Hi
I had the same experience playing on ipad, hd would stutter on ipad 2 not sure about later versions but believe apple restrict the hardware rendering to 'approved' specific formats.
I used a trick, I have auto decrypt setup for all recordings and then also have samba enabled, then on my pc at home running plex server (free) I connect the samba share to my library as a new source called Humax.
Plex transcodes on the fly and it works a treat - I believe its the audio container the ipad doesn't like as the load on my pc is really minimal.
I then run plex on the ipad which cost a few pounds but was cheap and plays everything
and fast forward works
Plex also has a dlna client which I've used to access the humax content on my sony tv which would only play hd not sd content direct from the humax!
I actually then went the whole hog and purchased a lifetime subscription to plex, to support them - its not required but adds another cool feature where you can sync content down to your ipad for offline use
and also if you set it up access it over the internet but that's all on the plex site
I have been tempted to get a roku/nowtv box and sideload plex for the additional tv's in the house as the plex client is much nicer than the dlna interface for a big library ~ markets just moving so much I can't decide which
Regards
Damian