Distortion of ASRC

[jian-yuan-cmd]

Hardware uses L71 board;
Software reference: https://www.xmos.com/documentation/XM-014785-PC/html/doc/programming_guide/asrc/overview.html

After compilation, download the firmware into the L71 board;
The customer tested the ASRC performance using AP and found two types of ASRC distortion:

1 .
0dB sine wave distortion:
it is OK after adjusting the signal amplitude to -0.1dB;

2
Distortion after AP switching sampling frequency:
for example:
After switching the sampling frequency of the AP instrument’s I2S_output from 44.1KHz to 48KHz,
The frequency of the 1KHz sine wave output by the AP instrument had changed to 0.9KHz after process by XU316_ASRC task;
It seems that the ASRC task has not detect the changes of I2S_Slave’s sampling frequency.
In this case, if turn off the I2S output of the AP instrument and then turn it on, the ASRC output will be OK.

[ed-xmos]

Hi, I believe 1) is related to https://github.com/xmosnotes/an02003/issues/35

We added some docs - https://github.com/xmosnotes/an02003/blob/d33241b0679add1746816b64763c03ede434670d/doc/rst/an02003.rst?plain=1#L327

for the code:

https://github.com/xmosnotes/an02003/blob/d33241b0679add1746816b64763c03ede434670d/app_an02003/src/utils.h#L78

Does this explain it for you?

We have added some notes and a pre-attenuate, post-gain to AN02003. Do you think adding documentation to this repo makes sense too?

[ed-xmos]

Regarding 2), this depends on the application used because ASRC task (assume you are using this) must be informed of the SR change. Can you please provide details of the app used? If confidential, please send via teams.

[jian-yuan-cmd]

This project is used for Sample rate conversion between USB and I2S_slave.
I built the project based on the information provided here.
https://www.xmos.com/documentation/XM-014785-PC/html/doc/programming_guide/asrc/overview.html
The customer uses the USB for connect mobile phone's USB;
and I2S for connect another XMOS chip.