Shairport-sync & Mpd to Alsa Samplerate Issue

[MickMorley]

Does anyone know how to use both MPD and Shairport-sync as a source? I am finding that I can use only one or the other because MPD is coming in at 48000Hz and shairport only supports 44100Hz. When I play both on the SnapCast webclient they sound fine. When I hear the airplay stream on my output speakers (dietpi vm) through Alsa it skips and high pitched. My rate on Alsa is set at 48000 for my usb 7.1 soundcard.

When I change the mpd to output to 44100:16:2 and change my asound.conf to rate 44100 both streams now sound the same but the audio crackles and doesn't sound as good as mpd on 48000.

My setup is using a docker (throotee/snapcast-shairport) to run my shairport-sync and snapserver in. It is reading the airplay process locally and reading from an mpd pipe.

My output is on a single dietpi virtual machine running 3 snapclient instances into a USB 7.1 soundcard (passthrough from host). Each port on the soundcard is split by asound.conf and goes to a multizone amplifier throughout the structure.

Here is my snapserver.conf from the docker on the host Unraid machine:

source = airplay:///usr/local/bin/shairport-sync?name=airplay&devicename=Airplay&params=--configfile=/etc/shairport-sync.conf
source = pipe:///tmp/snap/mpd1?name=mpd1&mode=read
source = pipe:///tmp/snap/mpd2?name=mpd2&mode=read

Here is my asound.conf in a VM (dietpi) also on the host Unraid machine:

pcm.stereo1_kitchen {
   type dmix
   ipc_key 1024
   slave {
       pcm "hw:1,0"
       period_time 0
       period_size 2048
       buffer_size 65536
       buffer_time 0
       periods 128
       rate 48000
       channels 8
    }
    bindings {
       0 0
       1 1
    }
}

pcm.stereo2_garage {
   type dmix
   ipc_key 1024
   slave {
       pcm "hw:1,0"
       period_time 0
       period_size 2048
       buffer_size 65536
       buffer_time 0
       periods 128
       rate 48000
       channels 8
    }
    bindings {
       0 2
       1 3
    }
}

pcm.stereo3_office {
   type dmix
   ipc_key 1024
   slave {
       pcm "hw:1,0"
       period_time 0
       period_size 4096
       buffer_size 65536
       buffer_time 0
       periods 128
       rate 48000
       channels 8
    }
    bindings {
       0 4
       1 5
    }
}

[MickMorley]

I just found this in my snapclient log

[Warn] (Alsa) Could not set sample rate to 44100 Hz, using: 48000 Hz

My previous setup used separate sinks in pulseaudio to route the audio to each channel. Shairport-sync and MPD worked without issues then but I didn't use Snapcast at all. Is Alsa causing this? Because I know my USB Soundcard worked before.

[MickMorley]

I cannot believe that it took me this long to figure it out, I figured that snapcast would have a way to resample the audio

I added the argument --samplerate 48000:16:* to my snapclient command and now its working.

dietpi@DietPi:~$ snapclient --help
Allowed options:
  --help                          produce help message
  -v, --version                   show version number
  -h, --host arg                  server hostname or ip address
  -p, --port arg (=1704)          server port
  -i, --instance arg (=1)         instance id when running multiple instances on the same host
  --hostID arg                    unique host id, default is MAC address
  -l, --list                      list PCM devices
  -s, --soundcard arg (=default)  index or name of the pcm device
  --latency arg (=0)              latency of the PCM device
  --sampleformat arg              resample audio stream to <rate>:<bits>:<channels>
  --player arg (=alsa)            alsa|file[:<options>|?]
  --mixer arg (=software)         software|hardware|script|none|?[:<options>]
  -d, --daemon [=arg(=-3)]        daemonize, optional process priority [-20..19]
  --user arg                      the user[:group] to run snapclient as when daemonized
  --logsink arg                   log sink [null,system,stdout,stderr,file:<filename>]
  --logfilter arg (=*:info)       log filter <tag>:<level>[,<tag>:<level>]* with tag = * or <log tag> and level = [trace,debug,info,notice,warning,error,fatal]