I thought I'd share my recipe for overlaying music playing on pCP
machines with audio jingles. This is a simplified version of a working
setup with multiple emitters, multiple sounds, multiple players.
It uses multicast over UDP to let many devices receive the order to do
something (generally: play a sound.) Each device can elect to execute or
discard the order, according to its local configuration. So you can
arbitrary link one event from one device to one receiver to one output.
What gets sent via multicast is a simple ASCII string, not audio itself.
In the case of pCP players they select a local wav file corresponding to
the string, but non-audio receivers are possible too. The payload is
extremely small so network load is minimal.
Local processing is fast enough to ensure the delay between sending
(pressing a button) and executing (hearing a sound) feels ok. I've
elected to let socat do the multicast magic, as it is ported to many
platforms.
When multiple audio receivers play a jingle, there is no sync mechanism
but in effect with pCP you get all receivers to play at the same
instant.
The system works as long as there is one emitter and one receiver active
on the network, so it's independent from LMS. To overlay an incoming
audio jingle over possibly playing music, I've determined a double ramp
works best: music volume goes down gradually while the jingle volume
goes up gradually, and back.
With the JustBoom amp HAT I've used -and all i2s devices?- there is no
hardware mixer so a software mixer is defined with ALSA with 2 sources
and 2 volume controls.
The script that manipulates volume controls is very basic, it works with
jingles that are 4 or 5 seconds long. YMMV.
This is how to play a jingle on pCP 3.22 (normal kernel version) with an
add-on amp on a Pi 3 wired via ethernet:
- *Setup pCP via the web interface*, at
http://<address-of-picoreplayer>:
- -Install the socat extension.- Select Main Page, Beta (bottom of
page), then Extensions. On that new page, make sure you're using the
Official piCore repository (default), then in "Available extensions
in the Official piCore repository" select socat.tcz and press Load.
- -Select your add-on DAC or amp.- Select Squeezelite Settings,
then pick your add-on model under "Choose Audio output". Click Save.
Reboot if needed, come back here, click Audio card control, and
disable the onboard soundcard.
- -Setup Squeezelite to use an ALSA audio mixer.- Select
Squeezelite Settings, then in field "Output setting" enter the value
"music" (without quotes). Press Save. If you restart Squeezelite as
prompted it will now fail, that's ok.
- -Set pCP to run a script at boot.- Select Tweaks, then under
"User commands", enter user command "/home/tc/gong.sh" (no quotes)
and press Save.
- *Locate a wav jingle file* and copy it under the name "action1.wav"
to pCP, e.g. "scp jingle.wav
tc@<address-of-picoreplayer>:~/action1.wav". The setup is known to
work with audio files ~ 4-5 secs. in duration, format "Signed 16 bit
Little Endian, Rate 44100 Hz, Mono"
- *Customize pCP via the shell*, at ssh
tc@<address-of-picoreplayer>:
- -Replace the stock /etc/asound.conf- file with this:
Code:
--------------------
## Onboard audio disabled in /boot/config.txt
## Otherwise volume sliders that use "control.card X"
## could attach to the wrong card at boot in pCP 3.2.0.
##
## Alsaequal removed from this file. Some issues controlling
## softvols with equal in pCP 3.2.0. Add it back if you want.
##
## Make sure hardware volume control "Digital" is set to
## a safe value, you probably don't want a jingle to play
## at full power by accident
##
## A) Devices available to applications
##
# Squeezelite is set to use this device
# This softvol allows to ramp down-up music when an application
# plays another sound.
# Nominal state is: 100%
pcm.music {
type softvol
slave.pcm plug:dmixer
control.name musicvol
control.card 0
}
# Same story here: ramp up-down sounds sent by other applications
# Nominal state is: 0%
pcm.gong {
type softvol
slave.pcm plug:dmixer
control.name gongvol
control.card 0
}
## B) Audio output device. Here: Justboom amp HAT
##
# Shared access to our audio card
pcm.dmixer {
type dmix
ipc_key 1234
ipc_key_add_uid true # Needed ?
ipc_perm 0666
slave {
pcm "hw:CARD=sndrpijustboomd,DEV=0"
}
}
# Whatever ctl magic thing
ctl.dmixer {
type hw
card 0
}
#EOF
--------------------
E.g. from the shell session on pCP, run "cp /etc/asound.conf
~/asound.conf.orig", then copy the code above, run "cat >
/etc/asound.conf", paste clipboard contents in the window, and hit
ctrl-d.
- -Install the gong.sh script:-
Code:
--------------------
#!/bin/sh
# Receive events via socat and play audio jingles
##
## vars
##
APLAY="/usr/local/bin/aplay"
AMIXER="/usr/local/bin/amixer"
APLAY_OPTS_GONG='-q -N -D gong'
AMIXER_OPTS_MUSIC="-D hw:CARD=sndrpijustboomd -q"
AMIXER_OPTS_GONG="-D hw:CARD=sndrpijustboomd -q"
AMIXER_VOLCTL_MUSIC='musicvol'
AMIXER_VOLCTL_GONG='gongvol'
RAMP_STEP_MUSIC='1.5%'
RAMP_SPEED_MUSIC='100000'
RAMP_LENGTH_MUSIC=20
RAMP_STEP_GONG='2.3%'
RAMP_SPEED_GONG='100000'
RAMP_LENGTH_GONG=10
BASE_GONG_VOL="10%" # Use only a % string or 0-255 int
SOCAT="/usr/local/bin/socat"
SOCAT_ADDR="UDP4-RECVFROM:12345"
SOCAT_OPTS="ip-add-membership=239.123.123.123:eth0"
# Accepted clients
CLIENTS='clt1 clt2'
# Actions sounds
SND_action1='/home/tc/action1.wav'
SND_action2='is-missing'
##
## functions
##
checkInstall(){
for EXE in "${AMIXER}" "${APLAY}" "${SOCAT}"
do
if [ ! -x "$EXE" ]; then
echo "Executable [$EXE] not found or executable. Exit"
exit
fi
done
}
InitializeAlsa() {
# pCP 3.2.0: used to block if Alsa equal was in use.
# Workaround: spawn then kill the aplay process
# echo "Opening ALSA to initialize controls."
${APLAY} $APLAY_OPTS_GONG /dev/null >/dev/null 2>&1
}
checkAction() {
unset PASS
CLT="${1}"
ACT="${2}"
for T in ${CLIENTS}
do
if [ "$T" == "$CLT" ]; then
eval "FILE=\$SND_${ACT}"
if [ -f "$FILE" ]; then
PASS=1
echo "Client [$T], requested sound [$FILE]"
fi
break
fi
done
}
doAction() {
ACTION="${1}"
# BACKGROUNDED Ramp music down then up
(
rampVolume 'music' 'down'
# NB usleep 1.000.000 = 1 sec.
SHIM='500000'
usleep $SHIM
rampVolume 'music' 'up'
)&
# BACKGROUNDED Ramp gong up then down
(
resetGongVol "${BASE_GONG_VOL}"
rampVolume 'gong' 'up'
SHIM='1500000'
usleep $SHIM
rampVolume 'gong' 'down'
)&
# BACKGROUNDED Play gong
( playGong )&
}
playGong() {
eval "GONG=\$SND_${ACTION}"
"${APLAY}" ${APLAY_OPTS_GONG} "${GONG}" >/dev/null 2>&1
}
rampVolume() {
# accepts args up or down
CONTROL='MUSIC'
[ "${1}" == "gong" ] && CONTROL='GONG'
UPDOWN='\-'
[ "${2}" == "up" ] && UPDOWN='+'
eval "STEP=\$RAMP_STEP_${CONTROL}${UPDOWN}"
eval "VOLCTL=\$AMIXER_VOLCTL_${CONTROL}"
eval "LENGTH=\$RAMP_LENGTH_${CONTROL}"
eval "SPEED=\$RAMP_SPEED_${CONTROL}"
eval "OPTS=\$AMIXER_OPTS_${CONTROL}"
i=0
while [ "$i" -lt ${LENGTH} ]
do
"${AMIXER}" ${OPTS} sset "${VOLCTL}" "${STEP}" >/dev/null 2>&1
usleep ${SPEED}
i=`expr $((i)) + 1`
done
}
resetGongVol() {
LVL="$1"
"${AMIXER}" ${AMIXER_OPTS_GONG} sset "${AMIXER_VOLCTL_GONG}" "${LVL}"
>/dev/null 2>&1
}
# Start here
checkInstall
InitializeAlsa
resetGongVol 0
# We listen continuously. Socat quits after receiving one frame
# echo "Now listening via ${SOCAT} ${SOCAT_ADDR},${SOCAT_OPTS}"
while true
do
LINE=`"${SOCAT}" "${SOCAT_ADDR}",${SOCAT_OPTS} -`
set -- ${LINE}
checkAction ${1} ${2}
# PASS is defined if client is known
# and action sound is found
[ "$PASS" ] && doAction ${2}
done
#EOF
--------------------
E.g. copy the code above, then from the shell session on pCP, run
"cat > /home/tc/gong.sh", paste clipboard contents in the window,
and hit ctrl-d. Then run "chmod +x /home/tc/gong.sh" to make the
script executable.
- -Save your setup- with "pcp bu" on the command line. If you see
"your backup is a little large", that's ok. Now reboot with "pcp rb"
I suggest you start playing music on that player after reboot to make
sure all went well. Make sure Squeezelite now uses the "music" output
device.
You can now use any machine on the network to send the order to play
your jingle, as long as the thing can run socat (I've used socat v 1.7).
If you need to install socat, I'll let you find how on linux, for
windows I've used 'this binary'
(http://blog.gentilkiwi.com/programmes/socat) and for OS X I've
installed it via Brew.
Now, enter "echo clt1 action1 | socat -
UDP4-DATAGRAM:239.123.123.123:12345,reuseaddr" from your client and you
should hear your jingle fade in and out of the music. If you "echo foo
bar ..." instead you'll hear nothing as the script receives but
disregards the call. And if you shutdown the LMS server the jingle will
still play.
You will certainly want to modify the script, I won't mind... You should
also define your own multicast address in the 239.0.0.0/8 network, and
pick your own UDP port. If you want to use wifi, pay attention to
SOCAT_OPTS in the script.
HTH
3 SB 3 Libratone Loop, Zipp Mini iPeng (iPhone + iPad) LMS 7.9
(linux) with plugins: CD Player, WaveInput, Triode's BBC iPlayer by bpa
IRBlaster by Gwendesign (Felix) Server Power Control by Gordon
Harris Smart Mix, Music Walk With Me, What Was That Tune? by Michael
Herger PowerSave by Jason Holtzapple Song Info, Song Lyrics by
Erland Isaksson AirPlay Bridge by philippe_44 WeatherTime by Martin
Rehfeld Auto Dim Display, SaverSwitcher, ContextMenu by Peter Watkins.
------------------------------------------------------------------------
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