OS/2, eCS & ArcaOS - Technical > Hardware

USBAUDIO: now supports 24-bit and sample frequencies > 65535 Hz

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Lars:
Wim and me, we have been working on updating the MMPM subsystem so that it will finally support WAV files with 24-bit and > 65535 Hz (there was a limitation in the MMPM subsystem components that would restrict the sample rate to a 16-bit value).

In fact, we updated the MMPM subsystem to support these sample rates beyond 48000 Hz:
64000, 88200,96000,176400,192000,352800,384000 Hz.

The MMPM subsystem still has an inherent limitation to only support a discrete number of sample rates but we picked the rates that are in common use today. But I think we can live with that and the supported rates can be extended if necessary (but will require an updated USBAUDIO installation, see end).

With this support you can finally use more recent USB audio devices and exploit their full capabilities.
While 16-bit, 44100 Hz stereo (CD-ROM quality) was about the best you could get in 1996, more than 20 years later this is about the minimum sample rate /bit-depth used. It will also pave the way to support USB audio 2.0 devices which normally only offer these higher sample rates.

By the way: UNIAUD would also need this MMPM subsystem update to support WAV files with sample rates higher than 48000 Hz.

Once we have everything nice and polished I will release a new version of my USB device drivers.
It will be necessary to rerun the USBAUDIO driver installation to get everything updated properly.

Lars

David McKenna:
Go, Lars and Wim, go! Any chance multiple streams could be added?...

Dariusz Piatkowski:
Lars,

This is pretty awesome stuff. Will this make for a completely separate solution from something like the AN stuff though?

Thanks,
 - Dariusz

Lars:

--- Quote from: David McKenna on January 17, 2018, 01:05:50 pm ---Go, Lars and Wim, go! Any chance multiple streams could be added?...

--- End quote ---

In principle, yes. But I don't see the concept of multiple simultaneous streams supported in the USB audio spec. And therefore the current installation restricts it to 1 stream. But thinking about it, maybe yes, I'll have to check if there are devices that support multiple interfaces with each having the same parameters.
What DOES work is having a simultaneous input (record) and output (playback stream).

Lars:

--- Quote from: Dariusz Piatkowski on January 17, 2018, 01:57:41 pm ---Lars,

This is pretty awesome stuff. Will this make for a completely separate solution from something like the AN stuff though?

Thanks,
 - Dariusz

--- End quote ---

Don't worry. You can combine my USBAUDIO.SYS with the AN driver stack and it should work just fine. The updated installation installs a new dll called USBAUDIF.DLL as a replacement for AUDIOIF.DLL alongside to the already existing AUDIOIF.DLL (in the \MMOS2\DLL dir) but it leaves AUDIOIF.DLL untouched so they don't step on each others toes.

Likewise the new installation overwrites SPI.INI (in the \MMOS2 dir) but our SPI ini update is "cumulative", which means it includes and adds on top of what is already in the default SPI.INI file.

In short: we try to keep things compatible with whatever comes with an AN installation.

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