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RE: tvapi-ACTION-24: use of Media Capture to realize recording requirements

From: Jon Piesing <Jon.Piesing@tpvision.com>
Date: Tue, 24 Feb 2015 15:26:50 +0000
To: Paul Higgs <paul.higgs@ericsson.com>, "public-tvapi@w3.org" <public-tvapi@w3.org>
Message-ID: <61761EDC91441E408304E42BC16CC1615FD708D7@BEBRUEX003.tpvision.com>
Dear Paul, all,

Since I've not participated in this group before, I apologise in advance if I've mis-understood something ....

I have a question about the proposal below to use the MediaStream Recording API for recording in a TV context. How would this work if the device was in standby at the time the recording needed to happen? Something would need to cause the device to wake up from standby, start the UA and load the page containing the calls to that API. I've had a quick look at the device API work and cannot see an API there to schedule a device to wake from standby. The OIPF browser group that I chaired created such an API but it would need to be supported by some kind of security model which OIPF never properly addressed. IMHO such an API would not be safe to make available to an arbitrary web page.

Have I missed something?

Regards

Jon Piesing
TP Vision
________________________________
From: Paul Higgs [paul.higgs@ericsson.com]
Sent: 19 February 2015 21:38
To: public-tvapi@w3.org
Subject: tvapi-ACTION-24: use of Media Capture to realize recording requirements

Hi

During the February 17 TV Control API conference call, I took an action [1] to review the MediaStream Recording API [2] for its relevance and use in fulfilling the requirements around recording [3]

It is possible to see that an TVTuner defined in the TV Control API can “output” via a MediaStream which can then me recorded through the MediaRecorder API. In order to do this, the MediaRecorder constructor requires the mime type of the TVTuner output, so a “readonly attribute DOMString  mimeType” attribute should be added to the TVTuner interface.

At a period denoted by the timeSlice property, the ondataavailable event handler is trigger, an argument to which is the recorded data. The application implementing this handler would then need to write the capture stream data to a file (perhaps via the File API [4]). The MediaStream Recording API also has the ability to throw a “MediaRecorderErrorEvent” with name=OutOfMemory

What this means is that there is no native recording functionality in the device implementing TVManager.  Instead one of the applications running on the terminal is the “recording scheduler” (how that application gets and manages data is probably application specific). Note that this requires the UA support some form of “background application”.

In essence, the requirement mapping table should, for each of the [recording.*] requirements, state “not supported, realized through the webapp and MediaStream Recording API”


[1] http://www.w3.org/community/tvapi/track/actions/24
[2] http://www.w3.org/TR/mediastream-recording/
[3] https://www.w3.org/community/tvapi/wiki/Main_Page/Technical_Requirement#Program_Recording_Requirements
[4] http://www.w3.org/TR/FileAPI/


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PAUL HIGGS
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Received on Tuesday, 24 February 2015 15:27:22 UTC

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