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Re: Web Audio API sequencer capabilities

From: Jussi Kalliokoski <jussi.kalliokoski@gmail.com>
Date: Wed, 3 Oct 2012 23:28:48 +0300
Message-ID: <CAJhzemXv152KGpCVmHZdB7miwQ8uTydL-BNdo1H45Z7KtUTsMw@mail.gmail.com>
To: Chris Rogers <crogers@google.com>
Cc: Srikumar Karaikudi Subramanian <srikumarks@gmail.com>, public-audio@w3.org
Let me be more specific, do you think the envelope functionality being in
the AudioParam is more powerful than if it were in a separate node? If you
do, why? What is the advantage it offers?

Cheers,
Jussi

On Wed, Oct 3, 2012 at 8:40 PM, Chris Rogers <crogers@google.com> wrote:

>
>
> On Wed, Oct 3, 2012 at 12:59 AM, Jussi Kalliokoski <
> jussi.kalliokoski@gmail.com> wrote:
>
>> Chris (Rogers), could I get your opinion regarding the introducing an
>> envelope node and simplifying the AudioParam?
>>
>
> AudioParam has been designed with lots of care and thought for
> implementing envelopes, so I believe it's in a very good spot right now.
>  As an example of how people are using these envelope capabilities in
> sequencer applications, here's a good example from Patrick Borgeat:
> https://dl.dropbox.com/u/15744891/www1002/macro_seq_test1002.html
>
> Chris
>
>
>
>
>>
>> Cheers,
>> Jussi
>>
>>
>> On Sat, Aug 25, 2012 at 8:19 AM, Srikumar Karaikudi Subramanian <
>> srikumarks@gmail.com> wrote:
>>
>>> > This would be a very basic setup, but with the current API design
>>> there are some hard problems to solve here. The audio is relatively easy,
>>> regardless of whether it's coming from an external source or not. It's just
>>> a source node of some sort. The sequencing part is where stuff gets tricky.
>>>
>>> Yes it does appear tricky, but given that scheduling with native nodes
>>> suffices mostly, it seems to me that the ability to schedule JS audio nodes
>>> using noteOn/noteOff (renamed now as start/stop), together with dynamic
>>> lifetime support solves the scheduling problems completely. Such scheduling
>>> facility need only be present for JS nodes that have no inputs - i.e. are
>>> source nodes.
>>>
>>> We (at anclab) were thinking about similar scheduling issues within the
>>> context of building compose-able "sound models" using the Web Audio API. A
>>> prototype framework for this purpose that we built (
>>> http://github.com/srikumarks/steller) will generalize if JS nodes can
>>> be scheduled similar to buffer source nodes and oscillators. A bare bones
>>> example of using the framework is available here -
>>> http://srikumarks.github.com/steller .
>>>
>>> "Steller" is intended for interactive high level sound/music models
>>> (think foot steps, ambient music generators and the like) and so doesn't
>>> have time structures that are editable or even a "play position" as a DAW
>>> would require, but it may be possible to build them atop/beside Steller. At
>>> the least, it suggests the sufficiency of the current scheduling API for
>>> native nodes.
>>>
>>> Best,
>>> -Kumar
>>>
>>> On 21 Aug, 2012, at 11:28 PM, Jussi Kalliokoski <
>>> jussi.kalliokoski@gmail.com> wrote:
>>>
>>> > Hello group,
>>> >
>>> > I've been thinking about how to use the Web Audio API to write a
>>> full-fledged DAW with sequencing capabilities (e.g. MIDI), and I thought
>>> I'd share some thoughts and questions with you.
>>> >
>>> > Currently, it's pretty straight-forward to use the Web Audio API to
>>> schedule events in real time, which means it would play quite well together
>>> with other real time APIs, such as the Web MIDI API. For example, you can
>>> just schedule an audiobuffer to play whenever a noteon event is received
>>> from a MIDI source.
>>> >
>>> > However, here's something of a simple idea of how to build a DAW with
>>> a plugin architecture using the Web Audio API:
>>> >
>>> >  * You have tracks, which may contain audio and sequencing data (e.g.
>>> MIDI, OSC and/or user-defined envelopes). All of these inputs can be either
>>> being recorded from an external source, or be static pieces.
>>> >
>>> >  * You have an effects list for each track, effects being available to
>>> pick from plugins.
>>> >
>>> >  * You have plugins. The plugins are given references to two gain
>>> nodes, one for input and one for output, as well as a reference to the
>>> AudioContext. In response, they will give AudioParam references back to the
>>> host, as well as some information of what the AudioParams stand for,
>>> min/max values and so on. The plugin will set up a sub-graph between the
>>> given gain nodes.
>>> >
>>> > This would be a very basic setup, but with the current API design
>>> there are some hard problems to solve here. The audio is relatively easy,
>>> regardless of whether it's coming from an external source or not. It's just
>>> a source node of some sort. The sequencing part is where stuff gets tricky.
>>> >
>>> > In the plugin models I've used, the sequencing data is paired with the
>>> audio data in processing events, i.e. you're told to fill some buffers,
>>> given a few k-rate params, a few a-rate params and some sequencing events
>>> as well as the input audio data. This makes it very simple to synchronize
>>> the sequencing events with the audio. But with the Web Audio API, the only
>>> place where you get a processing event like this is the JS node, and even
>>> there you currently only get the input audio.
>>> >
>>> > What would be the proposed solution for handling this case? And
>>> please, no setTimeout(). A system is as weak as its weakest link and
>>> building a DAW/Sequencer that relies on setTimeout is going to be utterly
>>> unreliable, which a DAW can't afford to be.
>>> >
>>> > Cheers,
>>> > Jussi
>>>
>>>
>>
>
Received on Wednesday, 3 October 2012 20:29:16 UTC

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