question on video pal

stef

Hi

I'm still learning in the prop. Is it possible to use the propeller for generating text on a tv (PAL signal). Yes I think because I found some exaples of it. Now my question. If you hook up a normal PAL camera to a comercial digital video recorder it is detecting the video signal. If you cut the coax or disconnect the camera, the vcr is generating a video loss alarm. Can I use the propeller with its tv out possabilaty to generate a fix text on a unicolered background to hook up on the vcr chanel instaid of a camera so I'm recording the text constant and will it bring the video loss detektion of the vcr to his rest telling everything is ok like with a normal camera.

Thanks for any answer.

Stefan
·

ericball

The Propeller can definitely produce a PAL TV signal of text on a colored background. And you can certainly connect it to a VCR and record that signal.

However, if you are trying to combine the signal from a camera and the Propeller (so the Propeller signal takes over when the camera is disconnected) then that's a different problem.

The easiest way would be an external video switch with the camera connected to one input and the Propeller to the other. However, because the two signals aren't synchronized (and the switch may cause a momentary loss of signal) there will be a brief interruption which may cause the VCR to generate the video loss alarm. Seamless switching will either require a much more sophisticated video switch or an electronic video switch along with a sync separator which the Propeller would use to generate a synchronized signal (which would also require custom programming).

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Composite NTSC sprite driver: Forum
NTSC & PAL driver templates: ObEx Forum
OnePinTVText driver: ObEx Forum

stef

Thanks for reakting.

It is the first case. The propeller is the only one connected to the vcr.

I will give it a try to set it up.



Thanks



Stefan

Mike Green

Either the TV_TEXT or the TV_TERMINAL object that's included with the Propeller Tool can do this. You'll need 3 resistors connected to a group of 4 I/O pins as shown in the DemoBoard schematic. You'll also have to modify the source code as described in the TV object included with the Propeller Tool. There's a bit that controls whether the video generator produces a PAL or NTSC video signal and the default is NTSC. It's described in a large block of comments at the end.

stef

Hi Mike



So if I understand it correct I can load a propeller with a spin program (still to search but tv_text can be it) that I modify a bit and put it in an endless loop. Display always the same text on an plain color background.

This with a few components (prop, eeprom, xtal,few resistors, powerregulator , ecc..)

stefan

Ariba

To change the TV_Text object to PAL use this tv-parameters in the DAT section:

DAT

tv_params               long    0               'status
                        long    1               'enable
                        long    0               'pins
                        long    %10011          'mode
                        long    0               'screen
                        long    0               'colors
                        long    cols            'hc
                        long    rows            'vc
                        long    5               'hx
                        long    1               'vx
                        long    0               'ho
                        long    0               'vo
                        long    0               'broadcast
                        long    0               'auralcog

Andy

Mike Green

Yes

You need a Prop, 5MHz crystal, 24LC256 EEPROM, pullup resistor for the EEPROM's SDA line, 3 resistors for the TV resistor ladder ADC (see DemoBoard schematic for details), and a PropPlug or equivalent for initial programming and debugging.

stef

HI Mike

Thanks. I will look in to it and test it.

Is sombody knowing how many charakters tv_text kan display on screen that is good readebel?



Stefan

Mike Green

tv_text normally displays 40 characters on a line and 13 lines. It's quite readable.

stef

Tanks

Stefan

Eagleman

I recently discovered the Maxim 7456 which is an "On-Screen-Display" (OSD) that will allow you to selectively add a text overlay on top of·your video input (camera, vcr output, tv video, etc..).· It has a builtin eeprom and text editing capability so that you can select "canned text" strings or programable texts.· I haven't tried one yet because my supplie was out of stock so it was backordered on my last order.· The overlay can be switched on and off by a single pin input.· It sounds like this chip might be handy for your project.· The chip costs about $20 - $28 USD depending on supplier.· It might just interesting and information to check the specs on this chip even you think it wouldn't work for you.