I’m using a Audient id44 digital audio interface, connected by USB. I see distortion — missing samples — in the output. To debug it I output digitally generated sine wave at CD resolution (with aplay) and looked at the output signal on an oscilloscope. The audio interface is intended for studio work and the Ubuntu is Ubuntu Studio 18.04, which should be optimised for latency etc.

My question: does this look like a bug or does it look like something is misconfigured?

Output is 440 Hz sine wave, which has a period of 2.27 ms, and we see that about 0.62 ms is just missing.

Environment

• Ubuntu Studio https://ubuntustudio.org/tour/audio/
• Ubuntu 18.04.4, freshly rebooted
  • Ubuntu Studio says it’s not LTS https://ubuntustudio.org/2019/04/ubuntu-studio-18-04-extended-support/
  • Files are nevertheless labelled LTS /.disk/info says Ubuntu-Studio 18.04 LTS "Bionic Beaver" - Release i386 (20180426) and /etc/os_release says PRETTY_NAME="Ubuntu 18.04.4 LTS"
• Kernel release: 4.15.0-111-lowlatency
• Architecture: i686
• Computer: Intel DG43GT motherboard with 8 GByte RAM
• CPU: Intel(R) Core(TM)2 Duo CPU E7600 @ 3.06GHz (family: 0x6, model: 0x17, stepping: 0xa)
• ALSA Driver version: k4.15.0-111-lowlatency
• ALSA Library version: 1.1.3
• ALSA sound card description USB-Audio – Audient iD44, Audient Audient iD44 at usb-0000:00:1a.7-6, high speed

Things ruled out

• It’s not the particular id44: The error does not happen with same hardware plugged into a Windows 10 Dell 780 computer
• It’s not the audio file: Tried lots of different audio files.
• It’s not the output rate: Tried lots of 44.1 kHz, 48 kHz etc.
• It’s not the analogue side: couldn’t explain scope image.
• It’s not the USB socket: It makes no difference what USB port is used.
• It’s not the higher-level sound program: makes no difference whether you use aplay, VLC, or ardour
• It’s not this particular computer: The error does appear with a stock Ubuntu 18.04 laptop