diff --git a/libavformat/au.c b/libavformat/au.c
index fa2e0c4513..670ec79e59 100644
--- a/libavformat/au.c
+++ b/libavformat/au.c
@@ -120,6 +120,8 @@ static int au_read_header(AVFormatContext *s)
     st->codec->sample_rate = rate;
     st->codec->bit_rate    = channels * rate * bps;
     st->codec->block_align = channels * bps >> 3;
+
+    st->start_time = 0;
     avpriv_set_pts_info(st, 64, 1, rate);
     return 0;
 }
@@ -134,6 +136,7 @@ static int au_read_packet(AVFormatContext *s,
     if (ret < 0)
         return ret;
     pkt->stream_index = 0;
+    pkt->duration     = ret / s->streams[0]->codec->block_align;
 
     return 0;
 }