Re "semi-log": A function that is linear about the origin, and which becomes logarithmic away from the origin, and which is symmetric about the origin is the inverse hyperbolic sine function (arcsinh/asinh). This is a more-or-less ideal "companding" function, and approximations to it appear in voice applications (the US & International 8-bit telephone voice standards), as well as in some proposed video standards. But those approximations aren't "smooth", whereas the arcsinh function itself is very smooth, and can therefore be used with 8-bit, 10-bit, 12-bit & higher depths without additional standards activities. This may well be the _only_ good use for the asinh library functions found in C/Fortran/etc. ever found! At 07:41 AM 1/18/2005, Allen Le Roy Limberg wrote: >The "semi-log" properties of analog TV signals concern more than display >characteristics and camera characteristics. These properties are probably >important in the practical transmission of TV through a radio link; there >may be an expert in TV broadcasting that can comment on this. In regard to >receiver design, these properties facilitated the use of automatic gain >control in vacuum-tube TV receivers without distorting the video signal too >much. This is one reason the analog TV system design deferred gamma >correction until the TV receiver. > >Al Limberg ---------------------------------------------------------------------- You can UNSUBSCRIBE from the OpenDTV list in two ways: - Using the UNSUBSCRIBE command in your user configuration settings at FreeLists.org - By sending a message to: opendtv-request@xxxxxxxxxxxxx with the word unsubscribe in the subject line.