Qam signals from Composite?

[Chazz]

Has anyone got practical advice on equipment to produce Qam signals from Composite.

I want to put six or eight a/v's into a qam.

I can find pc cards that will produce a DVB -asi stream from composite ( card comes with it's own connector for o/p)

I can find qam modulators that will accept a DVB-asi stream via a single input.

But the missing link is how I combine 6 DVB-asi outputs into one DVB-asi stream to feed to the modulator?

Anyone able to clue me in?

 

[spiney]

Sounds like you want to generate an MPEG2 transport stream, normally only done for broadcast applications on cable or DTT/satellite. Very expensive. The equipment doesn't take analogue sources, only digital ones.

Either professional broadcast rack mount equipment, or cheaper PC card version, eg see: http://www.dektec.com/Downloads/DataSheets.asp .

What are you doing, starting a cable tv system?

 

[spiney]

Perhaps I should explain further ....

A single channel video signal, in compressed mpeg2 form, is the Packetised Elementary Stream. It's this that is recorded on DVDs, computer files, etc.

Software for home PCs normally only deals with such elementary streams, ie, just a single video signal.

To combine several such streams to form a Multiplex (mux) would normally only be done by broadcasters, prior to transmission, it's not something the average home user would want! And then, using professional broadcasting equipment, so very expensive.

However, as you've found, there are several makes of plugin PC cards that can produce QAM, DTT, QPSK, etc, a cheaper option than using professional equipment. Where sold, these also have software that generates a transport stream from several elementary stream inputs. However, it's assumed these streams will be stored as mpeg2 files on the hard disc! Whether you can add yet more cards to produce several mpeg2 elementary streams from composite analogue inputs in real time, and then combine their outputs into the transport stream inputs, I don't know, but it would require some hefty processing!

For example, there's the above (via link) Dektek 110 QAM modulator, combined with the dtc 300 software. I think the software is downloadable in a 30 day trial version, so you can play around with it .....

Otherwise, there are some standalone non-PC gadgets that will do exactly what you're asking, but will be very expensive ......

for example, http://www.arfc.com.au/pdf/DME_1000-C_series_04-2004.pdf .

 

[Chazz]

Thanks for the help Spiney

I do the tech side of a small system feeding 2,000 homes.

The Dektec link was useful in that it seems they've a solution for taking multiple streams into a pc via their DTA124 or DTA120, which then using their DtLoop software, could be fed to their DTA110 to produce the qam rf output.
Though of course add to this the cost of conversion from a/v to DVB-asi.


I'm still looking around what's available from various companies, I'll keep this thread posted as I find out more options and prices. There are some PCI cards on the market that do nearly all the processing in hardware keeping the pc's processor demand very low, but I'm wading through their data sheets still at present.

It's certainly at prices above non commerical use, but looks as if it could be feasible for my needs.

 

[spiney]

Yes, there seem to be several different makes of card. I'm not sure what the reliability would be, of a pc based system left permanently switched on, whereas of course the dedicated rack mounted stuff is designed for such use!