sws: document color range >8bit oddity

libswscale/utils.c

@@ -1004,6 +1004,8 @@ int sws_setColorspaceDetails(struct SwsContext *c, const int inv_table[4],
     c->srcRange   = srcRange;
     c->dstRange   = dstRange;
 
+    //The srcBpc check is possibly wrong but we seem to lack a definitive reference to test this
+    //and what we have in ticket 2939 looks better with this check
     if (need_reinit && c->srcBpc == 8)
         ff_sws_init_range_convert(c);