RE: [AVT] FW: I-D Action:draft-ietf-avt-rtp-svc-04.txt

Hi Roni,

Thanks for reading the new draft and for your new comments. 

- Our intention was to summarize the definitions in a way easier to
understand - that's why we did not copy those definitions from the SVC
coding spec. However, if you (and others don't disagree) would like
those definitions to be phrased same as in the SVC coding spec, we can
certainly do that. I will do this change to the next version if no one
disagrees. 

- Similarly as above, the semantics of the U bit was phrased as
currently in the payload draft also to make it easier to understand. The
semantics from the SVC spec is as follows:

use_ref_base_pic_flag equal to 1 specifies that reference base pictures
are used as reference pictures for the inter prediction process.
use_ref_base_pic_flag equal to 0 specifies that decoded pictures are
used as reference pictures during the inter prediction process.
The values of use_ref_base_pic_flag shall be the same for all NAL units
of a dependency representation. use_ref_base_pic_flag shall be equal to
0 in filler prefix NAL units.

While the current semantics in the payload draft is as follows:

use_ref_base_pic_flag.  A value of 1 indicates that only reference base
pictures are used during the inter prediction process.  A value of 0
indicates that the reference base pictures are not used during the inter
prediction process. 

Except for the last sentence of the semantics in the SVC spec (which is
a limit to a conforming bitstream therefore no need to be mentioned in
the payload draft), both semantics are equivalent. In the payload draft,
I avoided having the sentence "use_ref_base_pic_flag equal to 0
specifies that decoded pictures are used as reference pictures during
the inter prediction process.", which could be confusing to people not
deeply familiar with the SVC spec, wherein "decoded picture" in SVC
context refers to the reconstructed picture used for output, while
another (optional) reconstructed picture from decoding of the same
access unit, "reference base picture", used for inter prediction but not
for output, is not a "decoded picture". I have checked the SVC spec,
found that a new definition of "decoded picture" is unfortunately not
present in Annex G.3. 

I therefore think it is a little bit better to have the current
semantics in the payload draft, unless a new definition of "decoded
picture" is added in the SVC spec (Annex G).  

- Regarding the RR bits, if you meant for the difference between
"Receivers SHOULD discard NAL units with RR not equal to '11'." in the
payload draft and "Decoders shall ignore the value of
reserved_three_2bits." in the SVC spec, then I would say that having the
difference is correct, because herein the intention is to specify the
RTP receiver's operation not the decoder's operation, and "SHOULD"
should be used in stead of "SHALL".

BR, YK 

>-----Original Message-----
>From: ext Even, Roni [mailto:roni.even@polycom.co.il] 
>Sent: Thursday, January 03, 2008 3:15 PM
>To: Thomas Schierl; Colin Perkins
>Cc: avt@ietf.org; tom.taylor@rogers.com
>Subject: RE: [AVT] FW: I-D Action:draft-ietf-avt-rtp-svc-04.txt 
>
>Thomas,
>
>I am reading the svc draft and as long as you address non 
>technical parts I noticed that the definitions in section 5.1 
>are different from the SVC (H.264 amendment 3) for the same 
>terms. I suggest that the definitions should be the same or 
>use different names.
>
>
>The same comment for section 3.3 comparing to G.7.4.1.1 for 
>the U and RR bits specifically.
>
>
>Roni
>
>> -----Original Message-----
>> From: Thomas Schierl [mailto:schierl@hhi.fhg.de]
>> Sent: Wednesday, January 02, 2008 7:36 PM
>> To: 'Colin Perkins'
>> Cc: avt@ietf.org; Even, Roni; 'Stephan Wenger'; tom.taylor@rogers.com
>> Subject: RE: [AVT] FW: I-D Action:draft-ietf-avt-rtp-svc-04.txt
>> 
>> Hi Colin,
>> 
>> Ok, I will try to fix the formatting before the conference call next
>week.
>> 
>> Happy new year!
>> Thomas
>> 
>> > -----Original Message-----
>> > From: Colin Perkins [mailto:csp@csperkins.org]
>> > Sent: Sunday, December 30, 2007 7:59 PM
>> > To: Thomas Schierl
>> > Cc: avt@ietf.org; 'Even, Roni'; 'Stephan Wenger';
>tom.taylor@rogers.com
>> > Subject: Re: [AVT] FW: I-D Action:draft-ietf-avt-rtp-svc-04.txt
>> >
>> > Thomas,
>> >
>> > On 18 Dec 2007, at 18:15, Thomas Schierl wrote:
>> > > I just submitted the -04 version of the RTP payload 
>draft for SVC.
>> > > Besides other changes, I corrected the formatting of the media
>type
>> > > section.
>> >
>> > There are so many formatting changes and problems with 
>this version 
>> > it's very difficult to find the technical changes. Please can you 
>> > ensure that future versions of the draft have consistent 
>formatting, 
>> > such that diff tools can be used (the xml2rfc tool is extremely 
>> > useful here).
>> >
>> > Thanks,
>> > --
>> > Colin Perkins
>> > http://csperkins.org/
>> 
>> 
>> 
>> ----
>> Visit us at
>> 
>> FOE 2008 (8th Fiber Optics Expo) / Tokio Big Sight, Japan / 16 - 18 
>> January 2008 / Booth 2 - 50 http://www.foe.jp/english
>
>_______________________________________________
>Audio/Video Transport Working Group
>avt@ietf.org
>https://www1.ietf.org/mailman/listinfo/avt
>

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