1. Have been reading a bit but still unable to understand -
what actually is gstreamer?


2. When installing KDE , do I need to install gstreamer or there is something equivalent default in KDE. What is that?


3. Going to install Debian (with lxde) with net-install cd and later install packages -
lame
ffmpeg
mencoder

Are these enough to enable the computer to play "almost all" the mp3 and videos from videocams?

GStreamer is a streaming media framework, based on graphs of filters
which operate on media data. Applications using this library can do
anything from real-time sound processing to playing videos, and just
about anything else media-related. Its plugin-based architecture means
that new data types or processing capabilities can be added simply by
installing new plug-ins.

gstreamer is a multimedia encoding and decoding framework. You generally don't use it directly (though there are tools available for that), it's mostly used as the backend for various media players such as totem. It has a plug-in based system for adding support for various codecs. It even has an ffmpeg plugin to provide you with libav support.

It's not absolutely necessary to have it, unless the player you want to use depends on it. If you have mplayer/mencoder, ffmpeg, and lame, you pretty much have everything you need for most media work. But you may find that certain media play better on one framework than another, or even only on one of them (usually the one you don't have installed ), so it's perfectly reasonable to have a variety of players and backends available. I personally have just about everything installed; mplayer, ffmpeg, xine, gstreamer, and vlc, along with several frontends and related tools. If something is playable at all on Linux, I'm probably going to be able to play it.

I use players like vlc and smplayer, so any idea what is the "default" packages that they depend on ?

IMO, it does not matter whether it is Totem or another. They are just front-end for GStreamer like what people said above.

What you need is plugins such as gst-plugins-bad, gst-plugins-ugly and gst-ffmpeg along with gst-plugins-good. Whether your media are playable depend on those plugins installed.

For Smplayer you need to check http://www.mplayerhq.hu/design7/news.html .

You have to research individual programs to discover what systems they support or are based on. One good way to learn is to watch the dependency packages they want to install. If you see a lot of "gst" dependencies, for example, then you can be pretty sure it's based on gstreamer. And smplayer is obviously based on mplayer just from the name. A few players like totem can use multiple backends.

AIUI, mplayer, xine, and gstreamer are the three big frameworks that you'll see most frontends based around. vlc is kind of an independent project. But in fact, most of these frameworks are built around many of the same tools, having plugins for calling on each other or dependencies on external codecs and libraries such as faad (for aac decoding). Almost all of them depend on or can use libavformat/libavcodec, for example.

Wikipedia is a good source of information about all these tools.

THANKS for the info.

Believe it or not , the section quoted above actually clears some confusion that I have.

Will give Wikipedia a revisit