Behringer X32 X-Live USB glitches

Hi, I have a Behringer X32 mixer. The default X-USB interface works great, it appears as a S32_LE multichannel and has no problems up to 32 channels I/O. Im using RaspberryPi4 as the host. 

Generally I will be using mpd to play background and interval music from disk or streaming.

I installed the newer X-live board in the X32 that has two SD slots for recording and playback, plus it has (according to the blurb) “the same USB interface as the X-USB board”. However when I play back audio, it has glitches and pops. If  I play a 1 minute duration wav file of 50Hz tone, it runs fine for about 40 sec, then glitch.

The X-Live card supports S24_3LE only. As far as I can tell thats the only difference.

I tested it thoroughly with a MacBook Pro running Catalina, and I dont get any glitches, so the board and cable are good. Only with Alsa driving it do I seem to get this problem. I tested 44.1 and 48, with the same result.

I tested with the default kernel 4.19 from raspbian, plus the version 5.4 below, same result. I tested both hw:1,0 and plughw:1,0, same result.

$ uname -a
Linux raspberrypi 5.4.49-v7l+ #1323 SMP Fri Jun 26 14:40:18 BST 2020 armv7l GNU/Linux



pi@moode-pa:~ $ cat /proc/asound/card*/stream0
BEHRINGER X-LIVE at usb-0000:01:00.0-1.4, high speed : USB Audio

Playback:
  Status: Stop
  Interface 1
    Altset 1
    Format: S24_3LE
    Channels: 16
    Endpoint: 1 OUT (ASYNC)
    Rates: 48000
    Data packet interval: 125 us

Capture:
  Status: Stop
  Interface 2
    Altset 1
    Format: S24_3LE
    Channels: 16
    Endpoint: 1 IN (ASYNC)
    Rates: 48000
    Data packet interval: 125 us
pi@moode-pa:~ $ 


alsacap

Card 1, ID `XLIVE', name `X-LIVE'
  Device 0, ID `USB Audio', name `USB Audio', 1 subdevices (1 available)
    16 channels, sampling rate 48000..48000 Hz
    Sample formats: S24_3LE
    Buffer size range from 12 to 21845
    Period size range from 6 to 10922

      Subdevice 0, name `subdevice #0'


lsusb

Bus 001 Device 004: ID 1397:050a BEHRINGER International GmbH 


pi@moode-pa:~ $ cat /proc/asound/XLIVE/usbmixer 
USB Mixer: usb_id=0x1397050a, ctrlif=0, ctlerr=0
Card: BEHRINGER X-LIVE at usb-0000:01:00.0-1.4, high speed
USB Mixer: usb_id=0x1397050a, ctrlif=0, ctlerr=0
Card: BEHRINGER X-LIVE at usb-0000:01:00.0-1.4, high speed
  Unit: 41
    Control: name="X-LIVE Internal Clock Validity", index=0
    Info: id=41, control=2, cmask=0x0, channels=1, type="BOOLEAN"
    Volume: min=0, max=1, dBmin=0, dBmax=0


pi@moode-pa:~ $ cat /proc/asound/card1/pcm0p/sub0/hw_params 
access: RW_INTERLEAVED
format: S24_3LE
subformat: STD
channels: 16
rate: 48000 (48000/1)
period_size: 5461
buffer_size: 21845

pi@moode-pa:~ $ cat /proc/asound/card1/pcm0p/sub0/sw_params 
tstamp_mode: NONE
period_step: 1
avail_min: 5461
start_threshold: 16384
stop_threshold: 21845
silence_threshold: 0
silence_size: 0
boundary: 1431633920


pi@moode-pa:~ $ cat /proc/asound/card*/stream0
BEHRINGER X-LIVE at usb-0000:01:00.0-1.4, high speed : USB Audio

Playback:
  Status: Running
    Interface = 1
    Altset = 1
    Packet Size = 336
    Momentary freq = 48000 Hz (0x6.0000)
  Interface 1
    Altset 1
    Format: S24_3LE
    Channels: 16
    Endpoint: 1 OUT (ASYNC)
    Rates: 48000
    Data packet interval: 125 us

Capture:
  Status: Stop
  Interface 2
    Altset 1
    Format: S24_3LE
    Channels: 16
    Endpoint: 1 IN (ASYNC)
    Rates: 48000
    Data packet interval: 125 us



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