+ /* This case is tricky. Requested running time precedes the
+ * segment base, so in a reversed segment where rate < 0, that
+ * means it's before the alignment point of (stop - offset).
+ * Before = always bigger than (stop-offset), which is usually +ve,
+ * but could be -ve is offset is big enough. -ve position implies
+ * that the offset has clipped away the entire segment anyway */