VDR is in principle only capable of handling digital DVB data streams(ISO/MPEG2) , the encoding of analogue TV is *not* foreseen inside the VDR.
So, for the use of analogue TV with VDR, the data going into VDR has to be MPEG2 format and all functions have to be handled like a DVB card. This is the purpose of the Analogtv plugin. This plugin simulates an complete virtual DVB-budget-card.
Some words about analog and VDR
The encoding of the analogue video und audio data will make either an software encoder like mp1e or ffmpeg (be careful-for that you need a fast computer, because it has to be realtime and even if you only like to view analogue TV) or the hardware encoder of a Hauppauge PVR 250/350-TV card.
Really useful seems to be for now only the hardware encoding solution with Hauppauge PVR 250 and PVR 350 cards.
These cards support 720x576 in PAL or NTSC in a very fine quality.
But in principle you can also use any Booktree BT848/878 card supported by bttv, any card supported by ivtv and some other cards like capture cards too. But with cards *not having the encoder* mostly with higher cpu load, less resolution and less stability. Starting in these days USB cards are supported too. For Hauppauge PVR cards we have here a extra page.