| '''OpenGL extension APPLE.ycbcr_422 |
| |
| This module customises the behaviour of the |
| OpenGL.raw.GL.APPLE.ycbcr_422 to provide a more |
| Python-friendly API |
| |
| Overview (from the spec) |
| |
| This extension provides a method for GL to read, store and optionally |
| process textures that are defined in Y'CbCr 422 video formats. This |
| extension supports the two common Y'CbCr 422 video formats (known by |
| QuickTime FourCC as '2vuy' and 'yuvs'). These formats represent one of the |
| most common 16 bit Y'CbCr formats in both standard and reverse byte |
| ordering. From a client stand point these can be assumed to be decoded |
| immediately (even though the implementation is free to optimize the data |
| storage and keep it in the native format) and otherwise function as any |
| other texture format. The texture command <internalformat> parameter |
| normally be should be specified as RGB, since Y'CbCr is just a form of RGB |
| data. This extension can be supported with either hardware or software |
| decoding and it is up to the specific implementation to determine which is |
| used. |
| |
| A new <format> is added, YCBCR_422_APPLE. Additionally, to handle the |
| difference in pixel size and byte ordering for 422 video, the pixel storage |
| operations treat YCBCR_422_APPLE as a 2 component format using |
| the UNSIGNED_SHORT_8_8_APPLE or UNSIGNED_SHORT_8_8_REV_APPLE <type>. |
| |
| The '2vuy' or k2vuyPixelFormat pixel format is an 8-bit 4:2:2 Component |
| Y'CbCr format. Each 16 bit pixel is represented by an unsigned eight bit |
| luminance component and two unsigned eight bit chroma components. Each pair |
| of pixels shares a common set of chroma values. The components are ordered |
| in memory; Cb, Y0, Cr, Y1. The luminance components have a range of [16, |
| 235], while the chroma value has a range of [16, 240]. This is consistent |
| with the CCIR601 spec. This format is fairly prevalent on both Mac and Win32 |
| platforms. The equivalent Microsoft fourCC is OUYVYO. This format is |
| supported with the UNSIGNED_SHORT_8_8_REV_APPLE type for pixel storage |
| operations. |
| |
| The 'yuvs' or kYUVSPixelFormat is an 8-bit 4:2:2 Component Y'CbCr format. |
| Identical to the k2vuyPixelFormat except each 16 bit word has been byte |
| swapped. This results in a component ordering of; Y0, Cb, Y1, Cr. This is |
| most prevalent yuv 4:2:2 format on both Mac and Win32 platforms. The |
| equivalent Microsoft fourCC is 'YUY2'. This format is supported with the |
| UNSIGNED_SHORT_8_8_APPLE type for pixel storage operations. |
| |
| The official definition of this extension is available here: |
| http://www.opengl.org/registry/specs/APPLE/ycbcr_422.txt |
| ''' |
| from OpenGL import platform, constant, arrays |
| from OpenGL import extensions, wrapper |
| import ctypes |
| from OpenGL.raw.GL import _types, _glgets |
| from OpenGL.raw.GL.APPLE.ycbcr_422 import * |
| from OpenGL.raw.GL.APPLE.ycbcr_422 import _EXTENSION_NAME |
|
|
| def glInitYcbcr422APPLE(): |
| '''Return boolean indicating whether this extension is available''' |
| from OpenGL import extensions |
| return extensions.hasGLExtension( _EXTENSION_NAME ) |
|
|
|
|
| |
