Subject: Re: [linux-audio-dev] App intercomunication issues, some views.
From: Paul Davis (pbd_AT_op.net)
Date: Wed Jul 24 2002 - 02:58:16 EEST
>[...]
>> UST = Unadjusted System Time
>
>I believe this is a good introduction to UST/MSC:
>
>http://www.lurkertech.com/lg/time/intro.html
i read this a year or two ago. it was a major impetus in the design of
JACK, because i believe that almost all of it is based on a complete
misconception of how to do this stuff, and some of it is just plain
wrong. Its worth noting that SGI's "DM" API has never really taken
off, and there are lots of reasons why, some technical, some
political.
the most fundamental problem with SGI's approach to audio+video is
that its not based on the desirability of achieving low latency for
realtime processing and/or monitoring. its centered on the playback of
existing, edited, ready-to-view material. the whole section at the end
of that page about "pre-queuing" the data makes this point very clear.
SGI tried to solve the problem of the Unix read/write API mismatch
with realtime streaming media by adding timestamps to data. CoreAudio
solves it by getting rid of read/write, and acknowledging the inherent
time-basis of the whole thing, but for some reason keeps timestamps
around without using them in many cases. JACK follows CoreAudio's
lead, but gets rid of the timestamps.
--p
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