[linux-dvb] networked digital tuner project

Brian Kuschak bkuschak at yahoo.com
Sat Jun 11 02:28:30 CEST 2005

Hi Wolfgang, 

Thanks for your input.  Comments inline.

> My idea would be to use an (embedded) processor for
> doing
> all the control and network stuff, and have an FPGA
> for
> the TS handling (and demux). Like this you could
> have a
> DVB card that is not only usable for such a server
> but
> also for a "stand-alone" PC.

My idea was at least initially to implement a very
minimalist solution, keeping things as simple as
possible.  A single FPGA would implement a minimal
Ethernet MAC, FIFOs to buffer data from the
tuners/demods, an i2c master, and a small state
machine to handle control packets.  In this case, no
CPU would be used in the device.  All control of the
tuners and parsing of the data would be done by the
client PCs.

If the data is multicast/UDP, then the state machines
wouldn't even need to ARP, and of course wouldn't need
to implement a TCP stack.

> Advantage: you could maybe integrate some more fun
> stuff,
> like packet time stamping (MPEG
> measurement/testing),
> accurate (synchronised) PCM/AC-3 output without
> resampling,
> PCR synchronisation on board, section
> filtering/version
> control, etc. Of course this would then be more
> targeted
> for the stand-alone PC, but this is what I am really
> missing from all the "solutions" available right
> now.

The timestamping part would be easy.  Reading the PCR
values from the packets wouldn't be too hard in an
FPGA, although it might not be much of an advantage if
the card just sends MPEG-TS over ethernet.  The tuners
I was considering output a byte-parallel MPEG TS data
stream.  The time delay from demodulation to ethernet
transmission would be very short.

> Do you have FPGA experience? Are there other people
> maybe
> already working on such a thing? Anybody already
> implemented
> a video decoder in an FPGA, to have a new
> full-featured
> board like this? ;-)

I've done several FPGA designs in the past, and have
some bits of VHDL code which can be leveraged for this
design.  A full video decoder is beyond my scope of
experience, though.


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