[wdmaudiodev] Re: 24bit WDM streaming

  • From: "DJ Sisolak" <dsisolak@xxxxxxxxxxxxxxxxxxxxxx>
  • To: <wdmaudiodev@xxxxxxxxxxxxx>
  • Date: Tue, 28 Sep 2004 08:48:35 -0700

Hi Tobias,

It is the device that will tell you via its pins what the acceptable
formats are. If the format on the pin tells you that the device accepts
24bit data, but does not use the WAVEFORMATEXTENSIBLE format then you
should probably assume that the data has to be packed 24bit. If the pin
exposes an extensible format then the format will tell you what the
valid bit count is and the package size.

The USBAudio.sys driver will not do any data format conversion. The data
sent to the driver is expected to match the size of the data it reports
that it is capable of. Once a format is selected, that is the format
that will be passed to the device. If you are going through kmixer, then
it is the intersection with KMixer that will decide the final format of
the data, but it will always be one of those the device listed it is
capable of. 

DJ

This posting is provided "AS IS" with no warranties, and confers no
rights

-----Original Message-----
From: wdmaudiodev-bounce@xxxxxxxxxxxxx
[mailto:wdmaudiodev-bounce@xxxxxxxxxxxxx] On Behalf Of wdm
Sent: Tuesday, September 28, 2004 6:53 AM
To: 'wdmaudiodev@xxxxxxxxxxxxx'
Subject: [wdmaudiodev] 24bit WDM streaming

Hi everyone,

so far I have only streamed 16bit stuff over WDM-KS and
I now want to also support 24bit. If I have a KS-WDM-
device which tells me that it supports 24bit (only and
not 32bit), can I still stream 32bit values to the driver,
or do I need to pack stuff into 24bit units?

I would think, that if I use WAVEFORMATEXTENSIBLE
and set wValidBitsPerSample to 24, I should be
able to still stream 32bits to the device - or
have I got it wrong there?

Also - what about USB 1.1 devices? would the USBAUDIO.SYS
shrink the data to 24bit before transmission before it
is sent over the interface (this would obviously save
precious bandwitdth)

Tobias
--
TE-SYSTEMS GmbH - competence in e-communications.
Max-von-Laue-Weg 19 - 38448 Wolfsburg  -  Germany
TEL: +49 (0)5361 895-0 - FAX: +49 (0)5361 895-999
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