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Re: Behavior of source nodes on connect/disconnect

From: Robert O'Callahan <robert@ocallahan.org>
Date: Fri, 13 Sep 2013 12:47:59 -0700
Message-ID: <CAOp6jLasth=L=4Mx=u8yN4q=hCnT6Gram2ia3DQskrsmdJfczg@mail.gmail.com>
To: Jer Noble <jer.noble@apple.com>
Cc: Chris Wilson <cwilso@google.com>, Raymond Toy <rtoy@google.com>, "public-audio@w3.org" <public-audio@w3.org>
On Fri, Sep 13, 2013 at 8:39 AM, Jer Noble <jer.noble@apple.com> wrote:

> I’m going to have to take up the mantle of Chris and disagree with you
> strongly here.  Disconnected nodes are disassociated from the graph
> entirely.  They do not participate in rendering to the destination node,
> and they no longer are connected to the destination node’s timeline.
>

OK, but that's not what the spec currently says and adding that behavior to
the spec is a large change. So this discussion should really be framed as a
proposal to make this change to the spec. As such, it would be helpful to
see the proposed change written down in more detail.

Philosophically speaking, disconnected nodes are collected by GC because
> they are no longer active. But if disconnected nodes continue to "play", we
> would either be GCing active objects, or not GCing disconnected objects,
> effectively leaking nodes with no end time.  Neither of which are good
> options.
>

In most cases, the ongoing playback of disconnected nodes is not
observable, and therefore they can be safely destroyed even though they're
active.


> Practically speaking, disconnecting a sub-graph is the only way deleopers
> can "pause" playback. If we force disconnected nodes to continue playing,
> the only way to pause playback would be to entirely tear down and re-create
> a subgraph.
>

I agree with Chris Wilson; if we're going to support pausing, let's support
it properly with a pause/resume API.

Pausing a MediaStream/ElementAudioSourceNode is not a problem. You just
drop data from the input stream while paused.

Rob
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Received on Friday, 13 September 2013 19:48:26 UTC

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