[gst-devel] why playbin can not recognized my aac decoder

[gtxia]

hello all.

I developed a aac decoder and it can deal with thus sink caps

GstStaticPadTemplate sink_factory = GST_STATIC_PAD_TEMPLATE ("sink",
    GST_PAD_SINK,
    GST_PAD_ALWAYS,
    GST_STATIC_CAPS (
		"audio/mpeg, "
		"mpegversion = (int) {2, 4}, "
		"rate = (int) [8000, 96000], "
		"channels = (int) [1, 6]")

When I use playbin to play aac audio file. It's OK. But I want to use it
to decoder aac framed audio in A/V file such as avi with its audio
format is aac. My acc decoder can not be recognized by playbin. If I
linked the caps manually. It's ok. I used --gst-debug=*5 to dump all
inforamtions into a file. I can not find any useful informations. 

The playbin always complains with 

** Message: don't know how to handle audio/mpeg, mpegversion=(int)4,
framed=(boolean)true, codec_data=(buffer)1290, rate=(int)32000,
channels=(int)2

my gstreamer version is gstreamer-0.10.10-2.fc6

Appreciate for any help.

Regards

XiaGuangTai