Multiple sampling rates ADAU1452
Hello,
finally got my ADAU1452 Board working. Based on the community help without any hastle. worked directly everything fine.
Now a small questions regarding programming:
I want to use a FIR filter at low frequencies. In order to avoid large amount of coefficients (getting short on computing resources rapidly!) I want to resample the low frequency part (fs/4 or similar), compute with short FIR, resample to fs and send it out.
As far as I understoof I could do it like this:
ASRC input from e.g. I2S; resample to fs/4; send to DSP core
Compute it in DSP core; send to another ASRC
Resample in ASRC to fs; send to DSP Core
Use any output in DSP core
So although my internal fs is then e.g. 48kHz I will only have computed this signal every 4. sequence. Correct?
Is there anything to remember for the FIR filter? I shorten the tabs to 1/4 and adjust to new sample rate. But is that all? Will it accordingly only be called every 4. sample? Or is it still called every sample (and I have to make it 48kHz) and no computing resources are saved?
Hope my question is clear....
cheers
Audio Signal Processors
adau1452
SigmaDSP Audio Processors
Hello Olombo,
Sorry for the delay. I had to inquire with several people around the company to get a grasp of the status of multi-rate processing for the ADAU1452 family of parts. The framework to support this is in place. There are a few other small details to be done to fully enable it. I think it may be ready for the next release but I am not sure. So at the moment it would require a custom cell to make it operational. Otherwise, your approach you mentioned would be exactly how you would implement it.
So now to switch over to your resource problem. What resource are you running short on?
Dave T
HI Olombo:
As Dave Mentions, this functionality will be available in an upcoming release. As for resources, since the 1452 is a quad core DSP, resource utilization might not be a problem for you given the fact that 4 multiplications and additions are being done every cycle. Memory however is indeed needed.
When doing the decimation, aren't you concerned of loosing higher frequencies?
Miguel
Hi Dave&Miguel,
thanks for taking care! However it is an interesting feature and I hope it will be implemented soon.
I do not really have a "resource problem". The Adau1452 really provides already a lot of possibilities. I can solve it for the moment using some IIR filters for the low freuquencies instead of very long FIRs (which in the end eat much ressources).
Since we wanted to use low sample rate and decimated FIR filter only for the low frequency drivers I do not really care if I loose something above e.g. 4kHz if using fs/6 at 48kHz.
Well then looking forward to upcoming releases! Thanks so far!
Olombo
Hello Olombo,
To add to what Miguel said. The DSP is capable of computing more FIR taps then there is memory on the part to hold. So you will not run out of computing resources only memory. We are coming out with a new part that will have more memory so if your application gets tight you may be able to solve it using only FIR filters in the near future.
Dave T
Will the new part be pin compatible? (Sounds great!)
-Ed
Hello Ed,
Yes, one of the variants will be pin compatible.
Dave T
Hello Dave,
well... nowadays it seems more comfortable to waste processing and memory ressources rather than take care on what we are doing ;-)
So use a pin compatible version with more memory might be a even easier solution to me. Any idea of the rough time range?
And: Can you tell if there is also something planned using more Data IO lines (just like ADAU 1442)?
Thanks!
HI Olombo:
The support for multi rate is independent from the newer part being released. We are expecting it to be included in a version of SigmaStudio this year (can't give you the exact date).
Newer parts will be both Pin compatible (same IO as the 1452) and a newer larger 88 pin package with more IO. Closer to the 1442.
Hope this helps.
Miguel
Hello Miguel,
if I ask too much for maybe not yet released information I am sorry. But it would be very interesting for me if the 88pin model will also be with at least similar (or larger) ressources (cpu&memory) compared to 1452. Samples expected for this year? Also happy if you can PM it :-)
Thanks!
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