OT Trying to copy a VHS tape in NTSC format (UK)

back.

converted

This raises a question that I've long wanted an answer to... If disks vary according to frame rate -- how can there be a zone-free recording?

Indeed - but as I said not actually PAL. That refers to phased alternate line. And designed to overcome problems with transmission that NTSC suffers from.

While introducing problems of its own, such as severe desaturation under conditions of excessive group-delay error.

Wasn't being jingoistic, BTW. There is always a downside being first like with NTSC. But I'm not sure what you mean by group delay?

IIRC was taught that NTSC gives the best off camera pictures, PAL for processing and recorded to tape and SECAM for transmission?

Because all players play all three frame rate disks. Zones refer only to encryption. If a disk is not encrypted, then it can be played on any DVD player. Home DVDs are not encrypted, in fact, I have never seen DVD encryption software for home users, but it may exist.

Commerical DVDs are encrypted if the producer wants to use it. There may be a licensing fee for involved. All licensed players are required to check the zone bits (1-8) before decrypting a DVD to make sure the player's zone is allowed by they DVD.

If you wish to produce a zone-free recording, you can leave it unencrypted or encrypt it with more than one zone allowed. Israel is in zone 2, I usually see zone 1 or 2 only disks for sale here, occasionaly I see disks for zone 2 and 4, 2 and 6, or 2, 4 and 6.

The following web page discusses the permitted resolutions and frame rates allowed by DVDs:

Note that I have found you can mix some of the video and audio encoding options in ways that are not permitted and they still work. Surprisingly doing so produced a DVD that could be played on everything I tried including several hard and soft players EXCEPT Windows Media Player.

Geoff.

NTSC and PAL are pretty much Tweedle-Dum and Tweedle-Dee. There's no significant difference between them. PAL is essentially NTSC with phase alternation. (Which was supposed to be part of NTSC, but the designers couldn't see any way to build an inexpensivd TV receiver to take full advantage of it, so it was dropped.)

At the time Europe adopted PAL, the transmission systems had a lot of non-linear group delay (the US systems didn't), which alters the hue. The phase alternation causes the hue shifts to be "opposite" (complementary) on alternate lines, so there is a visual averaging of the hue. This is good, up to a point, but as the averaging pushes the color towards white, the effect is visible desaturation.

Never seen this - despite having had colour TV since it started in the UK.

But I'm still not sure what you mean by 'non linear group delay'.

Phase shift in which the shift is not linearly proportional to the frequency, along a straight line that passes through the origin.

On BBC America.

Right. And just where would you get this?

From less-than-well-designed transmission systems.

The US had microwave systems which generally had low group-delay errors. In the late '50s, Europe had coax systems which generally did not. Which was one of the reasons PAL was selected. According to the books, anyhow.

I knew an old ATT guy who worked in both cross country coaxial & microwave video feeds. He told me how much of a pain it was to equalize a section of cross county coax used for network TV feeds, and keep it that way as the temperature changed.

The emergency lashup to cover the JFK assignation was via coax that wasn't properly equalized, and you could tell from the muddy video. There was barely enough extra capacity to do it without notice, but all of the three networks were able to get the live feed at all of their stations. Some sections of failing coax had to be used, since it was all that was available without dumping other customers.

That was at a time they were working to eliminate the last of the cross country coaxial trunklines. They still used coaxial feeds from the nearest microwave tower to the TV station. Now most of the microwave sites are gone, having been replaced with fiber optic cable.

Thanks for the explanation. Could explain why I've not heard of it. In the UK microwave links tended only to be used for linking say an outside broadcast back to a receiving area. To transmitters is generally cable - although one channel does use satellite. And of course satellite is getting more common for the former task.

Thanks for the confirmation. I didn't realize coax was so temperature-sensitive.

In message , William Sommerwerck writes

Its attenuation changes by appx .02dB per dB per degree C.

In the UK it would normally be buried underground - so kept at a fairly constant temperature. But just shows the difference between a small country like the UK and somewhere so vast as the US. Or perhaps that the co-ax was installed by a state owned company with a monopoly so costs perhaps weren't the main priority.

You should see what it does to solid aluminum jacketed coax during a sudden temperature drop. The shield can shrink three inches in a 500 foot run, and either pull the jacket out of the connector, or rip the aluminum. It is called a suckout in CATV slang.

CATV mostly solved the problems by using the video carrier of two channels to calculate the tilt, and compensate at each amplifier. The systems I worked on used Ch. 2 & Ch. 12. That meant that any headend needed a minimum of those two channels to work. A replacement signal at the same level had to be provided at the head end if those were off the air channels. We used locally generated video for both channels.

The ATT coax was miles long segments with tube amplifiers & equalizers at fixed distances. Without careful setup of a hundred or more of those terminals, the equalization destroyed the signal.

At what distance? At what frequency?

In message , Michael A. Terrell writes

Any and any. Think about it.