[mythtv] New idea for commercial flagging...
Nigel Pearson
nigel at ind.tansu.com.au
Tue Jan 4 01:38:18 EST 2005
I forgot to say at the time - I think this is a great idea!
The same principle could maybe be applied to station watermark
detection - do hashing on the luminance channel in the bottom
right hand corner of the frame (or wherever the station puts it).
> Any thoughts on a sensible hashing function? Might be almost a
> perfect identical frame for DVB users, but for analogue users there is
> going to be sufficient "noise" to make the detection of identical
> frames tricky. My first thought would be to break the frame up into,
> say, 8x8 pixel blocks, average the colour and then quantise this
> colour to a smaller range (say 1-8 instead of 1-256 for each colour).
That would have an advantage of working well for both analogue
and digital streams (and compressed streams conveniently already
divide the picture up into pixel blocks).
> Does this sound "fuzzy" enough to spot identical frames?
Yep.
Here are a few more simple algorithm ideas:
* Analogue: average about 8 bytes horizontally in the middle
of each even scanline (hopefully minimise effect of noise/ghosting),
and hash that across each "underscan safe" scanline in the field
* Digital: just add every 20th byte (or every 100th, or every 1000th)
into an 8bit variable.
> Anyone read any research papers on doing this that might have some
> better ideas..? Anyone got a couple of hours free to try coding this
> up...?
Free time? Good joke!
--
Nigel Pearson, nigel at ind.tansu.com.au| "Let's see how Spike is going"
Telstra BI&D, Sydney, Australia | ...
Office: 8255 4222 Fax: 8255 3153 |"I'd like to keep Spike as my
pet."
Mobile: 0408 664435 Home: 9792 6998 | Illyria - Angel
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