Subject: Re: [MMUSIC] draft-johansson-mmusic-image-attributes

From: Kyunghun Jung <[email-masked]>
Date: Tue, 01 Jul 2008 12:41:07 +0000 (GMT)

Hello,

Let me comment further
on “a=quality” from 3GPP’s point of view, i.e., that of mobile video telephony.

This attribute seems
to have similar objectives as that of H.245 videoTemporalSpatialTradeoff. However,
we found neither works properly

since it is unknown how many encoding methods
the far-end codec supports at the negotiated bit-rate. 3GPP discussed the
problems of

“a=quality” but this issue was of less importance for us.

http://www.3gpp.org/ftp/tsg_sa/WG4_CODEC/TSGS4_45/Docs/

(s3-070528.zip)

Even after we
fix the bit-rate and image size, we still have the freedom of temporalspatial
tradeoff. Note that “a=quality” is intended for in-call

control of video encoding
while “a=imageattr” for session setup.

a=imageattr:97 sar=255 [fr=[5:15],x=800,y=640] /

[fr=[15:30],x=480,y=320]

In that sense,
if fr of “a=imageattr” can be properly mapped to the values of “a=quality,” the
ambiguity of using “a=quality” might be reduced,

although we have witnessed far
smaller numbers of frame rates, than covered by “a=quality.”

For typical 3GPP
mobile video telephony of limited complexity and cost, frame rate would be controlled mainly by dropping
sampled video

frames
before video encoder, and available frame rates would
range as follows: 30, 15, 10, 7.5, 10, 5, … Current circuit-switched 3G-324M
usually supports 15, 7.5, 5 fps. Therefore
describing available frame rate as fr=[5:15] might not be
possible, at least for mobile phones.

Sincerely yours,

Kyunghun Jung

Samsung
Electronics Co., Ltd.

------- Original Message -------
Sender : Colin Perkins<[email-masked]>
Date : 2008-06-30 04:00 (GMT+09:00)
Title : Re: [MMUSIC] draft-johansson-mmusic-image-attributes

Hi,

The draft lists several issues in section 5. There are also possible

feature interactions with the "a=framerate:", "a=quality:" and

"a=orient:" attributes in RFC 4566. And, RFC 4175 also defines width

and height parameters which may conflict. I doubt any of these are

major issues, but the interactions need to be specified.

Cheers,

Colin

On 26 Jun 2008, at 15:52, Ingemar Johansson S wrote:

> Hi

> The image attribute draft has been updated to version -01 with some

> major changes.

> + Support for Sample Aspect Ratios (SAR)

> + Offer/answer for asymmetric display capabilities

> + Picture aspect Ratio range to limit the number of x and y

> resolution options

> Comments are welcome

> /Ingemar

> ======================================

> Filename:     draft-johansson-mmusic-image-attributes

> Revision:     01

> Title:         Negotiation of Generic Image Attributes in SDP

> Creation_date:     2008-06-26

> WG ID:         Independent Submission

> Number_of_pages: 13

> Abstract:

> This draft proposes a new generic session setup attribute to make

> it possible to negotiate different image attributes such as image

> size.

> A possible use case is to make it possible for a e.g a low-end

> hand- held terminal to display video without the need to rescale

> the image, something that may consume large amounts of memory and

> processing power.  The draft also helps to maintain an optimal

> bitrate for video as only the image size that is desired by the

> receiver is transmitted.

> http://tools.ietf.org/id/draft-johansson-mmusic-image-

> attributes-01.txt

> ======================================

> *******************************************

> Ingemar Johansson

> Senior Research Engineer, IETF "nethead"

> EAB/TVP - Multimedia Technologies

> Ericsson Research Ericsson AB

> Box 920 S-971 28 Luleå, Sweden

> Tel: +46 (0)8 4043042

> ECN: 850-43042

> ECC: 850-43074

> Mobile: +46 (0)730 783289

> *******************************************

> _______________________________________________

> mmusic mailing list

> [email-masked]

> https://www.ietf.org/mailman/listinfo/mmusic

--

Colin Perkins

http://csperkins.org/

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