[mythtv-users] MPEG Hardware decoding

[Marian Aldenhoevel]

Hi,

I am confused about the uses for MPEG-Hardware, be it de- or 
encoder-chips, by
MythTV. If there is a place on the web or a subject to search the 
mailinglist
archives I would appreciate a pointer.

I understand that MythTVs GUI is presented via X on the "normal" 
graphics adaptor
in the computer and displayed on a monitor directly or on a TV via the 
graphic
board TV-out or an external VGA-to-something converter.

So doesn't MythTV need to decode the video in any case to view it? If 
not how
can it overlay its GUI or OSD on top of it? Or allow sophisticated filtering
and processing of the video?

Take the case of a DVB-input (this is of concern to me because it is what I
would use). What happens to the data?

I gather it is delivered from the card as MPEG2, saved to disk as MPEG2 
(save
any optional transcoding) for buffering or "permanent" recording and 
decoded
in software to be viewed live (or "almost live", with a short processing
delay) or when it is replayed later.

A DVB-Card like the Hauppauge Nexus has a MPEG2 decoder-chip, but is that
of any use in MythTV? How could the GUI or OSD leave the computer that way?

VDR, another PVR-project, uses Hardware in the DVB card to present its GUI
and OSD. That approach is very easy on the CPU but rather severly limits 
the
things it can show on top of the video.

That said, what I really want to know is: Can MythTV profit from 
Hardware MPEG
_de_coding at all? And if so on what Hardware, are there cards that take 
MPEG
and deliver decoded frames back to the CPU instead of sending them out 
over a
cable? Are the "full-featured" DVB-cards amongst those or would the MPEG 
decoder
on them lie idle when using them with MythTV? Or am I all mixed up anyway?

Ciao, MM