| Name |
| |
| APPLE_rgb_422 |
| |
| Name Strings |
| |
| GL_APPLE_rgb_422 |
| |
| Contact |
| |
| Ken Dyke, Apple (kdyke 'at' apple.com) |
| |
| Status |
| |
| Shipping as of August 28, 2009 (Mac OS X v10.6) |
| |
| Version |
| |
| Last Modified Date: June 26, 2013 |
| Version: 1.5 |
| |
| Number |
| |
| OpenGL Extension #373 |
| OpenGL ES Extension #76 |
| |
| Dependencies |
| |
| OpenGL 2.0 or ARB_fragment_program is required when the GL is OpenGL. |
| OpenGL ES 2.0 is required when the GL is OpenGL ES. |
| Written against OpenGL 2.0. |
| There are interactions with OpenGL ES 2.0 and 3.0. |
| |
| Overview |
| |
| A common storage format for video data is 8-bit 422, with every four |
| bytes encoding two pixels. Within the four bytes there are two |
| luminance samples, and two chrominance samples that are shared between |
| both pixels. |
| |
| There is a previous extension, namely GL_APPLE_ycbcr_422 that provided |
| transparent support for this kind of data. However, that extension |
| left the exact conversion from Y'CbCr to RGB undefined. In reality, |
| it really had always been based on the ITU-R BT.601 standard, which |
| meant it was not particularly useful for dealing with high definition |
| video data, which is encoded using the Rec. 709 standard. |
| |
| In some cases the original extension was implemented via fixed function |
| hardware, but on more modern graphics processors this is done via |
| a combination of 422 sampling formats and fragment shader instructions. |
| |
| This extension essentially exposes a "raw" 422 texture format that |
| allows developers to access the raw pre-converted Y'CbCr components |
| so that they have full control over the colorspace conversion. |
| |
| In order to avoid defining entirely new color channels within GL, |
| the Y, Cb and Cr color channels within the 422 data are mapped into |
| the existing green, blue and red color channels, respectively. Developers |
| must write their own fragment shader/program to perform the desired |
| color space transformation. |
| |
| Note: Because of the use of the packed UNSIGNED_SHORT_8_8[_REV] types, the |
| correct type to use based on the layout of the data in memory (Cb Y Cr Y |
| versus Y Cb Y Cr) will necessarily be sensitive to host endianness. |
| |
| This extension differs from the EXT_422_pixels extension in a couple of |
| ways. First, this extension defines only a single new format, while |
| relying on two new type arguments to differentiate between the two |
| component orderings. Second, this extension provides no defined method |
| of filtering the chroma values between adjacent pixels. And lastly, |
| the color channel assignments are slightly different, essentially to |
| match more closely the rough meanings of the Y, Cb and Cr values in |
| 422 video data. |
| |
| New Procedures and Functions |
| |
| None |
| |
| New Tokens |
| |
| Accepted by the <format> parameter of DrawPixels, ReadPixels, TexImage1D, |
| TexImage2D, GetTexImage, TexImage3D, TexSubImage1D, TexSubImage2D, |
| TexSubImage3D, GetHistogram, GetMinmax, ConvolutionFilter1D, |
| ConvolutionFilter2D, GetConvolutionFilter, SeparableFilter2D, |
| GetSeparableFilter, ColorTable, and GetColorTable: |
| |
| RGB_422_APPLE 0x8A1F |
| |
| Accepted by the <internalformat> parameter of TexImage2D, TexImage3D, |
| CopyTexImage2D, TexStorage2D, and TexStorage3D: |
| |
| RGB_RAW_422_APPLE 0x8A51 |
| |
| Accepted by the <type> parameter of DrawPixels, ReadPixels, TexImage1D, |
| TexImage2D, GetTexImage, TexImage3D, TexSubImage1D, TexSubImage2D, |
| TexSubImage3D, GetHistogram, GetMinmax, ConvolutionFilter1D, |
| ConvolutionFilter2D, GetConvolutionFilter, SeparableFilter2D, |
| GetSeparableFilter, ColorTable, and GetColorTable: |
| |
| UNSIGNED_SHORT_8_8_APPLE 0x85BA |
| UNSIGNED_SHORT_8_8_REV_APPLE 0x85BB |
| |
| Additions to Chapter 3 of the OpenGL 2.0 Specification (Rasterization) |
| |
| Two entries are added to Table 3.5 (DrawPixels and ReadPixels type |
| parameter values and the corresponding OpenGL data types): |
| |
| type Parameter Corresponding Special |
| Token Name GL Data Type Interpretation |
| -------------- ------------- -------------- |
| UNSIGNED_SHORT_8_8_APPLE ushort Yes |
| UNSIGNED_SHORT_8_8_REV_APPLE ushort Yes |
| |
| |
| One entry is added to Table 3.6 (DrawPixels and ReadPixels formats): |
| |
| Format Name Element Meaning and Order Target Buffer |
| ----------- ------------------------- ------------ |
| RGB_422_APPLE G,B even column pixels Color |
| G,R odd column pixels |
| |
| |
| Two entries are added to Table 3.8 (Packed pixel formats): |
| |
| type Parameter GL Data Number of Matching |
| Token Name Type Components Pixel Formats |
| -------------- ------- ---------- ------------- |
| UNSIGNED_SHORT_8_8_APPLE ushort 2 RGB_422_APPLE |
| UNSIGNED_SHORT_8_8_REV_APPLE ushort 2 RGB_422_APPLE |
| |
| |
| Two entries are added to Table 3.10 (UNSIGNED SHORT formats): |
| |
| UNSIGNED_SHORT_8_8_APPLE: |
| |
| 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0 |
| +-------------------------------+-------------------------------+ |
| | 1st | 2nd | |
| +-------------------------------+-------------------------------+ |
| |
| |
| UNSIGNED_SHORT_8_8_REV_APPLE: |
| |
| 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0 |
| +-------------------------------+-------------------------------+ |
| | 2nd | 1st | |
| +-------------------------------+-------------------------------+ |
| |
| |
| One entry is added to Table 3.12 (Packed pixel field assignments): |
| |
| First Second Third Fourth |
| Format Element Element Element Element |
| ------ ------- ------- ------- ------- |
| RGB_422_APPLE green blue/red |
| |
| Add the following second paragraph to the end of the section entitled |
| "Conversion to RGB": |
| |
| If the format is RGB_422_APPLE, pixels are unpacked in pairs. For |
| even column pixels, the green and blue components are unpacked from the |
| even column pixel, and the red component is taken from the following odd |
| column pixel. For odd column pixels, the green and red components are |
| unpacked from the odd column pixel, and the blue component is unpacked |
| from the previous even column pixel. The row length must be even or |
| INVALID_OPERATION is generated. |
| |
| Additions to the GLX Specification |
| |
| None |
| |
| GLX Protocol |
| |
| None |
| |
| Dependencies on OpenGL ES 2.0 |
| |
| If the GL is OpenGL ES, RGB_422_APPLE format textures may not be used |
| in conjunction with mipmapping or repeat wrap modes. Add to the list |
| of conditions in section 3.8.2 under which (0,0,0,1) will be returned |
| from a sampler: |
| |
| - A two-dimensional sampler is called, the corresponding texture image |
| has format RGB_422_APPLE, and either the texture wrap mode is not |
| CLAMP_TO_EDGE, or the minification filter is neither NEAREST nor |
| LINEAR. |
| |
| Also, RGB_422_APPLE format textures may not be used as cube maps. The |
| following error condition is introduced: |
| |
| - INVALID_OPERATION is generated by TexImage2D, TexSubImage2D, and |
| CopyTexImage2D if <format> is RGB_422_APPLE and <target> is |
| TEXTURE_CUBE_MAP_*. |
| |
| Changes to OpenGL 2.0's Table 3.5 above are made to OpenGL ES 2.0's Table |
| 3.2 (TexImage2D and ReadPixels <type> parameter values and the |
| corresponding GL data types.) Changes to OpenGL 2.0's Table 3.6 above are |
| made to OpenGL ES 2.0's Table 3.3 (TexImage2D and ReadPixels formats). |
| Changes to OpenGL 2.0's Table 3.8 above are made to OpenGL ES 2.0's Table |
| 3.5 (Packed pixel formats). Changes to OpenGL 2.0's Table 3.10 above are |
| made to OpenGL ES 2.0's Table 3.6 (UNSIGNED_SHORT formats). Changes to |
| OpenGL 2.0's Table 3.13 are made to OpenGL ES 2.0's Table 3.7 (Packed |
| pixel field assignments). |
| |
| Mentions of DrawPixels, ReadPixels, TexImage1D, TexImage3D, GetTexImage, |
| TexSubImage1D, TexSubImage3D, GetHistogram, GetMinmax, ConvolutionFilter1D, |
| ConvolutionFilter2D, GetConvolutionFilter, SeparableFilter2D, |
| GetSeparableFilter, ColorTable, and GetColorTable in this extension |
| specification can be ignored for OpenGL ES. |
| |
| Mentions of TexStorage* and RGB_RAW_422_APPLE can be ignored unless EXT_texture_storage is present. |
| |
| Dependencies on OpenGL ES 3.0 |
| |
| All of the same dependencies for OpenGL ES 2.0 also exist for OpenGL ES 3.0 |
| except that TexImage3D and TexSubImage3D do apply here. |
| |
| Changes to OpenGL 2.0's Table 3.5 above are made to OpenGL ES 3.0's Table |
| 3.4 (Pixel data <type> parameter values and the corresponding GL data |
| types.) Changes to OpenGL 2.0's Table 3.6 above are made to OpenGL ES |
| 3.0's Table 3.5 (Pixel data formats). Changes to OpenGL 2.0's Table 3.8 |
| above are made to OpenGL ES 3.0's Table 3.6 (Packed pixel formats). |
| Changes to OpenGL 2.0's Table 3.10 above are made to OpenGL ES 3.0's Table |
| 3.7 (UNSIGNED_SHORT formats). Changes to OpenGL 2.0's Table 3.13 are made |
| to OpenGL ES 3.0's Table 3.10 (Packed pixel field assignments). |
| |
| When the GL is OpenGL ES 3.0, the following table entries are added to Table |
| 3.2: |
| |
| Format Type External Bytes per Pixel Internal Format |
| ------------- ---------------------------- ------------------------ ----------------- |
| RGB_422_APPLE UNSIGNED_SHORT_8_8_APPLE 2 RGB_RAW_422_APPLE |
| RGB_422_APPLE UNSIGNED_SHORT_8_8_REV_APPLE 2 RGB_RAW_422_APPLE |
| |
| When the GL is OpenGL ES 3.0, RGB_422_APPLE is also added to the Texture-only |
| color formats list in the Required Texture Formats subsection of section |
| 3.8.3. |
| |
| If the GL is not OpenGL ES 3.0 and the EXT_texture_storage extension is not |
| present, omit references to RGB_RAW_422_APPLE and TexStorage*. |
| |
| Details of how this extension interacts with EXT_texture_storage when the |
| GL is a version of OpenGL earlier than 3.0 can be found in the |
| EXT_texture_storage spec. |
| |
| Errors |
| |
| INVALID_OPERATION is generated if <format> is RGB_422_APPLE and <type> is |
| not one of UNSIGNED_SHORT_8_8_APPLE or UNSIGNED_SHORT_8_8_REV_APPLE. |
| |
| INVALID_OPERATION is generated if <type> is UNSIGNED_SHORT_8_8_APPLE or |
| UNSIGNED_SHORT_8_8_REV_APPLE and <format> is not RGB_422_APPLE. |
| |
| INVALID_OPERATION is generated if <format> is RGB_422_APPLE and <width> |
| is not even. |
| |
| New State |
| |
| None |
| |
| New Implementation Dependent State |
| |
| None |
| |
| Revision History |
| |
| 1.5 2013/06/26 lipchak Add ES3 interactions |
| 1.4 2010/04/06 lipchak Add ES interactions |
| 1.3 2009/09/03 kdyke First shipping version |
| |
