From: Randy Cushman <rcushman_linux@earthlink.net>
To: alsa-devel@alsa-project.org
Subject: [RFC] Standard for Multichannel Mixer Control Names
Date: Sat, 17 Mar 2007 17:51:54 -0400 [thread overview]
Message-ID: <45FC62FA.5080403@earthlink.net> (raw)
In an exchange with Takashi regarding my proposal for changing some
mixer control names, he recommended that I start a thread in attempt to
reach consensus regarding a convention/standard for mixer control names
in ALSA.
My name-changing effort was complicated by the fact that, as Takashi put
it: "Many apps assume either 'Master' or 'PCM' mixer exists."
(Background: The only multichannel audio adapter to which I have access
for testing is an Analog Devices AD1986A CODEC attached to an AC '97
chipset on a motherboard.)
In desiring to rename controls, I assumed that the AC '97 multichannel
driver control names represented an ALSA standard. Actually I don't
know how other drivers name their multichannel controls. (The AC '97
driver generically uses "Master" playback to control the front channel
pin attenuation, and "PCM" playback to control multichannel DAC levels
into the mixer. "Surround", "Center" and "LFE" playback controls adjust
pin attenuation for the respective channels.)
The AD1986/AD1986A CODECs are at variance with the AC '97 standard,
causing "Master" playback to control pin attenuation for all channels,
"PCM" playback to control only the front channel DAC levels, and
"Surround", "Center" and "LFE" playback controls to affect DAC levels
for their respective channels. Hence my original reasoning that these
control names are inappropriate.
(Other AD AC '97 multichannel CODECs are even less intuitive regarding
their control usage, but in the interest of brevity I'll save that
discussion for later.)
Questions:
What is the function of playback controls "Master" and "PCM" for
multichannel CODECs driven by modules other than snd_ac97_codec? Which
control controls the front channels only, and which controls all
channels? What is the function of playback controls with names such as
"Surround", "Center", and "LFE"?
Does ALSA need to standardize mixer control names, or should we continue
to use whatever names are convenient for a given chipset/CODEC? What
standard should we use?
Randy Cushman
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next reply other threads:[~2007-03-17 21:52 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-03-17 21:51 Randy Cushman [this message]
2007-03-19 14:38 ` [RFC] Standard for Multichannel Mixer Control Names Takashi Iwai
2007-03-19 15:22 ` Fons Adriaensen
2007-03-19 15:20 ` Takashi Iwai
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