XXX - Not complete. Name SGIX_ycrcb Name Strings GL_SGIX_ycrcb Version $Date: 1996/11/21 00:52:30 $ $Revision: 1.2 $ Number 101 Dependencies EXT_texture3D affects the definition of this extension EXT_subtexture affects the definition of this extension EXT_histogram affects the definition of this extension EXT_convolution affects the definition of this extension SGI_color_table affects the definition of this extension Overview This extension provides a method for OpenGL to read and store images that are defined in standard YCRCB 422 and 444 video formats. As with the CYMK extension, conversion to RGBA takes place immediately following the unpack pixel store, and preceding the pack pixel store operations, and is only available on transfers to and from memory. The algorithms that convert between YCRCB and RGBA are "black-box" in nature, and left undefined by the extension. Two new formats are added, YCRCB_422_SGIX and YCRCB_444_SGIX. To handle the difference in sampling rate for 422 video, the pixel storage operations treat YCRCB_422_SGIX as a 2 component format, where the first component represents chroma, and the second luma. The chroma component alternates between Cb and Cr values on a per pixel basis. If the specified image parameter is not a multiple of 2, then fragments or texels that result from processing the th column of pixels will have undefined color value. YCRCB_444_SGIX is defined as a 3 component format representing the Cb, Y, and Cr values per pixel. As with the CMYK extension, this extension doesn't preclude the possiblity of other higher quality conversion methods. Issues * What is standard packing for 444 YCRCB pixels? Does the 601 standard specify pixel alignment? * YCRCB_420_SGIX and other formats? * should there be conversion quality hint? New Procedures and Functions None New Tokens Accepted by the parameter of DrawPixels, ReadPixels, TexImage1D, TexImage2D, TexImage3DEXT, TexImage4DSGIS, TexSubImage1DEXT, TexSubImage2DEXT, TexSubImage3DEXT, TexSubImage4DSGIS, GetTexImage, ColorTableSGI, GetColorTableSGI, ConvolutionFilter1DEXT, ConvolutionFilter2DEXT, ConvolutionFilter3DEXT, GetConvolutionFilterEXT, SeparableFilter2DEXT, SeparableFilter3DEXT, GetSeparableFilterEXT, GetHistogramEXT, and GetMinmaxEXT: YCRCB_422_SGIX YCRCB_444_SGIX Additions to Chapter 2 of the 1.0 Specification (OpenGL Operation) None Additions to Chapter 3 of the 1.0 Specification (Rasterization) Two entries are added to table 3.5 (DrawPixels and ReadPixels formats): Target Name Type Elements Buffer ---- ---- -------- ------ YCRCB_422_SGIX Component [Cb,Cr] chroma value, Color Y luminance value YCRCB_444_SGIX Component Cb chroma value, Color Y luminance value, Cr chroma value Table 3.5: DrawPixels and ReadPixels formats. The third column gives a description of and the number and order of elements in a group. The new formats YCRCB_422_SGIX and YCRCB_444_SGIX are added to the discussion of Conversion to RGB. If the format is either of these two values, then the chroma and luminance values in each group are converted to R, G, and B values using an undefined algorithm. If the format is YCRCB_422_SGIX, the conversion algorithm may produce undefined RGB values for final pixel of any row where the rowlength is not a multiple of 2. Additions to Chapter 4 of the 1.0 Specification (Per-Fragment Operations and the Framebuffer) The new formats are added to the discussion of Obtaining Pixels from the Framebuffer. The new formats are added to the discussion of Index Lookup. A new section, "Conversion to YCrCb," is added immediately following the section "Conversion to L." Additions to Chapter 5 of the 1.0 Specification (Special Functions) None Additions to Chapter 6 of the 1.0 Specification (State and State Requests) None Additions to the GLX Specification None GLX Protocol None Errors None New State None New Implementation Dependent State None