[wdmaudiodev] Re: Control Tranfers using Winmm.dll to a USB device
- From: "Perry, Chris" <Chris_Perry@xxxxxxxx>
- To: <wdmaudiodev@xxxxxxxxxxxxx>
- Date: Fri, 29 Jun 2007 11:05:16 -0400
To use the "Message" API calls Larry is talking about below implies that the
programmer knows what custom messages are
defined by the audio device manufacturer. This information is potentially
unique to just that one device.
Keep in mind these messages were designed when ISA and/or PCI audio board
drivers were the norm.
Since USB itself provides a different mechanism to achieve the same
functionality,
I would guess that Microsoft saw no need to implement these "Message" APIs for
USB audio devices.
So... what is the mechanism for sending custom messages to a USB audio device?
Since a USB audio device is defined as a composite device it has an interface
to the audio stack for streaming audio and a control interface
for commands (like volume up/down, etc.). It can also have a HID interface. The
Microsoft USB audio class drivers take care of sending and receiving
the standard audio control messages but additional custom HID Reports can be
defined by the audio device firmware.
For instance, a USB pipe can be configured to accept HID messages from the PC.
Also, another USB pipe can be configured to send events/messages back to the PC.
If a developer knows what HID Reports are defined for a particular USB Audio
device,
then by definition there is now a mechanism to exchange custom information with
the device.
-Chris Perry
From: wdmaudiodev-bounce@xxxxxxxxxxxxx
[mailto:wdmaudiodev-bounce@xxxxxxxxxxxxx] On Behalf Of Larry Osterman
Sent: Thursday, June 28, 2007 7:02 PM
To: wdmaudiodev@xxxxxxxxxxxxx
Subject: [wdmaudiodev] Re: Control Tranfers using Winmm.dll to a USB device
In general, the MME messages (waveInMessage, waveOutMessage, mixerMessage,
midiMessage, etc) are used to communicate out-of-band information between
applications and the relevant "driver" in the user mode stack (in XP some
messages went into wdmaud.sys, I believe, but that was it). They have never
gone into the various audio drivers, and as far as I know, there has never been
a mechanism to allow user mode drivers to pass USB verbs directly onto the USB
bus (I may be wrong here, I'm not a driver guy).
From: wdmaudiodev-bounce@xxxxxxxxxxxxx
[mailto:wdmaudiodev-bounce@xxxxxxxxxxxxx] On Behalf Of Elios Elios Elios
Sent: Thursday, June 28, 2007 5:14 AM
To: wdmaudiodev@xxxxxxxxxxxxx
Subject: [wdmaudiodev] Control Tranfers using Winmm.dll to a USB device
Hello!
Does anyone know how to send control transfer and request to an USB audio
device using the winmm.dll API?
I tried with waveInMessage, but it didn't work.
Thanks!
________________________________
Excursiones y escapadas a sitios mágicos. No te lo pierdas en MSN
Entretenimiento <http://g.msn.com/8HMBESES/2734??PS=47575>
****************** WDMAUDIODEV addresses: Post message:
mailto:wdmaudiodev@xxxxxxxxxxxxx Subscribe:
mailto:wdmaudiodev-request@xxxxxxxxxxxxx?subject=subscribe Unsubscribe:
mailto:wdmaudiodev-request@xxxxxxxxxxxxx?subject=unsubscribe Moderator:
mailto:wdmaudiodev-moderators@xxxxxxxxxxxxx URL to WDMAUDIODEV page:
http://www.wdmaudiodev.com/
Other related posts:
