DVB-T need mpeg encoding?

Archived from groups: rec.video.desktop (More info?)

Tim wrote:

> I could find 19 DVB-T cards on http://www.videohelp.com/
> capturecards.php but neither if them supports hardware
> mpeg encoding/decoding.
>
> Is that because the digital streams are already mpeg so
> there is no need to encode it? Or have I just not found
> the right card?

DVB transmissions (regardless of whether it is DVB-T, DVB-C
or DVB-S) are based on MPEG-2. What you get from the card
is an MPEG-2 transport stream (usually containing several
multiplexed audio and video streams, grouped into tv or
radio programmes.) In other words, the MPEG-2 encoder is
at the broadcaster's end; you are just receiving the
already-encoded MPEG-2 data with your card.

However, some DVB cards _do_ have a built-in MPEG-2
_decoder_ chip, alongside with a video encoder and an
analogue video output ("tv out" ) connector. These are
usually called "full-featured" cards, while those cards
which can only receive the raw transport stream are
called "budget" cards.

Full-featured cards are usually a preferred choice for
hobbyist DIY PVR projects, since the software support
for them is somewhat better and the connection to the
tv is less problematic (as they have a "tv out" on their
own and you do not need to fuss about with the "tv out"
on the primary VGA display adapter card which may have
problems with scaling, interlacing etc.)

Here you have one example of a full-featured DVB-T card
("Technotrend DVB-T 1.2 Premium Edition" ):

<http://www.technotrend.de/english/products/pcproducts2-1.html>
<http://www.technotrend.de/english/products/pcproducts2-2.html>
<http://google.com/search?q=%22Technotrend+DVB-T+1.2+Premium%22>

> I am trying to turn my p200mhz into a pvr so I need to do
> as much as possible in hardware (I actually want to use
> the p200 to a few other things at the same time).

You need to have an MPEG-2 decoder in hardware (one way or
the other); a 200 MHz Pentium is simply not fast enough for
software-based, real-time MPEG-2 decoding.

> Should I maybe buy one DVB-T card and one encoder/decoder
> card? Is that the trick?

Yes, that is another way of achieving the same result. Some
people have used "budget" cards together with a separate
hardware MPEG-2 decoder / "tv out" card (such as "Hollywood
Plus DXR3", which was originally sold for decoding MPEG-2
data from DVDs.)

You might also want to see

<http://www.linuxdvb.tv/>
<http://www.linuxdvb.tv/software/apps/vdr-l.jpg>
<http://www.flood-net.de/flood/projects/vdr-progress.jpg>
<http://www.linuxtv.org/>
<http://www.cadsoft.de/vdr/>

--
znark