EINRICHTUNG ZUR ABTRENNUNG EINES VIDEOSIGNAL-EXTREMPEGELS

1451830 Video signal peak level measurement INST ELEKT I VYCHIS TEKHN AKAD NAUK LATVI SSR and LATVI NI INST EXPERIMENT I KLINICH MEDITSINY 26 June 1974 28313/74 Heading H4F Apparatus for measuring the peak levels of a video signal to be analysed comprises a comparator 1 to which the video signal is applied; a switching arrangement 7 receiving frame, line, trigger and if desired mask signals at inputs 23- 26, an output 8 being coupled to the comparator 1; a timing pulse generator 6; and at least one video signal peak clamping channel, e.g. white peak clamping channel 2 and/or black-white transition peak clamping channel 3 and black peak clamping channel 4. Each peak clamping channel includes a coincidence circuit 9 having three inputs respectively connected to the comparator 1, the switching arrangement 7 and the timing pulse generator 6; a pulse counter 10 receiving outputs from the circuit 9 and switching arrangement 7; a digital-analogue converter 11 receiving the output of the counter 10 and a reference voltage Uo and passing an output back to the switching arrangement 7. Preferably one clamping channel, e.g. channel 3, is connected to the comparator 1 via an inverter 5. The reference voltage fed to the converter of channel 3 may comprise the output of the converter of channel 2, and the reference voltage fed to the converter of channel 4 may comprise the output of the converter of channel 2 or channel 3 (Figs. 2 and 3, not shown). The outputs of the counters 10 of the channels are preferably supplied to a peripheral device 22 which may comprise an indicator, display, printer or digital computer. The clamping channels are enabled field sequentially by the outputs 15, 16 and 17 of the switching arrangement, the comparator 1 acting on the video signal input and the output of the respective digital-analogue converter 11 which is switched to output 8 of the switching means. The video signal levels in analogue form at the outputs of converter 11 may also be fed to peripheral devices effecting video quantizing at any clipping level.