Re: [AVTCORE] [payload] Some changes to rfc3984bis, SVC, and RCDO payload drafts

[Ye-Kui Wang <[e-mail]>]

The 1000 and 1200 are for Video Coding Layer (VCL) and Network Abstraction Layer (NAL), respectively, and the numbers (magic or not) were from the H.264/AVC spec. The unit of bits is for buffer size, and the unit of bits per second is for bitrate (which are clear from the text), they have to be different (which you call inconsistency). Many times you have to be inconsistent to be correct :-)

The changes are now sent to the (two) lists for review, and we authors welcome any comments, and particularly those that point out concrete further changes that are needed.

BR, YK

-----Original Message-----
From: Allison, Art [mailto:[e-mail]] 
Sent: Wednesday, March 23, 2011 10:37 AM
To: Ye-Kui Wang; [e-mail]; [e-mail]
Subject: RE: [AVTCORE] [payload] Some changes to rfc3984bis, SVC, and RCDO payload drafts

I admit significant ignorance of the technical details.  

My main point, based on decades of standards development experience, was that last minute changes such as these often result in failure to fix the issue precisely and that the due process group should be given time to assure the correct fix has been made.  Rushing can work, but often has a bad outcome. 

As to specifics; I saw that the values of 1000 and 1200 as the correct unit sizes for NAL stream overhead (in some cases).  In one place these are asserted to be bits (no rate units) as a multiplier and in another place these are described as bits-per-second. These are clearly different usages. Perhaps both usages are correct - I do not know - but it appeared to be inconsistent.  (And this type of inconsistency is exactly the kind of thing that I have seen happen when last minute patches are made to a standard.)

By magic number, I meant was it correct that these values have two different uses, perhaps due to their fundamental nature.

I do not assert anything is wrong, I suggest that unless there is a vital need to push this out fast, that the draft be referred back to the drafting group. Maybe all those folks have had time to carefully consider and respond before the deadline...and this is specious.

I believe that you <process managers> can make better decisions when more information is provided. I commented to so assist.
 

Art Allison
Senior Director Advanced Engineering, Science and Technology
National Association of Broadcasters
1771 N Street NW
Washington, DC 20036
Phone  [phone] 
Fax  [phone]
www.nab.org
Advocacy  Education  Innovation


-----Original Message-----
From: Ye-Kui Wang [mailto:[e-mail]] 
Sent: Wednesday, March 23, 2011 4:54 AM
To: Allison, Art; [e-mail]; [e-mail]
Subject: RE: [AVTCORE] [payload] Some changes to rfc3984bis, SVC, and RCDO payload drafts

The units of the values of 1000 and 1200 are clearly specified. Where is not clear, could you clarify? 

What is "that" in "Is that a coincidence, error or a magic number effect?"?

If you read carefully the previous two emails on this subject I sent out, you would have noticed that the factor you mentioned, which is not only for High profile, but for many other profiles, and the factor can be different for different profiles, has been addressed. Please let us know if you found any place that is not well addressed.

Finally, what is "this" in "I think this should be sent back for correction..."? I guess you meant for the entire draft. But if you don't point out the place that needs to be corrected, what we can do?

BR, YK

-----Original Message-----
From: [e-mail] [mailto:[e-mail]] On Behalf Of Allison, Art
Sent: Monday, March 21, 2011 4:47 PM
To: [e-mail]; [e-mail]
Subject: Re: [AVTCORE] [payload] Some changes to rfc3984bis, SVC, and RCDO payload drafts

It has been by experience that discovery of a significant technical issue that is 'patched' in a draft standard in a hurry to get it published is always risky and often results in an internal inconsistency.

Seems to me that is a few weeks delay for the formulating body to review is prudent - even if such change can be done. 

Just reading for consistency, as I am no expert in the codec; I see the 1000 and 1200 values expressed as pure multipliers and bits per second? Is that a coincidence, error or a magic number effect? And the High Profile factor of 1.25 (to these values) that is in the AVC standard seems to be relevant, but is not being discussed. Is that covered elsewhere in a clear fashion and independent?

I think this should be sent back for correction...and thanks go to the sharp eye who caught the discrepancy.

Art

Art Allison
Senior Director Advanced Engineering, Science and Technology
National Association of Broadcasters
1771 N Street NW
Washington, DC 20036
Phone  [phone] 
Fax  [phone]
www.nab.org
Advocacy  Education  Innovation


-----Original Message-----
From: [e-mail] [mailto:[e-mail]] On Behalf Of Charles Eckel (eckelcu)
Sent: Monday, March 21, 2011 1:52 PM
To: Ye-Kui Wang; [e-mail]; [e-mail]
Subject: Re: [AVTCORE] [payload] Some changes to rfc3984bis, SVC,and RCDO payload drafts

Hi YK,

Thank you for providing this clear description of the proposed changes.
The changes look good to me.

Cheers,
Charles

> -----Original Message-----
> From: [e-mail] [mailto:[e-mail]] On
Behalf Of Ye-Kui Wang
> Sent: Monday, March 21, 2011 1:11 AM
> To: [e-mail]; [e-mail]
> Subject: Re: [payload] Some changes to rfc3984bis, SVC,and RCDO
payload drafts
> 
> Further discussions with the same group of persons led to a decision
to stay with the unscaled units
> for max-br and max-cpb, thus fewer changes are needed to the three
payload formats listed in the title
> and H.241. With this, the changes needed are listed below (the
originally suggested changes are
> dropped from this email). This time I have highlighted the changes,
and I have also described the
> nature the changes below. Hope these may help understand better what
have been changed, and can lead
> to a quicker decision by the group, including WG chairs, and our AD.
> 
> 
> 
> BR, YK
> 
> 
> 
> ------------------------------------Start of suggested changes
--------------------------------------
> 
> 
> 
> Section 8.1:
> 
> OLD:
> 
>       profile-level-id:
>          A base16 [7] (hexadecimal) representation of the following
>          three bytes in the sequence parameter set NAL unit is
specified
>          in [1]: 1) profile_idc, 2) a byte herein referred to as
>          profile-iop, composed of the values of constraint_set0_flag,
>          constraint_set1_flag,constraint_set2_flag,
>          constraint_set3_flag, and reserved_zero_4bits in bit-
>          significance order, starting from the most-significant bit,
and
>          3) level_idc.  Note that reserved_zero_4bits is required to
be
>          equal to 0 in [1], but other values for it may be specified
in
>          the future by ITU-T or ISO/IEC.
> 
>  NEW: (note that the change here is purely editorial)
> 
>       profile-level-id:
> 
>          A base16 [7] (hexadecimal) representation of the following
> 
>          three bytes in the sequence parameter set NAL unit is
specified
> 
>          in [1]: 1) profile_idc, 2) a byte herein referred to as
> 
>          profile-iop, composed of the values of constraint_set0_flag,
> 
>          constraint_set1_flag,constraint_set2_flag,
> 
>          constraint_set3_flag, constraint_set4_flag,
constraint_set5_flag,
> 
>  and reserved_zero_2bits in bit-significance order, starting from the
most-significant bit, and
> 
>          3) level_idc.  Note that reserved_zero_2bits is required to
be
> 
>          equal to 0 in [1], but other values for it may be specified
in
> 
>          the future by ITU-T or ISO/IEC.
> 
> 
> 
> OLD:
> 
>          For example, in the table above, profile_idc equal to 58
>          (Extended) with profile-iop equal to 11xx0000 indicates the
>          same sub-profile corresponding to profile_idc equal to 42
>          (Baseline) with profile-iop equal to x1xx0000.  Note that
other
>          combinations of profile_idc and profile-iop (not listed in
>          Table 5) may represent a sub-profile equivalent to the common
>          subset of coding tools for more than one profile.  Note also
>          that a decoder conforming to a certain profile may be able to
>          decode bitstreams conforming to other profiles.  For example,
a
>          decoder conforming to the High 4:4:4 profile, at a certain
>          level, must be able to decode bitstreams conforming to the
>          Constrained Baseline, Main, High, High 10, or High 4:2:2
>          profile at the same or a lower level.
> 
>  NEW: (note that the change here is purely editorial)
> 
>          For example, in the table above, profile_idc equal to 58
> 
>          (Extended) with profile-iop equal to 11xx0000 indicates the
> 
>          same sub-profile corresponding to profile_idc equal to 42
> 
>          (Baseline) with profile-iop equal to x1xx0000.  Note that
other
> 
>          combinations of profile_idc and profile-iop (not listed in
> 
>          Table 5) may represent a sub-profile equivalent to the common
> 
>          subset of coding tools for more than one profile.  Note also
> 
>          that a decoder conforming to a certain profile may be able to
> 
>          decode bitstreams conforming to other profiles.
> 
> 
> 
> OLD:
> 
>          If the profile-level-id parameter is used for capability
>          exchange or session setup procedure, it indicates the subset
of
>          coding tools, which is equal to the default sub-profile, that
>          the codec supports for both receiving and sending.
> 
>  NEW: (note that the change here is purely editorial)
> 
>          If the profile-level-id parameter is used for capability
> 
>          exchange or session setup, it indicates the subset of
> 
>          coding tools, which is equal to the default sub-profile, that
> 
>          the codec supports for both receiving and sending.
> 
> 
> 
> OLD:
> 
>       max-cpb: The value of max-cpb is an integer indicating the
maximum
> 
>          coded picture buffer size in units of 1000 bits for the VCL
HRD
> 
>          parameters (see A.3.1, item i of [1]) and in units of 1200
bits
> 
>          for the NAL HRD parameters (see A.3.1, item j of [1]).
> 
> NEW: (note that the change here is purely editorial)
> 
>       max-cpb: The value of max-cpb is an integer indicating the
maximum
> 
>          coded picture buffer size in units of 1000 bits for the VCL
HRD
> 
>          parameters and in units of 1200 bits
> 
>          for the NAL HRD parameters.
> 
> 
> 
> OLD:
> 
>       max-dpb: The value of max-dpb is an integer indicating the
maximum
> 
>          decoded picture buffer size in units of 1024 bytes.  The max-
> 
>          dpb parameter signals that the receiver has more memory than
> 
>          the minimum amount of decoded picture buffer memory required
by
> 
>          the signaled highest level conveyed in the value of the
> 
>          profile-level-id parameter or the max-recv-level parameter.
> 
>          When max-dpb is signaled, the receiver MUST be able to decode
> 
>          NAL unit streams that conform to the signaled highest level,
> 
>          with the exception that the MaxDPB value in Table A-1 of [1]
> 
>          for the signaled highest level is replaced with the value of
> 
>          max-dpb.  Consequently, a receiver that signals max-dpb MUST
be
> 
>          capable of storing the following number of decoded frames,
> 
>          complementary field pairs, and non-paired fields in its
decoded
> 
>          picture buffer:
> 
> 
> 
>             Min(1024 * max-dpb / ( PicWidthInMbs * FrameHeightInMbs *
> 
>             256 * ChromaFormatFactor ), 16)
> 
> 
> 
>          PicWidthInMbs, FrameHeightInMbs, and ChromaFormatFactor are
> 
>          defined in [1].
> 
> 
> 
>          The value of max-dpb MUST be greater than or equal to the
value
> 
>          of MaxDPB given in Table A-1 of [1] for the highest level.
> 
>          Senders MAY use this knowledge to construct coded video
streams
> 
>          with improved compression.
> 
> NEW: (When this change can be considered as editorial can be
discussed, but the nature of this change
> as follows. On the other hand, if not changed, then the semantics of
max-dpb is simply equivalent to
> unspecified, as MaxDPB and ChromaFormatFactor are not found in the
latest H.264 spec any more. Note
> that compared to RFC 3984, the bits on the wire do not change.)
> 
>       max-dpb: The value of max-dpb is an integer indicating the
maximum
> 
>          decoded picture buffer size in units of 8/3 macroblocks.  The
max-
> 
>          dpb parameter signals that the receiver has more memory than
> 
>          the minimum amount of decoded picture buffer memory required
by
> 
>          the signaled highest level conveyed in the value of the
> 
>          profile-level-id parameter or the max-recv-level parameter.
> 
>          When max-dpb is signaled, the receiver MUST be able to decode
> 
>          NAL unit streams that conform to the signaled highest level,
> 
>          with the exception that the MaxDpbMbs value in Table A-1 of
[1]
> 
>          for the signaled highest level is replaced with the value of
> 
>          max-dpb * 3 / 8.  Consequently, a receiver that signals
max-dpb MUST be
> 
>          capable of storing the following number of decoded frames,
> 
>          complementary field pairs, and non-paired fields in its
decoded
> 
>          picture buffer:
> 
> 
> 
>             Min(max-dpb * 3 / 8 / ( PicWidthInMbs * FrameHeightInMbs),
16)
> 
> 
> 
>          Wherein PicWidthInMbs and FrameHeightInMbs are defined in
[1].
> 
> 
> 
>          The value of max-dpb MUST be greater than or equal to the
value
> 
>          of MaxDpbMbs * 3 / 8, wherein the value of MaxDpbMbs is given
in
> 
> Table A-1 of [1] for the highest level.
> 
>          Senders MAY use this knowledge to construct coded video
streams
> 
>          with improved compression.
> 
> 
> 
> OLD:
> 
>       max-br: The value of max-br is an integer indicating the maximum
>          video bitrate in units of 1000 bits per second for the VCL
HRD
>          parameters (see A.3.1, item i of [1]) and in units of 1200
bits
>          per second for the NAL HRD parameters (see A.3.1, item j of
>          [1]).
>          ...
> 
>          For example, if a receiver signals capability for Level 1.2
> 
>          with max-br equal to 1550, this indicates a maximum video
> 
>          bitrate of 1550 kbits/sec for VCL HRD parameters, a maximum
> 
>          video bitrate of 1860 kbits/sec for NAL HRD parameters, and a
> 
>          CPB size of 4036458 bits (1550000 / 384000 * 1000 * 1000).
> 
> NEW: (note that the change here is purely editorial)
> 
>       max-br: The value of max-br is an integer indicating the maximum
>          video bitrate in units of 1000 bits per second for the VCL
HRD
>          parameters and in units of 1200 bits
>          per second for the NAL HRD parameters.
>          ...
> 
>          For example, if a receiver signals capability for Main
profile Level 1.2
> 
>          with max-br equal to 1550, this indicates a maximum video
> 
>          bitrate of 1550 kbits/sec for VCL HRD parameters, a maximum
> 
>          video bitrate of 1860 kbits/sec for NAL HRD parameters, and a
> 
>          CPB size of 4036458 bits (1550000 / 384000 * 1000 * 1000).
> 
> 
> 
> ------------------------------------End of suggested changes
--------------------------------------
> 
> 
> 
> From: [e-mail] [mailto:[e-mail]] On Behalf Of
Ye-Kui Wang
> Sent: Sunday, March 20, 2011 4:21 AM
> To: [e-mail]; [e-mail]
> Subject: [AVTCORE] Some changes to rfc3984bis, SVC, and RCDO payload
drafts
> 
> 
> 
> Folks,
> 
> 
> 
> The three H.264/AVC related payload formats, namely,
draft-ietf-avt-rtp-rfc3984bis-12, draft-ietf-avt-
> rtp-svc-27, and draft-ietf-avt-rtp-h264-rcdo-08, are all at the AUTH48
stage.
> 
> 
> 
> The RFC-Editor has found the following problem: In
draft-ietf-avt-rtp-rfc3984bis-12, the definition of
> the max-dpb media parameter refers to the MaxDPB that was defined the
first version of the H.264/AVC
> spec, but not any more in the latest version (the 2010 version). The
parameter in the latest H.264/AVC
> version corresponding to MaxDPB is MaxDpbMbs, and the unit of the new
parameter (i.e., macroblocks) is
> different from the original one (i.e. 1024 bytes).
> 
> 
> 
> The problem applies also to the SVC payload format, the RCDO payload
format, and H.241.
> 
> 
> 
> A solution has been found and agreed, involving rfc3984bis authors and
some key people related to
> H.264/AVC (e.g., Gary Sullivan and Heiko Schwarz) and H.241 (e.g.,
Stephen Botzko and Patrick Luthi).
> Furthermore, we have found that there are also a couple of places that
need fixes due to similar
> changes from the initial version of H.264/AVC to the latest version.
> 
> 
> 
> Per Roni's suggestion, I am sending in below the changes to
draft-ietf-avt-rtp-rfc3984bis-12 for
> review by the Payload and AVTcore WGs. It seems that exactly the same
changes are needed to draft-
> ietf-avt-rtp-h264-rcdo-08 (co-authors of this draft may confirm), and
similar but slightly different
> changes are needed to draft-ietf-avt-rtp-svc-27.
> 
> 
> 
> Since the drafts are at the AUTH48 stage, please provide comments by
Monday, March 21, if any. Many
> thanks!
> 
> 
> 
> BR, YK
> 
> 

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