At Sun, 8 Oct 2006 18:27:26 -0400, Daniel Jacobowitz wrote: > > How is volume control supposed to work for surround sound codecs? Is there > typically a register which affects every channel, or do you have to adjust > them separately? I've been staring at the datasheets and prodding the > registers for mine (ICE1724, on a Shuttle SN25P). There's three pieces: > the vt1720, the vt1617a, and a wm8728. The vt1617a has ac97 volume control > registers, but the "master" volume doesn't affect the center/lfe or rear > surround channels. I am guessing that the wm8728 is just for the last two > channels (I've got jacks for 7.1 but the vt1617a only does 5.1). That's the standard behavior of AC97 codec. The "master" doesn't influence on surrounds. Some ac97 codec chips have an extended mode that behaves differently, though. > I cobbled together patches that add a stereo mute switch to the softvol > plugin, and set that in front of the card. Then I can actually change > volume or mute the whole set. But for various reasons this is > unsatisfactory, e.g. because it's not called "Master Playback", and because > it doesn't show up as the first mixer element - every application needs a > bit of configuration to find the right volume control. And one of the > applications I wanted to configure, gnome-settings-daemon, is basically > unconfigurable. It just grabs whatever gstreamer sees at the front of the > list. > > (The mute patches available on request, btw, one alsa-lib patch and one > kernel driver bugfix for user-created boolean controls.) > > Before I go any further with this I want to know how it works elsewhere. > I would think that having a single mixer control that affected all the > surround speakers would be a pretty standard thing to want! Do other chips > have a single register for it? Or does this one, and I'm just not seeing > it? > > If I have no other way to get this to work than with the softvol plugin, > I think this is the way to go: > - Rename the "Master" volume control/switch to "Front". > - In userspace, have softvol create a control/switch named "Master". Maybe it's an easiest way... > Potential problems: > - With a library older than kernel driver I think things would start > picking up the Headphone channel as the master volume control if > I made this change, yuck. > - The user-created controls don't exist right away, so saving and > restoring volume might not work. alsactl save & restore should work for softvol. The softvol mixer element doesn't exist only at the very fresh state. Takashi ------------------------------------------------------------------------- Take Surveys. Earn Cash. Influence the Future of IT Join SourceForge.net's Techsay panel and you'll get the chance to share your opinions on IT & business topics through brief surveys -- and earn cash http://www.techsay.com/default.php?page=join.php&p=sourceforge&CID=DEVDEV _______________________________________________ Alsa-devel mailing list Alsa-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.sourceforge.net/lists/listinfo/alsa-devel
