RPi3 + Hifiberry Digi+ + Shairport resampling

nbnb

Hi,

First off, thanks for this great project and for being the only RPi distribution that worked out of the box for RPi3!

I've been setting up RuneAudio with Digi+ SDPIF out to feed an external audio interface -- which uses a *fixed* sampling frequency. I would like to set the sampling frequency higher than 48K. So far I've had success with MPD, by using

redis-cli hset mpdconf audio_output_format "88200:*:2"

redis-cli hset mpdconf samplerate_converter "soxr high"

(either one of 96K or "very high" seemed to be too much for the RPi3)

Now streaming from OS X via Airplay gives no output since that is at 44.1K sampling rate. Is there a way to enable upsampling for Shairport?

I was thinking that alsa is actually the best place to perform upsampling since this would work for all audio sources. But there is not even an asound.conf !? Also, it seems that libsamplerate is not as good as sox. Does also support sox resampling? Where can I make the needed changes?

Any help is appreciated!

nbnb

bump.

basically, is there a way to resample everything to 88.2 including incoming airplay streams?

hondagx35

Hi nbnb,

you can try to change the rate by using dmix automatic sample rate conversion

- sudo nano /usr/share/alsa/alsa.conf
- defaults.pcm.dmix.rate 88200 (default is 48000)

Not tested, so no idea if this will work.

Frank

nbnb

thanks, i'll try...

ok, so here is what i don't know how to do: currently two alsa cards are set up: the internal bcm soandso... and my hifiberry digi+. in order to use alsa resampling i guess i would have to define a new alsa card (dmix) so that i can choose that card from the rune ui for audio output, yes? it seems i need

1. define dmix device
2. set sample rate to 88.2
3. ensure libsamplerate is used with high quality settings so that sound output is as good as possible despite not being bit perfect
4. make sure shairport uses that dmix device (mpd could still use the current setup with an alsa hw device.)
5. do all of the above in such a way that changes via the runeUI or system updates do not nuke everything.

how do i do that? do i have to make an .asoundrc in the root home directory? or better somewhere in /usr/share? will it not be overwritten by sonething runeplayer does?

hondagx35

Hi,

did you try to modify /usr/share/alsa/alsa.conf as shown above?

Frank

nbnb

i did now. edited the existing alsa.conf to change the sample rate (nothing else). did not work. shairport does reccognize that there is a stream and blocks audio output for mpd, but no output.