17-06-2019, 08:54 AM
(This post was last modified: 17-06-2019, 09:00 AM by ppppenguin.)
Before pulse & bar was invented the usual method of measuring a video system was a frequency sweep. This is OK as far as it goes but tells you nothing about the phase or group delay response. These are critical for video.
Constant group delay is equivalent to linear phase. Video measurements usaully specify group delay as it's more closely related to what you see as P&B errors.
The bar of P&B givea an smplitude reference for the pulse and indicates some low frequency distortions.
L. Weaver of the BBC and NW Lewis of the Post Office invented the 2T pulse and bar test as a quick and easy means of assessing a video path. The original work was published by Lewis in 1954. Proc IEE vol 10 part III no 72 pp258-270. The original P&B was conceived as a full frame test signal. I don't know when the idea of VITS was first suggested. This paper shows how P&B was extended to deal with the requirements of colour TV: https://www.bbc.co.uk/rd/publications/bbc_monograph_58
Constant group delay is equivalent to linear phase. Video measurements usaully specify group delay as it's more closely related to what you see as P&B errors.
The bar of P&B givea an smplitude reference for the pulse and indicates some low frequency distortions.
L. Weaver of the BBC and NW Lewis of the Post Office invented the 2T pulse and bar test as a quick and easy means of assessing a video path. The original work was published by Lewis in 1954. Proc IEE vol 10 part III no 72 pp258-270. The original P&B was conceived as a full frame test signal. I don't know when the idea of VITS was first suggested. This paper shows how P&B was extended to deal with the requirements of colour TV: https://www.bbc.co.uk/rd/publications/bbc_monograph_58
www.borinsky.co.uk Jeffrey Borinsky www.becg.tv
