I use gstreamer to stream a mp3 file via rtsp & rtp
and I only heard the sound for about half a second and it stops at once

The console displays :
WARNING: Element "alsasink0" warns:
gstbaseaudiosink.c (696): gst_base_audio_sink_render (): /pipeline0/alsasink0:
Unexpected discontinuity in audio timestamps of more than half a second (0:00:00.803061224), resyncing

My commadline is : gst-launch rtspsrc location = "rtsp://" ! rtpmpadepay ! queue ! mad ! alsasink

would anybody tell me where the problem is ?
and how can i solve it ~~
thank you guys in advance :)