webrtcbin cannot "create-offer" while "data-channel" exist

[givip]

Hi everyone!

I write application for video streaming, using Gstreamer and WebRTCBin.

The problem is following:
When I'm trying to "create-offer" first and then establish connection
everything works fine, but 
If remote peer already established "data-channel" I cannot "create-offer"
for streaming-channel.

In second case data-channel works well, I can exchange string messages
easily.

I receive assert in function /*sdp_media_from_transceiver*/

/g_assert (trans->mline == -1 || trans->mline == media_idx);/

I really don't understand how it should work.

May be someone can help me



--
Sent from: http://gstreamer-devel.966125.n4.nabble.com/