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

From: Robert O'Callahan <robert@ocallahan.org>
Date: Thu, 28 Aug 2014 14:04:37 +1200
Message-ID: <CAOp6jLbJnjQLWvJ3S+68t+i8nJ_1+sns6KwNBBUidtcb6ADDRQ@mail.gmail.com>
To: Chris Wilson <cwilso@google.com>
Cc: Harald Alvestrand <harald@alvestrand.no>, "public-media-capture@w3.org" <public-media-capture@w3.org>
On Thu, Aug 28, 2014 at 4:26 AM, Chris Wilson <cwilso@google.com> wrote:

> ROC, the challenge I have here is it's quite easy to prevent
> MediaStreamAudioDestinationNode from being created in an offline context -
> we simply remove the constructor from OfflineAudioContext.  There's an open
> issue on this (https://github.com/WebAudio/web-audio-api/issues/308), I
> just haven't gotten to it yet.  But once you can construct a recorder and
> hand it an arbitrary node, we'll have to deal with the interaction between
> OfflineAudioContext and MediaStreamRecorder in some way.
>

Right, but I don't think there's much new we need to say here. Recording an
offline AudioNode is just like recording the stream generated by a
non-offline MediaStreamAudioDestinationNode; the input data just arrives
faster (or maybe slower) than real time.

When a timeSlice parameter is given to MediaRecorder, we have to clarify
that data callbacks arrive every timeSlice-worth of *input* data, not every
timeSlice-worth of real time, since those are no longer even approximately
the same.

This seems like mostly convenience over the current way.  Am I missing
> something?
>

It is only convenience for the online AudioContext case. For the
OfflineAudioContext case it will be the only way to do recording (until we
add full-fledged offline MediaStreams I guess).

Rob
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Received on Thursday, 28 August 2014 02:05:05 UTC

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