Hardware Autopsy
the fi nal stage that occurs in User mode.
From here, audio moves to the audio driver
in Kernel mode, where it encounters the
kernel-mode driver known as Port Class
(portcls.sys).
Port Class works on what Microsoft calls
a mini-port model: By providing the generic
functionality that an audio device needs in
order to function within Vista, the hardware
vendor needs only to provide a set of mini-
port drivers to handle the hardware-specifi c
functions that their product is capable of
performing. In order to discourage hardware
vendors from creating complex drivers in
Kernel mode, Microsoft has built a technolo-
gy called System Effects into the Vista audio
pipeline. System Effects allows the hardware
vendor to create custom DSP effects pro-
grammed to operate in User mode.PUT THE LIME IN THE
COCONUT
Microsoft created a new class of mini-port
driver for Vista called WaveRT (RT being
short for real time). Using the vendor-supplied
WaveRT mini-port driver, Vista can capture
the audio data and store it in a region of DMA
memory so that it doesn’t require intervention
from the host CPU. The audio playback device
(here again, either a soundcard or an integrat-
ed audio chip) can then access this memory
directly, pass the data contained within it to its
digital-to-analog converter (DAC), and output
the result to your speakers.
Musicians using PC-based pro-audio
gear—such as Digidesign’s Pro Tools or
Cakewalk’s Sonar—want even less latency,
and Microsoft is accommodating them with
a feature known as WASAPI Exclusive mode.
In this mode, Vista maps the DMA memory
all the way up into application space, so the
audio is rendered to the hardware even faster.
Software using Exclusive mode bypasses the
entire Vista audio engine, and the OS doesn’t
perform any mixing or digital signal process-
ing at all. Over time, Vista’s WASAPI Exclusive
mode will likely displace ASIO (Audio Stream
Input/Output), a low-latency protocol devel-
oped and freely licensed by software-devel-
oper Steinberg.
These new processes signifi cantly reduce
the latency of the audio subsystem, which
should reduce or eliminate common problems
such as audio that’s out of sync with video and
audio glitches. It should also enable vendors
to create entirely new types of audio hardware
and audio applications without the need to
create complex drivers down in Kernel mode.
And Microsoft hopes that keeping developers
out of the kernel will render Vista more stable
overall—leaving only Microsoft to blame if the
OS doesn’t deliver on that promise.r & d BREAKING DOWN TECH —PRESENT AND FUTURE
62 MAXIMUMPC july 2007 july 2007 MAXIMUMPC 63
White Paper: Audio in Vista
Cell Phone
Yesterday’s $500 phone is today’s giveaway. We crack open the case on the best
cell-phone technology 2005 had to offer—Motorola’s RAZR V3.Any requests? What hardware—new or old—would you like to see go under
Maximum PC’s autopsy knife? Email your suggestions to [email protected].From here, audio moves to the audio driver
in Kernel mode, where it encounters the
kernel-mode driver known as Port ClassPort Class works on what Microsoft calls
a mini-port model: By providing the generic
functionality that an audio device needs in
order to function within Vista, the hardware
vendor needs only to provide a set of mini-
port drivers to handle the hardware-specifi c
functions that their product is capable of
performing. In order to discourage hardware
vendors from creating complex drivers in
Kernel mode, Microsoft has built a technolo-
gy called System Effects into the Vista audio
pipeline. System Effects allows the hardware
vendor to create custom DSP effects pro-
grammed to operate in User mode.PUT THE LIME IN THE
Microsoft created a new class of mini-port
driver for Vista called WaveRT (RT being
short for real time). Using the vendor-supplied
WaveRT mini-port driver, Vista can capture
the audio data and store it in a region of DMA
memory so that it doesn’t require intervention
from the host CPU. The audio playback device
(here again, either a soundcard or an integrat-
ed audio chip) can then access this memory
directly, pass the data contained within it to its
digital-to-analog converter (DAC), and outputMusicians using PC-based pro-audio
gear—such as Digidesign’s Pro Tools or
Cakewalk’s Sonar—want even less latency,
and Microsoft is accommodating them with
a feature known as WASAPI Exclusive mode.
In this mode, Vista maps the DMA memory
all the way up into application space, so the
audio is rendered to the hardware even faster.
Software using Exclusive mode bypasses the
entire Vista audio engine, and the OS doesn’t
perform any mixing or digital signal process-
ing at all. Over time, Vista’s WASAPI Exclusive
mode will likely displace ASIO (Audio Stream
Input/Output), a low-latency protocol devel-
oped and freely licensed by software-devel-These new processes signifi cantly reduce
the latency of the audio subsystem, which
should reduce or eliminate common problems
such as audio that’s out of sync with video and
audio glitches. It should also enable vendors
to create entirely new types of audio hardware
and audio applications without the need to
create complex drivers down in Kernel mode.
And Microsoft hopes that keeping developers
out of the kernel will render Vista more stable
overall—leaving only Microsoft to blame if the
OS doesn’t deliver on that promise.july 2007MAMAMAXIMXIMXIMXIMUUUUMMPPPCC 63
Cell Phone
Yesterday’s $500 phone is today’s giveaway. We crack open the case on the best
cell-phone technology 2005 had to offer—Motorola’s RAZR V3.Any requests? What hardware—new or old—would you like to see go under
Maximum PC’sMaximum PC’sMaximum PC’s autopsy knife? Email your suggestions to autopsy knife? Email your suggestions to [email protected].CAMERA LENS
This RAZR features only
a VGA-quality (0.3MP)
sensor, but newer mod-
els have 2MP sensors.SUPPLEMENTAL SCREEN
The RAZR sports a 96x80
external screen.CPU
This phone
features
a U800
Neptune
chipset,
which han-
dles all of the
RAZR’s cell
and multime-
dia functions.MOTOR
When you set your phone
to vibration mode, this small
motor turns a shaft that is
weighted on one side, caus-
ing the phone to shake.MEMORY
Later models of the
RAZR include a slot for
microSD cards. This
model has 5.5MB of
usable onboard SRAM.