RS output is not stable when using ADI surround algorithm
We use ADI surround algorithm to transform 2ch input to 5 ch output on ADAU1450 which ran on EVAL-ADAU1452MINIZ.
The following schematic is what we used:
For ADI Surround algorithm, the parameter settings are:
mode: music
size: small.
The connection to output is :
L: 0
C: 1
R: 2
LS: 32
RS:33
We put 1KHz 0dB sine signal as input source:
then check each channel's output.
We found that for RS channel, the output is not stable. The output
signal is output like the following image:
And the output of amplitude is changed periodically.
Can you help to confirm whether this output is correct or not ?
Audio Signal Processors
adau1452
adau1450
SigmaDSP Audio Processors
Hello WangTQ,
I do not have the time today to confirm this directly with lab measurements but I can mention a few things that should help.
This cell takes a stereo signal and produces a simulated LCRS signal. (and the "S" is a stereo surround).
So the way it figures out what signal to put in what channels has everything to do with the phase relationship of the signal. So putting in a sine wave perfectly in phase is telling the algorithm that this signal is meant for the center channel and so you should see most of the audio in the "C" output and none of the others. So the others will be down in the noise floor and that looks to me what you are looking at.
It will be difficult to test this using tones. You will have to alter the phase and I am not certain exactly what it is looking for to decide which channel to put it in. It is a good thought of how to test this but for now I suggest you use music and keep in mind that some songs will work better than others. It will all depend on how the song was mixed in the studio and how much out-of-phase information is present.
Dave T
Hello Dave,
Thanks for your quick reply!
Per your reply, what i got is that surround algorithm has the phase relationship of input signal. Sine wave input will lead to "C" output and none of others. But actually i can get all others output, and the output is exactly the sine wave, too. Only the RS channel is different, and the amplitude of RS channel is changed periodically.
Hello WangTQ,
I have put together a project that works on the EVAL-ADAU1452MINIZ. It has two oscillators that can change the phase and level. With this you can see how it adjusts based on level and frequency. There is heavy compression and some phase shifting on the surround signals as well to give a sense of movement so you will hear some of this if you listen to the surrounds by itself. It is not meant to be used in that way. You should setup speakers and hear them all at the same time.
Dave T
ADAU1452 ADI Surround Test.zip
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