avutil: elaborate documentation for av_get_random_seed

libavutil/random_seed.h

@@ -24,7 +24,12 @@
 #include <stdint.h>
 
 /**
- * Get a seed to use in conjunction with random functions.
+ * Get random data.
+ *
+ * This function can be called repeatedly to generate more random bits
+ * as needed. It is generally quite slow, and usually used to seed a
+ * PRNG.  As it uses /dev/urandom and /dev/random, the quality of the
+ * returned random data depends on the platform.
  */
 uint32_t av_get_random_seed(void);