clarify start/end timebase

git-svn-id: file:///var/local/repositories/ffmpeg/trunk@13254 9553f0bf-9b14-0410-a0b8-cfaf0461ba5b

libavformat/avformat.h

@@ -392,7 +392,7 @@ typedef struct AVProgram {
 typedef struct AVChapter {
     int id;                 ///< Unique id to identify the chapter
     AVRational time_base;   ///< Timebase in which the start/end timestamps are specified
-    int64_t start, end;     ///< chapter start/end time in AV_TIME_BASE units
+    int64_t start, end;     ///< chapter start/end time in time_base units
     char *title;            ///< chapter title
 } AVChapter;