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Drivers: DMIC: Move decimation factors 5 and 10 to less preferred 

This patch changes FIR decimation factors preference from
"2, 3, 4, 5, 6, 8, 10, 12" to "2, 3, 4, 6, 5, 8, 12, 10".

The prime number factor 5 and 10 (2*5) are less preferred because
when used for decimate for fist started FIR they restrict more the
configuration choices for the second FIR. If e.g. capture at 16 kHz
is started first with decimation factor 6, the 48 kHz stream can be
decimated from common 96 kHz CIC rate by 2.

Earlier the driver selected decimation by 5 to 16 kHz. There is no
integer decimation factor to decimate from 80 kHz to 48 kHz.

Similarly if decimate to 8 kHz programmed FIR to decimate by 10, the
same 80 kHz rate prevents 48 kHz for the other DAI. Decimation factor
12 sets up CIC to 96 kHz that is compatible with many other sample
rates.

Signed-off-by: Seppo Ingalsuo <seppo.ingalsuo@linux.intel.com>
This commit is contained in:
Seppo Ingalsuo 2020-11-10 15:43:06 +02:00 committed by Liam Girdwood
parent f5de034636
commit 190ce8bf7a
1 changed files with 17 additions and 9 deletions
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26
src/include/sof/audio/coefficients/pdm_decim/pdm_decim_table.h
View File

@ -40,9 +40,17 @@
#include "pdm_decim_int32_12_4156_5345_010_090.h"
#endif
/* Note: Higher spec filter must be before lower spec filter
* if there are multiple filters for a decimation factor. The naming
* scheme of coefficients set is:
/* Note 1: Higher spec filter must be before lower spec filter
* if there are multiple filters for a decimation factor. The first
* filter is skipped if the length is too much vs. overrun limit. If
* other order the better filter would be never selected.
*
* Note 2: The introduction order of FIR decimation factors is the selection
* preference order. The decimation factor 5 and 10 (2*5) cause a often less
* compatible output sample rate for CIC so they are not used if there other
* suitable nearby values.
*
* The naming scheme of coefficients set is:
* <type>_<decim factor>_<rel passband>_<rel stopband>_<ripple>_<attenuation>
*/
struct pdm_decim *fir_list[] = {
@ -56,20 +64,20 @@ struct pdm_decim *fir_list[] = {
#if CONFIG_INTEL_DMIC_FIR_DECIMATE_BY_4
&pdm_decim_int32_04_4318_5100_010_095,
#endif
#if CONFIG_INTEL_DMIC_FIR_DECIMATE_BY_5
&pdm_decim_int32_05_4325_5100_010_095,
#endif
#if CONFIG_INTEL_DMIC_FIR_DECIMATE_BY_6
&pdm_decim_int32_06_4172_5100_010_095,
#endif
#if CONFIG_INTEL_DMIC_FIR_DECIMATE_BY_5
&pdm_decim_int32_05_4325_5100_010_095,
#endif
#if CONFIG_INTEL_DMIC_FIR_DECIMATE_BY_8
&pdm_decim_int32_08_4156_5301_010_090,
#endif
#if CONFIG_INTEL_DMIC_FIR_DECIMATE_BY_10
&pdm_decim_int32_10_4156_5345_010_090,
#endif
#if CONFIG_INTEL_DMIC_FIR_DECIMATE_BY_12
&pdm_decim_int32_12_4156_5345_010_090,
#endif
#if CONFIG_INTEL_DMIC_FIR_DECIMATE_BY_10
&pdm_decim_int32_10_4156_5345_010_090,
#endif
NULL, /* This marks the end of coefficients */
};