Re: Web Audio API Proposal

Yeah, this looks like a limitation with Chris Marrin's idea.  Your diagram
shows that there will be cases where an AudioGainNode will still be
necessary, and I think this is probably a fairly common case.  This doesn't
mean we couldn't have both a per-output gain control and an AudioGainNode,
but I think I prefer the simpler approach of just an AudioGainNode.  Jer,
was this diagram representing your idea correctly?

[image: mixer-architecture-new.png]

On Mon, Jun 21, 2010 at 4:47 PM, Jer Noble <jer.noble@apple.com> wrote:

>
> On Jun 21, 2010, at 3:27 PM, Chris Marrin wrote:
>
> > On Jun 21, 2010, at 2:34 PM, Chris Rogers wrote:
> >
> >> Hi Chris,
> >>
> >> I'm not sure we can also get rid of the AudioGainNode and integrate the
> concept of gain directly into all AudioNodes.  This is because with the new
> model Jer is proposing we're connecting multiple outputs all to the same
> input, so we still need a way to access the individual gain amounts for each
> of the separate outputs.
> >
> > Right, but if every node can control its output gain, then you just
> control it there, right? So if you route 3 AudioSourceNodes into one
> AudioNode (that you're using as a mixer) then you control the gain of each
> channel in the AudioSourceNodes, plus the master gain in the AudioNode. For
> such a common function as gain, it seems like this would simplify things.
> The default gain would be 0db which would short circuit the gain stage to
> avoid any overhead.
>
>
> Actually, I don't agree that modifying the output gain is so common an
> operation that it deserves being promoted into AudioNode.  Sure, it's going
> to be common, but setting a specific gain on every node in a graph doesn't
> seem very likely.   How many nodes will likely have a gain set on them?
>  1/2?  1/4?  I'd be willing to bet that a given graph will usually have as
> many gain operations as it has sources, and no more.
>
> I can also imagine a simple scenario where it makes things more complicated
> instead of less:
>
>
>
>
> In this scenario, there's no way to change the gain of the Source 1 ->
> Reverb connection, independently of Source 2-> Reverb.  To do it, you would
> have to do the following:
>
>
>
>
> And it seems very strange to have to create a generic AudioNode in order to
> modify a gain.  Alternatively, you could create multiple AudioReverbNodes,
> but again, it seems weird to have to create multiple reverb nodes just so
> you can change the gain going to only one of them.
>
> Right now, every AudioNode subtype has a discreet operation which it
> performs on its input, and passes to its output.  To add in gain to every
> AudioNode subtype would make things more confusing, not less.
>
> -Jer
>
>