Television – Monitoring – testing – or measuring
Patent
1991-09-11
1994-03-29
Kostak, Victor R.
Television
Monitoring, testing, or measuring
348578, H04N 1700
Patent
active
052989968
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to the monitoring of stereo audio signals associated with TV video signals.
In broadcasting generally, and in television broadcasting in particular, the provision of stereo sound is becoming commonplace. This poses special problems in the production and monitoring of TV programmes. It is difficult to monitor sound quality adequately by ear, particularly under production conditions, and some form of instrumentation which gives an indication of sound amplitude and phase is desirable. In particular, it is desirable to be able to monitor the relationship between the two channels of a stereo audio signal.
A well-known technique for doing this is to provide a separate monitor consisting of a conventional oscilloscope which has the two channels of the stereo signal fed to its X and Y inputs respectively; the resulting display is a Lissajou figure. However, this arrangement has the disadvantage that it is separate from the display of the associated TV picture on a TV monitor. The operator therefore has to make an active effort to check the oscilloscope, and there is also ample opportunity for error in associating the oscilloscope display with the appropriate one of a large number of monitors in a typical array of TV monitors.
A stereo audio monitor has also been developed which uses a TV-type picture raster display instead of an oscilloscope vector-type display, with the Lissajou figure being synthesized from the two audio signals as a TV-type video signal. This, however, suffers from the same disadvantages as the oscilloscope display.
SUMMARY OF THE INVENTION
The main object of the present invention is to provide means for monitoring stereo audio signals associated with a TV video signal which alleviates or overcomes these problems. Subsidiary objectives are to achieve convenience and simplicity.
Accordingly the present invention provides an audio signal monitoring system for stereo audio signals associated with a TV video signal, comprising means for converting the two channels of a stereo audio signal to digital form and writing successive pairs of values into a memory to form a map therein of a Lissajou figure representing the relationship between the two channels, and means for reading out the memory linearly in synchronism with the operation of a TV monitor and inserting the output into the TV video signal being displayed on the monitor.
Preferably the memory is read out diagonally so as to produce a diamond display on the monitor in which identical signals on the two audio channels are represented by a vertical line.
The read-out means preferably comprise a line counter and a bit counter for each channel, the line counters being loaded with predetermined counts at the beginning of each field and counting lines and the bit counters being loaded from the line counters at the beginning of each line and counting bits along the lines, three of the counters counting in one direction and the fourth in the other. Preferably the counters are larger than the memory, the excess high order portion of the counts being used to control the enabling of the memory read-out. Preferably also there is a display location selection memory containing one or more pairs of prestored counts any pair of which can be selected for loading into the line counters.
The system may include means for generating a graticule on the diamond display. Such means may comprise either logic circuitry fed from the counters or a second memory operated in parallel with the first memory.
The means for inserting the memory output into the TV signal may comprise pulse stretching means, adder means, and gating means. The gating means are preferably controlled partially or wholly by the excess portion of the counts. The insertion means may include means for either superimposing the Lissajou figure on the video picture on the TV monitor or means for generating a uniform background to the Lissajou figure in the diamond. The insertion means may also include means for inserting the graticule at a dif
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Grant Chris
Hamlet Video International Limited
Kostak Victor R.
Stelling David N.
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