5. VQE Algorithm Function Introduction

5.1. Voice Quality Enhancement (VQE)

For speechsignalprocessing (SSP) algorithm, When near-endspeechsignalsuffertofromfar-endechointerferenceorisnear-endstationary noiseinterferencewhen, can usingSSPinalgorithmfunctiontosuppressiontheseinterference, therebyimprovespeechsignalquality. SSPinprovide a solutionsolution, includinglinenessechocancellation (AEC) , non-linenessechosuppression (AES) , speechnoise reduction (NR) , Automatic Gain Control (AGC ) , ...etc.function. SSPalgorithmsupport8kHzand16kHzsampling rate, mono, 16bitssamplinglengthspeechsignal. inconnectundertopagewillIntroductioneachalgorithmfunctionandtheuseparameter.

Parameterspara_fun_configcorrespondingtofile cvi_comm_aio.h inu32OpenMask, can controlmicrophonepathSSPalgorithmfunction, Parameterspara_spk_fun_configcan controlspeakerpathSSPalgorithmfunction, eachbitscorrespondingalgorithmfunctionas followsTable described.

para_fun_config	Description(microphone path)
Bit 0	0:Disable AEC 1:Enable AEC
Bit 1	0:Disable AES 1:Enable AES
Bit 2	0:Disable NR 1:Enable NR
Bit 3	0:Disable AGC 1:Enable AGC
Bit 4	0:Disable Notch Filter 1:Enable Notch Filter
Bit 5	0:Disable DC Filter 1:Enable DC Filter
Bit 6	0:Disable DG 1:Enable DG
Bit 7	0:Disable Delay 1:Enable Delay

para_spk_fun_config	Description (speaker path)
Bit 0	0:Disable AGC 1:Enable AGC
Bit 1	0:Disable EQ 1:Enable EQ

Table: para_fun_config/para_spk_fun_config Parameter Description

5.2. AEC/AES (Acoustic Echo Cancellation/Acoustic Echo Suppression)

anyfull-duplextalksystemarchitectureallstoreinwithechointerference. echocancellationdevicecancancellationthroughnear-endacousticpath couplingbackmicrophonespeakeroutputecho. usingtheprovide a solutionsolution, linenessselfsuitableshouldfiltermodule (AEC) combine withnon-linenessechosuppressionmodule (AES) canvalidlysuppressionecho, fromandimprovespeechtalkquality.

Figure: AEC+AESperformance before and after processing

Four adjustable parameters are provided for tuning AEC/AES performance:

para_aec_init_filter_len/para_aec_filter_len: selfsuitableshouldfilterlength. according tonotsameprototypeechotailtimeadjustappropriatefilterlength. If selectlongerlength, willcauserelativelyhighMIPSandpower consumption.

para_aec_init_filter_len: onlyused to onestartappearechowhentuning.

para_aes_std_thrd: residual echo detection threshold. valuesetlargerwhen, near-endspeechqualitybetterbutresidual echorelativelymultiple. conversely, valuesetsmallerwhen, near-endspeechqualityworsebutresidual echoless.

para_aes_supp_coeff: residual echo suppression strength. valuesetlarger, forresidual echosuppressionstrengthlarger, butat the same timealsowill affectnear-endspeechwithtoexceedmultipleaudio detailsloss/damage.

AEC/AESParameters	Adjustable Range	Description
para_aec_init_filter_len/para_aec_filter_len	1 - 13	8kHzsampling rate: [1,13]corresponding[20ms,260ms] 16kHzsampling rate: [1,13]corresponding[10ms,130ms]
para_aes_std_thrd	0 - 39	0: residual echodeterminethresholdminimum 39: residual echodeterminethresholdmaximum
para_aes_supp_coeff	0 - 100	0: residual echosuppressionstrengthminimum 100: residual echosuppressionstrengthmaximum

Table: AEC/AES Parameter Description

5.3. NR (Noise Reduction)

NRmodulecansuppressionsurroundingenvironmentstationary noise, for examplefannoise, air conditionernoise, enginenoise, white/pinknoise, ...etc.etc.. relying onproprietaryspeechintelligentSpeech VADalgorithm, NRcanretainspeechsignal, at the same timealsocanvalidlysuppressionstationary noise, fromandimprovespeechtalkquality.

Figure: NRperformance before and after processing

Three adjustable parameters are provided for tuning NR performance:

para_nr_init_sile_time:**initial silence duration. CODEC may produce meaningless random noise when powered on, **para_nr_init_sile_time can willthissegmentsignalsetbecomesilence.

para_nr_snr_coeff: signal-to-Noise Ratio (SNR) withtracking coefficientnumber. If parametervaluelarger, thenNRwillhavehasrelativelyhighnoise reductioncapability, butspeechsignalmaywillmore likelydistortion. mutualreversely​​, parametervaluesmaller, thenNRwillsuppressionlessnoisesignal, butwillhavehasbetterspeechqualityperformance. underTable isbased onnotsameSNRenvironmentunder, thisparameterappropriateadjustrange, ineachtypeSNRcaseunder, parametervaluelarger, forstationary noisesuppressionstrengththenlarger.

NRParameters	Adjustable Range	Description
para_nr_init_sile_time	0 - 250	corresponding0sto5s, eachstep20ms

Table: NR Parameter Description

Surrounding SNR Environment	Adjustment Range	Description
Low	0 - 3	0: innoise reductionin noise reductionnotaggressive 3: innoise reductionmost aggressive in noise reduction
Medium	4 - 10	4: innoise reductionin noise reductionnotaggressive 10: innoise reductionmost aggressive in noise reduction
High	11 - 25	11: innoise reductionin noise reductionnotaggressive 25: innoise reductionmost aggressive in noise reduction

Table: para_nr_snr_coeffParameter Description

5.4. AGC (Automatic Gain Control)

AGCmodulecanautomaticwilloutput leveladjusttopresetrange, withprovidemorecomfortable listening experience. If input signallower than"Target Low", thenAGCwillwilloutput leveltoward"Target Low"adjust. anotheroneaspect, If input signalhigher than"Target High", thenAGCwillwilloutput leveltoward"Target High"adjust.

Figure: AGCadjustsignallevel

Figure: AGCperformance before and after processing

providefouritemadjustableparameter, used to tuningmicrophonepathAGCperformance, ittheyrespectivelyis:

para_agc_max_gain: thisparameterissignalcanbeplacelargemaximumgain.

para_agc_target_high: thisparameterisAGCwillwillreach"Target High"horizontal. For higher than para_agc_target_high**input signal, AGCwillwillitsconvergenceto **para_agc_target_high.

para_agc_target_low: thisparameterisAGCwillwillreach"Target Low"horizontal. For lower than para_agc_target_low**input signal, AGCwillwillitsconvergenceto **para_agc_target_low. If inreach para_agc_target_low**beforethenalreadyreach **para_agc_max_gain , thenAGConlywillconvergenceto para_agc_max_gain .

para_agc_vad_ena: Speech-activated AGC function. enablethisfunctionandat the same timeopen enableNRandAEC/AESfunctionwhen, canmakeAGCavoidplacelargeresidual backgroundstationary noiseandresidualback sound, withobtainobtainbettereffect.

AGCParameters	Adjustable Range	Description
para_agc_max_gain	0 - 6	[0,6]corresponding maximumraiserisegainis[6dB,42dB], eachstep6dB
para_agc_target_high	0 - 36	0to36corresponding0dBto-36dB
para_agc_target_low	0 - 72	0to72corresponding0dBto-72dB
para_agc_vad_ena	0 - 1	0: Disable Speech-activated AGC function 1: Enable Speech-activated AGC function

Table: microphonepathAGC Parameter Description

para_spk_agc_max_gain, para_spk_agc_target_high, para_spk_agc_target_low these threeparameterused to tuningspeakerpathAGCperformance, itsparameterdefinitionandtuningrangewithmicrophonepathAGCsame.

5.5. Notch Filter

Notch FilterParameters	Adjustable Range	Description
para_notch_freq	0 - 1	0: notch frequency is 1kHz 1: notch frequency is 4kHz

5.6. DG (Digital Gain)

thisfunctionhashelpreduceresidual echo and residual stationary noise. If if the signal gain level in the microphone channel is low, enabling this function is not recommended.

DGParameters	Adjustable Range	Description
para_dg_target	1 - 12	1: least aggressive residual echo/noise suppression, but best speech quality 12: most aggressive residual echo/noise suppression, but poorest speech quality

5.7. Delay

thisfunctionused to delayreferencesignal, can makeAEC/AESaccelerateconvergenceonestartappearecho. If alreadythroughadjustparameterpara_aec_init_filter_lenaccelerateconvergenceinitialecho, thennotrecommendenablethisfunction.

DelayParameters	Adjustable Range	Description
para_delay_sample	1 - 3000	1 to 3000 corresponding to 1 to 3000 samples

5.8. Equalizer

thisfunctionisFor speechsignalperform equalizationprocessing, can alreadybytuningbandcenter frequency,

gainandquality factor, adjustoutthewantneed tospeechsignalpresentfrequency response, alsocancompensate

hardwareorspeakerunitthecausenotperfectfrequency response.

EqualizerParameters	Adjustable Range	Description
para_spk_eq_nband	1 - 5	1to5corresponding1to5 bands
para_spk_eq_freq[]	8kHz Fs: 0 - 9 16kHz Fs: 0 - 10	Band center frequency; see the para_spk_eq_freq table
para_spk_eq_gain[]	0 - 60	Band gain; see the para_spk_eq_gain table
para_spk_eq_qfactor[]	0 - 17	Band quality factor. 0: withpara_spk_eq_freqisincenterfrequency responsecurvelinemostsmooth, but foritsnearbyfrequencyeffect widest range 17: withpara_spk_eq_freqisincenterfrequency responsecurvelinemostsharp, but foritsnearbyfrequencyeffectnarrowest range

[Note]:

When para_spk_eq_nbandconfigureis1when, need toat the same timeconfigurethecorrespondingpara_spk_eq_freq[0], para_spk_eq_gain[0], para_spk_eq_qfactor[0].

When para_spk_eq_nbandconfigureis2when, need toat the same timeconfigurethecorrespondingpara_spk_eq_freq[0], para_spk_eq_gain[0], para_spk_eq_qfactor[0] and para_spk_eq_freq[1], para_spk_eq_gain[1], para_spk_eq_qfactor[1], wherearrayindex 0parameterwill affect shouldtofirstitemband, arrayindex 1parameterwillcorrespondingtoseconditemband. and so on.

para_spk_eq_freq Parameters	Corresponding center frequency (Hz)
0	100
1	200
2	250
3	350
4	500
5	800
6	1200
7	2500
8	3300
9	3990
10( only applies to a 16 kHz sampling rate )	7990

para_spk_eq_gain Parameters	Corresponding gain (dB)	para_spk_eq_gainParameters	Corresponding gain (dB)
0	-40	31	-9
1	-39	32	-8
2	-38	33	-7
3	-37	34	-6
4	-36	35	-5
5	-35	36	-4
6	-34	37	-3
7	-33	38	-2
8	-32	39	-1
9	-31	40	+0
10	-30	41	+1
11	-29	42	+2
12	-28	43	+3
13	-27	44	+4
14	-26	45	+5
15	-25	46	+6
16	-24	47	+7
17	-23	48	+8
18	-22	49	+9
19	-21	50	+10
20	-20	51	+11
21	-19	52	+12
22	-18	53	+13
23	-17	54	+14
24	-16	55	+15
25	-15	56	+16
26	-14	57	+17
27	-13	58	+18
28	-12	59	+19
29	-11	60	+20
30	-10

VQE For Audio Input and Audio Output twoitempathdifferencesamepoint, respectivelythrough UpVQE and DnVQE twoitemschedulinglogicto processingtwoitempathdata, UpVQEincludingAEC, AES, NR, AGC. DnVQEcurrentbeforenot supported. correspondingparameter can referenceTable header filecvi_comm_aio.h.