PipeWire: The Linux audio/video bus

The cs46xx series were multi-channel, multi-stream DSP-based 3d-positional-audio-capable controllers that were roughly comparable in capabilities to the Sound Blaster Live series.

(I owned a high-end CS4630 device in the late 2000 timeframe, mainly because it had drivers that were stable on the multiprocessor Win2K system that I was using for realtime video capture. I ended up selling it after that project was over due to zero Linux support..)

I stand corrected on the AD1816; a quick bit of research shows that supports six simultaneous streams mixed onto two output channels, although given its ISA nature it seems unlikely to achieve that with "CD quality" audio, and seems to have been sold nearly exclusively on bare-minimum cards as a super cheap way to met Microsoft's "MPC97" spec.

But yeah, these were both considerably more capable (at a chipset level) than most of their contemporaries. Until you pointed out the AD1816 I wasn't aware that any mainstream multi-stream ISA cards existed, and the PCI cards of that era tended to be the cheap bare-minimum crap that pretty much ended once onboard AC97 audio came along, leaving just the higher-end stuff targeted at gamers wanting to take advantage of native multi-stream 3D positional audio.

The market for all of this fancy stuff evaporated pretty quickly after Microsoft removed support for hardware-based multi-stream (and 3D positional) audio with Vista -- Despite the spec allowing for it, I don't know offhand of any "HD Audio" controller that implements multi-stream mixing; instead it's one stream per external audio codec. There may be more than one codec (ie two 2-channel codecs instead of one 4-channel codec) but that's pretty rare.

(Of course, pro audio hardware still exists, but those are nearly always single-stream-per-channel and rely on the CPU for mixing/dsp work, but specialized hardware can do whatever it wants, of course..)