Advanced Linux Sound Architecture/Configuration examples (Italiano)

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Quanto di seguito riportato dovrebbe servire come guida per le configurazioni più avanzate di ALSA. La configurazione viene salvata in /etc/asound.conf come indicato nell'articolo principale. Di nessuna delle configurazioni riportate di seguito è garantito il funzionamento.

Nota: Molte delle funzioni mostrate di seguito, sono ottenibili più facilmente utilizzando plugin alsa come upmix, il cui utilizzo è spiegato nell'articolo principale su ALSA.

Surround 7.1 con upmix da stereo tramite dmix

~/.asoundrc
# 2008-11-15
 #
 # This .asoundrc will allow the following:
 #
 # - upmix stereo files to 7.1 speakers.
 # - playback real 7.1 sounds, on 7.1 speakers,
 # - allow the playback of both stereo (upmixed) and surround(7.1) sources at the same time.
 # - use the 6th and 7th channel (side speakers) as a separate soundcard, i.e. for headphones
 #   (This is called the "alternate" output throughout the file, device names prefixed with 'a')
 # - play mono sources in stereo (like skype & ekiga) on the alterate output
 #
 # Make sure you have "8 Channels" and NOT "6 Channels" selected in alsamixer!
 #
 # Please try the following commands, to make sure everything is working as it should.
 #
 # To test stereo upmix :      speaker-test -c2 -Ddefault -twav
 # To test surround(5.1):      speaker-test -c6 -Dplug:dmix6 -twav
 # To test surround(7.1):      speaker-test -c6 -Dplug:dmix8 -twav
 # To test alternative output: speaker-test -c2 -Daduplex -twav
 # To test mono upmix:         speaker-test -c1 -Dmonoduplex -twav
 #
 #
 # It may not work out of the box for all cards. If it doesnt work for you, read the comments throughout the file.
 # The basis of this file was written by wishie of #alsa, and then modified with info from various sources by 
 # squisher. Svenstaro modified it for 7.1 output support.
 
 #Define the soundcard to use
 pcm.snd_card {
     type hw
     card 0
     device 0
 }
 
 # 8 channel dmix - output whatever audio, to all 8 speakers
 pcm.dmix8 {
     type dmix
     ipc_key 1024
     ipc_key_add_uid false
     ipc_perm 0660
     slave {
         pcm "snd_card"
         rate 48000
         channels 8
         period_time 0
         period_size 1024
         buffer_time 0
         buffer_size 5120
     }
 
 # Some cards, like the "nforce" variants require the following to be uncommented. 
 # It routes the audio to the correct speakers.
 #    bindings {
 #        0 0
 #        1 1
 #        2 4
 #        3 5
 #        4 2
 #        5 3
 #        6 6
 #        7 7
 #    }
 }
 
 # upmixing - duplicate stereo data to all 8 channels
 pcm.ch71dup {
     type route
     slave.pcm dmix8
     slave.channels 8
     ttable.0.0 1
     ttable.1.1 1
     ttable.0.2 1
     ttable.1.3 1
     ttable.0.4 0.5
     ttable.1.4 0.5
     ttable.0.5 0.5
     ttable.1.5 0.5
     ttable.0.6 1
     ttable.1.7 1
 }
 
 # this creates a six channel soundcard
 # and outputs to the eight channel one
 # i.e. for usage in mplayer I had to define in ~/.mplayer/config:
 #   ao=alsa:device=dmix6
 #   channels=6
 pcm.dmix6 {
     type route
     slave.pcm dmix8
     slave.channels 8
     ttable.0.0 1
     ttable.1.1 1
     ttable.2.2 1
     ttable.3.3 1
     ttable.4.4 1
     ttable.5.5 1
     ttable.6.6 1
     ttable.7.7 1
 }
 
 # share the microphone, i.e. because virtualbox grabs it by default
 pcm.microphone {
     type dsnoop
     ipc_key 1027
     slave {
         pcm "snd_card"
     }
 }
 
 # rate conversion, needed i.e. for wine
 pcm.2chplug {
     type plug
     slave.pcm "ch71dup"
 }
 pcm.a2chplug {
     type plug
     slave.pcm "dmix8"
 }
 
 # routes the channel for the alternative
 # 2 channel output, which becomes the 7th and 8th channel 
 # on the real soundcard
 #pcm.alt2ch {
 #    type route
 #    slave.pcm "a2chplug"
 #    slave.channels 8
 #    ttable.0.6    1
 #    ttable.1.7    1
 #}
 
 # skype and ekiga are only mono, so route left channel to the right channel
 # note: this gets routed to the alternative 2 channels
 pcm.mono_playback {
     type route
     slave.pcm "a2chplug"
     slave.channels 8
     # Send Skype channel 0 to the L and R speakers at full volume
     #ttable.0.6    1
     #ttable.0.7    1
 }
 
 # 'full-duplex' device for use with aoss
 pcm.duplex {
     type asym
     playback.pcm "2chplug"
     capture.pcm "microphone"
 }
 
 #pcm.aduplex {
 #    type asym
 #    playback.pcm "alt2ch"
 #    capture.pcm "microphone"
 #}
 
 pcm.monoduplex {
     type asym
     playback.pcm "mono_playback"
     capture.pcm "microphone"
 }
 
 # for aoss
 pcm.dsp0 "duplex"
 ctl.mixer0 "duplex"
 
 # softvol manages volume in alsa
 # i.e. wine likes this
 pcm.mainvol {
     type softvol
     slave.pcm "duplex"
     control {
         name "2ch-Upmix Master"
         card 0
     }
 }
 
 #pcm.!default "mainvol"
 
 # set the default device according to the environment
 # variable ALSA_DEFAULT_PCM and default to mainvol
 pcm.!default {
     @func refer
     name { @func concat 
            strings [ "pcm."
                      { @func getenv
                        vars [ ALSA_DEFAULT_PCM ]
                        default "mainvol"
                      }
            ]
          }
 }
 
 # uncomment the following if you want to be able to control
 # the mixer device through environment variables as well
 #ctl.!default {
 #    @func refer
 #    name { @func concat 
 #           strings [ "ctl."
 #                     { @func getenv
 #                       vars [ ALSA_DEFAULT_CTL
 #                              ALSA_DEFAULT_PCM
 #                       ]
 #                       default "duplex"
 #                     }
 #           ]
 #         }
 #}

Surround 5.1 con upmix da stereo tramite dmix, inversione canali destro/sinistro, cattiva disposizione degli speaker

Procedimento funzionante nella maggior parte dei casi senza ulteriori modifiche a programmi/files.

pcm.!default {
    type route
## forwards to the mixer pcm defined below
    slave.pcm dmix51
    slave.channels 6

## "Native Channels" stereo, swap left/right
    ttable.0.1 1
    ttable.1.0 1
## original normal left/right commented out
#    ttable.0.0 1
#    ttable.1.1 1

## route "native surround" so it still works but weaken signal (+ RL/RF swap) 
## because my rear speakers are more like random than really behind me
    ttable.2.3 0.7
    ttable.3.2 0.7
    ttable.4.4 0.7
    ttable.5.5 0.7

## stereo => quad speaker "upmix" for "rear" speakers + swap L/R
    ttable.0.3 1
    ttable.1.2 1

## stereo L+R => join to Center & Subwoofer 50%/50%
    ttable.0.4 0.5
    ttable.1.4 0.5
    ttable.0.5 0.5
    ttable.1.5 0.5
## to test: "$ speaker-test -c6 -twav" and: "$ speaker-test -c2 -twav"
}

pcm.dmix51 {
	type dmix
	ipc_key 1024
# let multiple users share
	ipc_key_add_uid false 
# IPC permissions (octal, default 0600)
# I think changing this fixed something - but I'm not sure what.
	ipc_perm 0660 # 
	slave {
## this is specific to my hda_intel. Often hd:0 is just allready it; To find: $ aplay -L 
		pcm surround51 
# this rate makes my soundcard crackle
#		rate 44100
# this rate stops flash in firefox from playing audio, but I don't need that
       rate 48000
       channels 6
## Any other values in the 4 lines below seem to make my soundcard crackle, too
       period_time 0
       period_size 1024
       buffer_time 0
       buffer_size 4096
	}
}