[wa2ise]

When I was at Samsung doing the KSO127 NTSC/PAL/SECAM demod chip, it could tell PAL from SECAM. We designed a subsystem that measured the frequency of the subcarrier bursts. If 3.58 proceed to the test to tell NTSC 3.58 or PAL at 3.58; or if 4.42 then test for PAL 4.43 or NTSC at 4.43. If not those, and if you get 4.25 and (the other SECAM freq) on alternating lines, then its SECAM. We didn't look at the scan rates for this.

If the device only relies on the horiz and vert scan rates, then it can only tell NTSC from PAL/SECAM. It cant tell PAL from SECAM though.

Some multistandard consumer VCRs can produce a PAL signal at NTSC scan rates, or NTSC at PAL scan rates. Our chip didn't care as it only looked at the subcarrier bursts. So it could decode these non-standard standards.