avformat/thp: set duration for audio stream too

Signed-off-by: Paul B Mahol <onemda@gmail.com>

libavformat/thp.c

@@ -135,6 +135,7 @@ static int thp_read_header(AVFormatContext *s)
             st->codec->codec_tag = 0;  /* no fourcc */
             st->codec->channels    = avio_rb32(pb); /* numChannels.  */
             st->codec->sample_rate = avio_rb32(pb); /* Frequency.  */
+            st->duration           = avio_rb32(pb);
 
             avpriv_set_pts_info(st, 64, 1, st->codec->sample_rate);