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Snaps, crackles, pops and drop outs - for information
#1
Hi all,

Wanted to drop my experience so that others facing a similar issue might find it. I spent hours looking and never found someone with the precise issue and therefore no solutions worked until I found something from a completely unrelated site.

I had intermittent popping and clicking, as well as periodic dropouts in the audio lasting for about 0.5 seconds. My hardware is as follows:

Moode v5
Raspberry Pi 3 B+
Pimoroni pHat DAC
iPad vs AirPlay

I also tried a iPhone XR and my iMac 27" (Late 2015) but had similar results (although the sound quality was also appalling on the iMac - don't use one, it's awful).

I was using the onboard bluetooth which eventually turned out to be the problem. I am using bluetooth for input, not output. Using a bluetooth dongle (generic - lsusb showed it as a Cambridge Silicon Radio, Ltd Bluetooth Dongle (HCI mode)) solved it completely. To use this all I needed to do was disable the integrated bluetooth in Moode. After a restart I then had to pair devices in Moode, rather than in the device's own pairing screen. 

Since this change, the pops and clicks are gone, there are no intermittent dropouts and the sound quality is significantly improved.

What didn't work (as suggested by others with similar but different issues):
 - Changing buffer size in Moode web interface made things much worse
 - Changing to 64 bit architecture in Moode WI either had no effect or made a bit things worse.
 - Disabling the onboard wifi. As Kent mentions below, interference as a result of the BT sharing the spectrum with WiFi was a strong suspect, but this seemed to make no difference. I'm not sure whether I was connected to 2.4 GHz or 5 GHz as both are available with identical SSIDs, but seeing as disabling the WiFi didn't help, I suppose this is academic.
 - Reducing distance/obstacles between iPad and RPi. This didn't seem to be a signal attenuation issue.

Anyway, like I say, this is just a 'for information' post to help anyone encountering these issues in the future.

Thanks all,

Bye!
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#2
@badgerchap

This is useful information. Thanks for posting.

To flesh out some details that could be useful to others,
  • there are three different versions of the RPi3---A+, B, B+. Which were you using?
  • since you have a DAC hat, I assume you are using Bluetooth for input and not output, yes?
  • were you also using the built-in WiFi as your network interface, and if so, at 2.4GHz or 5GHz?

The reason for the last question is, Bluetooth shares the 2.4GHz ISM band so there is the possibility of mutual interference.

Regards,
Kent
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#3
Thanks Kent, I've updated my original post with the details you suggested. I had meant to include them at the time but had forgotten!

I was surprised when disabling the onboard WiFi didn't work as interference was the most likely explanation for the behaviour. Ho hum.

Many thanks,

Guy
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#4
I thought AirPlay used WiFi, not Bluetooth?
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#5
(10-15-2019, 05:02 AM)Meestor_X Wrote: I thought AirPlay used WiFi, not Bluetooth?

Correct.
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#6
Im on Pi zero w
In my case, most of local / upnp playback's pop and click are completely eliminated by using "Performance" CPU Governor. For Bluetooth occasional dropout i gave up because of built in Bluetooth hardware issue (I guess). I can live with once in a while pop.
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#7
(10-15-2019, 11:22 AM)TheOldPresbyope Wrote:
(10-15-2019, 05:02 AM)Meestor_X Wrote: I thought AirPlay used WiFi, not Bluetooth?

Correct.
Now I'm even more confused. You said you were using AirPlay from your iPad, so why were you also using Bluetooth?
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