I am working on a WPF application that displays RTSP video streams. Currently, the application handles communication with two types of devices that use RTSP: cameras and archivers (pretty much DVR). Over the lifetime of the app the streams may and usually will be closed multiple times, so we need to make sure they are not cluttering the memory and network when we close them.
We had a go with the MediaElement. We needed to install LAV Filters for ME to display RTSP streams at all. We could see the video from the cameras but the stream wasn’t released until we stopped the video, invoked Close() on MediaElement and set its source to null. The video seemed to be released but we still decided to check memory usage using a profiler. We simply created a loop in which we initialized a new MediaElement (local reference), played RTSP stream and closed it after establishing the connection. Over half an hour of running the test we witnessed a steady increase in memory consumption, and as a result we lost 20MB of memory to all the MediaElements we created. The reason is still unknown to us (timers being bound to the dispatcher?) but after searching the Internet we accepted that there is a problem with MediaElement itself.
We decided this is negligible for our use case (no one is going to create MediaElements with that frequency). Unfortunately, MediaElement was not releaseing streams for archivers when using the same approach. After we got rid of the MediaElement for archivers stream, the archiver’s server still reported the connection being open.
We analyzed the packets with Wireshark. Cameras and archivers use the same version of the RTSP protocol, but when we close the connection on the camera the RTCP and data packets stop coming, which is not the case with the archivers.
We decided to abandon ME altogether and switch to the VLC Player. When we hit stop on the VLC player the connections are nicely closed, but VLC has a bug causing rebuffering of streams at the beginning of any connection. It’s a known issue: https://trac.videolan.org/vlc/ticket/9087. Rebuffering is not consistent. Sometimes it happens twice, sometimes three times. We tried playing around with buffer settings for VLC (network-buffer, live-buffer… you name it) but nothing helped.
There are many questions we are looking answers for:
- why ME is keeping the connection alive for archivers but not for cameras? Is archiver not handling RTSP termination packet correctly?
- which component is responsible for keeping the connection open on the client side and how could we possibly work around it (terminate the stream)?
- how to prevent VLC from rebuffering the stream after the connections is established?
Did you have any success with streaming multiple RTSP streams without performance/memory issues in your application? What components did you use?
Side note: we also played with MediaPlayerHQ, which behaves nicely, unless we kill the process. If we do that the stream remains open for couple of minutes.
I will appreciate any hints and suggestions!
