OpenGL.GL.APPLE.ycbcr_422

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 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