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Recording mixer of HDA sound cards using ALSA

Draft

If you have any suggestion for improving this document, please contact me: panard at inzenet.org

Introduction

ALSA configuration

You will need alsa-driver at least 1.0.19. We assume the main sound card (the one you hear the sound from) is the card 0 (hw:0).

Content of ~/.asoundrc : 
# if your sound card supports it:
#pcm.copy {                      
#       type plug                
#       slave {                  
#               pcm hw           
#       }                        
#       route_policy copy        
#}                               
# else :                         
pcm.aloopin {                    
        type hw;                 
        card 3;                  
        device 0;                
        subdevice 0;             
}                                

pcm.copy {
        type hw;
        card 3; 
        device 1;
        subdevice 0;
}                   
pcm.copy2 {         
        type plug   
        slave {     
                pcm "copy"
        }
        route_policy copy
}

pcm.multi {
   type multi
   slaves.a.pcm "hw:0,0,0" # main sound card
   slaves.a.channels 2
   slaves.b.pcm "aloopin" # aloop sound card
   slaves.b.channels 2
   bindings.0.slave a
   bindings.0.channel 0
   bindings.1.slave a
   bindings.1.channel 1
   bindings.2.slave b
   bindings.2.channel 0
   bindings.3.slave b
   bindings.3.channel 1
}
ctl.multi {
        type hw;
        card 0;
}

pcm.hdaloop {
        type route
        slave.pcm "multi"
        slave.channels 4;
        ttable.0.0 1
        ttable.1.1 1
        ttable.0.2 1
        ttable.1.3 1
# test:
#       ttable.2.2 1
#       ttable.3.3 1
}
ctl.hdaloop {
        type hw;
        card 0;
}

## select the one you want:
#pcm.!default { type plug; slave { pcm "hdaloop"; }}
#pcm.!default { type plug; slave { pcm "aloopin"; }}
#pcm.!default pcm.hdaloop
#pcm.!default pcm.aloopin

Recording script

The rec_output script : 
#!/bin/bash                            

if [[ x$1 == x-play ]]; then
        PLAY=true           
        shift               
else                        
        PLAY=false          
fi                          

DESTDIR=${DESTDIR:-/media/2/music}

QUALITY=${QUALITY:-6}

ALSA_CAPTURE="${ALSA_CAPTURE:-copy}"
ALSA_SAFE_PCM="plug:dmix"           

CAPTURE_QUALITY="${CAPTURE_QUALITY:-cd}"

# if your sound card supports it.
#CAPTURE_SOURCE="Mix"
#PCM_VOLUME="90%"

run_cmd() {
        echo $*
        "${@}"
}

if [ -z $1 ]; then
        tmpfile=`mktemp`

        # if your sound card supports it.
        #amixer cset iface=MIXER,name='PCM Playback Volume' $PCM_VOLUME
        #amixer cset iface=MIXER,name='Capture Source' $CAPTURE_SOURCE

        if $PLAY; then
                (sleep 1; run_cmd aplay -D $ALSA_SAFE_PCM $tmpfile)&
        fi
        run_cmd arecord -f $CAPTURE_QUALITY -D $ALSA_CAPTURE $tmpfile
else
        tmpfile=$1
fi

output=`kdialog --getsavefilename $DESTDIR '*.ogg *.mp3'`
if [[ "x$output" != "x" ]]; then
        artist=`kdialog --inputbox artist --title artist`
        title=`kdialog --inputbox title --title title`
fi

if [[ "x$output" != "x" ]]; then
        ext=${output/*./}
        if [[ "x$ext" == "x" ]]; then
                output="${output}.ogg"
                ext="ogg"
        fi
        case $ext in
                ogg ) oggenc -q $QUALITY $tmpfile -o "$output" --artist "$artist" --title "$title" ;;
                mp3 ) lame -h -V $QUALITY $tmpfile -o "$output" --ta "$artist" --tt "$title" ;;
                * ) echo "unknown '$ext' file extension!" >&2 ; false ;;
        esac
        [ $? -eq 0 ] && rm -iv $tmpfile
else
        rm -iv $tmpfile
fi

References
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