Re: [Fecframe] draft-zixuan-fecframe-source-mi ??

[zouzixuan <tendyntu at huawei.com>]

Hi, All
 The followings are from minutes of the last 75th IEFT meeting
 
> AB: We don't modify the source packets anyway so this is not 
> a problem.


[zou] In order to answer the concerns in the last meeting about why we
brought up this draft, I think we should first clarify the need of Source
Payload ID argued by Ali's comments as the above. We gave the following
scenario/explanation to show the need of Source Payload ID.

1) Combined protection of multiple source flows 

For the case where one FEC repair Flow providing protection to multiple
source flow, the explicit Source FEC Payload ID, according to the
"draft-fecframe-framework", has to be used no matter if the protected source
flows is "sequenced" or not.

2) Single Sequenced Flow Case

Per draft-fecframe-raptor, the FEC scheme defined for "Single Sequenced
Flow" protection works well for source packet in fixed size without explicit
source payload ID.  

But for the source packet of variable size, the source packets must be
padded with zeros to occupy the same amount of space (equals to the length
of Source Packet Information) in the source block for FEC encoding/decoding.
The padded bytes are not sent, but require on the receiver side that the
amount of repair data for recovering a lost source packet equals to the
length of Source Packet Information. But this probably has a downside: the
amount of repair data needed would be much more than the case where padding
is not used, and thus impact the FEC decoding efficiency. So an alternate to
handle this issue is to not use padding, and therefore the Source Payload ID
is still needed for making FEC works with variable source packet size.


> AB: Do we really need to consider non-framework capable receivers?
> 
> ME: I don't believe this violates our charter. But why are 
> you doing this work?
> 
> ZZ: For RTP receivers that my use FEC but do not support the 
> FECFramework.

[zou] As we had answered Marshall, the FECFramework source packet with
Source Payload ID lead to incompatibility to those receivers not align with
this Framework. The draft "draft-zixuan-fecframe-source-miu" is proposed for
solving this issue.

Zou ZiXuan, Senior Research Staff
Media & Communication Lab
HUAWEI TECHNOLOGIES CO.,LTD. 

Address: Huawei Industrial Base
Bantian Longgang
Shenzhen 518129, P.R.China
Tel: +86 0755 28789364
Fax: +86 0755 28788317
E-mail: tendyntu at huawei.com
www.huawei.com
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-----Original Message-----
From: fecframe-bounces at ietf.org [mailto:fecframe-bounces at ietf.org] On Behalf
Of Ali C. Begen (abegen)
Sent: Thursday, September 17, 2009 9:56 PM
To: gjshep at gmail.com; fecframe at ietf.org
Subject: Re: [Fecframe] draft-zixuan-fecframe-source-mi ??

There were several comments from myself and some others during the meeting
about the applicability of this draft, the validity of the problem and some
details on the bits on the wire.

Will the authors be addressing those comments with a revision before we move
forward?

-acbegen

> -----Original Message-----
> From: fecframe-bounces at ietf.org [mailto:fecframe-bounces at ietf.org] On
Behalf Of Greg
> Shepherd
> Sent: Thursday, September 17, 2009 9:47 AM
> To: fecframe at ietf.org
> Subject: [Fecframe] draft-zixuan-fecframe-source-mi ??
> 
> I'm following-up with action items from our last WG meeting in
> Stockholm. We wanted to get some feedback from the list on potential
> use cases for the proposal:
> 
> http://www.ietf.org/id/draft-zixuan-fecframe-source-mi-00.txt
> 
> ..and to ask if the WG members feels this is a draft we want to take
> on as a FECFrame WG Item.
> 
> Please respond by the end of next week - Sept 25th.
> 
> Thanks,
> Greg
> _______________________________________________
> Fecframe mailing list
> Fecframe at ietf.org
> https://www.ietf.org/mailman/listinfo/fecframe
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