I have never studied mpeg in great detail although I am very familiar with fourier series approximations. Mpeg2 is based on some fixed blocked size. It may be 16x16, but I don't remember. One thing that should be possible is if say it is 16x16 and if the full sized video was say 1920x1440 then decoding to 120x90 would be in fact trivial provided you had all the underlying structure in place. This makes the assumption that there is the equivalent to a dc level for the entire small block. You might be able to similarly get larger sizes by only decoding some of the coefficients that are used in the discrete cosine transform..
Then again there are forward and backwards predicted frames which may mess all that up. Overall it should be possible to optimize the decoding for a lower resolution than what your starting with, but it may in fact be very non trivial. It could take months of work. Well likely it would take a couple months just to really get the understanding of mpeg2 needed to do the actual work. Perhaps longer. Also since mpeg2 is a licensed algorithm, there probably are legal issues involved as well. If someone was going to do it I'd probably start with XVID. It should be somewhat documented and I don't think there would be legal issues in creating your own decoder. Then again this could all be an attempt to reinvent the wheel, so considerable additional research would be needed to make sure the problem hasn't already been solved. Robert Denier http://www.finiteinfinity.com/ses/ On Sun, 2005-03-06 at 19:17 -0500, Jonathan M. Cooper wrote: > I get where you're coming from. I just like to occasionally have a > baseball game on in realtime in a PIP window while watching a recorded > program. > > -----Original Message----- > > Date: Sun, 6 Mar 2005 13:02:55 -0800 > From: Brad Templeton <[EMAIL PROTECTED]> > Subject: Re: [mythtv-users] Dual HDTV Tuner Requirements > To: Discussion about mythtv <[email protected]> > Message-ID: <[EMAIL PROTECTED]> > Content-Type: text/plain; charset=us-ascii > > On Sun, Mar 06, 2005 at 07:59:10AM -0500, Jonathan M. Cooper wrote: > > Thanks for your response. Does that mean that PIP is not feasible > with, > > say, a P4 3.2GHz? > > I remain curious as to why people want PiP when they have MythTV. Many > people who use Myth stop watching live TV altogether, and I am amazed > that > the desire would remain to watch _two_ live TVs. > > But indeed, it might be a CPU problem since nobody has written yet a > "clever" mpeg decoder which knows it is decoding for a tiny size and > thus > avoids the cpu load of decoding for full size and rescaling. > > A number of people are interested in such a decoder, since it would > allow > some people with older processors to watch HDTV recordings on their > SDTVs. > Still SDTV, but a fair bit better than NTSC recording. > > The EyeTV program for the Mac has such a clever decoder, so it is > possible. > > > _______________________________________________ > mythtv-users mailing list > [email protected] > http://mythtv.org/cgi-bin/mailman/listinfo/mythtv-users
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