[old_tv_nut]

Kfbkfb: You have a mistaken impression that the tint errors were "fixed" by VIR or anything else.

What happened in general was that more stable solid state gear was used over time so that the drifts along the delivery chain were gradually reduced (but not "fixed"). Stability between programs took a big step backwards when analog cable came into general use. Every cable channel needed a proc amp to restore the burst and sync waveforms, but of course the cable company would set up the system and only check sporadically, unlike the broadcast stations that could check at least daily.

Regarding VIR, it was intended to carry a reference from the studio all the way to the receiver. The problem with mismatched color from program to program was partially due to the FCC requirement that burst and sync be restored to standard levels and waveforms before emission. Of course, the picture itself was not modified, so saturation errors persisted; plus if the phase of the regenerated burst was wrong, the hue was off. So VIR was intended to fix that.

However, VIR never worked reliably, due to local stations inserting it locally even on program material that didn't have it in the first place, and using it in a closed-loop sytem to correct transmitter distortions. So, many programs with VIR had VIR that was not carried all the way from the studio, and the result was that VIR often made the color worse instead of better.