Sunday 14 October 2012

1Ms/s DVB-S2 + H.264

Over the last few days I have been doing some tests
with 1 Ms/s on 437 MHz using DVB-S2 and H.264.
All went well except I can't seem to properly decode
the AAC audio that the Hauppauge HD-PVR produces.
The audio received by DVBDream is there but is very
distorted.

Of course doing tests across the shack is one thing but
finding someone else that lives close enough that has the
ability to receive the combination of low symbol rates
DVB-S2 and H.264 is another thing. None of the
DVB-S2 STBs I have looked at go below 2Ms/s.
As I have mentioned before I am using a DVBSky S960
USB dongle to achieve the low symbol rate on receive
and my own software on transmit.

I have started to look at doing an implementation of
DVB-S2 on an FPGA now I have working C code.
I am not sure how easy this will be as the normal S2
frames have 64800 bits in them which is too large to
use standard registers and will have to be done using
ram blocks. Implementing the LDPC code is going to
require quite a lot of lateral thinking. I should really
be doing other things but I have a pair of Terasic DE0
Nanos just sitting around saying program me!

Another problem is the design is going to be very large
and my 'free' web edition of Quartus II is very slow.
It only runs on one core and does not allow incremental
compilation and I have no budget for the $2500 they
want for the subscription edition.Still it will be interesting
to think about how to do S2 in an FPGA even if I never
actually do it.

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