"Peter L. Peres" wrote: > The color subcarrier is quadrature modulated with the color information, > so it is continuous (if there is color in the image) but its phase is not. No, the PAL color subcarrier *IS* continuous phase. It is the color *burst* that isn't continuous phase. Since the horizontal line time is not a multiple of the subcarrier phase, the subcarrier phase *relative to the line timing* varies from one line to another. As I described previously, the subcarrier phase for each successive line advances 90.576 degrees (not the 90 degrees that is usually given in simplified explanations). > The burst is indeed at +135 and -135 degrees, alternated every line, but > the difference between +135 and -135 is exactly 90 degrees and the crystal Yes, but as stated above, burst phase is relative to the subcarrier phase, which is continuous in time but advances relative to each scan line. If you looked at the same point within two consecutive scan lines (e.g., the exact midpoint of the color burst), there would NOT be a 90 degree phase difference between those two points: line subcarrier phase color burst phase color burst phase relative to line relative to subcarrier phase relative to line 1 0.000 +135 135.000 2 90.576 -135 315.576 3 181.152 +135 316.152 4 271.728 -135 136.728 5 2.304 +135 137.304 6 92.880 -135 317.880 etc. Eric