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Re: Thoughts and questions on the API from a modular synth point of view

From: Robert O'Callahan <robert@ocallahan.org>
Date: Fri, 3 Aug 2012 12:23:58 +1200
Message-ID: <CAOp6jLbc8RrOE7v-fyNG6i07P_eh8yn1d_izf0t8e8KrDjq80A@mail.gmail.com>
To: Chris Wilson <cwilso@google.com>
Cc: Peter van der Noord <peterdunord@gmail.com>, Chris Rogers <crogers@google.com>, "public-audio@w3.org" <public-audio@w3.org>
On Fri, Aug 3, 2012 at 4:41 AM, Chris Wilson <cwilso@google.com> wrote:

> Chris and I have talked through many different "pausing" behaviors - and
> I'm quite sure he's thought about it even more.  The problem is there isn't
> one logical solution - for example, your "I want to stop audiocontext from
> asking for more buffers [temporarily]": how does that deal with an upstream
> source from a microphone input (via getUserMedia)?  Is it really "pausing"
> - i.e. recording like a DVR?  How much time can it buffer?  You'd probably
> also want a fast-forward API then... and this starts looking less tenable.
>  It would also be a confusing challenge when audiocontext.currentTime
> doesn't always proceed forward at a steady rate - or (more likely) when
> branches of the audio graph want to get out of sync (because you really
> want to "pause" branches, not always the whole graph - that's what the
> Fieldrunners guys wanted<http://www.html5rocks.com/en/tutorials/webaudio/fieldrunners/>,
> so they could pause the game effects but keep the menu effects going).
>

These problems can all be solved:
1) Support currentTime on each AudioNode.
2) When a getUserMedia stream feeds into a paused node, drop data. For
authors who actually want DVR-like buffering we probably should invent an
entirely new kind of MediaStream that specifically does that.
3) When a media element stream feeds into a paused node, you have the
option of either pausing the media element or dropping data. We could
expose API to give the author control (c.f. the blockInput flag from MSP)
4) For each connection within in audio graph, you could provide the
equivalent of blockInput/blockOutput from MSP. Sensible defaults might be
to say that blockInput is true and blockOutput is false, i.e., a paused
stream feeding into a non-paused stream is treated as silence, but any
stream feeding into a paused stream is forced to pause.

Rob
-- 
“You have heard that it was said, ‘Love your neighbor and hate your enemy.’
But I tell you, love your enemies and pray for those who persecute you,
that you may be children of your Father in heaven. ... If you love those
who love you, what reward will you get? Are not even the tax collectors
doing that? And if you greet only your own people, what are you doing more
than others?" [Matthew 5:43-47]
Received on Friday, 3 August 2012 00:24:26 GMT

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