1/0 fix by (Tim Allen <tim at proximity dot com dot au>)

Originally committed as revision 2444 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavformat/mpeg.c

@@ -226,6 +226,10 @@ static int mpeg_mux_init(AVFormatContext *ctx)
     else
         /* every 2 seconds */
         s->pack_header_freq = 2 * bitrate / s->packet_size / 8;
+
+    /* the above seems to make pack_header_freq zero sometimes */
+    if (s->pack_header_freq == 0)
+       s->pack_header_freq = 1;
     
     if (s->is_mpeg2)
         /* every 200 packets. Need to look at the spec.  */