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Clock Recovery and Jitter Reduction
To deal with one of the major technical imperfections of the HDMI interface, the Vanity
uses a pair of low-jitter digitally controlled oscillators and an adaptive control algorithm to lock
onto the incoming audio frequency and output the audio data with perfect timing, completely free
of any jitter or noise of the HDMI interface.
Audio data from the HDMI interface is buffered in FIFO memory and clocked out with local
high precision oscillators. As a result, the output signal is completely isolated from the noisy HDMI
domain - interferences from the power supplies, video circuits, etc.
Eye diagram of the output S/PDIF signal. Generic HDMI audio extractor – left, Vanity
Effectiveness of the clock recovery system can be seen in the two oscilloscope waveforms
above. There are waveforms with persistence enabled of the output S/PDIF signal – from a generic
HDMI extractor on the left and the Vanity
show accumulated phase noise using the colour grade. The difference in signal edge timing and
definition can be clearly seen.
Block diagram of the clock recovery system
PRO
on the right. The time base is delayed by 10ms to
Page 8 of 19
– User Manual v1.2
Vanity
PRO
– right.
PRO
PRO