Windows 7: Some general questions about streaming shared media files.

Fellow geeks, please educate me.

Of all IT related stuff, video files is most certainly the thing I understand least. Streaming I can somehow understand but I have no idea how a media file is built / packed, what it contains and how it works.

I have two questions, two things about streamed video which I would like to be able to understand.

Background:
Most of our media content is stored on a few external WD 3TB USB3 shared network drives. I have no problems sharing the content from these drives (connected to Home Server) to other PCs and laptops at home.

Two of the TVs (living room & bedroom) are also connected to the network, both of them with individual IPTV DVRs for German television. No problems to watch shared streamed content on these TVs from server or any other networked PC.

I hate the German way to dub all foreign TV shows and movies. Back home in Scandinavia we are used to original audio with subtitles. As an ex-pat Finn I like need could not live without my Finnish television, which I subscribe from a Finnish service TVkaista - Telkkari netissä. The price I pay gives me a personal DVR located in Finland in this company's premises which stores all programs on Finnish channels I've subscribed from past four weeks. I use the service over a web interface, I can watch on PC or download any show on any channel I've subscribed from past 4 weeks. This far everything is OK.

I usually download shows, series and movies using the best quality this service has to offer, a so called 8 MB VLC quality, file extension .ts. Some news and such I occasionally download using lesser quality, 2 MB MPEG4, file extension .mp4.

Both of my issues only occur when streaming these video files, .mp4 and .ts files I have downloaded from the Finnish service, and only when streamed to the TVs. Streaming any other content like ripped DVDs or content copied from German DVRs, as well as streaming the mentioned Finnish content to other PCs have no problems.

The questions:

1. How is it possible that sometimes audio and video are not synced when streamed over the network to the television but is always in sync when streamed to other PCs? Sometimes I need to stop and restart the stream several times before it runs as intended, video and audio in sync. Notice that, as mentioned above, this only occurs when streaming the content I have downloaded from my Finnish TV service. Ripped DVDs and all other content is normally always in sync.
   
2. Why does the video stream quite often stop for a second or so when the type of content changes in video? I can not explain what I mean, so check this short video (sorry the quality, filmed from TV using handheld mobile phone just to show the issue). Check how video stream stops at 0:08 when moving from channel logo to show, and then at 0:18, 0:26 and 0:46 when credits are shown. Audio continues normally:

I mean, how come the TV "knows" what kind of signal is coming and make these annoying stops every time credits are shown?

I hope someone can understand this rant. I can live with both of these minor issues but I'd like to learn to understand them.

Kari