Re: Synchronizing with the actual USB device audio clock
Re: Synchronizing with the actual USB device audio clock
- Subject: Re: Synchronizing with the actual USB device audio clock
- From: philippe wicker <email@hidden>
- Date: Thu, 29 Dec 2005 10:47:18 +0100
On Dec 24, 2005, at 3:27 AM, david tay wrote:
Hi David,
Hi Philippe,
I believe Torrey is referring to the USB 2.0 audio specification
that should be ratified by now.
When an audio device is unplugged, the audio stream will be handled
by the default audio interface - usually the on-board audio.
The AppleUSBAudio sources are readily available at the darwin open
source and Apple developer web sites. If you need to, you could
download the sources.
I've downloaded these sources and started to study them.
A high speed USB 2.0 audio device will have to have the ability to
fall back to USB 1 transport when attached to a full speed (USB 1)
hub.
My device USB controller is a Cypress FX2-LP which handles this
automatically (well, not only the chip but also the firmware "main
loop" source code provided by Cypress). I've included the two
configurations (hi and full speed) in my USB descriptors table.
David
On Dec 21, 2005, at 10:46 PM, Torrey Holbrook Walker wrote:
Hi Philippe,
In the USB 1.1 audio class specification, there doesn't appear to
be a way to have input and output locked to the same sample rate.
The USB 2.0 audio specification does have a very clear definition
of clock domains and new descriptors to address issues like this,
Just to avoid a confusion. I've read in some postings that a 2.0
version of the Audio class specifications is being finalized. To my
knowledge, the current released version of the Audio class
specifications is 1.0. To my understanding, USB 1.1 is the last
released version for the full speed bus (the whole bus specs), and
USB 2.0 the last released version of the high-speed bus (the whole
bus specs, including full and low speed features). So, when you
mention the "USB 2.0 audio specification" do you refer to the "high-
speed bus" specification or to the yet-to-come 2.0 audio class spec?
Philippe
_______________________________________________
Do not post admin requests to the list. They will be ignored.
Coreaudio-api mailing list (email@hidden)
Help/Unsubscribe/Update your Subscription:
This email sent to email@hidden