[Matroska-devel] [Cellar] Colour Format proposal

Frank Galligan frankgalligan at gmail.com
Wed Jan 6 22:46:44 CET 2016


On Tue, Jan 5, 2016 at 1:33 PM, Michael Bradshaw <mjbshaw at google.com> wrote:

> On Tue, Jan 5, 2016 at 1:12 PM, Frank Galligan <frankgalligan at gmail.com>
> wrote:
>>
>> 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)
>>
>>
> FFmpeg supports more subsampling schemes like 4:1:0, 4:1:1, and 4:4:0.
>
Yes all the rest should have been included. Looking over some of the other
messages we could change too:
Element Name: ChromaSubsampling
Level:        5
ID:           [55][A3]
Mandatory:    ma
Multiple:     -
Default:      0
Type:         u
Description:  (0: Unspecified, 1: 4:4:4, 2: 4:4:0, 2: 4:2:2, 3: 4:2:1, 4:
4:2:0, 5: 4:1:1, 6: 4:1:0, 7: 3:1:1)



>
> Additionally, these formats assume 3-channel pixel formats. What about an
> alpha-channel or other color spaces with > 3 channels?
>
We could add another element to signify an alpha channel. Are there any
common formats where the alpha is subsampled?

>
> Perhaps a per-channel master element could exist that contains subsampling
> and bit information?
>
This seems like a little overkill to me, but if other people want to do it
this way, then it is fine with me.
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