PAL-encoded color recordings rely on circuitry in display devices and TBCs to decode and balance color information in the signal in accordance with the PAL standard. “The venetian-blind effect is produced when this colour balancing process is no longer operating correctly due to maladjusted demodulation circuitry”.1 The result: during playback, “pairs of lines [in the image] look like stripes that either remain stationary or drift slowly up or down the screen. The higher the colour saturation, the more visible the effect, depending on the particular TV or video signal, or the monitor settings.”2
Can it be fixed?
Playing a test tape will help to determine if the artifact has been recorded in the tape due to a faulty production system or if the display device is maladjusted. If the test tape does show the venetian-blind effect, the monitor requires repair. If not, then the error is recorded into the tape and cannot be fixed.
References
1. Johannes Gfeller, Agathe Jarczyk, and Joanna Phillips, “Venetian-Blind Effect (PAL)” in Compendium of Image Errors in Analogue Video (edited by Swiss Institute for Art Research, Zürich: Scheidegger & Spiess, 2012), 84. ↩
2. Gfeller, Jarczyk, and Phillips, “Venetian-Blind Effect (PAL)”, 84. ↩