The Full DVB-S Monty

This is a picture of my Linux box running transmit and receive on DVB-S.
Top left is the Xine display window showing a live picture, below that is the
DVB-S transmit program, to the right of that is the DVB-S receive program
(actually it controls a DVB-S card) and above that is the system load.

DVB-S EPG now working

I am glad to say that the EPG information for DVB-S now works.
DVB-T EPG does not seem to work. Somehow the fix to the power
problem has swapped the I and Q channels. The DVB-S STB can cope
with this but DVB-T cannot. I only discovered the problem when I was
trying to test the EPG for DVB-T.

DVB-T on 436 MHz

Just out of curiosity I did a quick test of my
DVB-T software on 436 MHz. Output power was
under a mW. My Samsung TV when told to
monitor 436 MHz successfully received the signal.
As could be expected the DVB-T signal drowns out
everything above 432.5 MHz so that was the first
and last time I try it.

The output power on DVB-T is considerably below
what I can achieve on DVB-S, so I am going to have to
re-think the driver amplifier as it does not have enough
gain for 1.3 GHz DVB-T although it will be fine for DVB-S.

My DATV experiments have shown me that I really need to
get a much higher quality camera to fully utilise the benefits
of Digital. Have looked at the price of even used studio quality
cameras I don't think that is going to happen any time soon.

More Xine!

In the picture above the left screen is the Linux monitor. It shows the DVB
transmitter application running. The window to the right is Xine and is
displaying the transport stream generated by the DVB software.
The screen to the right is the same signal being decoded by the satellite STB.

The next challenge is to write the DVB-S demodulation code so the USRP2
can be used both for transmit and receive.

DVB Primitive GUI

Above is the first primitive GUI for the DVB-S transmitter.
The GUI is based on QT4. The visible tab is the one for the
various FEC rates available in DVB-S.

I now have direct control of the Hauppauge PVR500 card using
the v4l2 API. This is necessary as the video bitrate needs changing
when any of the parameters are changed like the FEC code rate.

Originally I wrote the program in standard C but to make it easier
for me to integrate with the GUI I have changed the files to C++.
The whole DVB transmitter can now be developed from within the
QT4 development environment. For someone that is not a Linux natural
(I have used Visual C++ before) being able to use a visual development
environment again is nice. I know I have just upset the Linux hardcore
but that is the way it is.

Before I can proceed much further with the development I need the
new UHD for the WBX board. This will allow me to control the
transmitters frequency from the GUI.

I will probably finish off the 1.3 GHz PA next and will also have a think
about the GUI layout. Eventually I want to add DVB-T and when I have
figured out how best to do it, DVB-S and DVB-T receive.

Still no cigar

The SI tables are still not working. I have a set of SI tables provided by
Rob M0DTS and they work.

I have code that provides identical tables, same contents, checksums etc
and they don't work. Obviously I am missing something. I will figure it
out eventually.

On the theme of GUIs I have decided to use QT4 developed by Trolltech
(now owned by Nokia). http://qt.nokia.com/ I am setting up the
development environment as I type so more on that later.

I have also been looking at all the DVB applications available for Linux.
I just wish I knew what they all did. Hopefully down the line it will be possible
to add receive support to my software using a suitable Linux tool.
I will have to do the demodulator but once I have the program stream extracted
it should be possible to feed that to a 3rd party tool for display.

I am ramping up my enthusiasm for the new UHD (Universal Hardware Driver)
from Ettus Research http://www.ettus.com/

This will allow cross platform support for their products. It will also allow closer
integration between my code and the USRP2. Currently no support for the WBX
transceiver board I use exists but it is coming. So watch this space.

I am always keen to hear from anyone reading this Blog, if you have any
comments, criticisms, advice or questions please contact me, I don't byte.