digital TV modulator

yes I think they all have those now, but I like the idea of being able to use the tv's internal digital tuner to send the video via a single coax or even through the air a short distance, and without having an external box, just use the internal dvb-t receiver.

so i can have a tv virtually anywhere without a dozen rg58 cables going to it.

Colin =^.^=

well that wouldnt be too difficult to put together, ive got an old video card with vivo that must have the a to d on there somewhere, the uhf modulator is childs play, I made one when I was a young teenager with a bfy90, as part of a TV pattern generator using just basic logic gates. ive got a few spare PICs and an old bios flash chip or 2.

I had a quick look on wikipedia for DVB etc and it talked about many of the digital baseband encoders using QAM for cable tv as well, so theres probably a chip that would to that for you. maybe AMD.

I bet you could fit it all into a pocket sized box.

ofc this would become easier if it was part of a PCI card exept the PCI interface is probably just as complicated itself unless youve done it before. part of the signal would be to transfer digitaly stored movies, the other would be from the cable tv box, although the cable tv itself receives digital signals anyway .... and my cable tv box has a uhf output anyway, just a real shame its not DVB, would be so nice if they decided to do that ...

However I cant imagine for a minute I would end up doing all this, my original idea was to use something commercially availbale.

but its amasing what people do create, such as home made spectrum analysers etc etc.

Colin =^.^=

wow ive been googling on and off for a few days now and this ive just come accors this ...

it uses a standard vga card as a DAC and uses harmonics of this to generate VHF signal directly to a DVB tuner, unfortunatly its not UHF, but hey its close and may be room for upconverting, maybe simply selecting and amplifying higher harmonics ?

I wonder if the video out capability could be used instead, thus alowing use of the PC monitor as normal ... or in that case a DAC conected to the parallel port ? maybe just a small unix box, with hard disc to store movies ...

the software sounds complicated but has already been done.

Colin =^.^=

whats the HDTV broadcast standard status at now, are we likely to see HDTV tuners inside the TV or is DVB-t capable of this now anyway ? i was still a bit confused after reading lots of stuff i found on wiki it seems we have had BBC HD tv terestrial trial broadcasts here in the UK.

id realy like just to have a cable and a tv with no extra box so it is possible to move it anywhere as easily as possible, with the posibility of short range hop through the air. HDTV would be the ultimate, if the tuner inside the TV was capable.

seems theres already software to use the ADC on a PC video card to generate the baseband DVB-t signal.

Colin =^.^=

Almost sounds like any cheap VHF to UHF converter will finish the job. Size required to build one from transistors is about a pack of gum.

--
 JosephKK
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"colin" wrote in news:nZTci.135$% snipped-for-privacy@newsfe3-gui.ntli.net:

The DVB-T transmission system can carry HD. The question is can a DVB- tuner tune the HD in a form your display can use.

You have 3 tasks to fulfile, maybe 4.

1: Digitise video and audio.

2: Compress the video and audio.

3: Mux and DVB-T modulate

4: Convert to RF frequency.

Small Note: You have a HF carrier - that signal is by frequency identical to the old analog transmissions. It's carrier is identical even, 'cause some old TV's still lock in on digital transmissions. The signal they carry, however, varies muchly:Whilst the old analog standard contains a FM modulated line-by-line-image plus, overlaid easiyl due to its lower frequency, the audio, on a digital transmissions there is , like on a Modem, a digital encoded Datastream. One Carrier can carry several valid MPG streams actually, which in themselves are "just" normal MPG streams, typically 4 MBit per second.

I d>> >>> Hi,

On a sunny day (Tue, 19 Jun 2007 10:05:00 +0200) it happened =?ISO-8859-15?Q?R=FCdiger?= Leibrandt wrote in :

Whilst the old analog standard contains a FM modulated

AM with one suppressed sideband actually, neg modulation, peak amplitude = sync = black to make noise appear black and have sync before picture if signals are weak.

Well actually 'intercarrier' but audio can also be seen as a separate carrier (AM or FM) about 5.5Mhz higher (in Europe). In fact for the old TV stereo where I am, there were 2 FM carriers, one modulated with te sum (L+R) / 2 and and the other with the difference, so if you had a mono receiver with one detector you'd at get both channels :-)

Modulation = QAM so just quadrature, maybe with 64 'stars'. Where I am (Netherlands) it is QAM 64, with FEC 1/2, so lots of correction bits.... QAM 64, it is almost analog ;-)

I have seen a FPGA solution on the web some years ago.

I just bought a USB DTV box, plugged it in the PC, and, if must be, can use VGA out.... And I can record: ftp://panteltje.com/pub/dvb-t-nl.txt Less then 30 Euro. Of course I can also stream to the Internet, or just LAN via RJ45.

Solves OP problem... cheap coax from VGA. And you still have your PC screen available.

thats talking about receivers if im not mistaken, my problem, or rather what I would like to do is to utilise the DVB receiver already inside my TVs in the same way as with the earlier tuners, as its digital it shouldnt impare the quality.

I already have a cable tv box, so I get video into my pc from that if i need it, id just rather have less wires than I do now rather than add more to go to my tv in the living room and to also to tvs in other rooms.

I gues its just a question of price at the moment, as the only available ones are industrial ones. although that fpga solution sounds interesting if you can stil find where you saw it. using the DAC of a vga card as a IF qam modulator was interesting too, although i think that was just done with individual pictures rather than video.

Tvs without the old type tuner are perhaps upto $100 cheaper, so that would not be a high price to pay for a modulator.

an other option is to use those microwave video senders, but that still adds clutter at the tv.

Colin =^.^=

On a sunny day (Tue, 19 Jun 2007 12:07:24 GMT) it happened "colin" wrote in :

A 'digital tuner' in its simplest form (like I have for satellite for example) has an 8 bit databus and some i2c control signals.

Several places, just google 'fpga DVB-T modulator'

Yes, and then you have no PC display :-)

Analog is not nice, I tried some myself, too much interference, always needs tuning. I have wired the house with Ethernet, connector in every room. I have one switch, it is a star configuration.

But I have wireless too, mpeg2 transport stream via WiFi works very well here too. In fact I converted a Linksys access point to a web server, added an SDcard, so now I have all mp3s on it (no you cannot access those):

Log in with user 'guest' and password 'none' (without the quotes). It may or may not work, just testing a new name server I wrote... if you get 'address not resolved' try: http://81.207.135.196/panteltje/wap54g/index.html#wapserver The idea is (but speed is an issue) to put movies on it too (DivX likely). The whole thing uses only 5 Watt, very green server.

The universal connector for today is RJ54 I think, analog is dead.