Master Clock
The master clock allows devices that require accurate timing to be synchronised. The clock signal is distributed through the Facility Panels on BNC or Fibre depending upon the transmission distance. The same clock signal is also carried by the Dante protocol over ethernet, providing timing pulses to all Dante / AES67 devices on the network.
Clock synchronisation is critically important when pairing audio and video, or when using multiple audio or video devices together. If devices do not receive accurate clock signals they will drift, causing artefacts and communication problems.
Rates
The clock rates have been chosen to provide the greatest degree of interoperability between devices according to standards set by the Audio Engineering Society.
- Audio clock rate: 48kHz
- Video clock rate: 1080i50 (HD)
The house clock rates cannot be changed. If you require different clock rates, you must use standalone clocking generated by a local device as the master.
Clocking Rates for Recording
It is recommended that 48kHz be used in preference to 44.1kHz for audio recording [1], as this provides the greatest degree of compatibility between hardware and the latest audio format standards (eg. Blu-ray and Dolby Atmos) and can be easily down-converted to 44.1kHz for CD delivery. However, the recording studios each default to local 44.1kHz clocking for historical reasons. When producing audio recordings to be used with video, or using the Dante protocol to move audio between devices or facilities, a sampling rate of 48kHz must be used.
There are instructions provided on this wiki which describe how to change sample rates of the equipment provided in our studios.
Clocking
Devices can be clocked locally or synchronised to a high definition master clock which ensures every device receives the same timing pulse. This can be used to ensure a transmission 'lock' can be maintained between digital devices and is especially critical when working with audio for video content.
Hardware
New Adelphi uses an Antelope Isochrone Trinity master clock. This unit provides three audio clock outputs, three HD video clock outputs and four SD clock outputs.
- ↑ Audio Engineering Society, Inc., AES recommended practice for professional digital audio - Preferred sampling frequencies for applications employing pulse-code modulation (Audio Engineering Society, 2008) - AES5-2008
