[blubserl]

i recently replaced my old powerhungry htpc setup with a raspberry 2 & openelec. i am quite happy with its performance so far, however i have a huge problem, which i'm not sure can be solved and might lead me to replace that setup again
i own an arcam irdac as usb dac.

my setup is the following...
for music: raspberry - irdac - stereo amp
for video: raspberry - hdmi - av receiver

my music is stored on a nas, nfs is used as protocoll...

video wise everything is fine and music wise the the overall audio quality is excellent, but ~ every 30 seconds to 2 minutes i get a very short hickup/distortion/jitter noise when playing mp3s, which sounds like a buffering issue or something similar.
when i start to scan the music library, and try to play a mp3 file i get lots of stuttering, which i guess is normal because of the limited cpu power?

i already tried the various suggestions from the following thread:
http://openelec.tv/forum/124-raspberry-p...ing#132499

then i found this which sounded similar to my issue:
http://www.raspyfi.com/anatomy-of-a-pi-u...ues-on-pi/
http://www.runeaudio.com/forum/crackles-...-t934.html

to limit the usb speed i've added dwc_otg.speed=1 in the cmdline.txt yesterday and am not 100 % sure, but it seems to happen less often than before, however it has not completely solved the issue.

i was wondering if other people experience the same behaviour with other usb dacs? it is really just a short noise, but obviously very annoying and distracting from the music.

[popcornmix]

Can you test using either hdmi or analogue (e.g. with headphones) and confirm that works okay.
That would confirm it's a USB audio issue (rather than network/cpu issue).

[blubserl]

hi popcornmix!

thanks for your response.

yes, everything is fine using hdmi and playing mp3s from the exactly same source.
i enabled debugging with detailed audio component logging. this time i heard 2 short noises - one right in the beginning, when playback startet and another one after ~15 seconds...

http://xbmclogs.com/po4ekjmyd

and just to add: i also tried one of the last openelec testbuilds for raspberry 2 (build 0416) to see if it behaves different - but got the same results.

[blubserl]

ok...the setting dwc_otg.speed=1 has no positive effect so i'll remove that again from cmdline.txt.

but i noticed that the short stuttering nearly always happens when additional network traffic is happening like artist slideshow downloading a new image.
i can also provoke it by starting cu-lrc lyrics script. and i checked it again --> with hdmi both does not produce the stuttering.

[ktfzone]

I saw something similar with another DAC, Ifi Micro IDSD. We should try powering up the DAC using an active USB HUB, just to be sure. Sadly I have none of those at home Your DAC is however powered from mains I think, unlike mine which is taking the power from USB.

Regarding network, from what I know from the raspberry forums from dom, USB stack is also shared with ethernet and other devices, so that might be an issue.

[blubserl]

in the meanwhile i tried if overclocking changes something --> still no luck

does anyone have a hint what i could try next? as far as i could see the debug logs didn't give any hint.
any additional low-level logging i could enable somehow to track the problem down?

[speedwell68]

How are you connecting to the network?

[blubserl]

if you mean wired or wlan, then wired...

[blubserl]

i replaced the pi2 with a celeron chromebox and could not be happier. no clicks, pops, stuttering whatever. so personally for me the problem is solved.
unfortunately my conclusion regarding this topic is raspberry2 & usb dac might indeed be a bad combination.

[popcornmix]

Yes, I wouldn't recommend USB for audio on Pi.

HDMI direct is the best option
Then HDMI though a HDMI to optical/analogue splitter
Then I2S audio card (like HifiBerry)
Then USB

Many USB cards work fine. If you've got one lying around then feel free to give it a try,
but don't buy a new USB card for a Pi without some confirmation that it works well.

Remember USB audio will share USB bandwidth with ethernet/wifi/USB disk, whereas HDMI and I2S have dedicated interfaces.

[ktfzone]

Is there any way to give highest priority to USB stack, over ethernet ?