video too quick when play from http with ffmpeg avi demux

[bcxa sz]

Hi Developers,

I am using gstreamer to playback http file, with command:
   gst-launch playbin2 uri=http://xxx.xxx.xxx.xxx/test.avi

What I found is that: if use gstreamer avidemux, the audio and video
can playback at normal speed.
But use ffmped avi demux (ffdemux_avi), the video play too faster and
the audio play at normal speed.

Anybody can share the experience or idea? Thanks

BCXA