Always on PCM signal to DAC?

Hi there,

I am loving Volumio as part of my streaming set up. It would be perfect if it would output an always on PCM signal to my DAC. At the moment, as each track finished the PCM signal is dropped and then a new track comes a new PCM stream is started for the DAC to lock onto. My issue is that the DAC takes a moment to lock on and the beginning of each track is lost.

Is there a way to get Volumio broadcasting a continuous PCM stream on which tracks are layered?

The set up is as follows:

Music - Mostly Apple Lossless rips of CDs, plus a few mp3s.

Server - QNAP TS109ii network attached storage running Twonky Version: 7.2.8 uPnP

Rendering - Raspberry Pi with Hifiberry DAC running Volumio Beta 1.4

Control - Android phone running BubblePnP app

DAC/HiFi - Digital coaxial from Pi to Meridian 561 DAC and then to active speakers

[PS - it sounds amazing]

I have used volumio as upnp renderer with quite a few different dacs, usb and i2s and never encountered this problem. The lock unlock sounds particularly strange betwen tracks.
Generally i only experience unlock lock on start up or change of track bit rate.

You say pi to meridian with coax out but where is the coax coming out of on pi ?
Where does the hifiberry DAC fit into the the pi and dac scenario ?
What happens with hifiberry DAC RCA OUT Direct to active speakers (by pass the meridian). Do you still skip start of track ?

Kevin

Kevin

My mistake. I have a Hifiberry Digi, not a DAC. So the Pi now has a DAC coaxial and optical output on it. That feeds the Meridian a PCM signal.

I got a response over at HifiBerry suggesting I look at the MPD setup. There is an “always_on” option so I thought I’d have a go at it (as an amateur hack) but it didn’t work. Maybe someone that knows about the MPD daemon could help?

I used terminal on my Apple Mac

Then I added in the always_on “yes” line, as below to the bottom of the file and rebooted.

audio_output {

type “alsa”
name “Output”
device “hw:0,0″
dop “no”
always_on “yes”

}

Unfortunately, it doesn’t keep the PCM stream always on ……

Always on refers to the ability to select\deselect a particular output…
I think the issue is driver-related…

Thanks. Can you give me a clue of what I need to google for? Does the driver have a filename or something?

Sorry, a bit of a newbie here. :wink:

The driver is hardcoded in the kernel… Only the guy that made that can help us I think…

Is the driver called “ALSA”? Maybe there are configurations I can set?

Hi Andrew,

As i have no experience with hifiberry digi i can’t really help on that end. I always like to explore quick fixes or at least try to reassure myself that i have an idea where the problem lies.

In the streaming world there are often two and a half sides to every story. The server, the renderer and the secret half is how they communicate together. If you are not making progress then you can maybe try :-

  1. Try mounting the QNAP in volumio as a drive, library tab, still got the same problem ?

  2. Try another server on the QNAP, itunes, minim server, others etc. still got the same problem ?

  3. Try the analogue out on the RPI to analogue in on Meridian. If you don’t have the problem then it’s looking hifiberry digi and meridian based.

  4. Can you get your hands on (a lend) another DAC with coax IN.

I’m a sad bastard so i will look at the dlna standard sometime in the next week to have a look at how this effect could happen. However the solution could lie in the hands of the software developers as michelangelo suggests.

Kevin

Good suggestions. Here are some configurations I’ve tried.

b[/b]
Server: QNAP NAS folder mounted on Volumio.
Control: Volumio web interface
Render: Volumion Pi/Hifiberry into DAC.
RESULT: Dropped PCM stream between tracks

b[/b]

Server: Apple Mac iTunes
Control: iTunes/Airplay
Render: Volumio Pi/Hifiberry into DAC.
RESULT: Continuous PCM stream between tracks (NB: there is a quiet but audible click between tracks, but the DAC remains locked on, the PCM stream is continuous)

b [/b]

Server: Android phone music
Control: Android BubblePnP
Render: Volumio Pi/Hifiberry into DAC.
RESULT: Dropped PCM stream between tracks

b[/b]

Server: Android phone music
Control: Android BubblePnP
Render: Samsung Bluray BDF6500 HDMI into Samsung TV then TV optical into DAC.
RESULT: Continuous PCM stream between tracks (NB: no “click” between tracks like the Airplay option (2) above.)

b[/b]

Server: QNAP NAS Twonky Server
Control: Android BubblePnP
Render: Samsung Bluray BDF6500 HDMI into Samsung TV then TV optical into DAC.
RESULT: Continuous PCM stream between tracks (NB: no “click” between tracks like the Airplay option (2) above, but it will only play mp3. Most of my music is Apple Lossless - might need some transcode on fly).

b[/b]

Server: QNAP NAS Twonky Server
Control: Android BubblePnP
Render: Volumio Pi/Hifiberry into DAC.
RESULT: Dropped PCM stream between tracks.

b[/b]

Server: Volumio RAMplay (Pi’s SD card)
Control: Volumio webinterface
Render: Volumio Pi/Hifiberry into DAC.
RESULT: Continuous PCM stream between tracks.

SOME INITIAL CONCLUSIONS

I think it must be the way that Volumio/Hifiberry handles uPnP or a NAS indexed files. It’s clearly capable of a continuous PCM stream via HifiBerry because of both (2) Airplay and (7) RAMplay working.

In the RAMplay option, when the web interface “stop” button is pressed the PCM signal stops. When a track is played the PCM signal restarts and the DAC takes a second to lock. However, when it’s running through an album or playlist or I change tracks in the middle of playback the PCM signal is continuous, no drops, no gaps in PCM.

The Samsung TV optical out is truly “always on” where as the Pi stops when there is no source music.

What do you think?

Andrew,

Is the pi connected to your home network with a wireless dongle or hard wired into Ethernet port.

It’s clear to me that Test 3 is wireless streaming but what about the otehr cases that don’t work ?

Kevin

The Pi is hardwired ethernet. No wireless capability. The Android is running on wifi. :wink:

Andrew

Ok it seems that the problem is isolated to the combination of upnp renderer voumio (for pi version) + hifiberry digi + dac. Agreed ?

Can you beg steal or borrow another coax input DAC ? Just to test ?

Where are you based ? PM if you prefer.

Can anyone offer any positive experience with rendering on volumio upnp to hifiberry digi ?

I will also read standard to see how the communication echanges should work. This might also throw something up and i would like to undertsand how these things are meant to work :laughing:

Kevin

Kevin, thanks for thinking about this. Really appreciated.

I will have a think about the DAC test.

You could try your luck with other kernel profiles, i don’t know if it will work but its worth a shot.
Menu --> System --> Sound quality tweaks

And maybe DSD over PCM could be a solution. Just read some info about this and it could help.
Playback --> General music daemon options --> DSD over PCM

Another Digi post FYI

http://volumio.org/forum/sample-rate-problem-t2186.html

I thought I’d try a completely different setup. It works. I now have an “always on” PCM stream from the Pi to my receiver with no gaps or drop outs.

Thanks for trying to get Volumio working for me - it’s a great project that didn’t quite work with my quirky Meridian DAC.

New setup is

  • PiCorePlayer (a Squeezebox emulator)
  • Raspberry Pi with HifiBerry Digi
  • Coaxial out to Meridian DAC
  • Squeezeserver running on OS X
  • Music Library on QNAP

Nice One Andrew,

The important thing is to get something that works for you. :wink:

Spotify connect plug-in only.

Sorry to bring back to life an old thread but it didnt seem to get solved and I am having the same problem but it doesnt appear to be limited to just the S/PDIF(TOSLINK) output it effects the COAX too but only using the spotify connect plug-in.

Using:
Volumio 2.296
Raspberry Pi 3
Hifiberry Digi+ Pro
Audiolab MDAC+

Using the S/PDIF(TOSLINK) or the coax/RCA output when a new song starts or skipping I get a delay to the DAC this appears to be because the PCM signal goes off then on again for the S/PDIF but for the COAX I would expect it to be fine. Has anyone found a solution for this? Is this just a spotify connect issue?