Could NTSC VIR = PAL

[old_tv_nut]

Originally Posted by NewVista

Though I'm no expert on VIR, wouldn't locally regenerated (network sourced for instance) burst have precise phase lock to the original and, by extension, the VIR (regenerated?) bursts.

So I'm guessing from this the networks used VIR with their feeds?

Not sure if I understand your question completely.

The local burst must be reinserted to standard amplitude and clean waveform per FCC rules. Therefore, it at least loses its relation to the chroma amplitude, which may have changed due to analog transmission distortion over the network. In practice, the reinserted phase is also adjustable and therefore can be misadjusted. If there is significant phase distortion of the chroma over the network, the phase of the incoming burst may also vary over its width, making it difficult to know where to set the phase of the re-inserted burst. The VIR reference had a much wider burst of chroma during the active line, which was supposed to fix this by ignoring edge distortions. Unlike NTSC, the PAL burst, by alternating phase sequence from line to line, should average out to the correct phase even when phase distortion is present.

The whole idea of VIR was to insert it at the originating studio and not replace it anywhere along the chain, not even at network central control; but not every program had it inserted.

I would note that VIR, occurring once per field, had a much slower control action than color burst, and could not possibly compensate for fast signal variations like airplane flutter.

[NewVista]

=old_tv_nut;3170654
The local burst must be reinserted to standard amplitude and clean waveform per FCC rules. Therefore, it at least loses its relation to the chroma amplitude, which may have changed due to analog transmission distortion over the network. In practice, the reinserted phase is also adjustable and therefore can be misadjusted. If there is significant phase distortion of the chroma over the network, the phase of the incoming burst may also vary over its width, making it difficult to know where to set the phase of the re-inserted burst. The VIR reference had a much wider burst of chroma during the active line, which was supposed to fix this by ignoring edge distortions. ..
The whole idea of VIR was to insert it at the originating studio and not replace it anywhere along the chain, not even at network central control; but not every program had it inserted...

Some great info there!
Brilliant of General Electric to have a wider burst in active line - and at a luminance level of a typical flesh tone!

So, to me, the "problems" would have been easily avoidable with good broadcasting practice:
For example source material with VIR needed to be first reclaibrated thru a professional VIR processor
that also regenerated burst & VIR (with exact phase similitude) to the gated line 19 sample).
Was there such an instrument?

[kf4rca]

I remember quad videotapes (2 inch) coming in that had a sticker saying "Protected by VIRS- adjust proc amp to pass."
In reality burst and sync got "regenerated" 2 times. After leaving the switcher it went to a proc amp where it would get black and white clip and agc. (I thought the best AGC amp was the RCA TA19. You could always tell a station that had one of these on the air.) Sync and burst would also be regenerated. Then it went to the virs inserter where it sync and burst would be regenerated again.
NOW, all of this is ahead of a pre-corrector that was required to compensate for non-linearities in the modulation process of the transmitter. It had to look flat on the air.
AND don't forget the low pass filter. Video was band limited to 4.2 MHZ to avoid components bleeding over into the sound at 4.5 MHz.

[NewVista]

Originally Posted by old_tv_nut

.. If there is significant phase distortion of the chroma over the network, the phase of the incoming burst may also vary over its width, making it difficult to know where to set the phase of the re-inserted burst. The VIR reference had a much wider burst of chroma during the active line, which was supposed to fix this by ignoring edge distortions. .

Didn't know of this problem of burst phase distortion , nevertheless the burst must be the reference for regeneration I would think and not the higher level VIR chroma which may have phase shift wrt the burst?

To eliminate any guesswork, just have color bars on another vert interval line!