MPD is not offering any audio output

dzachareas

First, I'd like to thank everyone involved with this project. I installed Rune and had it up and running, connected to an NFS in no time.

The issue I'm having is with MPD. MPD doesn't list any audio output in the web interface, when I try to play music from another device, I get an error message that states something to the effect of, "MPD is not reporting any audio output". I'm sorry if this is covered somewhere, I did some searching and poking around the forum, but didn't see anything.

Orion

Hi dzachareas,
are you using an USB-DAC attached on BeagleBone Black?

Please follow this guide and post here your debug data.
Thanks.

dzachareas

No, I have my music on a NFS. I don't have any USB device connected. Unless I misunderstood your response.

ACX

Hi dzachareas, which output interface do you intend to use with your BBB?

dzachareas

So I have it running through ethernet, and I was testing it with the GMPC (Gnome Music Player Client) on Fedora. Both in the GMPC and the web browser, the audio was not selectable. It was default, no audio.

dzachareas

You guys rock, I really appreciate the help so far!

ACX

The BeagleBone Black does not have a built-in analog output as the Raspberry Pi does, so you are supposed to use it in combination with an external dedicated USB DAC in order to have a sound output from it. Or are you trying to get the sound out of the HDMI interface?

dzachareas

I think that is the answer. That makes a lot of sense. I have more raspis than BBBs, so I'll switch over. Thank you all for your help!! This is a great program.

ACX

You are welcome

Anyway, the BBB is a great board when combined with an asynchronous USB DAC.

eragefe

Is it possible to enable HDMI out?

BR G

eragefe

Yes? No? something else?

BR G

ACX

RuneAudio currently doesn't output to HDMI on the BBB, but we are working on it for those who need this feature.

eragefe

Thanks for your answer.

HDMI itself is not interesting. The reason I am asking is because enabling that will give you I2S on the header.
I have done several DAC constructions over the last years and I can tell you the sound is remarkable better when you use a ground isolated I2S directly from soc.
I have tried that with other images on BBB and it sounds much better than anything else by far.
You have done a remarkable nice job with the software (the best out there) so BBB+runeOS+I2S+somthing like dual mono PCM1794 +NOS mode +ground isolation +clock resync +discrete class A buffer/output stage could be the best total solution for many many years.
The USB BUS itself has construction issues from the beginning and in my eyes and ears are not the best way to transport sound. Some USB DACs sounds pretty decent but I believe that people like you and me are seeking for the highest end regarding audiophile sound.

BR G

ACX

I absolutely agree with you on considering I2S as THE way to go. We are currently focusing on I2S output on the Raspberry Pi, and BBB will be the next one to receive the treatment.
Would you please consider contributing to this feature with your knowledge? We are very busy in these days with the rework of the RuneUI (next release will introduce huge improvements on that front), and a help would speed up the development.

eragefe

It feels like you just opened Pandora’s Box.
1. Why beaglebone and not RPi ? Everything that has with your audio signal to do is related to ground. Your ground should be solid rock 0vDC 0vAC. My first thought was let’s do some measurement’s to the RPi ground. Placed the probe between a ground point near the HDMI connector and the I2S header ground pins.
Obviously you have high frequency ripple generated from the CPU and other guys on the board.
Ok not so unusual let’s start MPD playing something.
What a …. We almost have music between ground point and ground point on the same device.

Solid rock Nooot. Those devices are not made to play audio primarily.
I can see the same problem on BBB but the amplitude is 20 times lower.
That’s why I am talking about ground isolation
2. You hear often people talk about digital signals like “a zero is always zero and one is always one.” BUT your audio signal consists of wordclock, bitclock and data and for sure zero’s and ones are always zero’s and ones there but the most important is the relation between them in time.
There you have the problem.
That’s why I am talking about resync/reclock.
I could continue forever but people would stop reading. I can take more details on another post.
I will post here the layout of a pcb I recently made that accepts both RPi and BBB and has all those features I am talking about.

BR G

ACX

You don't have to persuade me about that, really

I like BBB a lot, first because it's a fully open source board, and then for the build quality. We are focusing on Raspberry Pi in these days because it's the most popular platform and because there are already some nice projects of I2S DACs around that we would like to support as soon as possible (we are talking about them around the forum). I'm aware of the Pi's limitations and I'm really interested in seeking the best possible sound quality from BBB.

eragefe

As you understand I am a hardware guy.
I have compiled some kernels for BBB/RPi/cubieboard but software is not my strongest area.
Here comes the layout I promised to post.
I hope you not misunderstood me. I think that RPi is a fantastic little thing.
But we have to know the issues around it if we will succeed to go around them.

BR G

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ACX

That design, together with the compatibility with Raspberry Pi and BeagleBone Black, is really interesting for anyone who wants to get the highest sound quality from both boards.
Are you considering to put it in production someday in the future?

eragefe

Yes Its only few weeks away.
The prototype sounds very nice. Together with RuneOs could it be an outstanding streaming solution.

BR G

dafart

eragefe wroteYes Its only few weeks away.
The prototype sounds very nice. Together with RuneOs could it be an outstanding streaming solution.

BR G

Hi eragefe, are you saying you are building custom made PCB to allow i2s support over the hdmi headers in both BBB and raspbery pi? That sounds amazing, will you sell it as a beagleboard cape?

What do you think of the hifiberry solution, could there be a problem with isolation / cpu related signal disturbances?

Would you also need a separate chip for clock resyncing (i'm no real hardware guy).

Sounds all very promising.

Would't it be sufficient to load / compile and load the apropriate kernel modules for the HDMI chip on the BBB in order to have it work?

Cheers,

Daf