[mythtv-users] Why does myth protocol perform worse than UPnP or SMB shares?

[Michael T. Dean]

On 10/18/2008 01:21 PM, Johnny Russ wrote:
> I have an SD frontend that is connected in just the next room over, 
> and it works most of the time, but I wouldn't say it was completely 
> reliable. I have been playing around with MythTV Player, XBMC, and 
> win32 Mythfrontend. I have found that all of them struggle to stream 
> (lots of pauses, rebuffering) a single SD recording when streaming 
> from the backend using the myth protocol. However, I can playback a 
> show with zero problems when I use SMB or the UPnP server. What is 
> wrong with the myth protocol or with the clients that causes it to be 
> so much less efficient? After all of my trouble I get the cleanest 
> picture and most reliable playback using UPnP with Windows Media 
> Player. That just seems wrong to me.

If you don't want Myth streaming the recording, set up a share (even a 
CIFS share using Samba, if you like) such that the recordings exist on 
the frontend at exactly the same absolute location as on the backend(s) 
and make sure you do /not/ enable:

Always stream recordings from the backend
Enable this setting if you want MythTV to always stream files from a 
remote backend instead of directly reading a recording file if it is 
accessible locally.

However, I'm guessing you'll find that it's not Myth's streaming the 
recording that causes the issue.  It's likely your system just can't 
keep up with all the extra stuff Myth's player does (things like exact 
seeking through the seek table, commercial skipping, 
deinterlacing--often with high-quality deinterlacers, ...).  So, I'm 
guessing you'll find the same problems even when you're not using Myth 
to stream the recordings.  (BTW, make sure you use the default 
configuration of the Slim playback profile group-- 
http://www.mythtv.org/wiki/index.php/Playback_profiles --if you're doing 
software decoding, but you may need to use XvMC to make things work, and 
doing so requires a lot of non-Myth configuration first.)

So, why does it work so well with WMP if your system is underpowered?  
Well, because there's a lot of money to be made in making video card 
drivers /for Windows/ that allow offloading of video decoding to the 
GPU.  And, since *nix doesn't have a good video-decoding-offload API, 
you're limited by what your CPU can provide.

Mike