Internet DRAFT - draft-deng-rtcweb-codecapi
draft-deng-rtcweb-codecapi
Network Working Group L. Deng
Internet-Draft L. Ni
Intended status: Informational Q. Yu
Expires: January 09, 2014 China Mobile
July 08, 2013
Proposal for reusing local codec APIs on mobile devices
draft-deng-rtcweb-codecapi-00.txt
Abstract
This document proposes the browser to make use of local codec APIs,
if available on a mobile device, and notifies RTCWEB applications to
allow for better tuning between device capability and media quality.
Status of This Memo
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provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on January 09, 2014.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Discussion . . . . . . . . . . . . . . . . . . . . . . . . . 2
2.1. Built-in media capabilities in mobile devices . . . . . . 2
2.2. MTI codecs for mobile devices? . . . . . . . . . . . . . 3
3. Proposal . . . . . . . . . . . . . . . . . . . . . . . . . . 3
3.1. Function Requirement for Browser . . . . . . . . . . . . 4
3.2. API Requirements for Browser . . . . . . . . . . . . . . 4
4. Security Considerations . . . . . . . . . . . . . . . . . . . 4
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4
6. References . . . . . . . . . . . . . . . . . . . . . . . . . 4
6.1. Normative References . . . . . . . . . . . . . . . . . . 4
6.2. Informative References . . . . . . . . . . . . . . . . . 4
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 4
1. Introduction
It is expected that by including the built-in real-time communication
capabilities into a general purpose browser, the development and
integration of person-to-person communication experience into a web
page, without pre-installation of any additional software.
There has been extensive discussion on the MTI video codec for RTCWEB
browsers for quite a period of time. Whereas so far the discussion
has mainly focused on evaluating one against another based on merits
as well as IPR issues.
2. Discussion
2.1. Built-in media capabilities in mobile devices
Unlike general purpose personal computers, smart phones have built-in
support for audio/video encoding/decoding functionalities, as their
traditional role is to serve as a phone.
Considering other types of mobile devices, like Wifi-only tablets,
users are increasingly expect that they also provide real-time media
channels in one way or another. For instance, watching streaming
clips from a web page, or chatting with family members and friends
through VoIP applications.
In all, it is expected that a mobile device provides some sort of
built-in media processing capabilities in the first place. For
instance, Android system provides various media encoding/decoding
support [android-codec-support]. IOS platforms also supply hardware-
accelerated codec APIs for built-in codecs [apple-codec-support].
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2.2. MTI codecs for mobile devices?
We made the following observations on this point for mobile devices:
o A couple of MTI codecs may not be sufficient for a general purpose
browser targeting the mobile users.
On the one hand, a user's expected/perceived media quality of a real-
time communication applications, which is largely dependent on the
device in hand and the type of service they are using, is hardly
possible to be covered by a handful of MTI codecs.
To begin with, as different devices vary in size of screen, hence a
HD video stream, which would be appreciated for a tablet user, could
turn out to be a waste of resources for a smaller-screened smart
phone.
Furthermore, considering the case of interworking, it is almost
always better to use the same choice of codec as the other end than
to choose another one and to do trans-coding in between.
o A universal package of codecs is not cost-effective for mobile
browsers.
Despite the rapid increase in processing power and wireless
bandwidth, portal mobile devices are bonded by short-lived battery
power and physical size, it would not be wise for a mobile browser to
include the bunch of all the potentially needed codecs. Since this
would consume much more resources and expand the installing package
as well. What's worse, it could mean extra expense for the browser
vender to include each patented codec algorithm.
3. Proposal
In summary, we believe it could be desirable for the browser to make
use of local media support provided by the end device system into the
candidate pool for various web applications to choose for their
specific RTCWEB usage cases and differential quality expectations
accordingly. Because reusing the local codec support has the
following advantages:
o It reduces the implementation complexity and potential patent cost
for general purpose browsers.
o It would eliminate the risk of degrading user experience when
compared with other real-time communication applications using the
same local facility.
Specifically, the indicated requirements are two-folded:
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3.1. Function Requirement for Browser
Firstly, a RTCWEB-compatible browser MAY make use of codec APIs
supported by a mobile device locally be default and include them into
SDP offer/answer exchange with the other end.
3.2. API Requirements for Browser
Moreover, it SHOULD be possible for the JS to be able to distinguish
the locally supported codecs from the other browser-bounded ones, and
be allowed to make proper choices based on the specific communicating
scenario in question.
4. Security Considerations
TBA
5. IANA Considerations
None.
6. References
6.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2234] Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax
Specifications: ABNF", RFC 2234, November 1997.
6.2. Informative References
[android-codec-support]
, "http://developer.android.com/guide/appendix/media-
formats.html#core", .
[apple-codec-support]
, "https://developer.apple.com/library/ios/#documentation/
AudioVideo/Conceptual/AVFoundationPG/Articles/
00_Introduction.html#//apple_ref/doc/uid/TP40010188", .
Authors' Addresses
Lingli Deng
China Mobile
Email: denglingli@chinamobile.com
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Lingfei Ni
China Mobile
Email: nilingfei@chinamobile.com
Qing Yu
China Mobile
Email: yuqing@chinamobile.com
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