Which output of VCube are you referring to when you talk about gamma shifting?
The preview window of VCube displayed from the graphics board of the PC?
The analog output of an AJA video board (either in component or composite)?
The SDI output of an AJA video board as seen through external conversion (like an SDI compatible video monitor or the analog output of another video deck like a Digi Betacam in input to a video monitor)?
What is the "source" you are comparing VCube to (QuickTime Player as seen on the same PC screen or a tape deck with the original video displayed to a monitor)?
I ask this not because I have a software patch for VCube in mind but because source and duplicate video is more or less degraded depending on the copy methods and formats used. One factor that plays an unpredictable role when comparing the results of video copies is not the video itself but the tolerances of the display device and its integral components which may compensate for tachnological shortcomings.
Gamma correction is a term which refers to non-linear luminance encoding and decoding present in many forms, whether hardware based or software based, that may alter the perceptual values of displayed picture. VCube is far from being the only link in your display chain that potentially alters the gamma of what you may be seeing as a defect in the luminosity of a picture. In addition to the gamma slider in VCube which allows for the adjustment of VCube's gamma to your PC's graphics board QuickTime interprets gamma, your graphics card itself, your PC monitor, your video monitor, the convertors of your AJA board, another video deck with convertors, etc.
Whatever discomfort this slight shift in gamma, perceived by you and your client, may cause while comparing VCube and some other "source" may produce it will only continue to vary from display device to display device wherever you look. Neither VCube nor QuickTime have cornered the market on gamma correction. Think of a large Hi-fi store that lines up dozens of TVs for display all showing the same source. Have you ever noticed how they all seem to display picture differently? They all have the same source and yet they look different. None of them have altered the source signal but simply try to reproduce it perceptually as best as possible. Every manufacturer includes some simple adjustments in their menus to make the sets more comfortable in the environment of the individual customers’ homes but these are corrective perceptual adjustments, not calibration adjustments. VCube allows for adjustment of the gamma to the preview window (thus the graphics board of your PC) but does not control how the stand alone QuickTime player will display (nor should it) to your PC's monitor. This logic follows though the entire chain of devices to any display from any digital image media source.
This phenomenon is a long standing industrial reality and every manufacturer may use their own power law interpretation tables to fit their own technology. We don't control them nor do they control us so we choose to allow for user corrections and hope that our clients are at least as satisfied with this they may be with their video display gear.
