NEWS their origin.
This orchestration ensures that all cameras, mixers and processors are “speaking the same language” in terms of timing, avoiding visual or auditory misalignment. Precise synchronisation eliminates delays and ensures a cohesive output.
A broadcast network typically employs various transmission equipment types, each components may include
single-ended clocks for general-purpose timing, low-jitter differential clocks essential for serialiser/deserialiser (SERDES) applications and specialised synchronisation devices to support standards like IEEE 1588 or audio video bridging/time-sensitive networking (AVB/TSN).
Professional Video Camera Synchronisation
Professional video cameras are at the heart of studio production and their performance relies on precise synchronisation. Here is how synchronisation cascades through a typical camera setup:
Genlock for synchronisation: Cameras synchronise their video processor sampling clocks, sync pulses and serial digital interface (SDI) clock to the studio’s master synchronisation signal via genlock. This ensures that all cameras are perfectly aligned with the studio’s timing reference. Low-jitter clocks: The video processor requires a clock with exceptionally low jitter (unwanted timing variations) because any timing inconsistencies directly affect the performance of the analog-to-digital (A/D) converter. High jitter can degrade the signal-to-noise ratio, impacting video quality. Audio-video synchronisation: Microphone audio signals are digitised using an audio processor. The audio sampling clock is synchronised with the video clock to ensure that the audio and video streams are perfectly aligned when embedded into the SDI stream.
Horizontal synchronisation (HSYNC): An HSYNC signal is extracted from the composite video signal generated by the master sync generator. To do this, the composite video signal, including the black burst reference, is fed into a sync separator. This separator removes unwanted portions of the signal and isolates the timing data. This extracted HSYNC signal is locked to a timing generator. produces a stable video sampling clock. SiTime provide a number of timing solutions for live broadcasts including the Cascade clock-system-on-a-chip family. The Cascade family includes network synchronisers, jitter cleaners and clock generators. These devices overcome quality and reliability
Fig 2: Professional video camera example using SiT95147/8 single-chip MEMS network synchroniser to synchronise the camera’s processors.
issues associated with traditional quartz timing solutions. Because the Cascade family integrates a MEMS resonator into the clock, there is no need for a quartz reference device. This increases system resiliency and eliminates the inherent weakness of quartz crystals such as activity dips and sensitivity to shock and vibration. Additionally, by integrating the resonator, it eliminates a device on the board, minimising the space allocated to timing and streamlining PCB board design.
In addition to the Cascade clock family, SiTime offers a complete lineup of silicon MEMS-based oscillators for broadcast, including low-jitter differential-ended oscillators, TCXOs and OCXOs that offer better performance and lower power consumption compared to traditional quartz crystal alternatives, plus important features like frequency.
Highly Precise Timing Hardware Is Critical for Live Broadcast
From the precise alignment of video and audio signals to the seamless integration of remote feeds, synchronisation enables broadcasters to deliver professional-grade content to their audiences. The use of master sync generators, HSYNC signals and advanced tools like frame synchronisers ensures that every component of the studio operates in harmony. Using
MEMS-based silicon precision timing chips offer superior stability that can reduce the need for constant re-synchronisation in high-data-rate applications, news, entertainment and live sports broadcasts, where multiple cameras are feeding data into the centralised processing hub. Precision timing ensures that all these streams stay in sync, so when the broadcast reaches your home, it looks smooth and uninterrupted.
FEBRUARY 2025 | ELECTRONICS FOR ENGINEERS 7
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