The control center is the core of an audiovisual production studio. Main functions consists on routing all the audio and video signals, synchronization, analysis and quality control of all audio and video signals. It includes the direction control equipment, audio control equipment, editing systems, post-production systems, continuity control and control center equipment.
The equipment of the control center is:
- Switching matrix: connects N inputs with M outputs.
- Quality monitoring systems: vectorscope and waveform monitor to check the signals.
- Processor and standard conversion: digital processing to changing one type of TV signal to another (50Hz to 60Hz, 625 lines to 575 lines, 4:3 to 16:9).
- Network equipment: satellite receivers and other receiver systems to code, modulate and send the signals.
Measures of the video signal
Several testing intruments are used to verify the content of the video signal:
- Waveform monitor to check the level each video signal component (luminance) respect to time. It also uses the black-burst to sinchronize the signal.
- Vectorscope displays a X-Y plot of the B-Y and R-Y signals to visualize chrominance. It is used to check tone and saturation variations.
- Lightning measure to check gain and delays between R-Y and B-Y, which causes tone variations.
- Diamond measure to prevent illegal colors in the RGB space (color gamut).
- Arrowhead measure displays a representation of the Y signal and the R-Y and B-Y modulated signals. It is used to check the color values after modulation in the PAL standard.
Measure of transmission parameters
When the signal is transmitted through the equipment and outside the control center, there is a degredation of the signals. Because of this degredation and the limitation of the system some parameters have to be verified using different measures:
- Eye pattern measured in a waveform monitor to analyze the duration, amplitude, synchronization with the system clock, noise, BER…of the digital signal.
- Jitter measurement gives a DC value of the phase modulation caused by the temporal instability.
- BER measurements using the auxiliary data from lines 5 and 318.
Like the video signal, the audio signal could have distortions and degredations. The testing equipment is used to normalize all audio levels from different sources, to detect distortions and measure the sound pressure:
- VUMeter measure the sound pressure.
- PPM detects peaks of the sound pressure that can produce distortions in the audio signal.
- Sonority normalize the audio levels from digital tv, radio, program changes, commercials… TheR-128 standard normalizes sonority in broadcasting systems.