AnsweredAssumed Answered

detect the lack of audio

Question asked by markhughes on Oct 20, 2015
Latest reply on Nov 24, 2015 by JeyasudhaMuthuPerumal


I have two AV channels from two ADV7612 with up to 8 channels of audio on
each.  I need to be able to sample rate convert all 16 channels, possibly delay
them and be able to switch them from either AV channel input to either AV
channel output.  This seems to be pretty much straight forward to do and the
ADAU1442 would seem to be the right fit.

I do have one slightly tricky question:
The audio coming from HDMI (via ADV7612) is not always present.  When the audio
disappears from HDMI, quite often you lose the audio clocks and framing data on
the I2S bus.  The AV is fed into an Audio video codec which doesn’t really like
the disappearance of the audio clocks.  What would be a better solution would
be to auto-detect when the audio is gone in the ADAU1442 and switch over to a
silent audio source, this would mean that codec would still see a valid I2S bus
and would just encode the silence.

It looks relatively easy to create the silence in the DSP;  I could use a tone
generator and attenuate the output massively with a volume control.  I can then
use a switch to swap to this source from one of the inputs if the audio

But I cant figure out how to detect the lack of audio,  any suggestions on what I could look at?