ at chapter Notes on timestamps handling
+By default, @command{ffmpeg} removes the initial offset in the input
+timestamps, so that they will start with 0. To disable this behaviour,
+you can apply the option @option{copyts}, which will disable the
+application of the offset removal and other magical heuristics used to
+fix input timestamps, depending on the @option{vsync} synchronization
+mode used, the input codec, the input timestamp values, the mood of
+the original code programmer and astrological influences.
+Note in particular that the @option{itsoffset} value has no effect if
+ at option{copyts} is not enabled, unless it is set to 0, in this case a
+magical synchronization mode will be enabled.
+If you want to understand this better, read the fine source of
+ at filenane{ffmpeg.c} code, good luck.
+Finally, note that many muxers will apply further heuristics, in
+particular they may reset the initial offset (some muxers don't
+support initial timestamps starting from 0, or they don't accept
+negative timestamps).
 @chapter Options
 @c man begin OPTIONS

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