PipeWire: The Linux audio/video bus [LWN.net]

PipeWire: The Linux audio/video bus

Posted Mar 7, 2021 12:44 UTC (Sun) by pizza (subscriber, #46)
In reply to: PipeWire: The Linux audio/video bus by jengelh
Parent article: PipeWire: The Linux audio/video bus

> Quite the contrary. People had actual proper soundcards (me: ad1816 or cs46xx on daughterboards),

Just because you had high-end audio gear (for the time) doesn't mean most folks did. Even before Intel standardized onboard audio with the bog-simple single-stream AC97 spec, the overwhelming majority of the audio chips on the market only supported a single hardware PCM stream. Multi-stream hardware was always the upper echelon of the market.

> there was ALSA's dmix that would do software mixing via shared memory

I recall having a lot of issues with dmix in its early days. Not surprising as the same sorts of driver/library/application bugs that made PA a bit rocky also affected dmix.

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PipeWire: The Linux audio/video bus

Posted Mar 7, 2021 15:15 UTC (Sun) by jengelh (subscriber, #33263) [Link] (1 responses)

>Just because you had high-end audio gear

I never thought of the two being particular high-end; ad1816 came with the package, the cs46xx was a 20€ second-hand thing.

PipeWire: The Linux audio/video bus

Posted Mar 10, 2021 3:28 UTC (Wed) by pizza (subscriber, #46) [Link]

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..)

PipeWire: The Linux audio/video bus

Posted Mar 8, 2021 14:21 UTC (Mon) by LtWorf (subscriber, #124958) [Link] (2 responses)

ALSA dmix is still there, it works fine. I've used it for years since I don't use pulseaudio because it's unpredictable and I don't feel like doing debug every time it fails.

Never had a problem with dmix.

PipeWire: The Linux audio/video bus

Posted Mar 9, 2021 16:39 UTC (Tue) by zlynx (guest, #2285) [Link] (1 responses)

People can say that about Pulseaudio too. Never had problems with it. Or not serious ones anyway. Yes, I have had it glitch and flip off USB headphones back to speakers or other things. But nothing seriously wrong.

Back when I ran Gentoo Linux I did run ALSA with dmix. And I did have problems sometimes. For example, if you nice some process which is acting as the dmix output to ALSA it gets under runs. If a process which is part of dmix gets hammered by OOM or a kill -9 signal things can get super messed up.

The best setup was on my home desktop running Gentoo because there I had a Soundblaster Audigy 2 card which managed a full 5.1 surround setup and I believe 16 independent input sources. The only real problem there was alsactl which had about 500 cryptically named visible controls.

PipeWire: The Linux audio/video bus

Posted Mar 9, 2021 17:32 UTC (Tue) by mathstuf (subscriber, #69389) [Link]

Ah, I remember trying to find the right things to mute/unmute in ALSA's mixer even with a simple laptop setup. Many unfun times when you need to do it on a quick turn around time.