Mixing Shairport-sync and RTP (with Gstreamer receiver) on RPI Zero 2 W

[Nathambetant]

Hello,

I would like to use my RPI for multiple music streaming services. Airplay and Bluetooth are currently working.
I also put a Gstreamer RTP-receiver as a service in systemd. But this hijacks ALSA and never releases it for other software to use. Is there a way to automatically stop Gstreamer-service when using Airplay or Bluetooth and restarting when nothing is used?

cat /etc/systemd/system/rtp-receiver.service
[Unit]
Description=RTP Audio Receiver
After=sound.target network-online.target

[Service]
Type=simple
Restart=always
RestartSec=5
ExecStart=/usr/bin/gst-launch-1.0 udpsrc port=46000 buffer-size=65536 ! \
    application/x-rtp,media=audio,payload=127,clock-rate=48000,encoding-name=L16,channels=2 ! \
    rtpjitterbuffer latency=200 ! \
    rtpL16depay ! \
    audioconvert ! \
    alsasink device=hw:0,0 buffer-time=200000 latency-time=100000
    
[Install]
WantedBy=multi-user.target

sudo lsof |grep snd
gst-launc  379                           root    7u      CHR      116,2      0t0        492 /dev/snd/pcmC0D0p
gst-launc  379 392 timer                 root    7u      CHR      116,2      0t0        492 /dev/snd/pcmC0D0p
gst-launc  379 393 rtpjitter             root    7u      CHR      116,2      0t0        492 /dev/snd/pcmC0D0p
gst-launc  379 394 udpsrc0:s             root    7u      CHR      116,2      0t0        492 /dev/snd/pcmC0D0p
gst-launc  379 395 gmain                 root    7u      CHR      116,2      0t0        492 /dev/snd/pcmC0D0p

[mikebrady]

Thanks for the question. Shairport Sync has hooks for programs or scripts you can execute when it goes active and inactive — please take a look at the Events page.

Also FWIW, Shairport Sync can be configured to output to PipeWire. If GStreamer could do the same, they could coexist…

[Nathambetant]

Thanks for pointing out events!

I'm trying this:
run_this_before_entering_active_state = "/usr/bin/systemctl stop rtp-receiver.service";
run_this_after_exiting_active_state = "/usr/bin/systemctl start rtp-receiver.service";

But it doesn't seem to work.
The command work in the command line.

Am I doing something wrong?

[p3ck]

I had to use sudo since shairport-sync doesn't typically run as root.. for example:

run_this_before_play_begins = "/usr/bin/sudo /usr/local/bin/unmute"

and

File: /etc/sudoers.d/shairport-sync

shairport-sync  ALL=NOPASSWD: /usr/local/bin/unmute, /usr/local/bin/mute

[Nathambetant]

Aha, I found it just as you wrote this.Thank you very much! For future reference, I took these steps:

• In /etc/shairport-sync.conf uncomment and edit these lines:

run_this_before_entering_active_state = "/usr/bin/sudo /usr/bin/systemctl stop rtp-receiver.service";
run_this_after_exiting_active_state = "/usr/bin/sudo /usr/bin/systemctl start rtp-receiver.service";

• Then I followed this page to make sudo for shairport-sync without password: run_this_before_entering_active_state is set but nothing happens #1485
• Reboot

Thank you fine people!

[p3ck]

BTW - it looks like you can use pipewiresink instead of alsasink..

/usr/bin/gst-launch-1.0 udpsrc port=46000 buffer-size=65536 !     application/x-rtp,media=audio,payload=127,clock-rate=48000,encoding-name=L16,channels=2 !     rtpjitterbuffer latency=200 !     rtpL16depay !     audioconvert ! pipewiresink

Setting pipeline to PAUSED ...
Pipeline is live and does not need PREROLL ...
Pipeline is PREROLLED ...
Setting pipeline to PLAYING ...
New clock: GstSystemClock