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ALSA驱动的一些调试测试工具

Using Alsamixer
===============

Alsamixer uses an ncurses interface, which may not display properly in
an xterm.

Start it by typing "alsamixer".

Optional flags:
alsamixer -h displays the available flags.
alsamixer -e starts in "exact" mode. See below...
alsamixer -c N selects the soundcard to control, where N is the number of
the card, counting from 1.
alsamixer -m selects which mixer device to control, counting from 0. This
is only applicable to soundcards that have more than one mixer to 
control. It is the same as the amixer -d flag.


Keyboard commands:
==================

Left & right arrow keys are used to select the channel (or device,
depending on your preferred terminology). You can also use n (next) 
and p (previous).

Up/down arrows control the volume for the currently selected device.
Both the left & right signals are controlled.
You can also use "+" or "-" to turn volumes up or down.

"M" toggles muting for the current channel (both left and right). You can
mute left and right independently by using , and . respectively.

SPACE toggles recording: the current channel will be added or removed from
the sources used for recording. This only works on valid input channels,
of course.

"L" re-draws the screen.

TAB does something interesting: it toggles the mode for volume display.
This affects the numbers you see, but not the operation of the level
controls. There seem to be two modes: one is percentages from 0-100, the
other is called "exact mode" and varies from channel to channel. This
shows you the settings as the soundcard understands them. All the channel
level ranges are from 0 to a power of 2 minus one (e.g. 0-31 or 0-63).

Quick Volume Changes
--------------------

PageUp increases volume by 10.
PageDown decreases volume by 10.
Home sets volume to 100.
End sets volume to 0.

You can also control left & right levels for the current channel
independently,
according to this chart:

Q  |  W  |  E    <-- UP
-------------
Z  |  X  |  C    <---DOWN

^     ^     ^
|     |     +-- Right
|     |
|     +--- Both
|
Left


If the current mixer channel is not a stereo channel, then all UP keys
will work like W, and all DOWN keys will work like X.


Exiting
=======

You can exit with ALT + Q, or by hitting ESC.


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Alsamixer has been written by Tim Janik <[e-mail]> and
been furtherly improved by Jaroslav Kysela <[e-mail]>.
This document was provided by Paul Winkler <[e-mail]>.