[linux-dvb] Re: automatic AD cutting [was "Timing recording"]

[Chris Pitchford <nova-t@intrepid.cx>]

There is a much bigger problem with this technology. DVB is not frame by
frame stream such as capturing an analog signal. The stream is GOP in that
there is a key frame followed by a series of delta frames (frames that
collectively only contain differences since the last keyframe)

0        25       50       75      100
K------->K------->K------->K------->
   ^Start of programme

if the program starts somewhere after a keyframe then you would like to
"drop" all the frame prior to the start.. This means that this GOP (group
of pictures) is not incomplete and must be rebuilt. There aren't many
tools Ive seen to do this.. certainly none that would on the fly.

Since effectively Mpeg-2 is quantum you can only cut to the nearest group
of pictures Keyframe. This means, almost certainly, there will be a bit
before and a bit after the program you want.

Also since so much is analog the process of recognising images becomes
impressively complex. Twined with the fact you would need to provide test
data to the recognition software which inself would be particularly
difficult.

I seem to recall of hearing a project that looked for the, and please
excuse the fact I forget its official name, but the little flashing black
and white square in the top left/right corner of the tv picture prior to
comercial breaks.

It also calculated to time between commercials (the black picture) to
calculate when a comercial had finished..

Maybe this kind of generic approach would be better suited?

My appologuies if this has all be said before, just my 2p worth

chris

On Fri, 13 Dec 2002, Alexandre CONRAD wrote:

> > I don't know what was the outcome of this...
>
> Well, I don't care about ads, really, I need to be able to record a
> program (an everyday episode), and start the recording from the 1st
> frame and stop it at the last frame.
>
> This would work in this case : the program always starts the same way
> and always ends the same way from an episode to an other. This means
> that usualy, these programs have a starting and ending generic.
>
> The idea here is to record the episode once manually. Extract from the
> stream the 1st and last frame from the episode's generics
>
> FrameA = 1st frame of starting generic
> FrameZ = Last frame of ending generic
>
> Once this is set up, I can record my favourite program everyday (or when
> ever the program shows, (once a week, every 2 days, only week ends,
> etc...)) without remembering to record it. My program will know that it
> have to start recording when it detects FrameA and stop when it detects
> FrameB.
>
> In my particular case, I want to have everything automated for my project.
> I want to record a program that shows everyday, in the early morning
> (6oclock, but I'm still sleeping) and then send that recorded to my
> video server. But I would like to be also able to have it trimed out
> nice and clean without retouching it manually.
>
> Do you get the idea ? And if you have any ideas, your suggestions are open.
>
> Regards,
>
> --
> Alexandre CONRAD
> Research & Development
> tel : +33 1 30 80 55 00
> fax : +33 1 30 56 50 20
> TLV
> 6, rue de la plaine
> 78860 - SAINT NOM LA BRETECHE
> FRANCE
>
>
>
> >
> >
> >
> > ---
> > Oh yes ! Please Sirs programmers ! Have something done for that ! This
> > would be so usefull ! You'll be able to record your everyday episodes
> > whithout thinking about even recording them. Go out on holidays, they
> > will be there when you come back, all ready to watch and trimed out !
> > :)))
> >
> > There are interesting document here about frame recognition :
> >
> > http://www.wisdom.weizmann.ac.il/~armin/AdvVision02/Papers/Lecture12/ActionRecognitionbyShapeMatchingtoKeyFrames.pdf
> >
> >
> > Wave your hands for people willing to work on that, with the open
> > source spirit ! ;)
> >
> > Regards,
> >
> >
> > _________________________________________________________________
> > MSN Search, le moteur de recherche qui pense comme vous !
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> >
> >
> >
>
>
>
>
>
> --
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