update -t option documentation

Patch by Godwin Stewart

Originally committed as revision 10146 to svn://svn.ffmpeg.org/ffmpeg/trunk

doc/ffmpeg-doc.texi

@@ -212,7 +212,8 @@ input filename
 Overwrite output files.
 
 @item -t duration
-Set the recording time in seconds.
+Restrict the transcoded/captured video sequence
+to the duration specified in seconds.
 @code{hh:mm:ss[.xxx]} syntax is also supported.
 
 @item -fs limit_size

ffmpeg.c

@@ -3601,7 +3601,7 @@ const OptionDef options[] = {
     { "y", OPT_BOOL, {(void*)&file_overwrite}, "overwrite output files" },
     { "map", HAS_ARG | OPT_EXPERT, {(void*)opt_map}, "set input stream mapping", "file:stream[:syncfile:syncstream]" },
     { "map_meta_data", HAS_ARG | OPT_EXPERT, {(void*)opt_map_meta_data}, "set meta data information of outfile from infile", "outfile:infile" },
-    { "t", HAS_ARG, {(void*)opt_recording_time}, "set the recording time", "duration" },
+    { "t", HAS_ARG, {(void*)opt_recording_time}, "record or transcode \"duration\" seconds of audio/video", "duration" },
     { "fs", HAS_ARG | OPT_INT64, {(void*)&limit_filesize}, "set the limit file size in bytes", "limit_size" }, //
     { "ss", HAS_ARG, {(void*)opt_start_time}, "set the start time offset", "time_off" },
     { "itsoffset", HAS_ARG, {(void*)opt_input_ts_offset}, "set the input ts offset", "time_off" },