dataCaptureStart

[ahmad]

hii ,,
i wanna know what is the values (interval) that dataCaptureStart may have ( for example from 0-1000),,
thanks in advance

[Michael]

Hi ahmad,

There’s no rule about what the value should be. I found 310 to work, but you should try values between 100 and 1000. You could connect a potentiometer to adjust the value, perhaps?

[ahmad]

thanks Michael for quick reply,but i have another question;
is adjusting dataCaptureStart value accurate ,in another word is it important to try each value from 100 to 1000 or i can increase the value 2 or more at a time (e.g 100,102,104)??

[Michael]

You can increase 2 or 4 or whatever. You just need to try different values so the closed caption info is aligned right. 310 worked for me.
You are in an NTSC country, right? This doesn’t work with PAL.

[ahmad]

its support the two type but i choose NTSC ,does u say that if i use the correct line value and give arbitrary value of dataCaptureStart it will result in capturing text that may be not “readable” or not arranged??

[Michael]

Are you decoding closed caption data from an NTSC broadcast? Are you in the United States or Canada?

[ahmad]

no, im decoding in jordan

[ahmad]

but i think it depend on the channel “i decode from satellite receiver” not on the place you are!!

[Michael]

It depends on what type of signal your satellite receiver sends to your TV. PAL or NTSC.

[ahmad]

i previously set the output of receiver to NTCS !!however ,you dont tell ,if i choose the right line does the shield will caputre text (whether it expected text or any other text) and setting dataCaptureStart is just to capture the right text??

[Michael]

The value of dataCaptureStart is simply used to adjust the timing so that you can find the right place to sample the closed captioning pixels. The white pixels represent a bit pattern of two ASCII characters. This article explains how it works:

http://nootropicdesign.com/projectlab/2011/03/20/decoding-closed-captioning/

Just try different values for dataCaptureStart to see if you can find the data. It is very difficult.

[ahmad]

ok ,
thank alot Michael
🙂

[Author]

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