Hi, I'd like to record only the sound from dvb-t tv.
I want the original mp2 stream. I know there are
some pvr software that will record the mpeg2 video+sound
but I need to record only mp2 sound...
How to do this please?

I use VideoRedo for this. It can output in elementary streams - ie, a separate stream for video and audio.

FFMPEG could also do it, using -vn and -acodec copy, with a suitable container format (MP2?). But I am guessing if you don't know about FFMPEG already then you may find it pretty difficult to use.

Edit: to clarify, first I record the programme on my PVR. It outputs it as an MPEG transport stream (TS), but you could also use a VOB or an MPG. Then, I'd use VideoRedo to separate it by saving it as elementary streams, so you can save the audio to a separate file.

I mention FFMPEG because VideoRedo isn't free.

You could also use the free ProjectX or bbDMUX to demux the audio stream.