Date: Fri, 18 Apr 1997 12:15:58 -0700 From: Amancio Hasty <hasty@rah.star-gate.com> To: Peter Dufault <dufault@hda.com> Cc: hackers@freebsd.org Subject: Re: video capture driver interface to file system? Message-ID: <199704181915.MAA06203@rah.star-gate.com> In-Reply-To: Your message of "Fri, 18 Apr 1997 07:44:13 EDT." <199704181144.HAA17161@hda.hda.com>
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I get : time dd if=/dev/zero of=/spare/test bs=3456000 count=30 30+0 records in 30+0 records out 103680000 bytes transferred in 36.080174 secs (2873600 bytes/sec) 0.000u 5.297s 0:37.18 14.2% 78+9000k 8+1641io 6pf+0w The partition is on a sd0: <SEAGATE ST15150W 0023> type 0 fixed SCSI 2 and the adapter is a 2940w. Tnks, Amancio >From The Desk Of Peter Dufault : > > Lets see, > > We can daisy chain buffers in physical memory pending upon the resolution > > and the amount of memory available for the system. > > > > A good resolution for mpeg is 320x240 30 frames/sec for yuv12 that translat es > > to 3456000 bytes/sec so lets called it 3.5MB/sec substain thruput. > > What kind of performance can you get now through the file system > to your disks? On my not-fancy system I see 1974857/sec saving 30 > seconds of "video" at a block size of 3456000 to a Fujitsu disk. > (dd if=/dev/zero of=/sd1/A/foo bs=3456000 count=30). Note that > I've optimized nothing. > > Since you can apparently collect the video into a suitably aligned > user buffer and I assume that there is some FIFO on the board to > give you some time to reprogram at frame done interrupt time, a > simple driver with no double buffering other than a regular start > queue (so that the done interrupt has a place to store incoming > data in), "team", and "dd" may be all you need to store video > through the file system on a lightly loaded fast system. It will > provide a starting point to see where to focus our efforts, and > "dd if=/dev/yuv12 of=~/clip.yuv" is a good interface to support > even if only for debugging. > > Peter > > -- > Peter Dufault (dufault@hda.com) Realtime Machine Control and Simulation > HD Associates, Inc. Voice: 508 433 6936
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