rtsp-server : Async done message handling in pause and play case

Submitted by Srimanta Panda (trollkarlen)

Link to original bug (#738279)

Description

In scenario when server is loaded, if you perform pause and play, rtsp-server play response contains range starting from 0.

The issue is basically when a pause carried out the multiudpsink perfroms the asynchronous state change. This send s a ASYNC DONE message to the bus.

But if the pause and play is quick enough then play request (with range) tries to do the rtsp_media_seek before the ASYNC DONE message is handled. But while performing seek and flush stop event has executed, but not the new segment event, in-between the async done is performed and query command fails because have_segment of basesink is false and resets the rtsp-media range start value to zero.

And because of that the server tries to send a reply back with incorrect range which starts from zero because of the failed query during async done.

So overall the issue is media_seek should wait till the async done is performed.

The other scenario to reproduce the issue is to send pause and play (with range) multiple time simultaneously using a script.

Version: 1.4.3