SONY BRAVIA KDL 50W828 - video stuttering

Hi, I have a brand new Sony Bravia KDL 50W828, along with a not-so-new desktop PC running Windows XP service pack 3, AMD Phenom 9500 quad core 2.21 Ghz and 3 GB RAM, wi-fi connected.
At first it all seemed to be working, the TV read correctly all the files shared, but when I try to see a .mkv file with external subtitles .srt the video begin stuttering and it's nearly impossible to properly enjoy the view...
What do you think the problem is? The PC is too old? The wi-fi connection is not strong enough? Or I just set Serviio wrong?

Please help me!!

[Illico]

In fact, when you use external subtitles with mkv, serviio/ffmpeg will transcode and burn the subtitle in a mpeg2video stream...It's quite cpu consuming.
To check this.

Press pause at the beginning of movie on remote control.
Wait some seconds or minutes for transcoding process to forge ahead.
Then resume the movie, stuttering should disappear.

Another solution to check your cpu power, enabled detailed logging and check on log file the ffmpeg command line used,
then retry the same command line on a local windows terminal and check the transcoding process rate (fps), it should be x2 or x3 compare to movie frame rate (25-30fps) ie ( >100 fps should be fine)

Thanks Illico for your answer!!
I'll try this evening both your suggestions. I'll let you know!

Hi again!
Here's what happened yesterday:
If I let buffer the video a little bit (few minutes) it won't stutter... much. It stutters anyway, but at least you can (sort of) see the video (I was watching the last episode of True Detective, and it was a torture having to pause and let it buffer all the time!).

But again, some weird things happened: watching the .mkv file with external subs .srt, it lost the connection twice...

And... it is normal that the TV takes FOREVER to connect with the server?

And... after exiting and reconnecting with the server many times due to connection failure, the media reader of my Sony crashed, and I can't do anything but restore the TV to default options... I bought the TV last saturday and I had to do it twice already!!

And... I added two folders in share, with .avi and .mkv files (without subs)... the TV read the folders but not the files!!!

What's happening with my TV!? ! I'm pretty much desperate!!! It's my first smart TV and I'm starting panicking!!

[Illico]

It's a newest sony TV.
Check that you use the latest firmware.

Could you provide information about format supported by your device model ? (see my signature link)