docs/MESA_ycbcr_texture.spec

   1 Name
   2
   3     MESA_ycbcr_texture
   4
   5 Name Strings
   6
   7     GL_MESA_ycbcr_texture
   8
   9 Contact
  10
  11     Brian Paul, Tungsten Graphics, Inc. (brian 'at' tungstengraphics.com)
  12     Keith Whitwell, Tungsten Graphics, Inc.  (keith 'at' tungstengraphics.com)
  13
  14 Status
  15
  16     Shipping (Mesa 4.0.4 and later)
  17
  18 Version
  19
  20     1.0
  21
  22 Number
  23
  24     TBD
  25
  26 Dependencies
  27
  28     OpenGL 1.0 or later is required
  29     This extensions is written against the OpenGL 1.4 Specification.
  30     NV_texture_rectangle effects the definition of this extension.
  31
  32 Overview
  33
  34     This extension supports texture images in the YCbCr format.  There is
  35     no support for converting YCbCr images to RGB or vice versa.  The
  36     intention is for YCbCr image data to be directly sent to the renderer
  37     without any pixel transfer operations.  Only 2D texture images are
  38     supported (not glDrawPixels, glReadPixels, etc).
  39
  40     A YCbCr pixel (texel) is a 16-bit unsigned short with two components.
  41     The first component is luminance (Y).  For pixels in even-numbered
  42     image columns, the second component is Cb.  For pixels in odd-numbered
  43     image columns, the second component is Cr.  If one were to convert the
  44     data to RGB one would need to examine two pixels from columns N and N+1
  45     (where N is even) to deduce the RGB color.
  46
  47 IP Status
  48
  49     None
  50
  51 Issues
  52
  53     None
  54
  55 New Procedures and Functions
  56
  57     None
  58
  59 New Tokens
  60
  61     Accepted by the <internalFormat> and <format> parameters of
  62     TexImage2D and TexSubImage2D:
  63
  64         GL_YCBCR_MESA                   0x8757
  65
  66     Accepted by the <type> parameter of TexImage2D and TexSubImage2D:
  67
  68         GL_UNSIGNED_SHORT_8_8_MESA      0x85BA /* same as Apple's */
  69         GL_UNSIGNED_SHORT_8_8_REV_MESA  0x85BB /* same as Apple's */
  70
  71 Additions to Chapter 2 of the OpenGL 1.4 Specification (OpenGL Operation)
  72
  73     None
  74
  75 Additions to Chapter 3 of the OpenGL 1.4 Specification (Rasterization)
  76
  77     In section 3.6.4, Rasterization of Pixel Rectangles, on page 102,
  78     add the following to Table 3.8 (Packed pixel formats):
  79
  80     type Parameter                GL Data   Number of        Matching
  81      Token Name                    Type     Components     Pixel Formats
  82     --------------                -------   ----------     -------------
  83     UNSIGNED_SHORT_8_8_MESA       ushort         3         YCBCR_422_MESA
  84     UNSIGNED_SHORT_8_8_REV_MESA   ushort         3         YCBCR_422_MESA
  85
  86
  87     In section 3.6.4, Rasterization of Pixel Rectangles, on page 102,
  88     add the following to Table 3.10 (UNSIGNED_SHORT formats):
  89
  90     UNSIGNED_SHORT_8_8_MESA:
  91
  92       15  14  13  12  11  10  9   8   7   6   5   4   3   2   1   0
  93     +-------------------------------+-------------------------------+
  94     |              1st              |              2nd              |
  95     +-------------------------------+-------------------------------+
  96
  97     UNSIGNED_SHORT_8_8_REV_MESA:
  98
  99       15  14  13  12  11  10  9   8   7   6   5   4   3   2   1   0
 100     +-------------------------------+-------------------------------+
 101     |              2nd              |              1st              |
 102     +-------------------------------+-------------------------------+
 103
 104
 105     In section 3.6.4, Rasterization of Pixel Rectangles, on page 102,
 106     add the following to Table 3.12 (Packed pixel fiedl assignments):
 107
 108                        First       Second     Third      Fourth
 109     Format             Element     Element    Element    Element
 110     ------             -------     -------    -------    -------
 111     YCBCR_422_MESA     luminance   chroma
 112
 113
 114     In section 3.8.1, Texture Image Specification, on page 125, add
 115     another item to the list of TexImage2D and TexImage3D equivalence
 116     exceptions:
 117
 118     * The value of internalformat and format may be YCBCR_MESA to
 119       indicate that the image data is in YCbCr format.  type must
 120       be either UNSIGNED_SHORT_8_8_MESA or UNSIGNED_SHORT_8_8_REV_MESA
 121       as seen in tables 3.8 and 3.10.  Table 3.12 describes the mapping
 122       between Y and Cb/Cr to the components.
 123       If NV_texture_rectangle is supported target may also be
 124       TEXTURE_RECTANGLE_NV or PROXY_TEXTURE_RECTANGLE_NV.
 125       All pixel transfer operations are bypassed.  The texture is stored as
 126       YCbCr, not RGB.  Queries of the texture's red, green and blue component
 127       sizes will return zero.
 128
 129
 130     In section 3.8.1, Texture Image Specification, on page 126, add
 131     another item to the list of TexImage1D and TexImage2D equivalence
 132     exceptions:
 133
 134     * The value of internalformat and format can not be YCBCR_MESA.
 135
 136
 137     In section 3.8.2, Alternate Texture Image Specification Commands, on
 138     page 129, insert this paragraph after the first full paragraph on the
 139     page:
 140
 141          "If the internal storage format of the image being updated by
 142     TexSubImage2D is YCBCR_MESA then format must be YCBCR_MESA.
 143     The error INVALID_OPERATION will be generated otherwise."
 144
 145
 146 Additions to Chapter 4 of the OpenGL 1.4 Specification (Per-Fragment
 147 Operations and the Frame Buffer)
 148
 149     None
 150
 151 Additions to Chapter 5 of the OpenGL 1.4 Specification (Special Functions)
 152
 153     None
 154
 155 Additions to Chapter 6 of the OpenGL 1.4 Specification (State and
 156 State Requests)
 157
 158     None
 159
 160 Additions to Appendix A of the OpenGL 1.4 Specification (Invariance)
 161
 162     None
 163
 164 Additions to the AGL/GLX/WGL Specifications
 165
 166     None
 167
 168 GLX Protocol
 169
 170     None
 171
 172 Errors
 173
 174     INVALID_ENUM is generated by TexImage2D if <internalFormat> is
 175     MESA_YCBCR but <format> is not MESA_YCBCR.
 176
 177     INVALID_ENUM is generated by TexImage2D if <format> is MESA_YCBCR but
 178     <internalFormat> is not MESA_YCBCR.
 179
 180     INVALID_VALUE is generated by TexImage2D if <format> is MESA_YCBCR and
 181     <internalFormat> is MESA_YCBCR and <border> is not zero.
 182
 183     INVALID_OPERATION is generated by TexSubImage2D if the internal image
 184     format is YCBCR_MESA and format is not YCBCR_MESA.
 185
 186     INVALID_OPERATION is generated by CopyTexSubImage2D if the internal
 187     image is YCBCR_MESA.
 188
 189 New State
 190
 191     Edit table 6.16 on page 231: change the type of TEXTURE_INTERNAL_FORMAT
 192     from n x Z42 to n x Z43 to indicate that internal format may also be
 193     YCBCR_MESA.
 194
 195 Revision History
 196
 197     20 September 2002 - Initial draft