What does ASRC_PHASELEN_28 mean?

4 posts / 0 new
Last post
fendou1997
Offline
Last seen: 1 week 5 days ago
Joined: 11/16/2017 - 5:32am
What does ASRC_PHASELEN_28 mean?

What does ASRC_PHASELEN_28 mean in the audiodriver.c? And what does the function DSPC_ASRC_STATE_LEN and DSPC_ASRC_GUARD_LEN mean?

//dspc_asrc_init_Q15(&DSPC_ASRC_48000_TO_48000_32M_080DB_PROPS, USB_ASRCBuffer, DSPC_ASRC_STATE_LEN(INPUT_BLOCKSIZE, OUTPUT_BLOCKSIZE, ASRC_FS_IN_48000, ASRC_PHASELEN_28), DSPC_ASRC_GUARD_LEN(ASRC_FS_IN_48000, ASRC_FS_OUT_48000, ASRC_PHASELEN_28, OUTPUT_BLOCKSIZE), STEREO_CHANNEL_COUNT,  &USB_ASRC);

 

 

wait for your reply!

thank you!

Axel Nilsson
Offline
Last seen: 13 hours 48 min ago
Joined: 12/19/2016 - 2:02pm

Hi,

 

The ST reference BSPs on the website provide low-performance ASRCs (Asynchronous Sample Rate Converter) to safely synchronize the USB audio coming into the system. The macros you mention in your question are just for initializing the ASRC instance with the proper parameters for the given ASRC coefficients. These values do not need to be changed for the given implementation.

 

Thanks

-Axel

fendou1997
Offline
Last seen: 1 week 5 days ago
Joined: 11/16/2017 - 5:32am

I want to use the i2s of stm32 with two 24-bit digital microphones. Is the ASRC_PHASELEN_28 parameter changed to 24?

Axel Nilsson
Offline
Last seen: 13 hours 48 min ago
Joined: 12/19/2016 - 2:02pm

Hi,

You won't need to use the ASRC at all for the I2S interface, so no need to call any of the ASRC functions in the audio path for I2S.

 

Thanks

-Axel