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USB Audio

Hi,

Just bought a pair a USB speakers (Logitech S150) for business and for testing.

If I plug those speakers on a regular computer, they behave as expected.
But If I plug them on a Dell-Wyse Thin-client (running the proprietary Operating System ThinOS), the level +/- and mute buttons don't work well ; Mute and level "-" don't work at all and level "+" does lower the volume...
Flabbergasting.

So, how USB audio is working ? I thought the the digital audio stream is sent to the device and then a DAC integrated into the USB device renders the analogic to the speakers. Is it more complex than that ? Is there is a bi-directional communication with local audio card for leveling ?

Re: USB Audio

Reply #1
I don't know anything about ThinOS, but I'm sort-of surprised they work at all!   

Did the speakers come with a driver, or do they use the drivers supplied with the operating system?    If they came with Windows drivers, those drivers probably don't work with ThinOS and I wouldn't be surprised if some features don't work.

Usually, drivers are supplied by the hardware manufacturer and they are specific to the hardware and the OS.      However, there are "class compliant" USB audio devices that can use Microsoft-supplied drivers.    Since the class compliant hardware is standardized someone could write a driver for a different operating system.  

Quote
So, how USB audio is working ? I thought the the digital audio stream is sent to the device and then a DAC integrated into the USB device renders the analogic to the speakers. Is it more complex than that ? Is there is a bi-directional communication with local audio card for leveling ?
You are correct, and the volume control in your application (or operating system) should be able to turn up or down the volume, but it may not be able to access any controls built-into the hardware.  

USB is bi-directional and the kind of information exchanged depends on the hardware & drivers.   USB has to be bi-directional because the operating system has to identify the device.

Re: USB Audio

Reply #2
I don't have similar product but I guess "HID-compliant device" might be the keyword.

Re: USB Audio

Reply #3
So, how USB audio is working ? I thought the the digital audio stream is sent to the device and then a DAC integrated into the USB device renders the analogic to the speakers. Is it more complex than that ? Is there is a bi-directional communication with local audio card for leveling ?

Never used those speakers, but Google says they use USB AUDIO for the audio part, and USB HID (keyboard) for the volume control.  Sounds like USB HID keyboard volume control isn't configured correctly on your thin client. 

Re: USB Audio

Reply #4
Thanks you all for your replies.

Sorry, I was talking about the built-in buttons. the ones supposed to control directly the local amplifier. they don't seem to be local from my experience and from what you mention  : HID volume control...

 

Re: USB Audio

Reply #5
A simple experiment:
When you use the speakers in Windows, open the system mixer and change/mute the volume using the buttons on the speaker, did the faders move?

PS: make sure the mixer is from your Logitech speakers, not other devices like soundcard, onboard audio chips or HDMI/DP output.

 
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