Broadcast?
Lee Marshall
Posts: 106
Ive been looking over the video generator part of the datasheet, there is a load of stuff i dont fully understand, the most prominent of which would be the broadcast option.
what does this actually do?
would i be correct in assuming that the baseband thing is what would go into your TVs composite video input?
would the broadcast be the sort of signal that would go into your aerial socket(modulated like the signal that comes off the air)?
one thing i dont understand is this aural sub-carrier? what is it? is it something to do with sound?
Also, somewhere i have read about using the propeller as a transmitter. It sounds rather cool, but i am concerned about the legalities of transmitting without a license etc...
I live in the UK.
Any insight would be appreciated.
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Holy parallel processing, Batman!
Post Edited (Mr Crowley) : 10/4/2007 7:21:02 AM GMT
what does this actually do?
would i be correct in assuming that the baseband thing is what would go into your TVs composite video input?
would the broadcast be the sort of signal that would go into your aerial socket(modulated like the signal that comes off the air)?
one thing i dont understand is this aural sub-carrier? what is it? is it something to do with sound?
Also, somewhere i have read about using the propeller as a transmitter. It sounds rather cool, but i am concerned about the legalities of transmitting without a license etc...
I live in the UK.
Any insight would be appreciated.
▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
Holy parallel processing, Batman!
Post Edited (Mr Crowley) : 10/4/2007 7:21:02 AM GMT
Comments
The "channel" transmitted on can be configured by an option in TV.SPIN
(b) You could also add a string of wire and really "broadcast" this, which needs a concession in most European countries.
(c) As a broadcast signal (in contrast to a compound video) does also carry the sound for a movie, this can be generated by a third COG; the number of this COG must also be configured in TV.SPIN, as the "Video COG" will redirect it to the "fourth" pin (three pins are needed for the video)
Yes, baseband is CVBS. Take the output from the three 'TV resistors' and feed it straight into the yellow RCA of your TV or to Video In of a SCART. Connect 0V as well.
Yes, although I never thought of running the signal via coax into an actual aerial socket.
I also live in the UK.
Technically you probably do need a licence but as you'll be transmitting just a few feet at most you are unlikely to get caught, and are unlikely to interfere with any other broadcasts ( see below ). Obviously though no one is going to say, go ahead and break the law
The maximum broadcast frequency the Propeller can use is limited and doesn't stretch into the UHF band, so you'll need a TV capable of receiving the older VHF channels. The Propeller crystal frequency is also apparently not very well 'tuned' for PAL generation but I don't really understand that side of things. If you're on VHF you shouldn't be interfering with others on UHF.
When I tried this ( wire hung from those three TV resistors near a handheld LCD TV which has UHF channels ) I could see "something" but it was worse than receiving Channel Five analogue in a snowstorm.
I dismissed broadcast in the UK as too poor quality and impractical, but writing this, it occurs to me that VHF in the UK used 512 lines, and UHF uses 625 lines, and I did nothing to drop lines when I tried !
If you tweak the video generator for 512 lines, you may get better results than I did.
The best alternative is probably to get yourself a video to UHF transmitter / sender which are available in shops ( I have no idea of their legal status ), generate baseband, and let the transmitter do the rest.
If you get a PAL VHF broadcast driver working I'd be interested in giving it a whirl, but I've decided to stick with baseband CVBS. That gives 40x16 text of reasonable enough quality for me.
Post Edited (hippy) : 10/4/2007 9:59:15 AM GMT
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Holy parallel processing, Batman!
We haven't had VHF broadcasts for over 20 years, so a combination of poor memory and probably thinking of something else
It may not have been PAL used either but I have no idea what was.