Re: kIOAudioDeviceTransportTypeUSB has strange effects
Re: kIOAudioDeviceTransportTypeUSB has strange effects
- Subject: Re: kIOAudioDeviceTransportTypeUSB has strange effects
- From: Jeff Moore <email@hidden>
- Date: Wed, 27 Jul 2005 11:58:55 -0700
You'll have to characterize the glitching better. Have you traced it
in the telemetry in HALLab? Are they overloads due to app activity or
due to the HAL getting errors from the driver when it calls the
kernel trap?
At any rate, the HAL's clock tracks USB devices slightly differently
in order to attempt to account for some of the problems that USB has.
On Tiger, this is limited to rejecting time stamps that are
considered too early. On earlier systems, the HAL also did more
filtering on the time stamps.
What this really means is that you probably have some issues with
your time stamps in general. The glitching you get is the HAL's way
of telling you this. The telemetry in HALLab should be able to focus
in on what it is about your time stamps that are causing trouble.
On Jul 27, 2005, at 7:50 AM, Fabian Renn wrote:
Hello list members,
i'm writing an audio driver for a usb high speed device ( See mail
'SPDIF audio in DVD Player' Vol 2 Issue 220 ). My device supports
up to 8 channels in/out at 96 kHz 32 bit. Yet when i set my
transport type to kIOAudioDeviceTransportTypeUSB my audio 'clicks'
at a sample rate of 44.1 kHz. It doesn't click if i don't set the
transport type or if i set it to
'kIOAudioDeviceTransportTypeOther'. Now, what could this be ( took
me ages to find out that the clicking game from
setDeviceTransportType )? What exactly does
kIOAudioDeviceTransportTypeUSB change in handling of my device?
Greetings from Germany
Fabian Renn
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--
Jeff Moore
Core Audio
Apple
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