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SubjectRe: real-time threaded IO with low latency (audio)
David Olofson <> wrote:
> I think this whole discussion is beginning to get confused by different
> definitions of "real time". (Not the first time...) Basically, there are
> two kinds:
> 1) Soft real time
> * Typically ms precision timing.
> * No guaranteed deadlines.
> 2) Hard real time
> * Usually significantly better than ms precision
> * Guaranteed deadlines.

Maybe three kinds, see:

Some types of processing (eg. multimedia) do not fit well into the
hard or soft real-time categories. The periodic requests made by
multimedia applications are sensitive to variations in timing. As
such, they are not well served by the loose guarantees provided by
soft real-time systems. Hard real-time systems are often faced with
providing guarantees at the expense of providing services. Thus, while
they can meet the timing requirements of a multimedia application,
many times they cannot meet it's other service requirements. For
example, real-time processes running under RTLinux have no access to
any of the Linux services.

A purely binary distinction between hard and soft real-time is clearly
not acceptable for all applications. Many applications have
requirements spanning a continuum between the two. ...

[With supposedly a demo where a modified xanim performs better on a
loaded system.]


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