U.S. Philips Corporation

Thomas C Mackereth

Atma Heerah

Anthony J Field

Tadeusz Zebrowski

A video signal processing arrangement for television signals encoded in digital form comprising means for compressing and/or expanding the size of the television picture represented by the video signal and means for rotating the television picture represented by the video signal is disclosed. The rotating means is separate from the compressing and/or expanding means and is switchable between a position prior to the compressing and/or expanding means in the video signal processing chain and a position subsequent to the compressing and/or expanding means. An arrangement having two separate video signal paths which are later combined to produce a composite picture is also described in which the rotating means can also be positioned after the combining means as well as before or after the compressing and/or expanding means in either path.

Video signal processing arrangement

The fading circuit comprises first and second video signal inputs (1,12) for receiving 8 bit parallel digitally encoded video signals and first and second fading control signal inputs (5,16) for receiving 8 bit parallel fading control signals. First and second multipliers (4,15) multiply the video signals by the fading control signals. The outputs of the multipliers (4,15) are truncated to 9 bits and fed to first and second inputs of an adding arrangement (11). A dither signal is fed from a dither signal generator (22) to the carry input (24) of the adding arrangement (11). The output of the adding arrangement (11) is fed to a ROM (28) which is programmed to add 1/256th of the output of the adding arrangement (11) to the output of the adding arrangement (11) and produce an 8 bit output which is applied to the output (31) of the fading circuit. By adding the dither signal amplitude transitions in the output signal at particular settings of the fading control signals are blurred and do not produce such a disturbing effect on the display screen.

Fading circuit for video signals

A television signal encoder for luminance and chrominance signals presented in digital form comprises luminance and chrominance channels in which the blanking and color burst signals are inserted digitally before the signals are converted to analogue form for modulation and transmission. The luminance signal is presented to a buffer circuit (2) and during the line period the output of the buffer circuit (2) is fed to a DAC (6) via a highway (5) under the control of an enable signal. During the blanking period a ROM (26) applies a digital version of the blanking level to the highway (5). A ROM (3) is enabled for a short period at the start and finish of the blanking period and is arranged as a variable multiplier to determine the slope of the blanking waveform. The output of the DAC (6) is filtered (8) and it is added to the modulated color subcarrier signal and the synchronizing pulse. The chrominance channel is basically similar to the luminance channel but includes means for demultiplexing the U and V signals and a further ROM for inserting the color burst amplitude. The U and V signals after filtering are fed to modulators to modulate the color subcarrier signal.

Television signal encoder

A video signal clamping circuit comprises a summing circuit (R1, R2, R9, 2) an analogue to digital converter (3), a programmable read only memory (6), a latch (7), a digital to analogue converter (9) and an integrator (11). The PROM (6) is addressed by the ADC(3) and produces a 4 bit output code which is dependent on the amplitude of the video signal. This is stored on the latch (7) and passed to the DAC(9) during a timing pulse applied to terminal (8) which occurs during the line blanking period. The DAC(9) produces an output which is stored on the capacitor (C1) in the integrator (11). The integrator (11) output is summed with the input video signal to clamp the video signal level to the reference voltage so that a clamped digital video signal is available from the output (5).

Clamping video signals

A film projection system for use with a continuous film motion telecine machine includes a film guide (17, 18) which guides the film (1) past a gate (13). The film guides (17, 18) form part of two endless bands (14, 15). The parts of the bands (14, 15) in contact with the film (1) are arranged to move at substantially the same velocity as the film and there is provided means (19, 20) for varying the spacing between the bands.

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Cambridge, United Kingdom

Thomas C Mackereth