Audio audiorecord create (I)

        AudioRecord create Related code flow 、 Focus on key interfaces 、 Parameter analysis and related log share Analysis and comparison .

1.frameworks/base/media/java/android/media/AudioRecord.java

Argument parsing ：

audioSource: MediaRecorder.AudioSource.MIC, Detailed definition requires check MediaRecorder.AudioSource;

sampleRateInHz： Default sample rate , Company Hz,44100Hz It is the only sampling rate that can guarantee the operation on all equipment ;

channelConfig： Describe the audio channel settings ,AudioFormat.CHANNEL_CONFIGURATION_MONO Guarantee to work on all equipment ;

audioFormat： Audio data is guaranteed to support this format , I'm going to set it to AudioFormat.ENCODING_16BIT;

bufferSizeInBytes： During the recording , The number of bytes of audio data written to the buffer ,getMinVufferSize() The value obtained .

  The main parsing process is native_setup Processing in function , It should be noted that it is different from different audio Called session Id.

@SystemApi
    public AudioRecord(AudioAttributes attributes, AudioFormat format, int bufferSizeInBytes,
            int sessionId) throws IllegalArgumentException {

        mRecordingState = RECORDSTATE_STOPPED;

        ...

        ///*add by shengjie for parse AudioRecorder
        //1.REMOTE_SUBMIX How is this sound source handled , No follow , You can follow up if there is a project need 
        //*/
        // is this AudioRecord using REMOTE_SUBMIX at full volume?
        if (attributes.getCapturePreset() == MediaRecorder.AudioSource.REMOTE_SUBMIX) {
            final AudioAttributes.Builder filteredAttr = new AudioAttributes.Builder();
            final Iterator<String> tagsIter = attributes.getTags().iterator();
            while (tagsIter.hasNext()) {
                final String tag = tagsIter.next();
                if (tag.equalsIgnoreCase(SUBMIX_FIXED_VOLUME)) {
                    mIsSubmixFullVolume = true;
                    Log.v(TAG, "Will record from REMOTE_SUBMIX at full fixed volume");
                } else { // SUBMIX_FIXED_VOLUME: is not to be propagated to the native layers
                    filteredAttr.addTag(tag);
                }
            }
            filteredAttr.setInternalCapturePreset(attributes.getCapturePreset());
            mAudioAttributes = filteredAttr.build();
        } else {
            mAudioAttributes = attributes;
        }

        ...

        ///*add by shengjie for parse AudioRecord
        //2.audioParamCheck Check the validity of parameters , assignment mRecordSource、mSampleRate、mAudioFormat
        //*/
        audioParamCheck(attributes.getCapturePreset(), rate, encoding);

        ///*add by shengjie for parse AudioRecord
        //3. Get the number of channels and the channel mask , The mono mask is 0x10, The dual channel mask is 0x0c;
        //*/
        if ((format.getPropertySetMask()
                & AudioFormat.AUDIO_FORMAT_HAS_PROPERTY_CHANNEL_INDEX_MASK) != 0) {
            mChannelIndexMask = format.getChannelIndexMask();
            mChannelCount = format.getChannelCount();
        }
        if ((format.getPropertySetMask()
                & AudioFormat.AUDIO_FORMAT_HAS_PROPERTY_CHANNEL_MASK) != 0) {
            mChannelMask = getChannelMaskFromLegacyConfig(format.getChannelMask(), false);
            mChannelCount = format.getChannelCount();
        } else if (mChannelIndexMask == 0) {
            mChannelMask = getChannelMaskFromLegacyConfig(AudioFormat.CHANNEL_IN_DEFAULT, false);
            mChannelCount =  AudioFormat.channelCountFromInChannelMask(mChannelMask);
        }

        audioBuffSizeCheck(bufferSizeInBytes);

        int[] sampleRate = new int[] {mSampleRate};

        ///*add by shengjie for parse AudioRecord
        // One Session It's just a conversation , Each session has a unique Id To mark . The Id The final management of is AudioFlinger in .
        // A session can be used by more than one AudioTrack Objects and MediaPlayer share .
        // Share one Session Of AudioTrack and MediaPlayer Share the same AudioEffect（ Sound effect ）.
        //*/
        int[] session = new int[1];
        session[0] = sessionId;
        //TODO: update native initialization when information about hardware init failure
        //      due to capture device already open is available.
        int initResult = native_setup( new WeakReference<AudioRecord>(this),
                mAudioAttributes, sampleRate, mChannelMask, mChannelIndexMask,
                mAudioFormat, mNativeBufferSizeInBytes,
                session, getCurrentOpPackageName(), 0 /*nativeRecordInJavaObj*/);
        if (initResult != SUCCESS) {
            loge("Error code "+initResult+" when initializing native AudioRecord object.");
            return; // with mState == STATE_UNINITIALIZED
        }

        mSampleRate = sampleRate[0];
        mSessionId = session[0];

        mState = STATE_INITIALIZED;
    }

 

2.frameworks/base/core/jni/android_media_AudioRecord.cpp

Main work ： call AudioRecord.cpp Of set The function interface , And set up
    audiorecord_callback_cookie *lpCallbackData Callback is used to transmit audio data buffer.

static jint
android_media_AudioRecord_setup(JNIEnv *env, jobject thiz, jobject weak_this,
        jobject jaa, jintArray jSampleRate, jint channelMask, jint channelIndexMask,
        jint audioFormat, jint buffSizeInBytes, jintArray jSession, jstring opPackageName,
        jlong nativeRecordInJavaObj)
{
    //ALOGV(">> Entering android_media_AudioRecord_setup");
    //ALOGV("sampleRate=%d, audioFormat=%d, channel mask=%x, buffSizeInBytes=%d "
    //     "nativeRecordInJavaObj=0x%llX",
    //     sampleRateInHertz, audioFormat, channelMask, buffSizeInBytes, nativeRecordInJavaObj);
   
    ...
    sp<AudioRecord> lpRecorder = 0;
    audiorecord_callback_cookie *lpCallbackData = NULL;

    // if we pass in an existing *Native* AudioRecord, we don't need to create/initialize one.
    if (nativeRecordInJavaObj == 0) {
        if (jaa == 0) {
            ALOGE("Error creating AudioRecord: invalid audio attributes");
            return (jint) AUDIO_JAVA_ERROR;
        }

        if (jSampleRate == 0) {
            ALOGE("Error creating AudioRecord: invalid sample rates");
            return (jint) AUDIO_JAVA_ERROR;
        }
        ///*add by shengjie for parse AudioRecord setup
        //1.got sample Rate from new AlsaRecord(44100hz/16khz)
        jint elements[1];
        env->GetIntArrayRegion(jSampleRate, 0, 1, elements);
        int sampleRateInHertz = elements[0];
        //*/

        // channel index mask takes priority over channel position masks.
        if (channelIndexMask) {
            // Java channel index masks need the representation bits set.
            localChanMask = audio_channel_mask_from_representation_and_bits(
                    AUDIO_CHANNEL_REPRESENTATION_INDEX,
                    channelIndexMask);
        }
        // Java channel position masks map directly to the native definition

        if (!audio_is_input_channel(localChanMask)) {
            ALOGE("Error creating AudioRecord: channel mask %#x is not valid.", localChanMask);
            return (jint) AUDIORECORD_ERROR_SETUP_INVALIDCHANNELMASK;
        }

        ///*add by shengjie for parse AudioRecord setup
        //2.got channel count from new AlsaRecord(1/2/4 ch)
        uint32_t channelCount = audio_channel_count_from_in_mask(localChanMask);
        //*/

        // compare the format against the Java constants
        ///*add by shengjie for parse AudioRecord setup
        //3.got audio format from new AlsaRecord(16bit/32bit)
        audio_format_t format = audioFormatToNative(audioFormat);
        if (format == AUDIO_FORMAT_INVALID) {
            ALOGE("Error creating AudioRecord: unsupported audio format %d.", audioFormat);
            return (jint) AUDIORECORD_ERROR_SETUP_INVALIDFORMAT;
        }
        //*/

        ///*add by shengjie for parse AudioRecord setup
        size_t bytesPerSample = audio_bytes_per_sample(format);

        if (buffSizeInBytes == 0) {
             ALOGE("Error creating AudioRecord: frameCount is 0.");
            return (jint) AUDIORECORD_ERROR_SETUP_ZEROFRAMECOUNT;
        }
        //4.1  Size of each sampling frame : Number of all channels  *  Number of bytes per frame 
        size_t frameSize = channelCount * bytesPerSample;
        //4.2  Number of sampling frames ： Minimum buffer size  /  Size of each sampling frame 
        size_t frameCount = buffSizeInBytes / frameSize;
        //*/

        ScopedUtfChars opPackageNameStr(env, opPackageName);

        // create an uninitialized AudioRecord object
        lpRecorder = new AudioRecord(String16(opPackageNameStr.c_str()));

        // read the AudioAttributes values
        auto paa = JNIAudioAttributeHelper::makeUnique();
        jint jStatus = JNIAudioAttributeHelper::nativeFromJava(env, jaa, paa.get());
        if (jStatus != (jint)AUDIO_JAVA_SUCCESS) {
            return jStatus;
        }
        ALOGV("AudioRecord_setup for source=%d tags=%s flags=%08x", paa->source, paa->tags, paa->flags);

        audio_input_flags_t flags = AUDIO_INPUT_FLAG_NONE;
        if (paa->flags & AUDIO_FLAG_HW_HOTWORD) {
            flags = AUDIO_INPUT_FLAG_HW_HOTWORD;
        }
        // create the callback information:
        // this data will be passed with every AudioRecord callback
        lpCallbackData = new audiorecord_callback_cookie;
        lpCallbackData->audioRecord_class = (jclass)env->NewGlobalRef(clazz);
        

        // we use a weak reference so the AudioRecord object can be garbage collected.
        ///*add by shengjie for parse AudioRecord setup
        //5.AudioRecord.java The pointer to is bound to lpCallbackData Callback data , In this way, the data can be notified to the upper layer through callback 
        lpCallbackData->audioRecord_ref = env->NewGlobalRef(weak_this);
        lpCallbackData->busy = false;
        //*/


        ///*add by shengjie for AudioRecord setup
        //6. call AudioRecord.cpp Of set function ,flags, His type is audio_input_flags_t, It's defined in audio-base.h in , As a sign of audio input , Here is AUDIO_INPUT_FLAG_NONE, No special settings 
        const status_t status = lpRecorder->set(paa->source,
            sampleRateInHertz,
            format,        // word length, PCM
            localChanMask,
            frameCount,
            recorderCallback,// callback_t
            lpCallbackData,// void* user
            0,             // notificationFrames,
            true,          // threadCanCallJava
            sessionId,
            AudioRecord::TRANSFER_DEFAULT,
            flags,
            -1, -1,        // default uid, pid
            paa.get());
        //*/

        ...

        // Set caller name so it can be logged in destructor.
        // MediaMetricsConstants.h: AMEDIAMETRICS_PROP_CALLERNAME_VALUE_JAVA
        lpRecorder->setCallerName("java");
    } else { // end if nativeRecordInJavaObj == 0)
        lpRecorder = (AudioRecord*)nativeRecordInJavaObj;
        // TODO: We need to find out which members of the Java AudioRecord might need to be
        ...

        // create the callback information:
        // this data will be passed with every AudioRecord callback
        lpCallbackData = new audiorecord_callback_cookie;
        lpCallbackData->audioRecord_class = (jclass)env->NewGlobalRef(clazz);
        // we use a weak reference so the AudioRecord object can be garbage collected.
        lpCallbackData->audioRecord_ref = env->NewGlobalRef(weak_this);
        lpCallbackData->busy = false;
    }

    nSession = (jint *) env->GetPrimitiveArrayCritical(jSession, NULL);
    if (nSession == NULL) {
        ALOGE("Error creating AudioRecord: Error retrieving session id pointer");
        goto native_init_failure;
    }
    // read the audio session ID back from AudioRecord in case a new session was created during set()
    nSession[0] = lpRecorder->getSessionId();
    env->ReleasePrimitiveArrayCritical(jSession, nSession, 0);
    nSession = NULL;

    ...

    ///*add by shengjie for parse AudioRecord setup
    //7. hold lpRecorder Objects and lpCallbackData The callback is saved to javaAudioRecordFields In the corresponding fields of 
    // save our newly created C++ AudioRecord in the "nativeRecorderInJavaObj" field
    // of the Java object
    setAudioRecord(env, thiz, lpRecorder);

    // save our newly created callback information in the "nativeCallbackCookie" field
    // of the Java object (in mNativeCallbackCookie) so we can free the memory in finalize()
    env->SetLongField(thiz, javaAudioRecordFields.nativeCallbackCookie, (jlong)lpCallbackData);
    //*/

    return (jint) AUDIO_JAVA_SUCCESS;

    ...///*Error Handler Process*///...
    
}

system/media/audio/include/system/audio-base.h 

typedef enum {
    AUDIO_INPUT_FLAG_NONE       = 0x0,
    AUDIO_INPUT_FLAG_FAST       = 0x1,
    AUDIO_INPUT_FLAG_HW_HOTWORD = 0x2,
    AUDIO_INPUT_FLAG_RAW        = 0x4,
    AUDIO_INPUT_FLAG_SYNC       = 0x8,
    AUDIO_INPUT_FLAG_MMAP_NOIRQ = 0x10,
    AUDIO_INPUT_FLAG_VOIP_TX    = 0x20,
    AUDIO_INPUT_FLAG_HW_AV_SYNC = 0x40,
    AUDIO_INPUT_FLAG_DIRECT     = 0x80,
} audio_input_flags_t;

 

3.frameworks/av/media/libaudioclient/AudioRecord.cpp

Analyze relevant audio parameters , Mainly to create AudioRecordThread and createRecord_l

status_t AudioRecord::set(
        audio_source_t inputSource,
        uint32_t sampleRate,
        audio_format_t format,
        audio_channel_mask_t channelMask,
        size_t frameCount,
        callback_t cbf,
        void* user,
        uint32_t notificationFrames,
        bool threadCanCallJava,
        audio_session_t sessionId,
        transfer_type transferType,
        audio_input_flags_t flags,
        uid_t uid,
        pid_t pid,
        const audio_attributes_t* pAttributes,
        audio_port_handle_t selectedDeviceId,
        audio_microphone_direction_t selectedMicDirection,
        float microphoneFieldDimension)
{
    status_t status = NO_ERROR;
    uint32_t channelCount;
    pid_t callingPid;
    pid_t myPid;

    // Note mPortId is not valid until the track is created, so omit mPortId in ALOG for set.
    ALOGV("%s(): inputSource %d, sampleRate %u, format %#x, channelMask %#x, frameCount %zu, "
          "notificationFrames %u, sessionId %d, transferType %d, flags %#x, opPackageName %s "
          "uid %d, pid %d",
          __func__,
          inputSource, sampleRate, format, channelMask, frameCount, notificationFrames,
          sessionId, transferType, flags, String8(mOpPackageName).string(), uid, pid);

    mTracker.reset(new RecordingActivityTracker());

    mSelectedDeviceId = selectedDeviceId;
    mSelectedMicDirection = selectedMicDirection;
    mSelectedMicFieldDimension = microphoneFieldDimension;

    ...

    ///*add by shengjie for parse AudioRecord set
    //1.get trabsferType TRANSFER_SYNC/TRANSFER_CALLBACK
    mTransfer = transferType;
    //*/

    ...

    if (pAttributes == NULL) {
        mAttributes = AUDIO_ATTRIBUTES_INITIALIZER;
        mAttributes.source = inputSource;
        if (inputSource == AUDIO_SOURCE_VOICE_COMMUNICATION
                || inputSource == AUDIO_SOURCE_CAMCORDER) {
            mAttributes.flags |= AUDIO_FLAG_CAPTURE_PRIVATE;
        }
    } else {
        // stream type shouldn't be looked at, this track has audio attributes
        memcpy(&mAttributes, pAttributes, sizeof(audio_attributes_t));
        ALOGV("%s(): Building AudioRecord with attributes: source=%d flags=0x%x tags=[%s]",
                __func__, mAttributes.source, mAttributes.flags, mAttributes.tags);
    }

    mSampleRate = sampleRate;

    // these below should probably come from the audioFlinger too...
    if (format == AUDIO_FORMAT_DEFAULT) {
        format = AUDIO_FORMAT_PCM_16_BIT;
    }

    // validate parameters
    // AudioFlinger capture only supports linear PCM
    if (!audio_is_valid_format(format) || !audio_is_linear_pcm(format)) {
        ALOGE("%s(): Format %#x is not linear pcm", __func__, format);
        status = BAD_VALUE;
        goto exit;
    }
    mFormat = format;

    if (!audio_is_input_channel(channelMask)) {
        ALOGE("%s(): Invalid channel mask %#x", __func__, channelMask);
        status = BAD_VALUE;
        goto exit;
    }
    mChannelMask = channelMask;
    channelCount = audio_channel_count_from_in_mask(channelMask);
    mChannelCount = channelCount;

    if (audio_is_linear_pcm(format)) {
        mFrameSize = channelCount * audio_bytes_per_sample(format);
    } else {
        mFrameSize = sizeof(uint8_t);
    }

    // mFrameCount is initialized in createRecord_l
    mReqFrameCount = frameCount;

    mNotificationFramesReq = notificationFrames;
    // mNotificationFramesAct is initialized in createRecord_l

    mSessionId = sessionId;
    ALOGV("%s(): mSessionId %d", __func__, mSessionId);

    callingPid = IPCThreadState::self()->getCallingPid();
    myPid = getpid();
    if (uid == AUDIO_UID_INVALID || (callingPid != myPid)) {
        mClientUid = IPCThreadState::self()->getCallingUid();
    } else {
        mClientUid = uid;
    }
    if (pid == -1 || (callingPid != myPid)) {
        mClientPid = callingPid;
    } else {
        mClientPid = pid;
    }

    mOrigFlags = mFlags = flags;
    mCbf = cbf;

    ///*add by shengjie for parse AudioRecord set
    //2.new AudioRecordThread to handle releated process
    if (cbf != NULL) {
        mAudioRecordThread = new AudioRecordThread(*this);
        mAudioRecordThread->run("AudioRecord", ANDROID_PRIORITY_AUDIO);
        // thread begins in paused state, and will not reference us until start()
    }
    //*/

    // create the IAudioRecord
    ///*add by shengjie for parse AudioRecord set
    //3.use createRecord_l to invork audio related devices/input parameters
    {
        AutoMutex lock(mLock);
        status = createRecord_l(0 /*epoch*/, mOpPackageName);
    }
    //*/

    ALOGV("%s(%d): status %d", __func__, mPortId, status);

    if (status != NO_ERROR) {
        if (mAudioRecordThread != 0) {
            mAudioRecordThread->requestExit();   // see comment in AudioRecord.h
            mAudioRecordThread->requestExitAndWait();
            mAudioRecordThread.clear();
        }
        goto exit;
    }

    mUserData = user;
    // TODO: add audio hardware input latency here
    mLatency = (1000LL * mFrameCount) / mSampleRate;
    mMarkerPosition = 0;
    mMarkerReached = false;
    mNewPosition = 0;
    mUpdatePeriod = 0;
    AudioSystem::acquireAudioSessionId(mSessionId, mClientPid, mClientUid);
    mSequence = 1;
    mObservedSequence = mSequence;
    mInOverrun = false;
    mFramesRead = 0;
    mFramesReadServerOffset = 0;

    ///*error handler process*///
}

 createRecord_l The method is implemented as follows ：

Important interfaces :AudioFliger.cpp createRecord_l Subsequently, a series of parameters will be parsed and distributed ;

// must be called with mLock held
status_t AudioRecord::createRecord_l(const Modulo<uint32_t> &epoch, const String16& opPackageName)
{
    const sp<IAudioFlinger>& audioFlinger = AudioSystem::get_audio_flinger();
    IAudioFlinger::CreateRecordInput input;
    IAudioFlinger::CreateRecordOutput output;
    sp<media::IAudioRecord> record;

    ...

    ///*loding input related parameters*/

    ///*add by shengjie for parse AudioRecord createRecord_l
    //1.IAudioFliger.cpp adopt Binder Interprocess communication call AudioFliger.cpp Of createRecord, Undertaking including audio input device structure getInputForAttr、createRecordTrack_l、getOrphanEffectChain_l And all other functions .
    record = audioFlinger->createRecord(input,
                                                              output,
                                                              &status);
    //*/

    ...

    // Starting address of buffers in shared memory.
    // The buffers are either immediately after the control block,
    // or in a separate area at discretion of server.
    void *buffers;
    if (output.buffers == 0) {
        buffers = cblk + 1;
    } else {
        // TODO: Using unsecurePointer() has some associated security pitfalls
        //       (see declaration for details).
        //       Either document why it is safe in this case or address the
        //       issue (e.g. by copying).
        buffers = output.buffers->unsecurePointer();
        if (buffers == NULL) {
            ALOGE("%s(%d): Could not get buffer pointer", __func__, mPortId);
            status = NO_INIT;
            goto exit;
        }
    }

    // invariant that mAudioRecord != 0 is true only after set() returns successfully
    if (mAudioRecord != 0) {
        IInterface::asBinder(mAudioRecord)->unlinkToDeath(mDeathNotifier, this);
        mDeathNotifier.clear();
    }
    mAudioRecord = record;
    mCblkMemory = output.cblk;
    mBufferMemory = output.buffers;
    IPCThreadState::self()->flushCommands();

    mCblk = cblk;
    
    ...
    
    // update proxy
    mProxy = new AudioRecordClientProxy(cblk, buffers, mFrameCount, mFrameSize);
    mProxy->setEpoch(epoch);
    mProxy->setMinimum(mNotificationFramesAct);

    ...
}

 

4.frameworks/av/media/libaudioclient/IAudioFlinger.cpp

virtual sp<media::IAudioRecord> createRecord(const CreateRecordInput& input,
                                                 CreateRecordOutput& output,
                                                 status_t *status)
    {
        Parcel data, reply;
        sp<media::IAudioRecord> record;
        data.writeInterfaceToken(IAudioFlinger::getInterfaceDescriptor());

        if (status == nullptr) {
            return record;
        }

        input.writeToParcel(&data);

        ///*add by shengjie for IAudioFlinger createRecord
        // adopt Binder Interprocess communication gets share buffer
        status_t lStatus = remote()->transact(CREATE_RECORD, data, &reply);
        if (lStatus != NO_ERROR) {
            ALOGE("createRecord transaction error %d", lStatus);
            *status = DEAD_OBJECT;
            return record;
        }
        //*/

        *status = reply.readInt32();
        if (*status != NO_ERROR) {
            ALOGE("createRecord returned error %d", *status);
            return record;
        }

        record = interface_cast<media::IAudioRecord>(reply.readStrongBinder());
        if (record == 0) {
            ALOGE("createRecord returned a NULL IAudioRecord with status OK");
            *status = DEAD_OBJECT;
            return record;
        }
        output.readFromParcel(&reply);
        return record;
    }

 

5.frameworks/av/services/audioflinger/AudioFlinger.cpp

getInputForAttr: Set up audio input Relevant information corresponds to audio device

checkRecordThread_l: establish recordThread To do recording Related configuration

getOrphanEffectChain_l: Issue the corresponding different gains

sp<media::IAudioRecord> AudioFlinger::createRecord(const CreateRecordInput& input,
                                                   CreateRecordOutput& output,
                                                   status_t *status)
{
    sp<RecordThread::RecordTrack> recordTrack;
    sp<RecordHandle> recordHandle;
    sp<Client> client;
    status_t lStatus;
    audio_session_t sessionId = input.sessionId;
    audio_port_handle_t portId = AUDIO_PORT_HANDLE_NONE;

    ...

    ///*add by shengjie for parse AudioFlinger createRecord
    //parse input related info and check all audio devices info
    lStatus = AudioSystem::getInputForAttr(&input.attr, &output.inputId,
                                      input.riid,
                                      sessionId,
                                    // FIXME compare to AudioTrack
                                      clientPid,
                                      clientUid,
                                      input.opPackageName,
                                      &input.config,
                                      output.flags, &output.selectedDeviceId, &portId);
    //*/



    {
        Mutex::Autolock _l(mLock);
        RecordThread *thread = checkRecordThread_l(output.inputId);
        if (thread == NULL) {
            ALOGE("createRecord() checkRecordThread_l failed, input handle %d", output.inputId);
            lStatus = BAD_VALUE;
            goto Exit;
        }

        ...

        ///*add by shengjie for AudioFlinger createRecord
        //2.create Record Tract to check recording audio buffer and data
        recordTrack = thread->createRecordTrack_l(client, input.attr, &output.sampleRate,
                                                  input.config.format, input.config.channel_mask,
                                                  &output.frameCount, sessionId,
                                                  &output.notificationFrameCount,
                                                  callingPid, clientUid, &output.flags,
                                                  input.clientInfo.clientTid,
                                                  &lStatus, portId,
                                                  input.opPackageName);
        //*/
        
    ...

        // Check if one effect chain was awaiting for an AudioRecord to be created on this
        // session and move it to this thread.
        ///*add by shengjie for parse AudioFlinger createRecord
        //3.enable audio input channer related effect
        sp<EffectChain> chain = getOrphanEffectChain_l(sessionId);
        //*/
        if (chain != 0) {
            Mutex::Autolock _l(thread->mLock);
            thread->addEffectChain_l(chain);
        }
        break;
    }
    // End of retry loop.
    // The lack of indentation is deliberate, to reduce code churn and ease merges.
    }

    output.cblk = recordTrack->getCblk();
    output.buffers = recordTrack->getBuffers();
    output.portId = portId;

    // return handle to client
    recordHandle = new RecordHandle(recordTrack);

    ...

    *status = lStatus;
    return recordHandle;
}

 

summary ：

        The following article will be helpful to AudioFlinger createRecord It's about getInputForAttr、checkRecordThread_l、getOrphanEffectChain_l Interface for more detailed analysis .

        Tracking the process , The purpose is to insert some items about audio microphone array under this process 、 Some special configurations and requirements for data processing , In the overall macro session、client Under control, take some other special channels to meet the needs of the project .