My TV when in 'auto' mode often switches to/from 16:9 when the ad break appears so I guess there is a physical change ? I think this would be a useful detection trigger to add to the list!
Andy. On Thu, 20 Jan 2005 00:00:05 GMT, Tom Hughes <[EMAIL PROTECTED]> wrote: > In message <[EMAIL PROTECTED]> > "Chris Pinkham" <[EMAIL PROTECTED]> wrote: > > > > Haven't updated my cvs version yet to try the new detection, but does > > > it also monitor for aspect ratio changes? Just noticed while watching > > > tv yesterday quite a few channels change aspect ratio when they switch > > > to the adverts (I'm in the UK). > > > > > > In this situation it could be a very accurate way for detecting ads. > > > > Is this a physical aspect ratio change or does the frame stay the same > > ratio and have black bars on the top/bottom? I have a sample of a UK > > broadcast that uses the black bars and will be trying to code up something > > to detect that transition so it can be used to determine where commercials > > start/stop. If you mean a physical frame aspect ratio change, then I'd > > like to detect this at some point but don't have any sample recordings > > to test with right now (I'm in the U.S. with analog cable). > > Well it would be black bars on the side of the program if anything > rather than black bars on the top and bottom of the adverts. > > In a DVB-T stream there are two ways of handling aspect ratios. For > simple 4:3 vs 16:9 it can be done with a simple flag. In that case > then the transmitted data is always the full picture area and the > flag tells the receiver what aspect ratio to use when displaying > the data - the resolution doesn't change, so would be 720x576 or > 704x576 in the UK depending on the channel. > > The other option is to use an AFD where a 16:9 picture is transmitted > and if the content is 4:3 then there are black bars on each side. There > is then an Active Format Descriptor (AFD) which indicates which part > of the transmitted picture to display. That allows more choice of > ratios but in the UK at least only 4:3 and 16:9 are used. > > Some channels use AFDs in the UK and some use the simple flag. Most > of the AFD channels don't have adverts however, but I think there is > one that does - certainly Five was, but it may have changed recently. > > I'm not sure how Myth handles those two cases however, or what you > see in the stream when you read it back from disk. > > Tom > > -- > Tom Hughes ([EMAIL PROTECTED]) > http://www.compton.nu/ > > > _______________________________________________ > mythtv-users mailing list > [email protected] > http://mythtv.org/cgi-bin/mailman/listinfo/mythtv-users > > >
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