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Re: CodecNode

From: Chris Rogers <crogers@google.com>
Date: Tue, 15 May 2012 14:28:34 -0700
Message-ID: <CA+EzO0=Yv=Rm=0rvVC7MH2-KSyS46Bn8rU1Wgvwwg8=0jKB5eg@mail.gmail.com>
To: robert@ocallahan.org
Cc: "Young, Milan" <Milan.Young@nuance.com>, "public-audio@w3.org" <public-audio@w3.org>
On Tue, May 15, 2012 at 2:16 PM, Robert O'Callahan <robert@ocallahan.org>wrote:

> On Wed, May 16, 2012 at 7:27 AM, Chris Rogers <crogers@google.com> wrote:
>
>>
>>> That's really a WebRTC question. Actually at Mozilla the #1 priority for
>>> MediaStream right now is not peer communication but using getUserMedia to
>>> capture audio and video streams and take photos. I think we'll need to
>>> resuscitate MediaStreamRecorder very soon, to record video clips in
>>> camera-using applications --- if someone else doesn't get to it first. If
>>> you just want to capture a bundle of video and transmit it to a server in
>>> non-real-time, then that's what you want too I guess.
>>>
>>
>> If we resuscitate MediaStreamRecorder then I'd like to make sure that the
>> design takes into account that a recording will start and stop at a precise
>> time (in relation to other audio events).  This is crucial for musical
>> applications such as digital audio workstations when people are recording
>> tracks into a multi-track editor -- essential for synchronization.
>>
>
> Sure. You can do that with MediaStream Processing :-)
>

I'm not sure I understand how.  It's no longer in the WebRTC spec, but
looking back at an older version I see:
http://dev.w3.org/2011/webrtc/editor/webrtc-20120112.html#mediastreamrecorder

[Constructor (MediaStreamTrackList? audioTracks, MediaStreamTrackList?
videoTracks)]
interface MediaStream {
    readonly attribute DOMString            label;
    readonly attribute MediaStreamTrackList audioTracks;
    readonly attribute MediaStreamTrackList videoTracks;
    MediaStreamRecorder record ();
             attribute boolean              ended;
             attribute Function?            onended;
};

The text says:
"record()
Begins recording the stream. The returned MediaStreamRecorder object
provides access to the recorded data."

What I'm saying is that the record() method needs to say *when* (exactly at
what time in relation to other audio events), otherwise it will just start
recording at "roughly" a certain time (when the record() method is invoked
from JS) which is not accurate enough for professional audio.  Recording in
digital audio work-station applications requires recording a stream with
sample-accuracy.

Chris




>
> 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 Tuesday, 15 May 2012 21:29:04 GMT

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