Facsimile and static presentation processing – Static presentation processing – Attribute control
Patent
1985-02-27
1988-05-31
Groody, James J.
Facsimile and static presentation processing
Static presentation processing
Attribute control
358 14, H04N 1118, H04N 1106
Patent
active
047484969
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to an improvement in the Multiplexed Analogue Component (MAC) type of television signal in which chrominance and luminance components are time compressed and are placed sequentially so as to occupy together with the necessary data, sync and clamping signals, a period substantially equal to the conventional line period e.g. approximately 64 .mu.S.
The presently proposed type of MAC signal provides an aspect ratio of approximately 4:3 and provides superior pictures to those available with either existing PAL or SECAM. It is also capable of modification to provide even better pictures.
It is an object of the present invention to add additional information to the MAC signal so as to enable extended definition picutres to be reproduced by a suitable receiver without interfering with the picutre reproduced by a standard MAC receiver.
The present invention proposes to make use of the time allocated to the data burst equivalent to two sound channels for additional video information without affecting the positions in the line interval of the basic chrominance and luminance information for the standard 4:3 aspect ratio picture.
The additional video information can represent additional lines of a television signal or can represent additional information for the existing lines of the signal to alter the aspect ration to produce an extended definition picture.
Features and advantages of the present invention wwill become apparent from the following description of an embodiment thereof given by way of example with reference to the accompanying drawings, in which:
FIG. 1 shows a representation of a frame of a standard MAC signal;
FIG. 2 shows a representation of a frame of a MAC signal according to the present invention;
FIG. 3 shows waveforms of the standard MAC signal and the two waveforms necessary for the present invention; and
FIG. 4 shows in block diagram terms a transmission/reception system for the MAC signal shown in FIG. 2.
The C-MAC specification conveys a vision signal on 576 lines of a frame, occupying 1296-203=1093 samples of each line. This is illustrated in FIG. 1.
The 203 data samples at the start of each line can convey synchronisation and 8 companded sound channels. For extended definition, we propose to use the time equivalent to two sound channels. In the conventional multiplex, the 8 sound channels are conveyed in 162 packets per frame, made up of 20 packets/frame/sound channel +2 packets/frame for BI and PI information. In reducing the 2 sound channels, BI and PI will remain essential, but maybe at a lower rate. Two sound channels, therefore require either 41 or, at the most 42 packets per frame. These packets are distributed over 624 lines so that we get the results: ##EQU1##
In order to avoid unnecessary limitations on the data channel, this proposal will assume a need for a 59 bit burst, although this is a matter of detail at this stage.
We therefore have a 4:3 aspect ratio picture conveyed in 1093 samples on 576 lines. In principle, we can have 1296-59=1237 samples on 624 lines, so that with the same information packing density, an aspect ratio of ##EQU2## i.e. 4.9:3 is theoretically possible. This does make assumptions however on transition times but it is clear that a 5:3 aspect ratio can be approached.
Our proposal is illustrated in FIG. 2. The main features are:
(i) The position of the 4:3 aspect ratio chrominance and luminance is not moved. This is particularly important when scrambling using rotation methods is considered.
(ii) The 5:3 aspect ratio luminance edges are sent on the same lines as the rest of the 4:3 ratio luminance and chrominance information. The boundary between L1 and L3 (left and right) is defined for each field to permit the 4:3 ratio picture to be the correct part of the 5:3 ratio picture.
(iii) The 5:3 aspect ratio chrominance edges are sent on a number e.g. 18 of inactive lines of each field interval. Each of these lines contains 16 blocks of C1 and C3, each block appropriate to one line of the field. The boundary between C1 and C3 (left
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Wendland, "Enhanced Picture Quality by Timeplex Techniques", SMPTE Journal, Oct. 1983, pp. 1034-1035.
Rhodes: "Time Division Multiplex of Time Compressed Chrominance for a Compatible High Definition Television System", IEEE Transactions on Consumer Electronics, vol. CE-28, No. 4, Nov. 1982, pp. 592-602.
Documents CCIR Study Groups, Period 1982-1986, Document 10-11S/106-E; Sep. 23, 1983; Draft Report: "Satellite Transmission of Multiplexed Analogue Component (MAC) Television Signals", pp. 1-19.
Drury Gordon M.
Windram Michael D.
Groody James J.
Independent Broadcasting Authority
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