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Re: Audio Workers - please review

From: Norbert Schnell <Norbert.Schnell@ircam.fr>
Date: Thu, 28 Aug 2014 18:06:40 +0200
Cc: "public-audio@w3.org" <public-audio@w3.org>
Message-Id: <CD2C3D94-A14B-4132-AD0C-2B0C1F5251F7@ircam.fr>
To: Chris Wilson <cwilso@google.com>
Ok, I see.
Certainly, anybody can easy build his own asynchronous workers on top the proposed synchronous audio worker and cope with the buffers and latencies in a way that suites him or her.

As I understand the name "AudioWorkerNode" makes sense to clearly distinguish it from the current ScriptProcessorNode and this need for distinction would be obsolete once the current ScriptProcessorNode vanishes. Just let's keep this in mind.

P.S.: If there was I vote, I'd vote for replacing the current ScriptProcessorNode" right away. After all, an upcoming standard shouldn't be held down by the past before really having one...

On 28 Aug 2014, at 17:38, Chris Wilson <cwilso@google.com> wrote:
> On Thu, Aug 28, 2014 at 7:16 AM, Norbert Schnell <Norbert.Schnell@ircam.fr> wrote:
> I am not sure if I followed all discussions that led to the "worker"-name for the node, but from my point of view the name is slightly misleading.
> Wouldn't be something like "SynchronousScriptProcessorNode" more appropriate?
> Not particularly.  The major difference in programming AudioWorkers (from ScriptProcessors) is that the code lives in a Worker - and thus all communication needs to go through the messaging interface.  The current design of ScriptProcessor is technically a synchronous programming interface as it is exposed to the developer - there's just an async "leave plenty of latency and pray we get a response back before we glitch" layer underneath that, with some developer control of the amount of latency.  To the developer, however, it still feels synchronous.  (you're called with buffers, you do your work, you return.)
>  or ultimately: Is it really not possible to formalise all this as an option of the "ScriptProcessorNode" (given at creation)?
> It already has the right name and the same "onaudioprocess" event.
> We could share the top-level name; however, the programming model for each is rather different in terms of communicating parameters, analysis and events; and furthermore, as previously discussed, I would really like to remove the current ScriptProcessor entirely.  It's a poor way to do audio programming, and yet it is so seductively easy that it will be (in fact, already is) naively used widely.
> It seems you me that, following this path, another future extension of the ScriptProcessorNode could be to schedule the "onaudioprocess" events neither in the main thread nor the audio thread but in an arbitrary worker thread.
> In neither of these cases the introduced formalisation of audio-rate parameters of the proposed AudioWorkerNode could hurt.
> Just that we need a "latency" parameter somewhere (why not writeable or at least configurable) and/or a separate input and output time.
> Does that make sense? Or do I miss something essential here?
> There are a lot of choices there.  Keep in mind that in order to call the asynchronous onaudioprocess, you have to have the input to hand the call - inputS, in fact, since AudioParams can contain inputs.  That introduces latency into each of those (you need to wait to receive enough (blocksize) of the inputs before you can ask for the output, and then you need to wait for the response to make its way across threads).
> With the AudioWorker design, I'm confident developers could implement the current ScriptProcessor design as an AudioWorker - simply by doing the buffering and async message posting across to the main thread themselves.  I doubt I will get to building that as a sample soon - as I want to build a couple of other samples first, and I'm a bit swamped as always - but I have done the mental exercise.
Received on Thursday, 28 August 2014 16:07:09 UTC

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