[SOLVED] Audio glitching on Pi 5

[simonb]

Not a lot else I can think of. You definitely know the flac files play OK on other devices?

If it really is something repeating at regular, predictable intervals, as it seems to be at 20-ish seconds, IMHO is something related to either a high-priority service locking the disc, or a buffer too small in relation to the connection speed / disc speed for the track's bit-depth + sampling-rate.

I've just asked him to bump the PCie speed up to pciex1_gen=3. The RPi is configured to use the least power possible. It looks good for sales and marketing but does restrict the IO performance.

[TheOldPresbyope]

I think all talk about speed is chasing a red herring.

Case in point. On my Pi 5 with moOde 9.0.4 flashed to an old* class 4 uSD card it is working fine playing FLAC files from SDCARD through a Khadas USB Tone 1 DAC.

This is stock with no adjustments to config.txt or anything else.

I don't see mentioned what happens if an Internet radio station is played instead of a stored track. That would eliminate many of the possibilities that have been suggested.

There's something going on here which is external to moOde itself. So far, not enough data has been presented to diagnose the cause. Unfortunately, I don''t have any HDMI-gear to use to try to replicate the OPs system, so I'll set down and shut up now. ETA: My bad, I was thinking of another thread at the same time. Actually, my Khadas DAC has a similar but newer SABRE ESS9038 DAC chip.

Regards,
Kent


*How old, you ask? It still had a copy of moOde 2.6 on it. Took forever for the Rasberry Pi Imager to flash moOde 9.0.4 to it and verify the result.

[simonb]

I think all talk about speed is chasing a red herring.

Case in point. On my Pi 5 with moOde 9.0.4 flashed to an old* class 4 uSD card it is working fine playing FLAC files from SDCARD through a Khadas USB Tone 1 DAC.

This is stock with no adjustments to config.txt or anything else.

I don't see mentioned what happens if an Internet radio station is played instead of a stored track. That would eliminate many of the possibilities that have been suggested.

There's something going on here which is external to moOde itself. So far, not enough data has been presented to diagnose the cause. Unfortunately, I don''t have any HDMI-gear to use to try to replicate the OPs system, so I'll set down and shut up now.

Regards,
Kent


*How old, you ask? It still had a copy of moOde 2.6 on it. Took forever for the Rasberry Pi Imager to flash moOde 9.0.4 to it and verify the result.

Good point.

[simonb]

What power supply are you using. Is it capable of supplying enough current? The RPi5 has an uprated PSU.

[robkyf]

First off, I want to say thank you again for all the helpful suggestions over the last few days - I really do appreciate the time that Forum members are taking to try and work out what's causing the glitching with my Pi 5 set up.

By way of an update:

@simonb - I tried the PCie speed change you suggested but it made no difference - the glitching remains. In terms of your question about the power supply, I'm using the official new Pi 5 one from The Pi Hut.

@TheOldPresbyope - The suggestion to try an internet radio was, in hindsight, one that should have occurred to me earlier. Unfortunately, trying the A.M. Ambient station to provide a suitably quiet backdrop, the glitching remains.

All this leads me to conclude that the problem is a more fundamental incompatibility between the Pi 5 and the ESS9018 Sabre32 DAC in my Audiolab 8200 CD.

I'm still inclined to try a better SD card so will report back on that once it arrives and I set it up in the next few days.

But what is still bugging me about all of this is is that, as stated in my original post, I’ve also been using a Pi Zero 2 W running moOde V9.0.4 with the music files stored on the SD card into the same DAC with no problem. The only difference from the Pi 5 set up, aside from whatever differences there may be between the Pi Zero/Pi 5 moOde variants, is that the volume of music files on the 128gb SD card is lower and the card is a different brand (but a similarly basic one to the one in the Pi 5).

[the_bertrum]

Are you using fixed (0db) output? If so have you tired backing off the "Max ALSA Vol" setting a bit? One of my DACs will click (not sure I'd call it a glitch) at times, seemingly when there is a "lot of music", by which I mean a large range of the spectrum at a high-ish amplitude rather than necessarily a single loud peak. By setting the Max ALSA volume to 94%, these clicks vanish. My understanding of how this stuff works is very basic, but it acts as if there is a gain on the input to the DAC so it clips when driven at 0db, thus requiring an attenuation of the feed to counteract the "gain" on the input.

Probably woeful misunderstanding there, but the upshot is that I got audible artefacts to go away by backing off the Max ALSA Volume, so it might work for you too.

[TheOldPresbyope]

Bottom line: since we don't yet understand where this artifact is occurring, we'll all keep throwing ideas at the wall until one sticks  

@robkyf 

The Pi 5 is a power hungry beast compared to the Pi Zero 2 W. Regarding this, @simonb asked a cogent question. Do you have an adequate power supply for it? Preferably an official Raspberry Pi supply specifically made for the Pi 5?

An easy way to check whether your specific uSD card is the culprit is simply swap it with the card that was in your Pi Zero 2 W. I routinely swap cards among different ARMv7/v8 model Pis as I test new moOde features and try to diagnose other users' problems.

The moOde connection to your CD player is via the Pi 5's USB interface controller to your receiver's USB interface controller to your ESS 9018 DAC chip. The Pi 5's USB subsystem is different from the Pi Zero 2 W's and I suppose it's possible the USB signal timing is subtly different 

Still, as I mentioned in my revised post above, I'm having no trouble playing from a Pi 5 to my Khadas USB Tone 1 board. It contains an XMOS USB interface controller driving an ESS 9038 DAC chip.

Because this glitching is semi-regular in nature, I'm still hoping we'll get to see some telltale signs in the system logs. At this point, however, I don't know what the specific error and/or warning messages would be.

By the way, what do you mean by "glitching". is is simply a momentary dropout or something else?


Regards,
Kent

[robkyf]

Thanks @TheOldPresbyope - the willingness of Forum members to give their time to help work this one through has been wonderful.

On the power supply question, I am using the official Pi 5 unit supplied by The Pi Hut.

In terms of swapping over the SD card from the glitch-free Pi Zero 2 W to the glitching Pi 5, I wasn't aware that was possible - I'd assumed there were bespoke moOde versions for different Pi models.

And by 'glitching' I mean there is a momentary stutter in the music accompanied by a slight clicking sound. I don't know if the MPD or iostat logs I've posted previously provide any pointers as to what might be going on - they seem to indicate something isn't right but I don't know enough to understand if this is actually the case or what to do in response.

@the_bertrum - In response to your question, yes, the output to the DAC is set at Fixed(0dB). I can try backing this off a bit but I'm not sure I understand how that will make a difference because I don't think the glitching I'm experiencing is the music clipping.

Clarifying whether there's an issue with the SD card I'm using in the Pi 5 seems like the next thing to rule out so I’ll report back when my new, faster card arrives.

[simonb]

Still, as I mentioned in my revised post above, I'm having no trouble playing from a Pi 5 to my Khadas USB Tone 1 board. It contains an XMOS USB interface controller driving an ESS 9038 DAC chip.

Because this glitching is semi-regular in nature, I'm still hoping we'll get to see some telltale signs in the system logs. At this point, however, I don't know what the specific error and/or warning messages would be.



Regards,
Kent

Wireshark is your friend

   

[TheOldPresbyope]

Full up neurosurgery, huh


As my grandmother would say, we shall see.

Regards,
Kent