Re: [Discuss-gnuradio] HDTV and the USRP

[Eric Blossom]

On Tue, Jul 27, 2004 at 10:24:16PM -0400, Dave Dodge wrote:
> On Tue, Jul 27, 2004 at 04:19:54PM -0700, Steve Schear wrote:
> > What are the plans to move some of the computational load over to the USRP 
> > for ATSC HDTV?  As any estimate of the been made as to whether, once this 
> > is done, it will be practical to view in real-time such content using a 1.5 
> > or so GHz PC?  Inquiring minds want to know.

We're interested in seeing what we can off-load into the FPGA, but for
Matt and I, it's a relatively low priority.  Others of course are free
to dive in and see what they can do.

The FPGA we're using does not contain hardware multipliers, so some of
the signal processing is a bit of a challenge.

> There's at least two steps: 8VSB demodulation to get the transport
> stream, and then MPEG decoding to display it.  I believe the GNU Radio
> stuff only handles the demodulation,

Correct.

> ... and I have no idea what the plans are for accelerating that.
> 
> Assuming you've got the transport stream, you then need to turn it
> into audio and video.  You can probably handle standard definition
> programs with software decoding on a 1.5GHz system.  But I'd be
> suprised if you could get clean playback of high definition programs
> with that.  And be warned that I've tried using an Athlon XP2400+ with
> a graphics card that has XvMC acceleration, and it still didn't give
> what I'd consider acceptable results.  I ended up buying a set-top box
> with a dedicated MPEG decoder (Roku HD1000; runs Linux and has SDK).
> 
>                                                   -Dave Dodge

Using Xine and an Athlon MP1800+ we've gotten reasonable results with
software MPEG decoding 1080i.  I think that the last few versions of
Xine have some problems with the 1080i stuff.  I've fallen back to an
earlier version for demoing.  They may be lacking 1080i transport
streams for testing.

Eric