PITCH TRANSPOSER

Hi Takepiro,

Unfortunately, there is no schedule for completion of the Pitch Transposer documentation and help files.

Best regards,

Coleman

Hi Takepiro,

Sometimes when official documentation is lacking, the best thing to do is just run a test and see what it does.

The pitch shifter for the ADAU1701 behaves as shown below when fed a steady tone while the slider is at min and max positions, for various settings of the Max Shift control:

It appears that the max shift control is calibrated in % change, either up or down.

If / when the pitch shifter is implemented on the ADAU145x, it may behave the same, or differently.

Best regards,

Bob

Dear Bob-san,

Thank you very much for your answer.

I already run and check the library.

In the evaluation , I think that Max shift is %.

At ADAU1761 , Max shift=100 means 10%.

But, frequency of output is strange , when Input frequency is under 500Hz.

Does the library have some limitation for input frequency and output frequency?

Best regards,

Takepiro

Hello Takepiro,

Yes, the transpose range is limited, definitely so when reducing pitch. Since your tests were with a ADAU1761, I re-ran my tests with a -1761 and found similar results to those of the -1701. This time around I tried a few Max Shift settings above 100 at 2000 Hz, and found the results shown in red below:

It appears that downward shifts exceeding 100 go past zero Hz, then begin adding to the output frequency -- perhaps due to an underflow in the algorithm. Thus it appears that the block is not designed to go over 100, at least on the downward side. Upward shifts can exceed 100, but extreme upward shifts on high input frequencies may run into aliasing (my tests did not go that high). Within the range that works, the Shift numbers always represent a percentage change from the input frequency,

Best regards,

Bob

Dear Bob-san,

Thank you for your answer.

I got a compleate calculation for this module on ADAU1761 by your advice.

Output frequency = Input frequency - (Input frequency x (Delay Reserved x 0.001) x Max shift(%))

Ex)

Inputu fequency = 1000

Delay Reserved = 2000

Max shift = 1

Output Min = 980, output Max = 1020.

In my examination , Delay reserved value might relate to output frequency.

Best regards,

Takepiro

when the pitch shifter is implemented on the ADAU145x?

Hi,

The pitch transposer is on our 'To Do' list for the ADAU145x, but we do not have a release date at this time.

Best regards,

Coleman

Hi,

I still can not use this function because of the amplitude modulation problem.Is there any method to remove?