More Input

DirectShow, that component that your Media player is built upon, consists of Filters, which you may have noticed while configuring that media player.

Each filter has one or more Input Pins and one or more Output Pins

A compressed image enters at the input pin of a "decoder filter" comes out uncompressed from the out pin to the next filter in the chain, which is called "Video Renderer Filter" which displays it, but since it has no output pin Sink it drops the image, and sends a ready message upstream to the "decoder Filter" the intermediate Transition filter, telling it to send the next image, which in turn tells the "File Filter" the Source to push another image downstream. that is called a DirectShow Graph.

OK, about twInput
we have 3 main filters in the twGraph :)
Source...
1- a Capture Filter "the camera driver" or a Video File Reader
2- any neccesary decoding/Resizing filters to make the images "Media Samples" sent understandable to the next filters
Transition..
3- a Sample Grabber , it reads the samples (images), and sends them to a callback where we can process them, you cna either have a copy of the data, or the original data that will be sent again down stream.
Sink...
4- again some decoders so the next uderstands the samples
5- a VideoRenderer "now you have your media player" or a Null Filter , it displays the images recived then Drops the allocated space for the images.
...

Each filter can have prefered media types, so when DS tries to connect an output pin with an input pin, it finds the most favourable media type, if pins dont prefer the same type, they can nevver connect, DS resolves this by inserting some filters in between "decoders/converters" in an action called "Intelligent connect"
...
All this ado is wrapped in a simple interface "start/capture/stop/readFromFile" so whenever a decision is made to support other platforms/devices it should be somehow easy "dreaming".
...
Note: we did not use ATL in order to convince DS to get programmed, maybe because even if we used it it wont look like C# com interface, "did they call that Interop ?"
or maybe because ATL is not a walk in the park, "i think"
or maybe because we didn't need to use any Events or Sinks or Monks or any of the other crazy COM stuff of which i am not aware and the ATL was built for.
just wanted to remind my self of that.