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