SageTV's Theater HD: Better SMB/CIFS Performance, At Least Reportedly...

Here’s another end-of-week attempt to tie up some loose ends. As I reported a month back, whereas SageTV’s Theater HD networked media extender worked well over CAT5, its ability to stream media over a powerline networking spur to the router was sub-par. When I reported my results to my SageTV contacts, they promptly headed to a local retailer to pick up a few HomePlug AV adapters, in an attempt to duplicate (and if possible, rectify) my findings.

Happily, I received an encouraging series of emails from one of the company’s software developers a few days ago, followed shortly thereafter by the public release of a beta firmware implementing the idea:

We did some more analysis on the situation and have come up with a solution now. With the new update; it can easily stream the DVR-MS files without any glitches at all over powerline…It was a performance issue with SMB transfers from Windows servers in general that was exacerbated by the latency of the powerline connection. So this actually benefits all SMB/CIFS network playback from Windows on the HD200.

Recall that the media server I was streaming from, my Dell XPS M1330 laptop, did not have a copy of SageTV Media Center installed on it, since it already supported the conceptually redundant Microsoft Windows Media Center capability. As such, the SageTV HD Theater was accessing DVR-MS recordings via the SMB/CIFS (Server Message Block/Common Internet File System) application layer protocol. The latency exacerbation comment above is interesting, considering that in both my earlier CAT5- and powerline-to-router tests of the SageTV HD Theater, the common server-to-router link was high-latency (at least in comparison to CAT5) 802.11n Wi-Fi.

The SageTV developer also commented that he believed both his company’s Media Center application and Microsoft’s Media Center Extender protocol employed SMB/CIFS at the application layer and TCP at the transport layer. I suspect he’s only partly right. Wikipedia’s entry for Windows Media Extender notes that whereas user interface information is sent from the Windows Media server to the Extender via the VNC-reminiscent RDP (Remote Desktop Protocol) at the application layer (and TCP at the transport layer):

The media files are streamed over a different protocol. To render the media, the Extender needs to have an implementation of the codec used to package the media locally installed on the Extender; having the codec on the host computer is not enough.

That ‘different protocol’, I believe, is RTSP (the Real Time Streaming Protocol) at the application layer, coupled with UDP (the User Datagram Protocol) at the transport layer. And given the enormous performance disparity between TCP and UDP over powerline networking that I’ve seen before, I suspect that SageTV HD Theater also supports (and whenever possible uses) UDP at the transport layer, coupled with either SMB/CIFS, RTP (the Realtime Transport Protocol) or RTSP at the application layer. Then again, maybe SageTV Media Server just harnesses an extended TCP window size…

I’ve pulled my SageTV HD Theater out of storage, and I’ll revisit my setup as soon as possible. Stay tuned for a potential follow-up report, particularly if my results aren’t up to par with SageTV’s optimistic projections. I’m off to take the dawg for his mid-morning stroll; happy weekend, all.