DVB-T modulators

rlogue

What are the options available for DVB-T modulators? I'm thinking about a way of distributing four specific DVB-S channels around the house.

watty

They use a MPEG2-TS input that has the entire data for the Multiplex
This can be via

• PCI bus for a PC card
• BNC connector for ASI signal
• Ethernet

They don't care how many TV/Radio/Data, or if the channels are MP2, HE-AAC, MPEG2, MPEG4 or whatever. The data simply has to fit in the bitrate the Modulator supports.

If you don't have all the channels pre-encoded in a Transport stream then you need:

1) A Re-multiplexer that can take various transport stream inputs and pick out the data you want and output a new Transport Stream. If you don't want to change encoding or bit rates and have Satellite or DTT receivers with ASI transport stream out BNC connectors, then you can use live off air.

2) If you want to change the bit rate or encoding of a channel then you need an expensive Transcoder

3) If you want Analogue inputs then you need a real time Encoder. (Professional Encoders use separate Analogue to Digital and Encode uncompressed digital)

4) If you want efficient encoding you might want a combined Encoder/Multiplex to do statistical Multiplex. About €10K per channel for professional ones

5) In theory you can use PCI or USB Sat/DTTtuners, access the Transport streams, re-multiplex (little CPU overhead as there is no encoding/decoding) with just software and drive a PCI DVB-T modulator card. I never found any inexpensive software to do this in realtime. Plenty of File based tools. ( I made my own test file with 4 x MPEG4 channels and played into Dektec card, which then drove 10.1GHz transmitter via UHF 450MHz up-converter).

PCI Cards etc http://www.dektec.com/
(you can use a PCI modulator only card and pre-encode a transport stream on PC for tests, or add a PCI ASI card also)

CATV/MATV cheaper gear. http://www.taylorbros.co.uk/

rlogue

The channels already come as transport streams and since they are all on the same transponder my pc can pick them up so in theory I could take four TV channels and four radio channels as transport streams and send them to a PCI modulator on the same PC.

This way could I push the DVB-T signal out onto my existing coax cable and allow any Freeview TV connected to it to pick up the extra channels?

watty

yes. But only in theory on PC.

You will have more joy with the standalone non-PC solutions from Taylor (Receiver -> Re-multiplexer -> Modulator) than PC unless you find the PC SW.

If you find in-expensive SW that lets you do it in real time, let me know. It's a couple of years since I was doing this, but I couldn't find any affordable solution to re-multiplex and feed the DVB-T card in real time. Maybe VLC can do it now. It couldn't then.

I had to
Capture / save file(s) of Transport stream from sat card.
open file(s)
selelct items to copy
click create and it would build a new single Transport Stream file.
Then open GUI for Modulator and load XML to set parameter and load TS file name and select "loop file".

I was able to do DVB-t and feed TV, DVB-set boxes and Motorola Cable /Hybrid IPTV box instead using DVB-c

The UHF/Microwave converters only worked at very low bitrate/QAM and high FEC on DVB-T. They worked fine at 64QAM on DVB-c I had 2mW at 10.1GHz bouncing off wall from TX to RX. With DVB-C changing the Symbol rate changes the RF bandwidth needed from 2MHz (near minimum) to over 8Mhz. I had some 2MHz IF filters and also some Recievers have DSP to adjust from 1.5MHz to 10MHz. Standard Cable is 6Mhz or 8MHz. DVB-t can be 5, 6, 7 or 8MHz.

Using MPEG4 SD with VBR it's possible to fit 10 channels in 4MHz on DVB-c I had a reason to want to try 4MHz

zg3409

Hi,

I have been reading with interest your problem. I am not sure of the exact application of your system but did you know you can send satellite and DVB-T over the same cable?

You need to combine sat and DVB-T at the start of the cable and then split them at the TV end. At the TV end you can use a seperate DVB-T and Sat tuner or a 2 in 1 unit. -I don't know of any 2 in 1 units that are saorview approved but I know many boxes are undergoing testing right now.

If you have more than one TV then you will need a seperate receiver for each TV. Also at the sat dish end you need a seperate connection on the LNB for each TV, so you can't run the cable around in a loop around the house. You need 1 LNB connection per TV.

Powercity sell splitters that seperate the power that is sent up the cable to power the LNB to make sure power does not go into the TV nor the DVB-T antenna.

I can explain more if required or I'm sure watty can link to the setup somewhere.

If you have an existing apartment block with dozens of TV's then a modulator might be the way to go. I got a price for this one at £650

http://www.promaxelectronics.com/ing/products/fichaprod.php?product=EN-106&IDfamilia=20

This takes composite in and gives DVB-T (MPEG2 not high definition) so you would need a Sat receiver near the antenna end. You can string a few of these in series (one per DVB-S channel) See the data sheets for details.

Dan

david.kriz

rlogue wrote: »

What are the options available for DVB-T modulators? I'm thinking about a way of distributing four specific DVB-S channels around the house.

You need DVB-S(S2)/DVB-T transmodulator. Try to search for RFtuote, Ikusi, Televes or Promax. You can set channels and parameters on it to the limit of about 25Mbit.

watty

Sat receiver with Transport stream out... Re-multiplexer ... Transport stream in to DVB-T modulator.

Its daft to go via analogue.

See http://www.taylorbros.co.uk/

Johnboy1951

5) In theory you can use PCI or USB Sat/DTTtuners, access the Transport streams, re-multiplex (little CPU overhead as there is no encoding/decoding) with just software and drive a PCI DVB-T modulator card. I never found any inexpensive software to do this in realtime. Plenty of File based tools. ( I made my own test file with 4 x MPEG4 channels and played into Dektec card, which then drove 10.1GHz transmitter via UHF 450MHz up-converter).

PCI Cards etc http://www.dektec.com/
(you can use a PCI modulator only card and pre-encode a transport stream on PC for tests, or add a PCI ASI card also)

I have been successfully multicasting all the streams from a USB tuner dongle with free software. Is this what you meant above?
Is there something more required for a PCI DVB-T modulator card?

I have never looked at such beasts so know nothing at all about what they require as input.

regards.

watty

Software to make your transport stream be fed to the Dektec card.

On a home cable you can easily run at high QAM, low FEC and low guard band and have nearly twice the capacity of "over the air" DTT.