Date: Fri, 17 Jan 1997 09:13:14 -0600 (CST) From: Jim Lowe <james@miller.cs.uwm.edu> To: batie@aahz.jf.intel.com, hasty@rah.star-gate.com Cc: freebsd-multimedia@freebsd.org Subject: Re: realaudio player Message-ID: <199701171513.JAA22741@miller.cs.uwm.edu>
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> Make a mountain out of a molehill, it sounds like. The vic sender is a > data source for some tests and at least part of the problem was a > misunderstanding of the operation of the little interior window (i.e. > vic says it's sending out 30fps, but that's not what it shows). It was > prompted by various test receivers asking "can't you get the bitrate > higher?" When I crank the slider up to max, it peaks at around 280Kbps, > so I have to answer "no" and they go away thinking "what a puny machine". The little window in vic is really just a fancy icon. To really see the video, you have to click on the icon and a real window comes up. The icon window is only updated once per second (or whatever is specified by the -U option). > > Now that the question has gotten the spotlight on it however, I'm wondering > if it's just that vic can't figure out a reason to put out more data. > Perhaps that's just all that's changing, since it's just a camera pointed > at a lab. I am ignoring the case when there's no one there --- the data > rate drops to 175K or less when it's just staring at static monitors. The > 280+Kbps rate is with people moving around, waving arms, etc. > > Maybe I'll hook a vcr up with an action movie and see what happens... > Much will depend on your cpu/memory speed. The h.261 compress/decompression algorithms in vic are very memory/cpu intensive. You can see this by setting the bandwidth sliders and fps sliders all the way up (with a low ttl), then transmit a small window with a lot of motion (TV commericals switch images about every 3-5 seconds -- great test). Vic will keep up at about 30fps. If you change the size to a normal window the bit rate will go down and you will not approach the maximum fps or bandwidth. Mpeg has the same problems as h.261, just a little more pronounced -- although there is hardware assist available for mpeg these days. One could make a few modifications to the meteor driver for vic to avoid one memory copy of the input frame and it might be able to keep up at normal size, 30fps -- I have never tried this. -Jim
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