ffmpeg: add enc_time_base option

add a per-stream option for setting the encoder timebase.
the following values are allowed:
0 - for video, use 1/frame_rate, for audio use 1/sample_rate (this is
  the default)
-1 - match the input timebase (when possible)
>0 - set the timebase to provided number

Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

1 files changed, 24 insertions, 0 deletions

diff --git a/doc/ffmpeg.texi b/doc/ffmpeg.texi
index e72da8c473..dcc0cfb341 100644
--- a/doc/ffmpeg.texi
+++ b/doc/ffmpeg.texi
@@ -1176,6 +1176,30 @@ Try to make the choice automatically, in order to generate a sane output.
 
 Default value is -1.
 
+@item -enc_time_base[:@var{stream_specifier}] @var{timebase} (@emph{output,per-stream})
+Set the encoder timebase. @var{timebase} is a floating point number,
+and can assume one of the following values:
+
+@table @option
+@item 0
+Assign a default value according to the media type.
+
+For video - use 1/framerate, for audio - use 1/samplerate.
+
+@item -1
+Use the input stream timebase when possible.
+
+If an input stream is not available, the default timebase will be used.
+
+@item >0
+Use the provided number as the timebase.
+
+This field can be provided as a ratio of two integers (e.g. 1:24, 1:48000)
+or as a floating point number (e.g. 0.04166, 2.0833e-5)
+@end table
+
+Default value is 0.
+
 @item -shortest (@emph{output})
 Finish encoding when the shortest input stream ends.
 @item -dts_delta_threshold