The proportional bandwidth was chosen because experience demonstrates that in most environments, vibration is dominated by broadband, or random, energy rather than tonal, or periodic energy. With a proportional bandwidth, the center frequencies of the individual bands are standardized, and the bandwidth of each band is 23 percent of its center frequency. Often depicted with the vibration criteria VC curves are the four ISO guidelines related to the effects of vibration on people in various types of buildings or environments.
And some vibration charts also depict the NIST-A criterion — originally developed for metrology applications — alongside the VC curves. In conjunction with the vibration criteria VC curves, a table was developed to define the maximum level, or amplitude, for each criterium and to describe how and where each criterium is deemed to be most applicable. This is done by smoothing borders of adjacent blocks. In VC-1 parlance, this data is called the sequence layer. The format of this data is as follows:.
In the case of simple or main profile data encapsulated in a general container format, the max coded width and height parameters will come from the container format rather than being encoded in the sequence layer. Observe that the total number of bits that comprise the sequence layer for simple or main profile data is 32 which, incidentally, ought to be the size of the extradata transmitted from the ASF container to a VC-1 decoder. Inter block is composed from AC coefficients starting from top left corner.
The only catch that it could be divided into subblocks which need to be decoded separately. AC coefficient is coded by special value which decomposes into number of zeroes before coefficient, coefficient value and if this is the last non-zero coefficient.
All information needed to decode them is contained in special tables. AC prediction is simply adding seven AC coefficient values from first row of block above or first column of block left of the current one to the corresponding coefficients of the destination block. Source block is the same which DC value was used for prediction. This process is performed only when the special bit is set.
This Wiki aims to provide a complete, independent, and understandable description of the VC-1 format. Until such time, here are some external references on the format. Source material is stored like sprite which is transformed and cropped afterwards sprite dimensions are usually bigger than output.
Frames are preceded by two bits with undiscovered meaning. Adequate in most instances for optical microscopes to X, microbalances, optical balances, proximity and projection aligners, etc. A challenging criterion to achieve. Assumed to be adequate for the most demanding of sensitive systems including long path, laser-based, small target systems, E-Beam lithography systems working at nanometer scales, and other systems requiring extraordinary dynamic stability.
Appropriate for extremely quiet research spaces; generally difficult to achieve in most instances, especially cleanrooms. Not recommended for use as a design criterion, only for evaluation. It is not relevant to imaging associated with probe technologies, AFMs, and nanotechnology.
The information given in this table is for guidance only. In most instances, it is recommended that the advice of someone knowledgeable about applications and vibration requirements of the equipment and processes be sought.
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