Date: Mon, 18 Mar 2002 09:56:09 -0500 From: Jason Andresen <jandrese@mitre.org> To: "Steve O'Hara-Smith" <steve@sohara.org> Cc: Mike Meyer <mwm-dated-1016708329.7ca34a@mired.org>, freebsd-multimedia@freebsd.org Subject: Re: Some video Capture questions (Was: Some audio capture questions) Message-ID: <3C960009.FDCF003A@mitre.org> References: <20020315074048.A12682@hostwiththemost> <15506.40571.544247.899130@guru.mired.org> <20020316084125.3b2b0874.steve@sohara.org> <15507.9577.337812.353727@guru.mired.org> <20020316145438.7695fac0.steve@sohara.org>
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Steve O'Hara-Smith wrote: > > On Sat, 16 Mar 2002 04:58:49 -0600 > Mike Meyer <mwm-dated-1016708329.7ca34a@mired.org> wrote: > > MM> Since you seem to have a grasp of these numbers, let me ask this one: > > I'm getting a grasp for them :) > > MM> I've got two machines, A and B. B has enough oomph to capture > MM> real-time video - it's done it. B doesn't, or at least didn't when I > MM> tried using MS's software on it without tuning. However, the video > MM> feed of interest is tied to B. How much oomph does B need in order to > MM> get the bits to A to capture them? I don't need on-the-fly encoding, > MM> so I'll give it up to get good quality. > > Hmm there's a good one. It all comes down to byte shuffling bandwidth > though. First biggie is full resolution (640x480 for NTSC or 768x576 PAL) > or half resolution. All real time video handling I've seen going to date > has been in half res - (full res is rather a lot of bps ~30Mbyte/sec for > RGB24 or ~20Mbtye for most useful YUV formats). This is too much for nearly > all systems - going to half res quarters the bandwidth (5-7.5Mbytes per > second). Actually, I'm able to encode at full resolution on an AthlonXP 1700 using Charles Henrich's (henrich@sigbus.com) mencoder hacks and a BT878 card. It's certainly feasable with modern hardware to encode good quality video at full frame rate. One strange thing about PC hardware though: I cannot dump raw YUY2 frame data to my HD in realtime, I have to encode the data somehow to avoid saturating the bus. -- \ |_ _|__ __|_ \ __| Jason Andresen jandrese@mitre.org |\/ | | | / _| Network and Distributed Systems Engineer _| _|___| _| _|_\___| Office: 703-883-7755 To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-multimedia" in the body of the message
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