I thought I should post some details on this wee device - cost about $25 - and can be used to digitise VCR tapes etc.
The device I have is a Silvercrest VG2000 (Video Grabber) but was sold with other names also.
LSUSB gives
Device 015: ID eb1a:2863 eMPIA Technology, Inc. Video GrabberI tested it today using a DVD player on both Composite Video and S-Video outputs of the player.
The results were very good ..... I did not have a VCR to test with, so I am not sure how it would behave with a VCR. One thing is for sure .... the device itself is not introducing any artefacts or disturbances to the video.
I played the video stream in VLC ....... selecting for composite video and audio the following
Video: /dev/video0
Audio: hw:2,0 (from the drop-down menu)
It took a little while to figure out how to record from the S-Video signal ......
Video: /dev/video0:input=1
Audio: hw:2,0 (from the drop-down menu)
That was all it took!

Of course the numbers of the devices above will change according to the hardware present.
The only negative I happened across with this is the video bitrate is huge!
That needs to be dropped before saving, else it would use >1GB per minute

The only warning to anyone thinking of getting something similar is to make sure the device is supported in Linux BEFORE you buy it.
BTW, I tried to use PCLinuxOS-PVR instead of VLC, and while I could record the video, I could not record the audio, as the app does not allow selection of a separate audio channel.
That covers it for now.