Date: Sat, 16 Mar 2002 14:54:38 +0100 From: "Steve O'Hara-Smith" <steve@sohara.org> To: Mike Meyer <mwm-dated-1016708329.7ca34a@mired.org> Cc: freebsd-multimedia@freebsd.org Subject: Re: Some video Capture questions (Was: Some audio capture questions) Message-ID: <20020316145438.7695fac0.steve@sohara.org> In-Reply-To: <15507.9577.337812.353727@guru.mired.org> References: <20020315074048.A12682@hostwiththemost> <15506.40571.544247.899130@guru.mired.org> <20020316084125.3b2b0874.steve@sohara.org> <15507.9577.337812.353727@guru.mired.org>
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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).
So as long as you have enough oomph to saturate a 100BaseT from
memory there should be enough oomph to handle realtime video capture and
dump to LAN (as long as nothing else is happening). If you want full
resolution though that had better be a gigbit ethernet and enough oomph
to half saturate it from RAM.
MM> Between them is a 100BaseT network and a switch. I can put a second
MM> ethernet card in B and move the link from A to that instead of the
MM> switch if required, but I don't think it's required.
It may well be - you want at least half the bandwidth for
uncompressed video.
MM> I'm already doing this with audio to play it on A with esound, just by
MM> doing "ssh -n B esdrec | esdcat" on A. Is there a similar tool for
MM> video? Well, a similar tool that will work with the ATI AIW? Or should
Look into ffmpeg - the capture isn't working properly yet (audio
slips terribly and my bt848 driver is still a hack) but the streaming server
stuff seems to be good.
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