Subject: Re: [linux-audio-dev] ALSA vs OSS/free
From: Paul Davis (pbd_AT_Op.Net)
Date: Mon Mar 11 2002 - 03:30:50 EET
>> > and a lot of extra CPU cycles when all the high end applications use
>> > non-interleaved data so that editing is easy.
>> You can effectively process interleaved data with SIMD as you can
>> parallelize operations for 2-4 channels.
>
>This leaves all the other CPU out in the cold. It's a bad solution to
>require a specific CPU for your application.
its also nonsense.
what's slow about using interleaved data is the issue of transfer
to/from disk, not the issue of processing them, where SIMD can be used
more effectively to handle parallelism on a single channel (since the
processing on a single channel is the same for all samples; not
guaranteed to be true for N channels, where 1 channel may be processed
1 way, and another channel processed another.
lets take the simplest case: a stereo interleaved file. if i want to
do a nonlinear edit on a chunk of the file for just one channel, i now
have to read it in a very non-optimal way. one channel's data exists as a
contiguous segment of the file, but the other exists as a (potentially
large) series of sections of the file, possibly overlapping with the
contiguous segment of the unedited channel. is it any wonder that no
high end DAW uses anything other than mono files as its native file
format?
the workarounds for this issue all cost vastly more in program
complexity than the simple solution of using a non-interleaved data
format.
--p
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