W3C home > Mailing lists > Public > public-media-capture@w3.org > August 2014

Re: Extending MediaRecorder to record from Web Audio node faster than real time?

From: Robert O'Callahan <robert@ocallahan.org>
Date: Wed, 27 Aug 2014 00:58:16 +1200
Message-ID: <CAOp6jLbh9xO7S=KT8mJNgNyzOpWAOkqcgo9w97sGtrwf+TcjGQ@mail.gmail.com>
To: Jim Barnett <1jhbarnett@gmail.com>
Cc: "public-media-capture@w3.org" <public-media-capture@w3.org>
On Thu, Aug 21, 2014 at 2:19 AM, Jim Barnett <1jhbarnett@gmail.com> wrote:

> The OfflineAudioContext is not required to render faster than real time,
> is it?  Could we say that when attached to a PeerConnection it should
> render in real time?

That would make it mostly useless.

The proposal here is to allow a MediaRecorder to be constructed for an
AudioNode. That does not enable connection of OfflineAudioContext to
MediaStreams or PeerConnections --- by design, since we don't want to open
that can of worms. Yet :-).

By the way, is it correct to say that an OfflineAudioContext isn't linked
> to a clock at all?  It must have some sense of what the timing would be
> when the audio is played in real time.  Otherwise, MediaRecorder can't
> process it.  The MediaRecorder API lets the caller say "give me 200ms
> buffers of audio".  It would be fine for the MediaRecorder to return those
> buffers more often than once every 200ms, but the amount of data has to be
> correct.

That's right.

In any case, I agree that since it is already possible to create a
> MediaStream from an AudioNode (and hence to record from the AudioNode), we
> should figure out how that works (or forbid it)

I'm not aware of additional spec work that needs to be done for that case.
MediaStreamAudioDestinationNode has existed for a while. Firefox has been
shipping it + MediaRecorder for a while now.

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Received on Tuesday, 26 August 2014 12:58:43 UTC

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