doc/ffmpeg,doc/ffplay: reference timespec definitions

Reference time definition syntax in option descriptions when appropriate.

Fixes trac ticket #4595.
Signed-off-by: Ganesh Ajjanagadde <gajjanagadde@gmail.com>
Signed-off-by: Stefano Sabatini <stefasab@gmail.com>

doc/ffmpeg.texi

@@ -280,13 +280,15 @@ data read from the input file.
 When used as an output option (before an output filename), stop writing the
 output after its duration reaches @var{duration}.
 
-@var{duration} may be a number in seconds, or in @code{hh:mm:ss[.xxx]} form.
+@var{duration} must be a time duration specification,
+see @ref{time duration syntax,,the Time duration section in the ffmpeg-utils(1) manual,ffmpeg-utils}.
 
 -to and -t are mutually exclusive and -t has priority.
 
 @item -to @var{position} (@emph{output})
 Stop writing the output at @var{position}.
-@var{position} may be a number in seconds, or in @code{hh:mm:ss[.xxx]} form.
+@var{position} must be a time duration specification,
+see @ref{time duration syntax,,the Time duration section in the ffmpeg-utils(1) manual,ffmpeg-utils}.
 
 -to and -t are mutually exclusive and -t has priority.
 
@@ -305,7 +307,8 @@ will be preserved.
 When used as an output option (before an output filename), decodes but discards
 input until the timestamps reach @var{position}.
 
-@var{position} may be either in seconds or in @code{hh:mm:ss[.xxx]} form.
+@var{position} must be a time duration specification,
+see @ref{time duration syntax,,the Time duration section in the ffmpeg-utils(1) manual,ffmpeg-utils}.
 
 @item -sseof @var{position} (@emph{input/output})
 
@@ -325,7 +328,7 @@ the time duration specified in @var{offset}.
 @item -timestamp @var{date} (@emph{output})
 Set the recording timestamp in the container.
 
-@var{date} must be a time duration specification,
+@var{date} must be a date specification,
 see @ref{date syntax,,the Date section in the ffmpeg-utils(1) manual,ffmpeg-utils}.
 
 @item -metadata[:metadata_specifier] @var{key}=@var{value} (@emph{output,per-metadata})

doc/ffplay.texi

@@ -47,9 +47,17 @@ Disable video.
 @item -sn
 Disable subtitles.
 @item -ss @var{pos}
-Seek to a given position in seconds.
+Seek to @var{pos}. Note that in most formats it is not possible to seek
+exactly, so @command{ffplay} will seek to the nearest seek point to
+@var{pos}.
+
+@var{pos} must be a time duration specification,
+see @ref{time duration syntax,,the Time duration section in the ffmpeg-utils(1) manual,ffmpeg-utils}.
 @item -t @var{duration}
-play <duration> seconds of audio/video
+Play @var{duration} seconds of audio/video.
+
+@var{duration} must be a time duration specification,
+see @ref{time duration syntax,,the Time duration section in the ffmpeg-utils(1) manual,ffmpeg-utils}.
 @item -bytes
 Seek by bytes.
 @item -nodisp