MymsMan
Ad detector
I typically only record programmes in SD since I often experience picture breakups on HD programmes due to a fairly weak signal - though I cant really be sure how much is due to the signal and how much might be due to to concurrent activity.However, a lot of people never see a problem with doing both at the same time. MymsMan habitually decrypts and runs ad-detection against recordings which are in progress. Other people find this causes problems with their boxes.
I don't notice any problems when decrypting and recording at the same time (other than the media list being slow to react), others find it unacceptable. No idea why there is this variance.