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恩，不是去掉了就是改了名字。
Runtime Configuration
There are a number of sysctl( variables available. hw.snd.* tunables
are global settings and dev.pcm.* are device specific.
hw.snd.latency_profile Define sets of buffering latency con-
version tables for the hw.snd.latency
tunable. A value of 0 will use a low
and aggressive latency profile which
can result in possible underruns if the
application cannot keep up with a rapid
irq rate, especially during high work-
load. The default value is 1, which is
considered a moderate/safe latency pro-
file.
hw.snd.latency Configure the buffering latency. Only
affects applications that do not
explicitly request blocksize / frag-
ments. This tunable provides finer
granularity than the
hw.snd.latency_profile tunable. Possi-
ble values range between 0 (lowest
latency) and 10 (highest latency).
hw.snd.report_soft_formats Controls the internal format conversion
if it is available transparently to the
application software. When disabled or
not available, the application will
only be able to select formats the
device natively supports.
hw.snd.compat_linux_mmap Enable to allow PROT_EXEC page map-
pings. All Linux applications using
sound and mmap(2) require this.
hw.snd.feeder_rate_round Sample rate rounding threshold, to
avoid large prime division at the cost
of accuracy. All requested sample
rates will be rounded to the nearest
threshold value. Possible values range
between 0 (disabled) and 500. Default
is 25.
hw.snd.feeder_rate_max Maximum allowable sample rate.
hw.snd.feeder_rate_min Minimum allowable sample rate.
hw.snd.verbose Level of verbosity for the /dev/sndstat
device. Higher values include more
output and the highest level, four,
should be used when reporting problems.
Other options include:
0 Installed devices and their allo-
cated bus resources.
1 The number of playback, record,
virtual channels, and flags per
device.
2 Channel information per device
including the channel's current
format, speed, and pseudo device
statistics such as buffer overruns
and buffer underruns.
3 File names and versions of the cur-
rently loaded sound modules.
4 Various messages intended for
debugging.
hw.snd.maxautovchans Global VCHAN setting that only affects
devices with at least one playback or
recording channel available. The sound
system will dynamically create up this
many VCHANs. Set to ``0'' if no VCHANS
are desired. Maximum value is 256.
hw.snd.default_unit Default sound card for systems with
multiple sound cards. When using
devfs(5), the default device for
/dev/dsp. Equivalent to a symlink from
/dev/dsp to
/dev/dsp${hw.snd.default_unit}.
hw.snd.default_auto Enable to automatically assign default
sound unit to the most recent attached
device.
dev.pcm.%d.[play|rec].vchans
The current number of VCHANs allocated
per device. This can be set to preal-
locate a certain number of VCHANs.
Setting this value to ``0'' will dis-
able VCHANs for this device.
dev.pcm.%d.[play|rec].vchanrate
Sample rate speed for VCHAN mixing.
All playback paths will be converted to
this sample rate before the mixing
process begins.
dev.pcm.%d.[play|rec].vchanformat
Format for VCHAN mixing. All playback
paths will be converted to this format
before the mixing process begins.
dev.pcm.%d.polling Experimental polling mode support where
the driver operates by querying the
device state on each tick using a
callout(9) mechanism. Disabled by
default and currently only available
for a few device drivers.
详见：man snd |
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发表于 2008-03-23 23:54
发表于 2008-03-24 22:01
