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

[Adam Fineberg <[e-mail]>]

Bernard,

I apologize if I come across as being difficult here but I stil am not 
seeing the benefits.  Since the fields are not the same for the codecs, 
we will be multiplexing the bits and that seems to me to add complexity 
rather than add clarity.  Also, I can't find an IETF VP9 document for 
the payload format to reference.  If the group thinks generalization is 
the right approach I would appreciate some collaboration on getting the 
right bit definitions for the other codecs.

Regards,
Adam

On 7/23/13 12:07 PM, Bernard Aboba wrote:
> I do not think it is necessary to "support all forms of scalability 
> for all codecs".   In fact, I would make that an explicit "non-goal".  
> All that was suggested is to try to create a single extension that 
> supports a few common cases. If it is possible to handle VP8, VP9 and 
> H.264/SVC in a single extension that would be sufficient.  So why not 
> limit it to that?
>
> ------------------------------------------------------------------------
> Date: Tue, 23 Jul 2013 08:53:45 -0700
> From: [e-mail]
> To: [e-mail]
> CC: [e-mail]; [e-mail]; [e-mail]; 
> [e-mail]
> Subject: Re: [avtext] [rtcweb] Fwd: New Version Notification for 
> draft-fineberg-avtext-temporal-layer-ext-00.txt
>
> I've been thinking about this and given the ease at which RFC5285 
> allows for the specification of a header extension and the complexity 
> introduced by trying to generalize the header extension to support all 
> forms of scalability for all codecs that the generalization might not 
> be the best approach.  I'm not sure what we really gain by trying to 
> capture all this in a single header extension rather than one per that 
> can succinctly explain the fields without the complexity of 
> multiplexing the bits.
>
> Thoughts?
>
> Regards,
> Adam
>
> On 7/19/13 3:44 PM, Stephan Wenger wrote:
>
>     Hi,
>
>     From: Adam Fineberg <[e-mail] <mailto:[e-mail]>>
>     Date: Friday, 19 July, 2013 15:12
>     To: Stephan Wenger <[e-mail] <mailto:[e-mail]>>
>     Cc: Justin Uberti <[e-mail]
>     <mailto:[e-mail]>>, Bernard Aboba
>     <[e-mail] <mailto:[e-mail]>>,
>     "[e-mail] <mailto:[e-mail]>" <[e-mail]
>     <mailto:[e-mail]>>, "[e-mail]
>     <mailto:[e-mail]>" <[e-mail] <mailto:[e-mail]>>
>     Subject: Re: [avtext] [rtcweb] Fwd: New Version Notification for
>     draft-fineberg-avtext-temporal-layer-ext-00.txt
>
>     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.
>
>     StW: Good luck :-)
>
>     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.
>
>     StW: well, if you would copy the layer_id into your header
>     extension (just as you need to do for the simple case), a really
>     smart middle box could use this information just as a decoder uses
>     it, assuming that it intercepted the VPS in the first place.
>      Insofar, I wouldn't rule out the second option on technical
>     grounds.  Whether any of the actual products would bother to do
>     that, ever, is another question.  I think the case ought to be
>     documented, though.  I can help drafting text.
>     While we are at it: doing this right could mean that you need
>     multiple specs.  First, a generic header extension mechanism
>     dedicated to side information required for pruning of RTP packet
>     streams—ideally not only for scalable video, although that is the
>     main customer today.  And second, for each "payload" (at present
>     we are talking about H.264/SVC, H.265v1 (HEVC), H.265v2 (including
>     scalable and 3D extensions, which are not yet finalized), VP8, and
>     VP9 (I know little about the latter), plus Daala, and whatnot) a
>     mapping of the bits available in the generic header extension to
>     the bits in the payload itself (NAL header and VPS in case of
>     H.265, NALU header in SVC, and the fields you mention for VP8).
>
>     Stephan
>
>
>     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
>
>
> -- 
> Regards,
> Adam

-- 
Regards,
Adam