Electronic music - notes on audio APIs

From Helpful
Jump to: navigation, search
The physical and human spects dealing with audio, video, and images

Vision and color perception: objectively describing color · the eyes and the brain · physics, numbers, and (non)linearity · color spaces · references, links, and unsorted stuff

Image: file formats · image processing

Video: format notes · encoding notes · On display speed


Audio physics and physiology: Basic sound physics · Human hearing, psychoacoustics · Descriptions used for sound and music

Digital sound and processing: capture, storage, reproduction · programming and codescs · some glossary · Audio and signal processing - unsorted stuff


Electronic music: Some history, ways of making noises · Gaming synth · on APIs (and latency) ··· microphones · studio and stage notes · Effects · sync ·

Music electronics: device voltage and impedance, audio and otherwise · amps and speakers · basic audio hacks · Simple ADCs and DACs · digital audio · multichannel and surround ·

Noise stuff: Stray signals and noise · sound-related noise names · electronic non-coupled noise names · electronic coupled noise · ground loop · strategies to avoid coupled noise · Sampling, reproduction, and transmission distortions · (tape) noise reduction


Unsorted: Visuals DIY · Signal analysis, modeling, processing (some audio, some more generic) · Music fingerprinting and identification

For more, see Category:Audio, video, images


On drivers and APIs

Windows APIs

Some history

On ASIO wrappers

This article/section is a stub — probably a pile of half-sorted notes, is not well-checked so may have incorrect bits. (Feel free to ignore, fix, or tell me)


ASIO in itself usually refers to a driver talking directly to the sound hardware, exposing just the ASIO API, much of the point being ignoring windows's sound architecture completely.


ASIO wrappers are different (and in this context, the above is often called 'native ASIO' in contrast).

ASIO wrappers open a sound card via a regular Windows sound API (in practice typically WDM/KS or WASAPI), force settings that are lower latency (small buffer, exclusive if possible), and present it via ASIO API.

Yes, this is counter to ASIO's shortest-path-to-the-hardware principle.

And yes, you will only get latencies that were always possibly to get from that underlying sound API anyway.

So why add a layer?


Convenience, mostly.

  • It lets you have just one place to configure a small-buffer, possibly-exclusive way to these existing APIs.
You figure out the details just once, in the wrapper's settings, rather than for every DAW-soundcard combination you have, which is usually more work, and the config details may vary somewhat between DAWs which is sometimes more fiddly and/or confusing.
and some programs (basically, things that are not the most common DAWs) may not allow all that tweaking - but can still talk ASIO
also not unimportantly, using that wrapper can also be easier to explain to people who care more about music than decades of programing history.
  • There's also some DAWs/software that speak mainly or only ASIO, because their approach is to figure out low latency in something external, and talk to that.


There's a few more useful reasons hiding in the details, like

  • you can often force WASAPI cards down to maybe say, 5-10ms without exclusive mode, which means you don't have to dedicate a sound card, to a DAW that only talks ASIO.
Which is good enough e.g. for when playing some piano on a laptop on the go, so pretty convenient
  • some ASIO wrappers can talk to on different sound cards for input and output, at the cost of slightly higher latency (will probably glitch at the lowest latencies), which DAWs talking native ASIO will typically refuse to do (for latency and glitch reasons).


As far as I can tell

  • ASIO4ALLv2 is a WDM/KS wrapper.
needs to force exclusive mode
can talk to different sound cards for input and output
  • FL Studio ASIO (a.k.a. FLASIO) is a WASAPI wrapper.
Comes with FL studio (including the demo), also usable in other DAWs
can talk to different sound cards for input and output
  • "Generic Low Latency ASIO Driver" is similar to ASIO4ALL but with different options
Comes with Cubase


And there appear to also be ASIO multiclient wrappers, basically ASIO in ASIO.

ftp://ftp.steinberg.net/Download/Hardware/ASIO_multiclient_driver/



"So which API is best?"

Linux APIs

Kernel level

Higher level

OSX APIs

Why latency exists (the long version)

Latency and physics

Latency in the real world exists because of distance and the speed of sound.


For some context of how long a millisecond is, and what distance does with sound:

a mic on a guitar cab has maybe 1ms to get sound from speaker to mic.
talking to someone at one or two meters is 3ms to 6ms
a smallish practice space easily has ~15ms of delay from one wall to the other
opposite ends of a 15m bus would be 40ms
two frames in 24fps movie are ~42ms apart
halfway across a sports field is easily 100ms

Most of that is just length divided by the speed of sound. Use wolfram alpha if you're lazy.


So distance alone is

why bands tend to watch their drummers
why in larger spaces you may want to use headphones instead (but not bluetooth ones)
one of a few reasons orchestras have conductors


In musical context

Hardware, and the nature of digital audio

Why larger buffers are generally useful

Lowering latency

In general

tl;dr

zero latency does not exist, a few milliseconds of relative offsets happens all over the place
amounts of added latency can matter, though
latency matters when hearing yourself live, or syncing to something live (e.g. looper pedals)
digital input, output, and/or processing have some latency
In ways that are (looking at forums) usually partly misunderstood


Decide how low is necessary

The basic steps

API stuff

Windows API tweaking

Use a sound API designed for lower latency

Use sound API settings that lower the latency: exclusive mode

Use sound API settings that lower the latency: smaller buffer sizes

Linux API tweaking

OSX API tweaking

DAW considerations

Considering effects

Higher sample rates?

"Delay compensation?"

End-to-end latency

Further considerations

Hardware bus?

On network latency

Unsorted