RE: synchronization issue with Logic 7.1- help please
RE: synchronization issue with Logic 7.1- help please
- Subject: RE: synchronization issue with Logic 7.1- help please
- From: Philip Lukidis <email@hidden>
- Date: Fri, 5 Aug 2005 14:17:34 -0400
Hi, thanks for your reply.
I realize that no device can do anything but drift from their nominal rate.
However, I'd like to emphasize that when Logic tells me that "MIDI and audio
synchro has been lost", audio is still playing very clearly- no dropouts are
in evidence. Doesn't that prima facie support the hypothesis that the
current timestamps are still accurate? I'm using clock_get_uptime. Perhaps
I could try clock_get_system_nanotime()? I read on the archives that this
is unaffected by power saving (if true, it would be nice for that to be
documented...).
I also tried an interesting test...when ordered by the HAL set 44100 to my
device, I actually set 48000. Logic immediately popped up the *same* error,
and to that it added that it measured 48000 as a sample rate. I realize
that this is a gross difference, but it does prove that Logic is computes
the actual rate.
I you have any idea what I could be doing wrong, please let me know. Is it
still in your judgment probable that it is a timestamp issue? CubaseSX 3.x
and iTunes work fine...
thanks,
Philip Lukidis
-----Original Message-----
From: William Stewart [mailto:email@hidden]
Sent: Friday, August 05, 2005 1:54 PM
To: Philip Lukidis
Cc: email@hidden
Subject: Re: synchronization issue with Logic 7.1- help please
All devices drift from their "nominal" sample rate. The main and
crucial thing for a device is to provide, through its time stamps, as
accurate a picture as possible concerning the progression of time;
from that the HAL can discern the device's actual sample rate. Its
really then a "simple" matter for the driver - it reports the
progression of time according to its crystal, translating that to the
CPU clock times required by the HAL.
Bill
On 05/08/2005, at 5:46 AM, Philip Lukidis wrote:
> I was wondering, does anyone on the list think that a small drift
> in device
> sample rate could cause this? Just how precise does the reported
> sample
> rate to the HAL have to be?
>
> thanks,
>
> Philip Lukidis
>
> -----Original Message-----
> From: Philip Lukidis
> Sent: Thursday, August 04, 2005 2:04 PM
> To: email@hidden
> Subject: RE: synchronization issue with Logic 7.1- help please
>
>
> Several days ago when I sent this we had massive internal server
> issues, so
> I have opted to send this again, sorry if this turns our to be a
> double
> send.
>
> I will also ask an additional question: could skewed timestamps
> account for
> this? Let me say that when Logic reports bad audio/MIDI
> synchronization,
> audio still continues to play.
>
> If skewed timestamps could not be responsible, does anyone else
> know what
> could be?
>
> thanks,
>
> Philip Lukidis
>
> -----Original Message-----
> From: Philip Lukidis
> Sent: Friday, July 29, 2005 3:43 PM
> To: email@hidden
> Subject: synchronization issue with Logic 7.1- help please
>
>
> Hello. I'm responsible for the maintenance of a 1394 kext (top
> edge is
> coreaudio) which I did not write. MacOSX is not my primary
> environment, so
> forgive me if I am asking a naive questions.
>
> I have a problem when looping a simple project (one of the demos)
> in Logic
> 7.1. After perhaps 45-60 min, I get a popup saying that
> synchronization
> between MIDI and audio was lost. Meanwhile, audio is still going
> on in the
> background, so it would appear that my timestamps are OK (otherwise, I
> thought this might be pertinent
> http://lists.apple.com/archives/coreaudio-api/2002/Sep/msg00308.html).
>
> There is nothing being sent over the MIDI at all, nor am I
> synchronizing off
> a remote source/clock, nor is there any MIDI input. It even occurs
> when I
> have uninstalled my MIDI plugin, though my kext has changed
> considerably
> since then (I will redo this test and post the results).
>
> If anyone has a clue why this could be occurring, I'd appreciate a
> reply.
>
> thanks,
>
> Philip Lukidis
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