Re: [rtcweb] [avtext] Fwd: New Version Notification for draft-fineberg-avtext-temporal-layer-ext-00.txt

[Adam Fineberg <[e-mail]>]

Stephan,

Thanks for the info and the reference.  I'm not sure I follow as I'm not 
at all familiar with H.265.  I'll review the reference and see what I 
can figure.  It seems though to me that you are suggesting that except 
in the simple case, that the data for H.265 would not be well suited to 
a header extension, am I understanding you correctly?  There is no 
reason the middlebox couldn't get out of band signaling of the VPS as 
you mention but that would not be within the scope of this header extension.

Any insights are appreciated.

Regards,
Adam

On 7/19/13 8:33 AM, Stephan Wenger wrote:
> Hi,
> I also believe that 16 bits should be enough.  For H.264 and VP8 that 
> has already been demonstrated.  For H.265, some initial thoughts 
> below.  Apologies for the word-count.
>
> The scalable version of H265 (called SHVC) is currently under 
> development.  The current working draft can be found here: 
> http://phenix.int-evry.fr/jct/doc_end_user/documents/13_Incheon/wg11/JCTVC-M1008-v3.zip. 
>  Therein, the options for defining layering structures are 
> considerably more complex.  To start, we have 3 bits for the temporal 
> ID in the NAL unit header of the H.265 version 1 (HEVC) base 
> specification (temporal scalability is already nicely supported in 
> version 1).  Just like in SVC.  In the scalable extension, the NAL 
> unit header contains a six bit field that points into a data structure 
> known as "Video Parameter Set" (VPS).  Inside the VPS, those six bits 
> are mapped to to a position in a directed graph (specified through 
> "dimension_id[][]"), which tells you about the reference relationship 
> of the layer in question and its parent layer.  One can recursively 
> follow the graph to determine what used to be called dependency_id, 
> quality_id, view_id, and whatnot.  The six bit pointer field can (or: 
> is to be when possible) organized by the encoder such that it is 
> prudent for a middle box to throw away NAL units (belonging to layers) 
> with higher values of the six bit field first, before throwing away 
> NAL units with lower values.  Relying on this feature, 3+6 bits == 9 
> bits should be fine for the header extension.
>
> That said, the ordering by the encoder is just a recommendation, and 
> there may well be cases where different pruning strategies may be 
> advisable.  For example, a layering structure could be constructed 
> that expands into two branches, one using 2D scalable tools only, the 
> other including view_id for multi view coding.  By looking at the six 
> bit field alone, a middle box will not be able to meaningfully remove 
> NAL units belonging to one of the branches completely while pruning 
> the other branch.  In order to meaningfully deal with that scenario, 
> there would be two options: one to represent the dimension_id[][] (and 
> associated control info) in the header extension, or require the 
> middle box to have access to the VPS and be able to interpret its 
> content.  The further could take considerably more than 16 bits and we 
> would be talking about a variable length data structure.  The latter 
> requires the middle box to have state and a mechanism to intercept the 
> VPS (through signaling---as the encrypted in-band VPS would not be 
> useful under the assumption that the middle box does not have the key 
> to the media---which is the motivation of the draft in the first 
> place).  I personally don't mind at all the second mechanism, as I'm a 
> big fan of out-of-band parameter set transmission and any middle box 
> must be in the signaling path anyway to meaningfully manipulate RTP. 
>  I do not like the first option due to its variable, and possibly 
> substantial, overhead.
>
> Stephan
>
>
> From: Justin Uberti <[e-mail] <mailto:[e-mail]>>
> Date: Friday, 19 July, 2013 06:32
> To: Bernard Aboba <[e-mail] 
> <mailto:[e-mail]>>
> Cc: "[e-mail] <mailto:[e-mail]>" <[e-mail] 
> <mailto:[e-mail]>>, "[e-mail] <mailto:[e-mail]>" 
> <[e-mail] <mailto:[e-mail]>>
> Subject: Re: [rtcweb] Fwd: New Version Notification for 
> draft-fineberg-avtext-temporal-layer-ext-00.txt
>
> Agree those are the right codecs to design for. Since in each case 
> there are fairly low limits on the number of supported layers (i.e. 3 
> spatial layers for SVC), I think it should be possible to pack the 
> temporal, spatial, quality layer ids into 16 bits.
>
>
> On Fri, Jul 19, 2013 at 1:56 AM, Bernard Aboba 
> <[e-mail] <mailto:[e-mail]>> wrote:
>
>     If we can support VP8/9 as well as H.264/5 SVC
>     that would be a start. It seems doable to me.
>
>     On Jul 18, 2013, at 8:34 PM, "Adam Fineberg" <[e-mail]
>     <mailto:[e-mail]>> wrote:
>
>>     Bernard,
>>
>>     Are there other codecs you are thinking should be supported?  If
>>     it's generalized I would think we want to be able to cover all
>>     known scalable codecs. I'll look into the H264/SVC fields to see
>>     how to encode them in a generalized header.
>>
>>     Regards,
>>     Adam
>>
>>     On 7/18/13 7:40 PM, Bernard Aboba wrote:
>>>     I think it may be possible to generalize this.  For example, for
>>>     H.264/SVC which can support temporal, spatial and quality
>>>     scalability, you would need the quality_id and dependency_id in
>>>     addition to the temporal_id (what you call the temporal layer
>>>     index).
>>>
>>>     ------------------------------------------------------------------------
>>>     Date: Thu, 18 Jul 2013 08:45:38 -0700
>>>     From: [e-mail] <mailto:[e-mail]>
>>>     To: [e-mail] <mailto:[e-mail]>
>>>     CC: [e-mail] <mailto:[e-mail]>; [e-mail]
>>>     <mailto:[e-mail]>
>>>     Subject: Re: [rtcweb] Fwd: New Version Notification for
>>>     draft-fineberg-avtext-temporal-layer-ext-00.txt
>>>
>>>     Bernard,
>>>
>>>     Good question.  I'm not familiar enough with the parameter
>>>     requirements of all other scalable codecs to be able to
>>>     generalize.  If you'd like to help specify them, I'd be fine
>>>     revising the draft to generalize.
>>>
>>>     Regards,
>>>     Adam
>>>
>>>     On 7/17/13 8:26 PM, Bernard Aboba wrote:
>>>
>>>         Since the need is not codec specific (e.g. it arises with
>>>         any codec supporting temporal, spatial and quality
>>>         scalability), why
>>>          a VP8-specific RTP extension?
>>>
>>>         ------------------------------------------------------------------------
>>>         Date: Wed, 17 Jul 2013 17:09:46 -0700
>>>         From: [e-mail] <mailto:[e-mail]>
>>>         To: [e-mail] <mailto:[e-mail]>
>>>         Subject: [rtcweb] Fwd: New Version Notification for
>>>         draft-fineberg-avtext-temporal-layer-ext-00.txt
>>>
>>>         Hi,
>>>
>>>         I'm working on WebRTC services and have found that while
>>>         developing services that forward VP8 video streams if we
>>>         want to take advantage of the VP8 temporal scaling we must
>>>         get the temporal layer information from the RTP header which
>>>         requires us to decrypt the SRTP packets. This is undesirable
>>>         both because the middle-box needs to have access to the keys
>>>         as well as the because of the added overhead of the
>>>         decrypt/encrypt cycle. This draft proposes an RTP header
>>>         extension that will allow us to use the VP8 temporal layer
>>>         information included in the header extension and therefore
>>>         do forwarding without SRTP decryption. Comments welcome.
>>>
>>>         Regards,
>>>         Adam Fineberg
>>>         fineberg at vline.com <mailto:fineberg%20at%20vline.com>
>>>
>>>         -------- Original Message --------
>>>         Subject: 	New Version Notification for
>>>         draft-fineberg-avtext-temporal-layer-ext-00.txt
>>>         Date: 	Tue, 09 Jul 2013 10:02:05 -0700
>>>         From: 	internet-drafts at ietf.org
>>>         <mailto:internet-drafts%20at%20ietf.org>
>>>         To: 	Adam Fineberg<fineberg at vline.com>
>>>         <mailto:fineberg%20at%20vline.com>
>>>
>>>
>>>
>>>         A new version of I-D, draft-fineberg-avtext-temporal-layer-ext-00.txt
>>>         has been successfully submitted by Adam Fineberg and posted to the
>>>         IETF repository.
>>>
>>>         Filename:	 draft-fineberg-avtext-temporal-layer-ext
>>>         Revision:	 00
>>>         Title:		 A Real-Time Transport Protocol (RTP) Header Extension for VP8 Temporal Layer Information
>>>         Creation date:	 2013-07-08
>>>         Group:		 Individual Submission
>>>         Number of pages: 6
>>>         URL:http://www.ietf.org/internet-drafts/draft-fineberg-avtext-temporal-layer-ext-00.txt
>>>         Status:http://datatracker.ietf.org/doc/draft-fineberg-avtext-temporal-layer-ext
>>>         Htmlized:http://tools.ietf.org/html/draft-fineberg-avtext-temporal-layer-ext-00
>>>
>>>
>>>         Abstract:
>>>             This document defines a mechanism by which packets of Real-Time
>>>             Tranport Protocol (RTP) video streams encoded with the VP8 codec can
>>>             indicate, in an RTP header extension, the temporal layer information
>>>             about the frame encoded in the RTP packet.  This information can be
>>>             used in a middlebox performing bandwidth management of streams
>>>             without requiring it to decrypt the streams.
>>>
>>>
>>>         _______________________________________________ rtcweb
>>>         mailing list [e-mail] <mailto:[e-mail]>
>>>         https://www.ietf.org/mailman/listinfo/rtcweb
>>>
>>>
>>>     -- 
>>>     Regards,
>>>     Adam
>>
>
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-- 
Regards,
Adam