Document ffplay -ast, -vst, and -sst options.

Originally committed as revision 17694 to svn://svn.ffmpeg.org/ffmpeg/trunk

doc/ffplay-doc.texi

@@ -87,6 +87,21 @@ quality broadcast) it is necessary to change that. This option is mainly
 used for debugging purposes.
 @item -threads @var{count}
 Set the thread count.
+@item -ast @var{audio_stream_number}
+Select the desired audio stream number, counting from 0. The number
+refers to the list of all the input audio streams. If it is greater
+than the number of audio streams minus one, then the last one is
+selected, if it is negative the audio playback is disabled.
+@item -vst @var{video_stream_number}
+Select the desired video stream number, counting from 0. The number
+refers to the list of all the input video streams. If it is greater
+than the number of video streams minus one, then the last one is
+selected, if it is negative the video playback is disabled.
+@item -sst @var{subtitle_stream_number}
+Select the desired subtitle stream number, counting from 0. The number
+refers to the list of all the input subtitle streams. If it is greater
+than the number of subtitle streams minus one, then the last one is
+selected, if it is negative the subtitle rendering is disabled.
 @end table
 
 @section While playing

ffplay.c

@@ -2489,9 +2489,9 @@ static const OptionDef options[] = {
     { "fs", OPT_BOOL, {(void*)&is_full_screen}, "force full screen" },
     { "an", OPT_BOOL, {(void*)&audio_disable}, "disable audio" },
     { "vn", OPT_BOOL, {(void*)&video_disable}, "disable video" },
-    { "ast", OPT_INT | HAS_ARG | OPT_EXPERT, {(void*)&wanted_audio_stream}, "", "" },
-    { "vst", OPT_INT | HAS_ARG | OPT_EXPERT, {(void*)&wanted_video_stream}, "", "" },
-    { "sst", OPT_INT | HAS_ARG | OPT_EXPERT, {(void*)&wanted_subtitle_stream}, "", "" },
+    { "ast", OPT_INT | HAS_ARG | OPT_EXPERT, {(void*)&wanted_audio_stream}, "select desired audio stream", "stream_number" },
+    { "vst", OPT_INT | HAS_ARG | OPT_EXPERT, {(void*)&wanted_video_stream}, "select desired video stream", "stream_number" },
+    { "sst", OPT_INT | HAS_ARG | OPT_EXPERT, {(void*)&wanted_subtitle_stream}, "select desired subtitle stream", "stream_number" },
     { "ss", HAS_ARG | OPT_FUNC2, {(void*)&opt_seek}, "seek to a given position in seconds", "pos" },
     { "bytes", OPT_BOOL, {(void*)&seek_by_bytes}, "seek by bytes" },
     { "nodisp", OPT_BOOL, {(void*)&display_disable}, "disable graphical display" },