There are a couple of threads about stuttering, skipping or faltering when streaming media.
Most concern ATV.
I have had this problem when streaming over home network. My music is on an external USB drive.
I connect wirelessly through a wireless repeater that in turn connects to a router which connects to the computer that hosts the USB drive via ethernet.
What happened:-
I connected with my iPhone to my MacPro wirelessly and found my shared music through the music app.
Playback was intermittent.
I played back directly through iTunes on my MacPro.
Playback was intermittent.
I considered the possibilities - especially whether the MacPro had insufficient memory to buffer the music.
I closed down all memory hungry applications (Firefox and iTunes in this case) and restarted iTunes.
No luck.
I did not shut down the MacPro or any of the routers, or the host to the USB drive.
I found out, inter alia, that the whole chain supports PHY Modes:802.11 a/b/g/n.
So OK.
I down loaded the iPhone Remote app. This itself, works. But it remoted to the MacPro that still played intermittently.
However I do believe that the Remote app aids in discovery of the shared library. i.e. use this first just to connect and connecting through the Music app to the shared library seems less painful.
I came back to it the next day.
Everything works and days latter continues to work.
Just to prove that buffering and network congestion or capacity are not issues I can use the Remote app to control the MacPro to play one song while the iPhone Music app connects and plays another song.
The conclusion is that i don't know what the problem is apart from that it must be something to do with wifi networking and can remedy itself.
Shut downs and start ups of devices (network or computer) may or may not help. Certainly in this case it has not proven necessary.
However it is necessary to shut down my terminal adaptor/router from time to time in order to regain internet connectivity speed.
I think that routers can hold out of date information and the best way to flush it is to shut them down.
They also flush and resynchronise certain registers themselves.