doc/filters: add acrossover examples

doc/filters.texi

@@ -541,6 +541,29 @@ Set filter order. Availabe values are:
 Default is @var{4th}.
 @end table
 
+@subsection Examples
+
+@itemize
+@item
+Split input audio stream into two bands (low and high) with split frequency of 1500 Hz,
+each band will be in separate stream:
+@example
+ffmpeg -i in.flac -filter_complex 'acrossover=split=1500[LOW][HIGH]' -map '[LOW]' low.wav -map '[HIGH]' high.wav
+@end example
+
+@item
+Same as above, but with higher filter order:
+@example
+ffmpeg -i in.flac -filter_complex 'acrossover=split=1500:order=4th[LOW][HIGH]' -map '[LOW]' low.wav -map '[HIGH]' high.wav
+@end example
+
+@item
+Same as above, but also with additional middle band (frequencies between 1500 and 8000):
+@example
+ffmpeg -i in.flac -filter_complex 'acrossover=split=1500 8000:order=4th[LOW][MID][HIGH]' -map '[LOW]' low.wav -map '[MID]' mid.wav -map '[HIGH]' high.wav
+@end example
+@end itemize
+
 @section acrusher
 
 Reduce audio bit resolution.