Add MPEG_sampler_ycbcr

extensions/2.0/Vendor/MPEG_sampler_YCbCr/README.md

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+# MPEG_sampler_YCbCr 
+
+## Contributors
+
+* ISO/IEC SC29 WG3 (MPEG Systems) - Scene Description Breakout Group
+* Contacts
+  * Thomas Stockhammer (MPEG-I Scene Description BoG Chair, [email protected])
+
+## Status
+
+Based on [ISO/IEC FDIS 23090-14/AMD 1](https://www.iso.org/standard/84769.html)
+
+## Dependencies
+
+Written against the glTF 2.0 specification and ISO/IEC FDIS 23090-14.
+
+## Overview
+
+A sampler-level extension is described to sample a video texture natively in parallel processing devices such as GPUs. This extension shall be present if the format of the referencing video texture is set to YCbCr. 
+A texture object in the textures array may use a sampler with the “MPEG_sampler_YCbCr” sampler extension to provide information to the Presentation Engine to sample the video texture when the texture format is a chroma format such as YCbCr.
+
+The YCbCr sampler extension is identified by `MPEG_sampler_YCbCr`. 
+
+## glTF Schema Updates
+
+The format of the `MPEG_MPEG_sampler_YCbCr` glTF extension is as follows:
+
+
+**`MPEG_MPEG_sampler_YCbCr` Properties**
+
+|   |Type|Description|Required|
+|---|---|---|---|
+|**ycbcrModel**|`integer`|Describes the color matrix for conversion between color models. The supported formats are defined by the VkSamplerYcbcrModelConversion enumeration in clause 13.1 of Vulkan 1.3.|Yes|
+|**ycbcrRange**|[`integer`]|Describes whether the encoded values have headroom and foot room, or whether the encoding uses the full numerical range.|Yes|
+|**chromaFilter**|`integer` `[1-*]`|Describes the filter for chroma reconstruction.|Yes|
+|**components**|`integer` `[1-*]`|Applies a swizzle to the [r,g,b,a] components based on VkComponentSwizzle enums prior to range expansion and color model conversion. If present, the array shall include 4 values, each of which corresponding to the r,g,b,a components in order of appearance. |No|
+|**xChromnaOffset**|[`integer`] |Describes the sample location associated with downsampled chroma components in the x dimension. xChromaOffset has no effect for formats in which chroma components are not downsampled horizontally.|No|
+|**yChromnaOffset**|[`integer`] |Describes the sample location associated with downsampled chroma components in the y dimension. yChromaOffset has no effect for formats in which the chroma components are not downsampled vertically.|No|
+|**extensions**|`object`|JSON object with extension-specific objects.|No|
+|**extras**|[`any`](#reference-any)|Application-specific data.|No|
+
+Additional properties are allowed.
+
+* **JSON schema**: [MPEG_MPEG_sampler_YCbCr.schema.json](/Extensions/MPEG_MPEG_sampler_YCbCr/schema/MPEG_MPEG_sampler_YCbCr.schema.json)
+
+### MPEG_MPEG_sampler_YCbCr.ycbcrModel
+
+Describes the color matrix for conversion between color models. The supported formats are defined by the VkSamplerYcbcrModelConversion enumeration in clause 13.1 of Vulkan 1.3.
+
+* **Type**: `integer`
+* **Required**: Yes
+* **Minimum**: ` >= 0`
+
+### MPEG_MPEG_sampler_YCbCr.ycbcrRange
+
+Describes whether the encoded values have headroom and foot room, or whether the encoding uses the full numerical range.
+
+* **Type**: `integer`
+* **Required**: No
+* **Minimum**: ` >= 0`
+
+### MPEG_MPEG_sampler_YCbCr.chromaFilter
+
+Describes the filter for chroma reconstruction.
+
+* **Type**: `integer`
+* **Required**: No
+* **Minimum**: ` >= 0`
+
+
+### MPEG_MPEG_sampler_YCbCr.components
+
+Applies a swizzle to the [r,g,b,a] components based on VkComponentSwizzle enums prior to range expansion and color model conversion. If present, the array shall include 4 values, each of which corresponding to the r,g,b,a components in order of appearance. 
+
+* **Type**: `integer`
+* **Required**: No
+* **Minimum**: ` >= 0`
+
+
+### MPEG_MPEG_sampler_YCbCr.xChromaOffset
+
+Describes the sample location associated with downsampled chroma components in the x dimension. xChromaOffset has no effect for formats in which chroma components are not downsampled horizontally.
+
+* **Type**: `integer`
+* **Required**: No
+* **Minimum**: ` >= 0`
+
+
+### MPEG_MPEG_sampler_YCbCr.yChromaOffset
+
+Describes the sample location associated with downsampled chroma components in the y dimension. yChromaOffset has no effect for formats in which the chroma components are not downsampled vertically.
+
+* **Type**: `integer`
+* **Required**: No
+* **Minimum**: ` >= 0`

extensions/2.0/Vendor/MPEG_sampler_YCbCr/schema/MPEG_sampler_YCbCr.schema.json

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+{
+    "$schema" : "http://json-schema.org/draft-07/schema",
+    "title" : "",
+    "type" : "object",
+    "description": "defines an extension to support YCbCr formatted textures.",    
+    "properties" : {
+        "ycbcrModel": {
+            "type": "integer",
+            "description": "color matrix conversion model",
+            "gltf_detailedDescription": "color matrix conversion model",
+            "minimum": 0            
+        },
+        "ycbcrRange": {
+            "type": "integer",
+            "description": "range used for the color encoding",
+            "gltf_detailedDescription": "range used for the color encoding",
+            "minimum": 0            
+        },
+        "chromaFilter": {
+            "type": "integer",
+            "description": "filter for chroma reconstruction",
+            "gltf_detailedDescription": "filter for chroma reconstruction",
+            "minimum": 0            
+        },        
+        "components": {
+            "type": "array",
+            "description": "swizzle applied to the RGBA components prior to range expansion and color model conversion",
+            "items": {
+                "type": "integer"
+            },
+            "minItems": 1            
+        },
+        "xChromaOffset": {
+            "type": "integer",
+            "description": "sample location associated with downsampled chroma in the x dimension",
+            "gltf_detailedDescription": "sample location associated with downsampled chroma in the x dimension",
+            "minimum": 0            
+        },
+        "yChromaOffset": {
+            "type": "integer",
+            "description": "sample location associated with downsampled chroma in the y dimension",
+            "gltf_detailedDescription": "sample location associated with downsampled chroma in the y dimension",
+            "minimum": 0            
+        }
+    }
+}