[HN Gopher] Audio from Scratch with Go: Stereo Panning
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Audio from Scratch with Go: Stereo Panning
Author : Insanity
Score : 62 points
Date : 2020-07-25 12:22 UTC (1 days ago)
(HTM) web link (dylanmeeus.github.io)
(TXT) w3m dump (dylanmeeus.github.io)
| PaulDavisThe1st wrote:
| [ Edited/Deleted reply because I missed the fact that this code
| distributes a single mono signal across 2 outputs. The
| terminology for this stuff is never totally clear: some people
| would call this a mono panner, some would call it a stereo
| panner, some call it a 1in/2out panner ]
| Insanity wrote:
| Hey there, yep I'm actually aware of what you're saying. I
| actually wrote this at the bottom of the post:
|
| "There is actually a flaw with this panning function that we
| are using. However it is not apparent to us yet because we can
| only set a pan for an entire audio source"
|
| I'm working from something simple up to something more complex,
| but tackling it in small parts. Next I'm writing about applying
| breakpoints where the pan can be set throughout the track and
| you can notice the power dip - and then we'll work on fixing
| that. ;-)
| [deleted]
| PaulDavisThe1st wrote:
| For some reason, I just realized that despite your talk about
| 2 channel WAV files, this code is actually a 1 input to 2
| output panner.
|
| So I take back what I said about it being a balance control
| entirely. Sorry for that.
| [deleted]
| akx wrote:
| Wonder if this should take into account pan laws:
|
| * https://en.wikipedia.org/wiki/Pan_law
|
| * https://www.image-line.com/support/flstudio_online_manual/ht...
| (search for "panning law")
| pierrec wrote:
| I believe this minimal implementation actually over-compensates
| for pan law because it has a -6dB center. In other words, if
| you ask this tool for zero panning, it will actually divide the
| amplitude by 2 (probably not what most people would expect!) In
| DAWs, -3dB or 0dB center is more common. In a tool like this I
| would suggest a 0dB center by default, so that zero panning
| does not change the amplitude. This would be what you second
| link calls triangular pan law.
| sramsay wrote:
| Wow, this is really cool. I wonder how far the author plans to go
| with this? DSP gets pretty complex pretty quickly . . .
| Insanity wrote:
| Her, author here! :)
|
| Glad you liked it! I don't have concrete plans actually, just
| doing this for fun so we'll see how far I get :)
| nkozyra wrote:
| Might have been an interesting point to stream this data
| (basic sine) to an audio output instead of file. That's more
| immediately hands on.
|
| (Sorry, this refers to the first entry in your audio/go
| series)
| Insanity wrote:
| Thanks, that's a good idea!
| slx26 wrote:
| that can easily get pretty tricky if you don't want to
| depend a lot on libraries, which the last time I checked
| weren't great for golang in this area. I have worked with
| ALSA (advanced linux sound architecture) a bit,
| implementing basic midi input from a keyboard + sound
| generators + plugins with go interfaces and pkg/plugin +
| stream to audio output... and it's a mess of devices,
| buffers and formats. and that's only for one OS. and if you
| start doing anything non-trivial, making the programs work
| well in real-time is not for the faint of heart.
|
| if there was a single format supported everywhere, minimum
| buffer sizes and a common API for all OSes, it would be a
| whole another, much more pleasant story
| mgraczyk wrote:
| This is a fun tutorial for processing audio in Go, but generally
| panning will sound bad if you only adjust the amplitude/level.
|
| The two important missing pieces are phase delay and frequency-
| specific attenuation (the "head" model). Audio coming from the
| left side of your head reaches your left ear first, then your
| right ear later. Also, your head blocks certain frequencies more
| than others. Both of these effects are super noticeable and
| necessary to make panning sound "3D".
|
| Adding these things to the Go code would actually be fairly
| straightforward, you just need to add a filter to `applyPan`. The
| filter would only need around 12 taps to sound good.
|
| Here's a javascript tutorial which includes both of these
| additional features:
|
| https://developer.mozilla.org/en-US/docs/Web/API/Web_Audio_A...
| qmmmur wrote:
| You say this like it's bog standard but adding HRTF and
| compensation for speaker distance are not part of a standard
| panning algorithm. This is more likely to exist in another
| module, such as for ambisonics or correction.
| pierrec wrote:
| The tutorial you linked to doesn't explain how to implement any
| of that stuff. But it doesn't matter because the panner in the
| article is fine as it is. Simple panning is often the best
| option in music, since filtering your sounds will just make
| your mix sound bad on common sound systems. Left/right delay
| will be great on headphones but create phase effects on common
| speaker setups, often making things worse as well. I don't
| think a general-purpose tool should add potentially unwanted
| effects like that.
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(page generated 2020-07-26 23:00 UTC)