Microsoft Video 1 or MS-CRAM
is an early
lossy
In information technology, lossy compression or irreversible compression is the class of data compression methods that uses inexact approximations and partial data discarding to represent the content. These techniques are used to reduce data size ...
video compression and decompression algorithm (
codec
A codec is a computer hardware or software component that encodes or decodes a data stream or signal. ''Codec'' is a portmanteau of coder/decoder.
In electronic communications, an endec is a device that acts as both an encoder and a decoder o ...
) that was released with version 1.0 of
Microsoft's Video for Windows
Video for Windows was a suite of video-playing and editing software introduced by Microsoft in 1992. A runtime version for viewing videos only was made available as a free add-on to Windows 3.1, which then became an integral component of Windows ...
in November 1992. It is based on MotiVE, a
vector quantization
Vector quantization (VQ) is a classical quantization technique from signal processing that allows the modeling of probability density functions by the distribution of prototype vectors. Developed in the early 1980s by Robert M. Gray, it was ori ...
codec which Microsoft licensed from
Media Vision. In 1993, Media Vision marketed the Pro Movie Spectrum, an ISA board that captured video in both raw and MSV1 formats (the MSV1 processing was done in hardware on the board).
Compression algorithm
Microsoft Video 1 operates either in an
8-bit
In computer architecture, 8-bit integers or other data units are those that are 8 bits wide (1 octet). Also, 8-bit central processing unit (CPU) and arithmetic logic unit (ALU) architectures are those that are based on registers or data bu ...
palettized color space or in a
15-bit RGB color space.
Each frame is split into 4×4 pixel blocks.
[ Each 4×4 pixel block can be coded in one of three modes: skip, 2-color or 8-color.][ In skip mode, the content from the previous frame is copied to the current frame in a conditional replenishment fashion.][ In 2-color mode, two colors per 4×4 block are transmitted, and 1 bit per pixel is used to select between the two colors.][ In 8-color mode, the same scheme applies with 2 colors per 2×2 block.][ This can be interpreted as a 2-color palette which is locally adapted on either a 4×4 block basis or a 2×2 block basis. Interpreted as ]vector quantization
Vector quantization (VQ) is a classical quantization technique from signal processing that allows the modeling of probability density functions by the distribution of prototype vectors. Developed in the early 1980s by Robert M. Gray, it was ori ...
, vectors with components red, green, and blue are quantized using a forward adaptive codebook with two entries.
Use in NetShow Encoder
The codec was available in Microsoft NetShow Encoder,Windows Media Encoder
Windows Media Encoder (WME) is a discontinued, freeware Multimedia, media codec, encoder developed by Microsoft which enables content developers to convert or capture both live and prerecorded audio, video, and computer screen images to Windows Me ...
, and made available via the SDK. The NetShow encoder allowed the user to select a 2 pass option, where in the first pass the video was analyzed to create a color palette, and in the second pass converted to the palettized color space and encoded. Before encoding, the video could be scaled. Later versions of Windows Media Encoder dropped support for Microsoft Video 1 and only supported Windows Media Video
Windows Media Video (WMV) is a series of video codecs and their corresponding video coding formats developed by Microsoft. It is part of the Windows Media framework. WMV consists of three distinct codecs: the original video compression technolog ...
.
See also
* Indexed color
In computing, indexed color is a technique to manage digital images' colors in a limited fashion, in order to save computer computer data storage, memory and Hard disk drive, file storage, while speeding up display refresh and file transfers. It ...
* Color quantization
In computer graphics, color quantization or color image quantization is quantization applied to color spaces; it is a process that reduces the number of distinct colors used in an image, usually with the intention that the new image should be as ...
* Block truncation coding, a similar coding technique for grayscale content
* Color Cell Compression
Color Cell Compression is a lossy compression, lossy image compression algorithm developed by Campbell et al., in 1986, which can be considered an early forerunner of modern texture compression algorithms, such as S3 Texture Compression and Adapt ...
, a similar coding technique for color content, based on block truncation coding
* Apple Video, a codec based on a similar design
* QuickTime Graphics, a codec based on a similar design
* Smacker video, a codec based on a similar design
* S3 Texture Compression
S3 Texture Compression (S3TC) (sometimes also called DXTn, DXTC, or BCn) is a group of related lossy texture compression algorithms originally developed by Iourcha et al. of S3 Graphics, Ltd. for use in their Savage 3D computer graphics accele ...
, a texture compression format based on a similar design
References
External links
Microsoft Video 1 - MultimediaWiki
Microsoft Video 1 decoder - FFmpeg
Microsoft Video 1 encoder - FFmpeg
Video codecs
Film and video technology
Lossy compression algorithms
Microsoft proprietary codecs
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