>By the way, BeOS streaming movies is ridiculously impressive.
Streaming playback of movies is nothing compared to the task of
multichannel recording. You have to simultaneously read/write N (with
N typically >= 24) files at the same time with up to 9MB/sec in each
direction (32bit/96kHz recording) per file, to allow for instantaneous
"punch out" (transition from recording to playback). Doing this from a
single disk is possible but its not trivial. Obviously, any level of
RAID technology would be good.
because of the number of files, unless you have N disks available, you
are almost always going to have to face seek deadlines because you
need to read from two different files within an extremely short space
of time, and so there is no filesystem design that will actually solve
the problem for you. needless to say, some filesystems will make the
job easier, as long as you make certain assumptions that i don't want
to make :)
interleaving the blocks of each channel's files, for example, is one
trick that can do wonders. until, that is, you decide to change the
block size you work with during playback/recording, and then it
becomes worse than it was with just a regular old unfragmented ext2
fs. etc.
almost all the multimedia filesystems that i've seen have been focused
on audio/video with relatively low numbers of "parallel" channels
and/or have assumed interleaved data. this is of little use for HDR
applications, because of the overhead of {de,re}interleaving whenever
you need to access the data for a single channel. i was originally
intrigued by the Clockwise FS, for example, until i found out that its
just a layer on top of ext2.
ultimately, i would rather assume that the underlying fs is not going
to help me, do the best job i can with the existing tools, and then if
an fs design is available to make things even faster, all the better.
--p
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This archive was generated by hypermail 2b29 : Fri Mar 31 2000 - 20:47:23 EST