[Matroska-devel] [Cellar] Colour Format proposal

Frank Galligan via Matroska-devel matroska-devel at lists.matroska.org
Mon Feb 8 23:23:05 CET 2016


On Mon, Feb 8, 2016 at 9:15 AM, Jerome Martinez <jerome at mediaarea.net>
wrote:

> Sorry for the late answer, here are my comments:
>
> On 22/01/2016 23:54, Frank Galligan wrote:
>
> [...]
>
> - 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?
>
>
> That was me.
> I am OK with that as long as we are clear that we don't follow FFmpeg list.
>
OK, I changed the text to see ISO/IEC 23001-8 document, which has the same
values as FFmpeg as well as the 264 ITU doc.

>
>
> [...]
>
> 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)
>
>
>
> If we don't follow FFmpeg list, what is the purpose of  value 3 and why
> unspecified is 2 rather than 0?
>
That is the way it is specified in ISO/IEC 23001-8 and 264 ITU doc.

Using FFmpeg list (which is based on MPEG list, with same oddities) is not
> bad, and I am not against it, just wondering if it is good to take the same
> oddities rather than a clean list without oddities.
>
I don't think there are any oddities. Looks like FFmpeg's list matches
exactly to  ISO/IEC 23001-8 and 264 ITU doc, except for #10 in Primaries
and #16 and #17 in Transfer function, which were added here [1]. Also #18
in Transfer, which is HLG [2].

I think this is the whole issue. Do we follow some list (standardized or
not)? What if the list goes stale? What if the list doesn't include
algorithms from different lists (E.g. maybe HLG)?



> Does anyone plan to transfer from DPX? If yes, we may need to add now
> missing elements in the list (e.g. "Printing density") but I am not expert
> enough for know which one is worth it.
>
>
>
>
> [...]
>
>
> 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)
>
>
> I am more, as some other people, for something more generic, e.g.
> ChromaSubsamplingHorz and ChromaSubsamplingVert, with a value of the
> subsampling (0 unspecified and default). I am afraid that someone crazy
> used e.g. a vertical subsampling of 4 (which can not be defined by X:X:X
> values), it is possible (and I have a file like that if I remember well)
> with FFV1.
>
>
>
>
> [...]
>
> 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))
>
>
> 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)
>
>
> Same remark as with Matrix.
>
>
> [...]
>
>
>
[1]
https://github.com/FFmpeg/FFmpeg/commit/c3cd6dd106b1381933e2f24898eeec0d8aa17746
[2] http://www.arib.or.jp/english/html/overview/std-b67.html
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