tkvideo , by Pat Thoyts, provides a video display widget for the Tk toolkit that can be used to display video data from files or from video capture devices. This includes most webcams and AVI or WMV files.
At this time the widget only works for Windows. On this platform it uses the DirectShow APIs to obtain and display video and so can support any video sources supported by DirectX.
For a unix alternative either embed a player (ffmpeg etc) into a Tk frame using the window ID or you could try tkgst which is a widget that supports GStreamer media streams.
Is there a way to adjust volume level with tkvideo ?
PT: as of 2011 there is a volume widget command to read and set the volume (0=silent, 100=maximum).
I used this awesome lib to make an app to screencast with your webcam as picture-in-picture PiP
I also used this to make a prototype video browser http://www.youtube.com/watch?v=_sRcD2IhZnA