Re: [Cellar] Colour Format proposal

2016-02-03 7:25 GMT+01:00 Dave Rice <[email protected]>:
>
> On Jan 22, 2016, at 5:54 PM, Frank Galligan via Matroska-devel
> <[email protected]> wrote:
>
> On Thu, Jan 14, 2016 at 4:04 AM, Steve Lhomme <[email protected]> wrote:
>>
>> 2016-01-06 23:30 GMT+01:00 Frank Galligan <[email protected]>:
>> >
>> >
>> > On Tue, Jan 5, 2016 at 1:58 PM, Jerome Martinez <[email protected]>
>> > wrote:
>> >>
>> >> Thanks for your detailed proposal.
>> >> It is a lot of items, I am not expert in all domains but I have some
>> >> comments:
>> >
>> > Neither am I, but I figured we might as well start from a proposal and
>> > iterate from there.
>> >
>> >>
>> >> Name: MatrixCoefficients (or Matrix. You don't use "Colour" with
>> >> "Primaries" element, so I would not use it here too)
>> >
>> >  Sounds good to me.
>> >
>> >>
>> >>
>> >>
>> >>
>> >>
>> >> Element Name: BitsPerChannel
>> >> Level:        5
>> >> ID:           [55][A2]
>> >> Mandatory:    ma
>> >> Multiple:     -
>> >> Default:      8
>> >> Type:         u
>> >> Description:  Number of bits per channel. This number may be less for
>> >> specific
>> >>               channels depending on the ColourFormat and
>> >> ChromaSubsampling.
>> >>
>> >>
>> >>
>> >> BitsPerChannel is misleading, used to be the technical count of bits.
>> >> I propose QuantizationBits or ValidBitsPerChannel
>> >> Not mandatory, not default (this value is often unknown)
>> >
>> > When authoring the video, I'm not sure why the software would not know
>> > the
>> > bits per channel. Can you describe a use case where the this is unknown?
>>
>> When remuxing an older file. Either from Matroska source or AVI or other.
>>
>> Now if elements are mandatory with a default value to "unknown" it's fine.
>>
>> > I really think we should make this mandatory and have authoring software
>> > populate the element (or default) vs software thinking this was
>> > non-mandatory and not populating this element because the developer
>> > didn't
>> > think it was needed.
>> >>
>> >>
>> >>
>> >>
>> >> Element Name: ChromaSubsampling
>> >> Level:        5
>> >> ID:           [55][A3]
>> >> Mandatory:    ma
>> >> Multiple:     -
>> >> Default:      0
>> >> Type:         u
>> >> Description:  (0: 4:2:0, 2: 4:2:2, 4: 4:4:4)
>> >>
>> >>
>> >> FFV1, for example, permits "weird" chroma values, more possibilities.
>> >> And the following chroma values were seen at least once in some specs:
>> >> 4:4:4
>> >> 4:2:2
>> >> 4:2:1
>> >> 4:1:1
>> >> 4:2:0
>> >> 4:1:0
>> >> 3:1:1
>> >>
>> >> So having a list is maybe not the solution.
>> >> I like the way it is done in FFV1, except the power of 2 (so 3 can not
>> >> be
>> >> expressed).
>> >> I propose to find a way for describing Chroma subsampling (e.g.
>> >> h_chroma_subsample and v_chroma_subsample; a ratio per plane with any
>> >> number
>> >> of plane, think to alpha channel with a subsampling).
>> >
>> > I'm fine with coming up with a more extensible solution (Micheal asked
>> > for
>> > that as well).
>> >>
>> >>
>> >>
>> >>
>> >>
>> >>
>> >> Element Name: ColourRange
>> >> Level:        5
>> >> ID:           [55][A4]
>> >> Mandatory:    ma
>> >> Multiple:     -
>> >> Default:      1
>> >> Type:         u
>> >> Description:  (0: Unspecified, 1: Defined by
>> >> ColourMatrix/TransferFunction,
>> >>               2: Full range)
>> >>
>> >>
>> >> I don't understand the 1 value.
>> >> in at least AVC and HEVC, range is orthogonal to
>> >> ColourMatrix/TransferFunction.
>> >> I propose 0: unspecified 1: Broadcast range 1: Full range
>> >> and Default:0
>> >
>> > I thought someone mentioned to me before that the range could change
>> > based
>> > on the matrix and transfer function. I'm fine with your proposal.
>> >
>> >>
>> >>
>> >>
>> >> I got requests for having information about "Capture Gamma Equation"
>> >> (or
>> >> "Tone Curve"), e.g. "same as transfer characteristic", Scene Linear,
>> >> S-Log,
>> >> Cine-Log, Log-C...
>> >> I am not an expert of this domain, but looks like it is sometimes
>> >> important.
>> >
>> > Someone who knows more about  this should propose something to this list
>> > to
>> > be included.
>> >
>> >>
>> >> there are also other colour ideas with e.g. EBU Tech 3349.
>> >
>> > If this is important to people, then we could add this as well.
>> >>
>> >>
>> >>
>> >>
>> >>
>> >>
>> >> I can post a link to a formatted document if that would be easier. For
>> >> Matrix, Range, and Primaries, I'm pretty much using values that map
>> >> directly
>> >> to values defined in FFmpeg.
>> >>
>> >>
>> >> I don't like the idea to use the source code of a piece of software for
>> >> lists. Too much subjective, may have historical flaws.
>> >> Lists from FFmpeg are nearly same as the ones in H.26x, I think I
>> >> prefer
>> >> we base our list on their list (I don't think there are copyright
>> >> issues
>> >> with such list) directly.
>> >
>> > I don't know the H.26x list. I started with my own, but then switched to
>> > FFmpeg as they already had an extensive list and assumed they have seen
>> > a
>> > lot of the video already.
>> >
>> > If deciding between H.26x and FFmpeg, my guess is that FFmpeg would be
>> > better as it handles a lot more video than H.26x.
>> >
>> >>
>> >> Or that we have a prefix with the origin of the list (e.g. ARIB
>> >> STD-B67,
>> >> from Japan, is not in ITU/ISO list, a 18 will be used in the future for
>> >> something in ITU/ISO)
>> >
>> > Yeah HLG is relatively new, but has been requested by a few people.
>> >
>> >
>> >
>> > _______________________________________________
>> > Cellar mailing list
>> > [email protected]
>> > https://www.ietf.org/mailman/listinfo/cellar
>> >
>>
>>
>>
>> --
>> Steve Lhomme
>> Matroska association Chairman
>
>
> So I updated my original proposal based on comments from this list.
>
> Changes:
> - Added more common ChromaSubsampling values
> - ColourMatrix renamed to Matrix
> - Added a default value of 0 to BitsPerChannel to signify "unspecified".
> - Added "decoded" to BitsPerChannel note.
> - Added ChromaSittingHorz and ChromaSittingVert elements.
>
>
> In this case, I think the intended term is ‘siting’ rather than ‘sitting’.
>
> - Added Broadcast range to Range element.
> - Removed mandatory flag for elements with unspecified defaults.
> - Updated element IDs.
>
>
> - I kept "Defined by Matrix/TransferFunction" in Range element because there
> are ranges that fall outside of Broadcast and Full depending on the TF. E.g.
> xvYCC (61966-2-4)
> - Does someone want to propose something better for ChromaSubsampling?
> - I know some people expressed that they don't think starting from FFmpeg
> for the TransferFunction is a good idea as they might have got something
> wrong or too subjective. But I just used it as a starting point for a list.
> I can reorder the list however we want. I also don't think following another
> list, so we will be compatible with future additions, will give us what we
> want as that list most likely will be incomplete with something that is
> defined only in a different list. So should we just start with a list,
> re-order it (so we are not explicitly following it), then add what is
> currently missing? Then in the future if someone needs to add something to
> the list it can be brought up here?
>
>
> I think Jerome’s main point was that FFmpeg’s list themselves were based on
> something else, so we should follow the source for a vocabulary authority.
> For instance, see ITU Recommendation H.264 at
> https://www.itu.int/rec/T-REC-H.264-201402-I/en, article E 39577. Pages 387
> (pdf page 409) gives a table of color primaries, page 388 has transfer
> characteristics, and 392 has Matrix coefficients. The information in the ITU
> docs provides a lot more context than FFmpeg source code.
>
> This is what I currently have:
>
> The parent element would be Video [E0].
>
>
> Element Name: Colour
> Level:        4
> ID:           [55][A0]
> Mandatory:    -
> Multiple:     -
> Default:      -
> Type:         m
> Description:  Settings describing the colour format.
>
>
> Element Name: Matrix
> Level:        5
> ID:           [55][A1]
> Mandatory:    -
> Multiple:     -
> Default:      2
> Type:         u
> Description:  Colour Matrix of the video. (0: IEC 61966-2-1 (sRGB), 1:
> BT709,
>              2: Unspecified, 3: Reserved, 4: FCC, 5: BT470BG, 6: SMPTE 170M,
>              7: SMPTE 240M, 8: YCOCG, 9: BT2020 Non-constant Luminance,
>              10: BT2020 Constant Luminance)
>
>
> I suggest referencing a specific ITU document for these values and their
> meaning.
>
> Element Name: BitsPerChannel
> Level:        5
> ID:           [55][A2]
> Mandatory:    -
> Multiple:     -
> Default:      0
> Type:         u
> Description:  Number of decoded bits per channel. This number may be less
> for
>              specific channels depending on the Matrix and
> ChromaSubsampling. A
>              value of 0 is unspecified.
>
>
> Element Name: ChromaSubsampling
> Level:        5
> ID:           [55][A3]
> Mandatory:    -
> Multiple:     -
> Default:      0
> Type:         u
> Description:  (0: Unspecified, 1: 4:4:4, 2: 4:4:0, 3: 4:2:2, 4: 4:2:1, 5:
> 4:2:0,
>              6: 4:1:1, 7: 4:1:0, 8: 3:1:1)
>
> Element Name: ChromaSittingHorz
>
>
> Siting
>
> Level:        5
> ID:           [55][A4]
> Mandatory:    -
> Multiple:     -
> Default:      0
> Type:         u
> Description:  How Chroma is subsampled horizontally. (0: Unspecified, 1:
> Left
>              collocated , 2: Half)
>
> Element Name: ChromaSittingVert
>
>
> Siting
>
> Level:        5
> ID:           [55][A5]
> Mandatory:    -
> Multiple:     -
> Default:      0
> Type:         u
> Description:  How Chroma is subsampled vertically. (0: Unspecified, 1: Top
>              collocated , 2: Half)
>
>
> Element Name: Range
> Level:        5
> ID:           [55][A6]
> Mandatory:    -
> Multiple:     -
> Default:      0
> Type:         u
> Description:  (0: Unspecified, 1: Broadcast range, 2: Full range, 3: Defined
> by
>              Matrix/TransferFunction)
>
>
> I think a description (beyond the list) is needed.
>
> Element Name: TransferFunction
> Level:        5
> ID:           [55][A7]
> Mandatory:    -
> Multiple:     -
> Default:      2
> Type:         u
> Description:  Transfer Function. (0: Reserved, 1: ITU-R BT.709, 2:
> Unspecified,
>              4: Gamma 2.2 curve, 5: Gamma 2.8 curve, 6: SMPTE 170M,
>              7: SMPTE 240M, 8: Linear, 9: Log, 10: Log Sqrt,
>              11: IEC 61966-2-4, 12: ITU-R BT.1361 Extended Colour Gamut,
>              13: IEC 61966-2-1, 14: ITU-R BT.2020 10 bit,
>              15: ITU-R BT.2020 12 bit, 16: SMPTE ST 2084,
>              17: SMPTE ST 428-1 18: ARIB STD-B67 (HLG))
>
>
> Consider referencing ITU document as an external authority for the
> vocabulary.
>
> Element Name: Primaries
> Level:        5
> Mandatory:    -
> Multiple:     -
> ID:           [55][A8]
> Default:      2
> Description:  (0: Reserved, 1: ITU-R BT.709, 2: Unspecified, 4: ITU-R
> BT.470M,
>               5: ITU-R BT.470BG, 6: SMPTE 170M, 7: SMPTE 240M, 8: FILM,
>               9: ITU-R BT.2020, 10: SMPTE ST 428-1)
>
>
> Consider reference to ITU document. Needs a description besides list.
>
> Element Name: MaxCLL
> Level:        5
> ID:           [55][A9]
> Mandatory:    -
> Multiple:     -
> Default:      -
> Type:         u
> Description:  Maximum brightness of a single pixel in candelas per square
>              meter (cd/m²).
>
>
> Element Name: MaxFALL
> Level:        5
> ID:           [55][AA]
>
>
> [55][AA] is already in use as FlagForced.
>
> Mandatory:    -
> Multiple:     -
> Default:      -
> Type:         u
> Description:  Maximum brightness of a single full frame in candelas per
> square
>              meter (cd/m²).
>
>
> Element Name: MasteringMetadata
> Level:        5
> ID:           [55][D0]
> Mandatory:    -
> Multiple:     -
> Default:      -
> Type:         m
> Description:  SMPTE 2086 mastering data.
>
>
> I’m not well experienced in MasteringMetadata but wouldn’t this data need to
> change from scene to scene rather than be stored within the Tracks element
> where the same values would apply to all scenes?
>
> Element Name: PrimaryRChromaticityX
> Level:        6
> ID:           [55][D1]
> Mandatory:    -
> Multiple:     -
> Default:      -
> Type:         f
> Description:  Valid value is in the range 0 <= f <= 1.
>
>
> The description is actually a range. When we initially drafted information
> on expressing ranges in EBML definitions, I ignored float, see
> https://github.com/Matroska-Org/ebml-specification/blob/master/specification.markdown#expression-of-range.
> I can update this definition to include floats and greater-than-or-equal
> values. But the description for this and the following elements should be
> moved to range (suggested formatting as "0-1”). Then these elements need
> actual descriptions.

Rather "0.0-1.0" then.

> Element Name: PrimaryRChromaticityY
> Level:        6
> ID:           [55][D2]
> Mandatory:    -
> Multiple:     -
> Default:      -
> Type:         f
> Description:  Valid value is in the range 0 <= f <= 1.
>
>
> Element Name: PrimaryGChromaticityX
> Level:        6
> ID:           [55][D3]
> Mandatory:    -
> Multiple:     -
> Default:      -
> f
> Description:  Valid value is in the range 0 <= f <= 1.
>
>
> Element Name: PrimaryGChromaticityY
> Level:        6
> ID:           [55][D4]
> Mandatory:    -
> Multiple:     -
> Default:      -
> Type:         f
> Description:  Valid value is in the range 0 <= f <= 1.
>
>
> Element Name: PrimaryBChromaticityX
> Level:        6
> ID:           [55][D5]
> Mandatory:    -
> Multiple:     -
> Default:      -
> f
> Description:  Valid value is in the range 0 <= f <= 1.
>
>
> Element Name: PrimaryBChromaticityY
> Level:        6
> ID:           [55][D6]
> Mandatory:    -
> Multiple:     -
> Default:      -
> Type:         f
> Description:  Valid value is in the range 0 <= f <= 1.
>
>
> Element Name: WhitePointChromaticityX
> Level:        6
> ID:           [55][D7]
> Mandatory:    -
> Multiple:     -
> Default:      -
> Type:         f
> Description:  Valid value is in the range 0 <= f <= 1.
>
>
> Element Name: WhitePointChromaticityY
> Level:        6
> ID:           [55][D8]
> Mandatory:    -
> Multiple:     -
> Default:      -
> Type:         f
> Description:  Valid value is in the range 0 <= f <= 1.
>
>
> Element Name: LuminanceMax
> Level:        6
> ID:           [55][D9]
> Mandatory:    -
> Multiple:     -
> Default:      -
> Type:         f
> Description:  Maximum luminance. Shall be represented in candelas per square
>              meter (cd/m²). Valid value is in the range 0 <= f <= 9999.99
>
>
> Add a Range value and split the Description and Range.
>
> Element Name: LuminanceMin
> Level:        6
> ID:           [55][DA]
> Mandatory:    -
> Multiple:     -
> Default:      -
> Type:         f
> Description:  Minimum luminance. Shall be represented in candelas per square
>              meter (cd/m²). Valid value is in the range 0 <= f <= 999.9999
>
>
> Add a Range value and split the Description and Range.
>
> Best Regards,
> Dave Rice
>
>
> _______________________________________________
> Cellar mailing list
> [email protected]
> https://www.ietf.org/mailman/listinfo/cellar
>



-- 
Steve Lhomme
Matroska association Chairman
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