Name MESA_ycbcr_texture Name Strings GL_MESA_ycbcr_texture Contact Brian Paul, Tungsten Graphics, Inc. (brian 'at' tungstengraphics.com) Keith Whitwell, Tungsten Graphics, Inc. (keith 'at' tungstengraphics.com) Status Shipping (Mesa 4.0.4 and later) Version 1.0 Number TBD Dependencies OpenGL 1.0 or later is required This extensions is written against the OpenGL 1.4 Specification. NV_texture_rectangle effects the definition of this extension. Overview This extension supports texture images stored in the YCbCr format. There is no support for converting YCbCr images to RGB or vice versa during pixel transfer. The texture's YCbCr colors are converted to RGB during texture sampling, after-which, all the usual per-fragment operations take place. Only 2D texture images are supported (not glDrawPixels, glReadPixels, etc). A YCbCr pixel (texel) is a 16-bit unsigned short with two components. The first component is luminance (Y). For pixels in even-numbered image columns, the second component is Cb. For pixels in odd-numbered image columns, the second component is Cr. If one were to convert the data to RGB one would need to examine two pixels from columns N and N+1 (where N is even) to deduce the RGB color. IP Status None Issues None New Procedures and Functions None New Tokens Accepted by the and parameters of TexImage2D and TexSubImage2D: YCBCR_MESA 0x8757 Accepted by the parameter of TexImage2D and TexSubImage2D: UNSIGNED_SHORT_8_8_MESA 0x85BA /* same as Apple's */ UNSIGNED_SHORT_8_8_REV_MESA 0x85BB /* same as Apple's */ Additions to Chapter 2 of the OpenGL 1.4 Specification (OpenGL Operation) None Additions to Chapter 3 of the OpenGL 1.4 Specification (Rasterization) In section 3.6.4, Rasterization of Pixel Rectangles, on page 102, add the following to Table 3.8 (Packed pixel formats): type Parameter GL Data Number of Matching Token Name Type Components Pixel Formats -------------- ------- ---------- ------------- UNSIGNED_SHORT_8_8_MESA ushort 3 YCBCR_422_MESA UNSIGNED_SHORT_8_8_REV_MESA ushort 3 YCBCR_422_MESA In section 3.6.4, Rasterization of Pixel Rectangles, on page 102, add the following to Table 3.10 (UNSIGNED_SHORT formats): UNSIGNED_SHORT_8_8_MESA: 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0 +-------------------------------+-------------------------------+ | 1st | 2nd | +-------------------------------+-------------------------------+ UNSIGNED_SHORT_8_8_REV_MESA: 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0 +-------------------------------+-------------------------------+ | 2nd | 1st | +-------------------------------+-------------------------------+ In section 3.6.4, Rasterization of Pixel Rectangles, on page 102, add the following to Table 3.12 (Packed pixel fiedl assignments): First Second Third Fourth Format Element Element Element Element ------ ------- ------- ------- ------- YCBCR_422_MESA luminance chroma In section 3.8.1, Texture Image Specification, on page 125, add another item to the list of TexImage2D and TexImage3D equivalence exceptions: * The value of internalformat and format may be YCBCR_MESA to indicate that the image data is in YCbCr format. type must be either UNSIGNED_SHORT_8_8_MESA or UNSIGNED_SHORT_8_8_REV_MESA as seen in tables 3.8 and 3.10. Table 3.12 describes the mapping between Y and Cb/Cr to the components. If NV_texture_rectangle is supported target may also be TEXTURE_RECTANGLE_NV or PROXY_TEXTURE_RECTANGLE_NV. All pixel transfer operations are bypassed. The texture is stored as YCbCr, not RGB. Queries of the texture's red, green and blue component sizes will return zero. The YCbCr colors are converted to RGB during texture sampling using an implementation dependent conversion. In section 3.8.1, Texture Image Specification, on page 126, add another item to the list of TexImage1D and TexImage2D equivalence exceptions: * The value of internalformat and format can not be YCBCR_MESA. In section 3.8.2, Alternate Texture Image Specification Commands, on page 129, insert this paragraph after the first full paragraph on the page: "If the internal storage format of the image being updated by TexSubImage2D is YCBCR_MESA then format must be YCBCR_MESA. The error INVALID_OPERATION will be generated otherwise." Additions to Chapter 4 of the OpenGL 1.4 Specification (Per-Fragment Operations and the Frame Buffer) None Additions to Chapter 5 of the OpenGL 1.4 Specification (Special Functions) None Additions to Chapter 6 of the OpenGL 1.4 Specification (State and State Requests) None Additions to Appendix A of the OpenGL 1.4 Specification (Invariance) None Additions to the AGL/GLX/WGL Specifications None GLX Protocol None Errors INVALID_ENUM is generated by TexImage2D if is MESA_YCBCR but is not MESA_YCBCR. INVALID_ENUM is generated by TexImage2D if is MESA_YCBCR but is not MESA_YCBCR. INVALID_VALUE is generated by TexImage2D if is MESA_YCBCR and is MESA_YCBCR and is not zero. INVALID_OPERATION is generated by TexSubImage2D if the internal image format is YCBCR_MESA and is not YCBCR_MESA. INVALID_OPERATION is generated by CopyTexSubImage2D if the internal image is YCBCR_MESA. New State Edit table 6.16 on page 231: change the type of TEXTURE_INTERNAL_FORMAT from n x Z42 to n x Z43 to indicate that internal format may also be YCBCR_MESA. Revision History 20 September 2002 - Initial draft 29 April 2003 - minor updates 3 September 2003 - further clarify when YCbCr->RGB conversion takes place 19 September 2003 - a few more updates prior to submitting to extension registry.