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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: Tue, 7 Aug 2012 12:50:42 +1200
Message-ID: <CAOp6jLYC0z3=BCgvf8s8r1FSFeQCA8rTBHWUw9ZGUt-Pt35-3A@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 Tue, Aug 7, 2012 at 8:28 AM, Chris Wilson <cwilso@google.com> wrote:

> On Fri, Aug 3, 2012 at 9:57 PM, Robert O'Callahan <robert@ocallahan.org>wrote:
>
>>  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.
>>>>
>>>
>>> How does it drop data, exactly?  Because that's probably going to sound
>>> like a glitch.
>>>
>>
>> Can you describe an example you're concerned about in more detail?
>>
>
> Well, the gUM stream may potentially have a very hard-edged transition in
> the stream then - because it's picking up mid-stream - while the other data
> will not.  As they'll all be (potentially) feeding through a processing
> node graph, the resulting data may be a bit confusing (e.g. a gUM and a
> bufferSource both feeding into a convolution node, and it is paused -
> what's the state data when it's resumed?
>

If you pause the convolution node, then its state is frozen while it's
paused. When you resume, you would get a sharp transition in the gUM
stream. But that's expected, isn't it? As you say, it's just like starting
playback in the middle of a media stream. That's not wrong if it's what the
author asks for.

I suppose it might make sense to specify some automatic fading or blending
when a paused node feeds into a non-paused node to reduce the impact of
those transitions.

I wasn't talking about API complexity - I was talking about implementation
> complexity.
>

OK. As an implementor, I think it's quite manageable.


>
>> Note that some things are impossible now. For example, right now you
>> can't have a source with an echo effect applied to it, pause the
>> source+echo, and later resume the source+echo in such a way that the echo
>> is paused concurrently with the source.
>
>
> Not true; you can always insert a JSNode and record (buffer) the audio.
>

I don't see how that would work given I want to actually pause the source
(say, an HTML <video> element).

Rob
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Received on Tuesday, 7 August 2012 00:51:11 GMT

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