- A clock determines the speet at which one or more systems + A clock determines the speed at which one or more systems operate. In the audio world this is generally referred to as Word Clock. It does not carry any absolute reference to a point in time: A clock is used to keep a system's sample rate regular and accurate. - Word clock is usually at the frequency of the sample rate—at 48 kHz, its period is about 20 μs. Word Clock is the most + Word clock is usually at the frequency of the sample rate—at 48 kHz, + its period is about 20 μs. Word Clock is the most common sample rate based clock but other clocks do exist such as Black and Burst, Tri-Level and DARS. Sample rates can be derived from these clocks as well.
@@ -34,16 +35,17 @@- JACK provides clock synchronization and is not concerned with time code + JACK (Ardour does this internally if using the ALSA backend) provides + clock synchronization and is not concerned with time code (this is not entirely true, more on jack-transport later). On the software side, jackd provides sample-accurate synchronization between all JACK applications. - On the hardware side, JACK uses the clock of the audio-interface. + On the hardware side, JACK and Ardour use the clock of the audio-interface. Synchronization of multiple interfaces requires hardware support to sync the clocks. If two interfaces run at different clocks the only way to align the signals is via re-sampling (SRC—Sample Rate Conversion), which is - expensive in terms of CPU usage and may decreases fidelity if done + expensive in terms of CPU usage and may decrease fidelity if done incorrectly.