+ * @defgroup lavu_math_rational AVRational
+ * @ingroup lavu_math
+ * Rational number calculation.
+ *
+ * While rational numbers can be expressed as floating-point numbers, the
+ * conversion process is a lossy one, so are floating-point operations. On the
+ * other hand, the nature of FFmpeg demands highly accurate calculation of
+ * timestamps. This set of rational number utilities serves as a generic
+ * interface for manipulating rational numbers as pairs of numerators and
+ * denominators.
+ *
+ * Many of the functions that operate on AVRational's have the suffix `_q`, in
+ * reference to the mathematical symbol "ℚ" (Q) which denotes the set of all
+ * rational numbers.
+ *