sn986系列音频编解码器编程指南

Overview

SDKArchitecture

Features:

Audiocodecformats:

Hardwareaudiocodec

MS-ADPCM

A-LAW

Softwareaudiocodec

A-LAW

Mu-LAW

G.722

G.726

AudioCodecsamplerate

8/16/24/32/44.1/48Kbps

SN986SeriesSDK ludesaudiocodecdriverandudiomiddleware.

Interface

ALSA-Lib

Plug-in

ALSA-CORE

ALSADeviceDriver(AudioContro Drier)

SIGDriver

R2RDriver

I2S viceDriver

Figure01.AudioCodecSoftwarStack

AudioCodecDriver

AudioCodecDiverarebasedonAdvancedLinuxSoundArchitecture(ALSA).AudioCodecdriver luesaudiocontrollerdriver,Sigma-DeltaADCdriver,R2RDACdriver,AIC23driverandtw286 driver.

1. AdioMiddleware

AudioMiddleware ludesALSAlibrary,softwareaudiocodec(A-LAW,Mu-LAW,G.722,G.726)plugin,sonixaudiolibraryandaudiotesttools。

AudioCodecDriver

AudioCodecDriver

AudioCodecDriverludesaudiocontrollerdriverandAD/DAcodecsub-moduledivers.Inaddition,therearetwokindsofAD/DAcodecsub-moduledriver,whichisintnalcodecdriverandexternalcodecdriver.

Theaudiocontrollerdriverisma odecdriver,controlsI2S,digitaladustfunction,DDRbufferandallhardwarefunctioninaudiocontrollerhardware.

TheinternalAD/DAcodecsub-moduledrivercontrolsinternalcoec,whichisinsideSN986seriesIC.ThereareSigma-DeltaADCdriverandR2RDACdrivrforinternalcodec.

Additionally,theyareaplug-in,hooktoaudiocontrollerdiverandco-workwithit.

TheexternalAD/DAcodecsub-moduledrivercontrol ternalcodec,whichi ternalAD/DAICconnecttoSN986seriesICbyI2Sforaudodatatransfer,andothercontrolsignal(ex:I2CorSPI)forcontrolsettings.Currently,wesuportTITLV320AIC23codecdriverandTECHWELLTW2866codecdriver,andtheyaebothADCandDACdriver.

AudioCodecDriverUsageDescriptions

AudioCodecDriverludesaudiocontrolerdriverandAD/DAcodecsub-moduledrivers.Audiocontrollerdriverismaodedriver,andthismodulemustbeinsertedfirstlybeforeothercodecsub-modules.

TheAD/DAcodecsub-mod drivers ludeADorDAcodecsub-moduledriver,orbothinonemodule.SN986seriessupportonechannelandmonomodeaudioonbothADandDApath.Astheresult,onlyonADcodecsub-moduledriverandoneDAcodecsub-moduledrivercanbehookedorplug-in.

Thefollowing reusages:

Audioontrollerdriver:

ins odsnx_aud_core.ko[audio_cap=capability]

caabilitybit0standsforyornot,bit1standsforrecordornot,anddefaultis3bit0|bit1)

InternalSIGADCcodecsub-moduledriver:

insmodsnx_aud_sigma.ko[mic_in=enable]

enable1standsforenablemicrophone(differential)insignal,0standsforsinglendsignal

InternalR2RDACcodecsub-moduledriver:insmodsnx_aud_r2r.ko

ExternalTITLV320AIC23codecsub-moduledriver:snx_aud_aic23.ko[audio_cap=capability]

capabilitybit0standsforyornot,bit1standsforrecordrot,anddefaultis3(bit0|bit1)

ExternalTechwellTW2866codecsub-moduledriver:snx_aud_aic23.ko[audio_cap=capability]

capabilitybit0standsforyornot,bit1standsf recordornot,anddefaultis3(bit0|bit1)

AudioMiddleware

ALSALibrary

ALSALibraryIntroduction

TheALSALibrarycontainstheuserspacelibrarythatdeveloperscompileASAapplications

.

ApplicationprogrammersshouldusethelibraryAPIratherthanthekernelAI.ThelibraryoffersthefullfunctionalityofthekernelAPIandaddsmajorimprovem sinusabilitymakingtheapplicationcodesimplerandbetterlooking.Inaddition,futurefix orcompatibilitycodemaybecedinthelibrarycodeinsteadofthekerneldriver.

ALSALibraryCommonAPI

ThedetaileddescriptionofALSALibraryAPIs,pleaserefero“ALSAproject-theClibraryreference”.

ThedescriptionofALSAlibrarycommonAPIs:

FunctionName Descriptions

int snd_pcm_open(snd_pcm_t**pcm,constchar

*name,snd_pcm_stream_tstream,intmode)

OpensaPCM

int snd_pcm_close(snd_pcm_t*pcm) ClosePCMhandle

snd_pcm_hw_params_alloca Allocateaninvalidsnd_pcm_hw_params_tusingstandardalloca.

int snd_pcm_hw_params_any(snd_pm_t*pcm,snd_pcm_hw_params_t*params)

int snd_pcm_hw_params_setaccess(snd_pcm_t

*pcm,snd_pcm_hw_param_*params,snd_pcm_access_t_acess)

int snd_pcm_formawidh(snd_pcm_format_tformat)

int snd_pcmh rams_set_format(snd_pcm_t

*pcm,snd cm_w_params_t*params,snd_pcmformt_tval)

int s pcm_hw_params_set_channels

(snd_cm_t*pcm,snd_pcm_hw_params_t*params,u ignedintval)

FillparamswithafullconfigurationspaceforaPCM.

Restrictaconfigurationspacetocontainonlyoneaccesstype.

ReturnnominalbitsperaPCMsample.

Restrictaconfigurationspacetocontainonlyoneformat.

Restrictaconfigurationspacetocontainonlyonechannelscount.

int snd_pcm_hw_params_set_rate(snd_pcm_t

*pcm,snd_pcm_hw_params_t*params,unsignedintval,intdir)

int snd_pcm_hw_params_set_period_size(snd_pcm_t*pcm,snd_pcm_hw_params_t*params,snd_pcm_uframes_tval,intdir)

int snd_pcm_hw_params(snd_pcm_t*pcm,snd_pcm_hw_params_t*params)

snd_pcm_sframes_tsnd_pcm_readi(snd_pcm_t

*pcm,void*buffer,snd_pcm_uframes_tsize)

Restrictaconfigurationspacetocontainonlyonerate.

Restrictaconfigurationspacetocontainolyoneperiodsize.

InstallonePCMhardwareconfiguratnchosenfromaconfigurationspaceandsd_pcm_prepareit.

Readinterleavedfram omaPCM.

int snd_pcm_prepare(snd_pcm_t*pcm) PreparePCMforus

int snd_pcm_wait(snd_pcm_t*pcm,inttimeout) WaitforaPCMobcomeready.

int snd_pcm_drain(snd_pcm_t*pcm) StopaPCMpeservingpendingframes.int snd_pcm_start(snd_pcm_t*pcm) StartaPCM.

int snd_pcm_drop(snd_pcm_t*pcm)

StopaPCMdrop

pendingframes.

int snd_pcm_pause(snd_pcm_t*pcm,intenable) PauseesumePCM.

snd_pcm_sframes_tsnd_pcm_writei(snd_pcm_t

*pcm,constvoid*buffer,snd_pcm_uframes_tsize)snd_pcm_sframes_tsnd_pcm_readi(snd_pcm_t

*pcm,void*buffer,snd_pcm_uframes_tsize)

constchar*snd_pcm_stream_name(constsnd_pcm_stream_tstream)

constchar*snd_pcm_access_namecontsnd_pcm_access_t_access)

constchar*snd_pcm_format_nam(constsnd_pcm_format_tformat)

constchar*snd_pcm_fomadescription(constsnd_pcm_format_tfo at)

constchar*snd_pmsbformat_description(constsnd_pcm_subformat_tsubformat)

WrteinterleavedframestoaPCM.

ReadinterleavedframesfromaPCM.

GetnameofPCMstreamtype

GetnameofPCMaccesstype

GetnameofPCMsampleformat

GetdescriptionofPCMsampleformat

GetdescriptionofPCMsamplesubformat

constchar* error(interrnum) Returnsthemessageforanerrorcode.

Table01.ALALibaryCommonAPIDescriptions

ALSALibraryUsageDescriptions

3.31 Generaloverview

ALSAusestheringbuffertostoreoutgoing(yback)and oming(capture,record)samples.Therearetwopointersbeingmaintainedtoallowaprecisecommunicationbetweenapplicationanddevicepointingtocurrentprocessedsamplebyhardwareandlastprocesedsamplebyapplication.Themodernaudiochipsareallowedtobeprogrammedthetransfertimeperiods.Itmeansthatthestreamofsamplesisdividedtosmallchunks.Devieacknowledgestoapplicationwhenthetransferofachunkiscomplete.

PCMnamingconventions

TheALSAlibraryusesagenericstringrepresentationfornamesofdevices.Thedevicesmightbevirtual,physicaloramixofboth.Thegenericstringispassedtosnd_pcm_open().Itcontainstwoparts:devicenameandarguments.Devicesandarumentsaredescribedinconfigurationfiles.Theusualcefordefauefinitionsisatur/share/alsa/alsa.conf.

About/usr/share/alsa/alsa.conffilesyntax,seeConfiguraionfes

Blockedandnon-blockedopen

TheALSAPCMAPIusesadifferentbehaviourwhenthedeviceisopenedwithblockedornon-blockedmode.Themodecanbespecifiedwihmodeargumentinsnd_pcm_open()function.Theblockedmodeisthedefault(wihoutSND_PCM_NONBLOCKmode).Inthismode,thebehaviouristhatiftheresourcehavealreadyusedwithanotherapplication,thenitblocksthecaller,untilresourcesareThenon-blockedbehaviour(withSND_PCM_NONBLOCK)doesn'tblokthecallerinanywayandreturns-EBUSYerrorwhentheresourcesarenotavailable.No thatthemodealsodeterminesthebehaviourofstandardI/Ocalls,returning-EAGAINwhennon-blockedmodeisusedandtheringbufferisfull(yback)orempty(capt e).

Example:

intrc;

snd_pcm_t*hanle

rc=snd_pm_open(&handle,"hw:0,0",SND_PCM_STREAM_CAPTURE,SND_PCM_NONBLOCK);if(rc<0)

{

fintf(stderr,"unabletoope mdevice:%s\n",snd_strerror(rc));exit(1);

}

Setuptheparamsofdevice

TheALSAPCMdeviceusestwogroupsofPCMrelatedparameters.Thehardwareparameterscontainsthestreamdescriptionlikeformat,rate,countofchannels,ringbffersizeetc.Thesoftwareparameterscontainsthesoftware(driver)relatedparametes. hecommunicationbehaviourcanbecontrolledviatheseparameters,likeautomaticstart,automaticstop,interrupting(chunkacknowledge)etc.Thesoftwareparamerscanbemodifiedatanytime(whenvalidhardwareparametersareset).It ludestherunningstateaswell.

Hardwarerelatedparameters

TheALSAPCMdevicesusetheparameterrefiningsystemforhardwareparameters-snd_pcm_hw_params_t.Itmeans,thatapplicationchoosetheful-rangeofconfigurationsatfirstandthenapplicationsetssingleparametersuntilallaametersareelementary(definite).

Accessmodes

ALSAknowsaboutfiveaccessmodes.Thefirstthreeanbeusedfordirectcommunication.

SND_PCM_ACCESS_MMAP_INTERLEAVEDdeterminesthedirectmemoryareaandinterleavedsampleorganization.Interleavedrganizationmeans,thatsamplesfromchannelsaremixedtogether.

SND_PCM_ACCESS_MMAP_NONINERLEAVEDdeterminesthedirectmemoryareaandnon-interleavedsampleorganizatin.Eachchannelhasaseparatebufferinthecase.

SND_PCM_ACCESS_MMAP_OMPLEXrepresentsthecomplexdirectmemoryorganization.Thesampleoganizationdoesnotfittheinterleavedornon-interleavedaccessmodesinthecase.

Thelasttwoaccesmodesdescribetheread/writeaccessmethods.TheSND_PCM_ACCESS_RW_INTERLEAVEDrepresentstheread/writeinterleavedaccess,andtheSND CM_ACCESS_RW_NONINTERLEAVEDrepresentsthenon-interleavedaccess.

Form s

Thfulllistofformatsisavailableinsnd_pcm_format_tenumeration.

Example:

snd_pcm_hw_params_t*params

/*Allocateahardwareparametersobject.*/snd_pcm_hw_params_alloca(¶ms);

/*Fillitinwithdefaultvalues.*/snd_pcm_hw_params_any(handle,params);

/*Setthedesiredhardwareparameters.*/

/*Interleavedmode*/

snd_pcm_hw_params_set_access(handle,params,SND_PCM_ACCESS_RW_INTERLEAVED);

/*SND_PCM_FORMAT_S16Format*/snd_pcm_hw_params_set_format(handle,params,SND_PCM_FORAT_S16);

/*onechannel(mono)*/snd_pcm_hw_params_set_channels(handle,params,1);

/*8KHzsamplingrate*/snd_pcm_hw_params_set_rate(handle,params,8000,0);

/*Writetheparameterstothedriver*/

rc=snd_pcm_hw_params(handle,params)if(rc<0)

{

fprintf(stderr,"unabletoset parameters:%s\n",snd_strerror(rc));exit(1);

}

Softwarerelatedparameters

Theseparmeters-snd_pcm_sw_params_tcanbemodifiedatanytime ludingtherunningstte.

Mnimmavailablecountofsamples

Thiparametercontrolsthewakeuppoint.Ifthecountofavailablesamplesisequalorgreater

thanthisvalue,theapplicationwillbeactivated.

Timestampmode

Thetimestampmodespecifies,iftimestampsareactivated.Currently,onlySND_PCM_TSTAMP_NONEandSND_PCM_TSTAMP_MMAPmodesareknownThemmapmodemeansthattimestampistakenoneveryperiodtimeboundary.Correspondingpositionintheringbufferassignedtotimestampcanbeobtainedusingsnd_pcm_htimestamp()function.

Transferalign

Theread/writetransferscanbealignedtothissamplecount.Themoduloisignoredbydevice.Usually,thisvalueissettoone(noalign).

Startthreshold

Thestartthresholdparameterisusedtodeterm hest tpointinstream.Foryback,ifsamplesinringbufferisequalorgreaterthanthestartthresholdparametersandthestreamisnotrunning,thestreamwillbestartedautomaticllyfromthedevice.Forcapture,iftheapplicationwantstoreadcountofsamplesequalogreaterthenthestreamwillbestarted.Ifyouwanttouseexplicitstart(snd_pcm_start),youcansetthisvaluegreaterthanringbuffersize(insamples),butusetheconstantMAXINTisnotabadidea.

Stopthreshold

Similarly,thestopthresholdparameteisusedtoautomaticallystoptherunningstream,whentheavailablesamplescrossesthis undary.Itmeans,foryback,theemptysamplesinringbufferandforcapture,thefille(used)samplesinringbuffer.

Silencethreshold

Thesilencethresholdspecifescountofsamplesfilledwithsilenceaheadofthecurrentapplicationpointerforpayack.Itisusableforapplicationswhenanoverrunispossible(liketasksdependingo workI/Oetc.).Ifapplicationwantstomanagetheaheadsamplesitself,thesnd_pcm_rewind()functionallowstoforgetthelastsamplesinthestream.

Example:

interr;

/*getthecu nts rams*/

err=snd_cm_sw_params_current(handle,s rams);iferr<)

{

printf("Unabletodeterminecurrentsramsforyback:%s\n",snd_strerror(err));returnerr;

}

/*startthetransferwhenthebufferisalmostfull:*/

/*(buffer_size/avail_min)*avail_min*/

err=snd_pcm_sw_params_set_start_threshold(handle,srams,(buffer_size/period_size)period_size);if(err<0)

{

printf("Unabletosetstartthresholdmodeforyback:%s\n",snd_strerro r);returnerr;

}

/*allowthetransferwhenatleastperiod_sizesamplescanbeprocesed

/*ordisablethismechanismwhenperiodeventisenabled(akainterptlikestyleprocessing)*/ err=snd_pcm_sw_params_set_avail_min(handle,srams,period_event?buffer_size:period_size);

if(err<0)

{

printf("Unabletosetavailminforyback:%s\n,snd_trerror(err));returnerr;

}

/*enableperiodeventswhenrequested*/if(period_event)

{

err=snd_pcm_sw_params_s period_event(handle,s rams,1);if(err<0)

{

printf("Unabletoetperiodevent:%s\n",snd_strerror(err));returnerr;

}

}

/*writetheparamerstotheybackdevice*/err=snd_pcsw_params(handle,srams);if(err<0)

{

prtf("Unabletosets ramsforyback:%s\n",snd_strerror(err));turnerr;

}

Handshak weenapplicationandlibrary

TheALSAPCMAPIdesignusesthestatestodeterm hecommunicationphasbtweenapplicationandlibrary.Theactualstatecanbedeterminedusingsnd_pcm_sate()call.Therearethesestates:

SND_PCM_STATE_OPEN

ThePCMdeviceisintheopenstate.Afterthesnd_pcm_open()opnall,thedeviceisinthisstate.Also,whensnd_pcm_hw_params()callfails,thenthisstateisenteredtoapplicationcallingsnd_pcm_hw_params()functiontosetrightcmmunicationparameters.

SND_PCM_STATE_SETUP

ThePCMdevicehasacceptedcommunicationparamete anditiswaitingforsnd_pcm_prepare()calltopreparethehardwareforselectedoperation(ybackorcapture).

SND_PCM_STATE_PREPARED

ThePCMdeviceispreparedforoperation.Applicationcanusesnd_pcm_start()call,writeorreaddatatostarttheoperation.

SND_PCM_STATE_RUNNING

ThePCMdevicehasbeenstartedandisunning.Itprocessesthesamples.Thestreamcanbestoppedusingthesnd_pcm_dro()orsnd_pcm_drain()calls.

SND_PCM_STATE_XRUN

ThePCMdevicereachedovrrun(capture)orunderrun(yback).Youcanusethe-EPIPEreturncodefromI/Ofunctios(snd_pcm_writei(),snd_pcm_writen(),snd_pcm_readi(),snd_pcm_readn())todterm hisstatewithoutcheckingtheactualstateviasnd_pcm_state()call.Itisrecommendedtousethehelperfunctionsnd_pcm_recover()torecoverfromthisstte,butyouc sousesnd_pcm_prepare(),snd_pcm_drop()orsnd_pcm_dran()calls.

SND_PCMSTATE_DRAINING

Thedevic isinthisstatewhenapplicationusingthecapturemodecalledsnd_pcm_drain()functionUntilalldataarereadfromtheinternalringbufferusingI/Oroutines

(snd_pm_readi(),snd_pcm_readn()),thenthedevicestaysinthisstate.

Managingthestreamstate

Thefollowingfunctionsdirectlyandindirectlyaffectthestreamstate:

snd_pcm_hw_params

Thesnd_pcm_hw_params()functionbringsthestreamstatetoSND_PCM_STATE_SETUPifsuccessfullyfinishes,otherwisethestateSND_PCM_STATE_OPENisenteed.WhenitisbroughttoSETUPstate,thisfunctionautomaticallycallssnd_pcm_prepare()functiontobringtothePREPAREDstateasbelow.

snd_pcm_prepare

Thesnd_pcm_prepare()functionentersfromSND_PCM_STATE_SETUPtotheSND_PCM_STATE_PREPAREDafsuccessfulfinish.

snd_pcm_start

Thesnd_pcm_start()functionenterstheSND_PCM_STATE_RUNNINGaf successfulfinish.

snd_pcm_drop

Thesnd_pcm_drop()functionenterstheSND_PCM_STATE_SETUPstate.

snd_pcm_drain

Thesnd_pcm_drain()functionentersthSND_PCM_STATE_DRAINING,ifthecapturedevicehassomesamplesintheringbfferotherwiseSND_PCM_STATE_SETUPstateisentered.

snd_pcm_pause

Thesnd_pcm_pause()funcionenterstheSND_PCM_STATE_PAUSEDorSND_PCM_STATE_RUNNING.

snd_pcm_writei,ndpcm_writen

Thesnd_pcm_writei()andsnd_pcm_writen()functionscanconditionallystartthestream-SND_PCM_SATE_RUNNING.Theydependonthestartthresholdsoftwareparameter.

snd_pcmredi,snd_pcm_readn

Thes _pcm_readi()andsnd_pcm_readn()functionscanconditionallystartthestream-SNDPCM_STATE_RUNNING.Theydependonthestartthresholdsoftwareparameter.

Forthedetailusage,pleaserefertoapp/example/src/audio/ac/snx_audio_codec.c

SoftwareAudioCodecPlugin

WecurrentlysupportA-LAW,Mu-LAW,G.722andG.726softwareaudiocodec.

Themaindifferencweenhardwareaudiocodecandsoftwareaudiocodecisdevicename.Callsnd_pcm_open()functionwithdifferentdevicenameparametecnusethecorrespondingsoftwareaudiocodec.

DeviceName Descriptions

hw:0 Hardwareaudiocodec(PCM,MS-ADPCM,A-LAW)

snx_audio_alaw SoftwareA-LAWcodec

snx_audio_mulaw SoftwareMu-LAWcodec

snx_audio_g722 SoftwareG.722codec

snx_audio_g726 SoftwareG.726codec

Table02.DeviceNameDescriptions

SonixAudioLibrary

SonixAudioLibrarycurrentlyonlyprovidescontrlthevolumeofmicrophonesandspeaker.It’sbasedontheALSALibrary.

FunctionName Descriptions

HerearethedescriptionoixAudioLibraryAPI.

intsnx_audio_mic_vol_get_items(intcadnum,int*items)Gettheitemsofmicrophonevolume

adjustment.

intsnx_audio_mic_vol_set(intcadnum,intvol) Setthevolumeofmicrophone.intsnx_audio_mic_vol_get(intcd_num,int*vol) Getthevolumeofmicrophone.intsnx_audio_mic_vol_setmue(intcard_num,intmute) Setthemicrophonemute.

intsnx_audio_mic_v_getmute(intcard_num,int*mute)Determinewhetherthemicrophone

ismute.

intsnx_audio_sk_vol_get_items(intcard_num,int*items)Gettheitemsofspeakervolume

adjustment.

intsnx_audispk_vol_set(intcard_num,intvol) Setthevolumeofspeaker.intsnxau_spk_vol_get(intcard_num,int*vol) Getthevolumeofspeaker.intsnx_dio_spk_vol_set_mute(intcard_num,intmute) Setthespeakermute.

itsnxaudio_spk_vol_get_mute(intcard_num,int*mute)Determinewhetherthespeakerismute.

Table03.SonixAudiolibraryAPIDescri