Re: Host Time epoch
Re: Host Time epoch
- Subject: Re: Host Time epoch
- From: John Iversen <email@hidden>
- Date: Thu, 10 Feb 2005 13:09:18 -0800
At 12:53 PM 2/10/2005, Doug Wyatt wrote:
Steve has a case where an audio device's sample time appears to be moving
backwards.
I am not aware of any situations where the system's host time goes
backwards. More fundamental things than MIDI would probably break if it did.
Yes, that seemed improbable. I'm afraid I jumped the gun a little and
generalized incorrectly from his question about AudioDeviceGetCurrentTime
to HostTime in general. I'm right in the middle of a project and I'm
viewing the universe somewhat through the lens of 'HostTime' and 'MIDI'.
Thanks.
John
Doug
On Feb 10, 2005, at 12:21, John Iversen wrote:
Steve,
Sorry, I'm not aware of this issue, but it's of interest to me, and is
rather fundamental. Would you mind elaborating? What is the nature of the
non-monotonicity--I can't imagine you mean actual reversals in the host
time, I hope. Instead, do you mean that the rate of increase of the
HostTime is variable, so it drifts away from 'real time'? How large is
the effect in your experience?
To take a concrete example: Given that MIDITimeStamps are based on
'HostTime' (right?), are you saying that if midi events are received in
at exactly 1 sec intervals the increases in Host time (as seen in the
MIDITimeStamp of incoming packets) would not be identical (give or take
some small margin of error)? If that's really the case, I don't see how
any sequencer could possibly work reliably and not show tempo drift, so I
may not be getting the drift of what you're talking about here.
Thanks,
John
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