-used for the video files. It affects the frame size and the frame
-rate specified when encoding pages as video. The two standards can be
-specified as "525", "525/60", "NTSC" or "ntsc" and as "625", "625/50",
-"PAL" or "pal" respectively.
+used for the existing video files. It affects the frame size and the
+frame rate specified when encoding pages as video. The standard of
+525-line frames and 59.94\ Hz interlaced fields, commonly called NTSC,
+can be specified as "525", "525/60", "NTSC" or "ntsc". The standard
+of 625-line frames and 50\ Hz interlaced fields, commonly called PAL,
+can be specified as "625", "625/50", "PAL" or "pal"; this is the
+default.