One thing I have noticed when encoding VCDs is that often videos with complex backgrounds don't compress nearly as well as those with simple ones. Part of the problem is that TV cameras seam to have the focus so that the entire image is clear rather than focusing on the foreground (and blurring the backgrounds). The result is that a good number of bits are wasted trying to perfectly encode the background and as a result the foreground image suffers. I was wondering if there is any way to separate the foreground objects from the background so that more bits can be spend on the foreground. Is this sort of thing even remotely possible? -- http://kevin.atkinson.dhs.org --- >8 ---- List archives: http://www.xiph.org/archives/ Ogg project homepage: http://www.xiph.org/ogg/ To unsubscribe from this list, send a message to 'theora-dev-request@xiph.org' containing only the word 'unsubscribe' in the body. No subject is needed. Unsubscribe messages sent to the list will be ignored/filtered.
jbradford@dial.pipex.com
2002-Sep-01 15:37 UTC
[theora-dev] Seperating Forground from Background
> I was wondering if there is any way to separate the foreground objects from > the background so that more bits can be spend on the foreground. Is this > sort of thing even remotely possible?By far the easiest way to implement something like that would be to assume that backgrounds are stationary. That covers things like weather forecasters moving around in front of a detailed map. Not very advanced, but it is a starting point. John. --- >8 ---- List archives: http://www.xiph.org/archives/ Ogg project homepage: http://www.xiph.org/ogg/ To unsubscribe from this list, send a message to 'theora-dev-request@xiph.org' containing only the word 'unsubscribe' in the body. No subject is needed. Unsubscribe messages sent to the list will be ignored/filtered.
This is actually one of the things very new codecs like RealVideo 9 do (http://www.realnetworks.com/solutions/leadership/realvideo.html). In tests, RV9 has been shown to somehow detect what part of frame is out of focus, and apply more compression to that part of the frame. The result is that the information that the viewer is really looking at looks better, sometimes a great deal so. There's a nice comparison of RealVideo 9 to MPEG-4-based codecs here: http://www.doom9.org/codec3-2.htm . One thing commented on a lot in that article is how the foreground content tends to look much better with RV9 than it does with MPEG-4. This is another example of why using PSNR or MSE to design a video codec doesn't really work. If you compared the frames, you would probably see that RealVideo's PSNR/MSE is actually worse than MPEG-4's, but looks quite a bit better to the human eye. Word on the street is that some future codecs like H.26L and VP5 also have some kind of psycho-visual modeling. I'd be curious what would be involved in getting that kind of code into VP3... -Henry ----- Original Message ----- From: Kevin Atkinson <kevin@atkinson.dhs.org> Date: Sun, 1 Sep 2002 17:05:33 -0400 (EDT) To: theora-dev@xiph.org Subject: [theora-dev] Seperating Forground from Background <p>>> One thing I have noticed when encoding VCDs is that often videos with > complex backgrounds don't compress nearly as well as those with simple > ones. Part of the problem is that TV cameras seam to have the focus so > that the entire image is clear rather than focusing on the foreground (and > blurring the backgrounds). The result is that a good number of bits are > wasted trying to perfectly encode the background and as a result the > foreground image suffers. > > I was wondering if there is any way to separate the foreground objects from > the background so that more bits can be spend on the foreground. Is this > sort of thing even remotely possible? > > -- > http://kevin.atkinson.dhs.org > > --- >8 ---- > List archives: http://www.xiph.org/archives/ > Ogg project homepage: http://www.xiph.org/ogg/ > To unsubscribe from this list, send a message to 'theora-dev-request@xiph.org' > containing only the word 'unsubscribe' in the body. No subject is needed. > Unsubscribe messages sent to the list will be ignored/filtered. > >-- _______________________________________________ Get your free email from http://mymail.operamail.com Powered by Outblaze --- >8 ---- List archives: http://www.xiph.org/archives/ Ogg project homepage: http://www.xiph.org/ogg/ To unsubscribe from this list, send a message to 'theora-dev-request@xiph.org' containing only the word 'unsubscribe' in the body. No subject is needed. Unsubscribe messages sent to the list will be ignored/filtered.