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Eli
May 13, 2006, 08:25:40
When developing video applications, it would be a good idea to have code to detect video presence from the capture input, examples:
- do we need to Compress the signal ?
- built-in-test ?
- start-stop recording ?
- etc...

Is there a way to assess presence of a video signal using a Montivision filter, verses availability of specific signaling from the capture hardware?

Thank you

Marc Cymontkowski
May 15, 2006, 09:09:25
Hi Eli,

you could access IMVHistogram to request the image histogram from most of the MontiVision DirectShow filters. E.g., if most of the histogram entries are located between 0 and 10, then the image is black and there must be something wrong.

You could also use MV Mean to get the mean luminance of the image.


Best Regards,

Marc Cymontkowski

Eli
May 15, 2006, 09:39:43
Your answer is correct for some of the conditions, others are not covered, when no signal is available e.g.,

1. Video received over an RF link such as TV contains snow that is random noise outputed from the receiver

2. Video from a VCR source, some have a blue screen, but others don't

Best Regards,
Eli

Marc Cymontkowski
May 15, 2006, 09:48:33
Eli,

You can check both scenarios using the histogram. In one case the blue channel is completely around 255 and in case of random noise the level is similiar for all histogram entries (uniform histogram).

MV Cooccurrence could also be used to check whether the image contrast is too low (black/blue) or too high (noise).


Best Regards,

Marc Cymontkowski