本篇介绍
AudioRecord可以用来采集PCM，本篇介绍下AudioRecord的创建流程。
源码介绍
public AudioRecord(int audioSource, int sampleRateInHz, int channelConfig, int audioFormat,
int bufferSizeInBytes)
这儿的souce可以选择的如下：
AudioSource.DEFAULT,
AudioSource.MIC,
AudioSource.VOICE_UPLINK,
AudioSource.VOICE_DOWNLINK,
AudioSource.VOICE_CALL,
AudioSource.CAMCORDER,
AudioSource.VOICE_RECOGNITION,
AudioSource.VOICE_COMMUNICATION,
AudioSource.UNPROCESSED,
AudioSource.VOICE_PERFORMANCE,
关于采样率，除了44100Hz所有设备上都保证支持，其他频率就不一定支持了，这时候可以通过使用参数SAMPLE_RATE_UNSPECIFIED，让设备自己去决策使用的采样率。
channelConfig是采样通道，当前所有设备都保证支持单声道，多声道就不一定支持了。
bufferSizeInBytes是buffer大小，用来存采集的数据，一般是直接用接口getMinBufferSize的返回值作为buffer大小。
现在看下getMinBufferSize的实现：
static public int getMinBufferSize(int sampleRateInHz, int channelConfig, int audioFormat) {
int channelCount = 0;
switch (channelConfig) {
case AudioFormat.CHANNEL_IN_DEFAULT: // AudioFormat.CHANNEL_CONFIGURATION_DEFAULT
case AudioFormat.CHANNEL_IN_MONO:
case AudioFormat.CHANNEL_CONFIGURATION_MONO:
channelCount = 1;
break;
case AudioFormat.CHANNEL_IN_STEREO:
case AudioFormat.CHANNEL_CONFIGURATION_STEREO:
case (AudioFormat.CHANNEL_IN_FRONT | AudioFormat.CHANNEL_IN_BACK):
channelCount = 2;
break;
case AudioFormat.CHANNEL_INVALID:
default:
loge("getMinBufferSize(): Invalid channel configuration.");
return ERROR_BAD_VALUE;
}
int size = native_get_min_buff_size(sampleRateInHz, channelCount, audioFormat);
if (size == 0) {
return ERROR_BAD_VALUE;
}
else if (size == -1) {
return ERROR;
}
else {
return size;
}
}
可以看到Java侧没做啥逻辑，实现下沉到了native，接着看下native_get_min_buff_size的内容：
static jint android_media_AudioRecord_get_min_buff_size(JNIEnv *env, jobject thiz,
jint sampleRateInHertz, jint channelCount, jint audioFormat) {
size_t frameCount = 0;
audio_format_t format = audioFormatToNative(audioFormat); // 把java 的格式转成native的
status_t result = AudioRecord::getMinFrameCount(&frameCount, // 获取最小帧数
sampleRateInHertz,
format,
audio_channel_in_mask_from_count(channelCount));
return frameCount * channelCount * audio_bytes_per_sample(format);
}
这儿的关键就是获取最小帧数，接着看下getMinFrameCount的实现：
status_t AudioRecord::getMinFrameCount(
size_t* frameCount,
uint32_t sampleRate,
audio_format_t format,
audio_channel_mask_t channelMask)
{
if (frameCount == NULL) {
return BAD_VALUE;
}
size_t size;
status_t status = AudioSystem::getInputBufferSize(sampleRate, format, channelMask, &size);
if (status != NO_ERROR) {
ALOGE("%s(): AudioSystem could not query the input buffer size for"
" sampleRate %u, format %#x, channelMask %#x; status %d",
__func__, sampleRate, format, channelMask, status);
return status;
}
// We double the size of input buffer for ping pong use of record buffer.
// Assumes audio_is_linear_pcm(format)
if ((*frameCount = (size * 2) / (audio_channel_count_from_in_mask(channelMask) *
audio_bytes_per_sample(format))) == 0) {
ALOGE("%s(): Unsupported configuration: sampleRate %u, format %#x, channelMask %#x",
__func__, sampleRate, format, channelMask);
return BAD_VALUE;
}
return NO_ERROR;
}
这儿关键的方法是getInputBufferSize，继续看下实现：
status_t AudioSystem::getInputBufferSize(uint32_t sampleRate, audio_format_t format,
audio_channel_mask_t channelMask, size_t* buffSize)
{
const sp<AudioFlingerClient> afc = getAudioFlingerClient();
if (afc == 0) {
return NO_INIT;
}
return afc->getInputBufferSize(sampleRate, format, channelMask, buffSize);
}
这时候的afc并不是AudioFlinger，而是AudioSystem自己定义的一个Client，用来向AudioFligner注册回调，感知audio io变化的。因此这时候实现还在AdioSystem里面：
status_t AudioSystem::AudioFlingerClient::getInputBufferSize(
uint32_t sampleRate, audio_format_t format,
audio_channel_mask_t channelMask, size_t* buffSize)
{
const sp<IAudioFlinger>& af = AudioSystem::get_audio_flinger();
if (af == 0) {
return PERMISSION_DENIED;
}
Mutex::Autolock _l(mLock);
// Do we have a stale mInBuffSize or are we requesting the input buffer size for new values
if ((mInBuffSize == 0) || (sampleRate != mInSamplingRate) || (format != mInFormat)
|| (channelMask != mInChannelMask)) {
size_t inBuffSize = af->getInputBufferSize(sampleRate, format, channelMask);
if (inBuffSize == 0) {
ALOGE("AudioSystem::getInputBufferSize failed sampleRate %d format %#x channelMask %#x",
sampleRate, format, channelMask);
return BAD_VALUE;
}
// A benign race is possible here: we could overwrite a fresher cache entry
// save the request params
mInSamplingRate = sampleRate;
mInFormat = format;
mInChannelMask = channelMask;
mInBuffSize = inBuffSize;
}
*buffSize = mInBuffSize;
return NO_ERROR;
}
这儿可以看到buffersize是从AudioFlinger请求过来的，接下来就看下AudioFliner的实现：
size_t AudioFlinger::getInputBufferSize(uint32_t sampleRate, audio_format_t format,
audio_channel_mask_t channelMask) const
{
status_t ret = initCheck();
AutoMutex lock(mHardwareLock);
mHardwareStatus = AUDIO_HW_GET_INPUT_BUFFER_SIZE;
sp<DeviceHalInterface> dev = mPrimaryHardwareDev->hwDevice();
std::vector<audio_channel_mask_t> channelMasks = {channelMask};
if (channelMask != AUDIO_CHANNEL_IN_MONO)
channelMasks.push_back(AUDIO_CHANNEL_IN_MONO);
if (channelMask != AUDIO_CHANNEL_IN_STEREO)
channelMasks.push_back(AUDIO_CHANNEL_IN_STEREO);
std::vector<audio_format_t> formats = {format};
if (format != AUDIO_FORMAT_PCM_16_BIT)
formats.push_back(AUDIO_FORMAT_PCM_16_BIT);
std::vector<uint32_t> sampleRates = {sampleRate};
static const uint32_t SR_44100 = 44100;
static const uint32_t SR_48000 = 48000;
if (sampleRate != SR_48000)
sampleRates.push_back(SR_48000);
if (sampleRate != SR_44100)
sampleRates.push_back(SR_44100);
mHardwareStatus = AUDIO_HW_IDLE;
// Change parameters of the configuration each iteration until we find a
// configuration that the device will support.
audio_config_t config = AUDIO_CONFIG_INITIALIZER;
for (auto testChannelMask : channelMasks) {
config.channel_mask = testChannelMask;
for (auto testFormat : formats) {
config.format = testFormat;
for (auto testSampleRate : sampleRates) {
config.sample_rate = testSampleRate;
size_t bytes = 0;
status_t result = dev->getInputBufferSize(&config, &bytes); // 从hal层获取bytes
if (result != OK || bytes == 0) {
continue;
}
if (config.sample_rate != sampleRate || config.channel_mask != channelMask ||
config.format != format) {
uint32_t dstChannelCount = audio_channel_count_from_in_mask(channelMask);
uint32_t srcChannelCount =
audio_channel_count_from_in_mask(config.channel_mask);
size_t srcFrames =
bytes / audio_bytes_per_frame(srcChannelCount, config.format);
size_t dstFrames = destinationFramesPossible(
srcFrames, config.sample_rate, sampleRate);
bytes = dstFrames * audio_bytes_per_frame(dstChannelCount, format); // 重新计算bytes
}
return bytes;
}
}
}
return 0;
}
这时候就完成了getMinBufferSize的实现介绍。
接下来继续看下AudioRecord的实现流程：
public AudioRecord(AudioAttributes attributes, AudioFormat format, int bufferSizeInBytes,
int sessionId) throws IllegalArgumentException {
mRecordingState = RECORDSTATE_STOPPED;
// remember which looper is associated with the AudioRecord instanciation
if ((mInitializationLooper = Looper.myLooper()) == null) {
mInitializationLooper = Looper.getMainLooper();
}
// 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;
}
int rate = format.getSampleRate();
if (rate == AudioFormat.SAMPLE_RATE_UNSPECIFIED) {
rate = 0;
}
int encoding = AudioFormat.ENCODING_DEFAULT;
if ((format.getPropertySetMask() & AudioFormat.AUDIO_FORMAT_HAS_PROPERTY_ENCODING) != 0)
{
encoding = format.getEncoding();
}
audioParamCheck(attributes.getCapturePreset(), rate, encoding);
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};
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*/); // 真正实现的地方
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;
}
可以看到Java层只是做了一个参数检查，实现还是在native，接着看下native_setup的实现：
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)
{
audio_channel_mask_t localChanMask = inChannelMaskToNative(channelMask);
jint* nSession = (jint *) env->GetPrimitiveArrayCritical(jSession, NULL);
audio_session_t sessionId = (audio_session_t) nSession[0];
env->ReleasePrimitiveArrayCritical(jSession, nSession, 0);
nSession = NULL;
sp<AudioRecord> lpRecorder = 0;
audiorecord_callback_cookie *lpCallbackData = NULL;
jclass clazz = env->GetObjectClass(thiz);
if (clazz == NULL) {
ALOGE("Can't find %s when setting up callback.", kClassPathName);
return (jint) AUDIORECORD_ERROR_SETUP_NATIVEINITFAILED;
}
// if we pass in an existing *Native* AudioRecord, we don't need to create/initialize one.
if (nativeRecordInJavaObj == 0) { // native的audio record还没创建，那么就需要创建
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;
}
uint32_t channelCount = audio_channel_count_from_in_mask(localChanMask);
// compare the format against the Java constants
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;
}
size_t bytesPerSample = audio_bytes_per_sample(format);
if (buffSizeInBytes == 0) {
ALOGE("Error creating AudioRecord: frameCount is 0.");
return (jint) AUDIORECORD_ERROR_SETUP_ZEROFRAMECOUNT;
}
size_t frameSize = channelCount * bytesPerSample;
size_t frameCount = buffSizeInBytes / frameSize;
ScopedUtfChars opPackageNameStr(env, opPackageName);
// create an uninitialized AudioRecord object
lpRecorder = new AudioRecord(String16(opPackageNameStr.c_str())); // 创建AudioRecord
// 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.
lpCallbackData->audioRecord_ref = env->NewGlobalRef(weak_this);
lpCallbackData->busy = false;
const status_t status = lpRecorder->set(paa->source, // set 配置
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());
if (status != NO_ERROR) {
ALOGE("Error creating AudioRecord instance: initialization check failed with status %d.",
status);
goto native_init_failure;
}
// 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) // 已经创建了native的AudioRecord
lpRecorder = (AudioRecord*)nativeRecordInJavaObj;
// 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;
{
const jint elements[1] = { (jint) lpRecorder->getSampleRate() };
env->SetIntArrayRegion(jSampleRate, 0, 1, elements);
}
{ // scope for the lock
Mutex::Autolock l(sLock);
sAudioRecordCallBackCookies.add(lpCallbackData);
}
// save our newly created C++ AudioRecord in the "nativeRecorderInJavaObj" field
// of the Java object
setAudioRecord(env, thiz, lpRecorder); // 关联Java对象
// 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;
// failure:
native_init_failure:
env->DeleteGlobalRef(lpCallbackData->audioRecord_class);
env->DeleteGlobalRef(lpCallbackData->audioRecord_ref);
delete lpCallbackData;
env->SetLongField(thiz, javaAudioRecordFields.nativeCallbackCookie, 0);
// lpRecorder goes out of scope, so reference count drops to zero
return (jint) AUDIORECORD_ERROR_SETUP_NATIVEINITFAILED;
}
可以看到一共做了一下几件事
- 如果native的AudioRecord还没创建，那么就进行创建，创建后关联上Java对象
- 如果native的AudioRecord已经创建了，那么就直接Java对象
接下来看下AudioRecord的创建：
AudioRecord::AudioRecord(
audio_source_t inputSource,
uint32_t sampleRate,
audio_format_t format,
audio_channel_mask_t channelMask,
const String16& opPackageName,
size_t frameCount,
callback_t cbf,
void* user,
uint32_t notificationFrames,
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)
: mActive(false),
mStatus(NO_INIT),
mOpPackageName(opPackageName),
mSessionId(AUDIO_SESSION_ALLOCATE),
mPreviousPriority(ANDROID_PRIORITY_NORMAL),
mPreviousSchedulingGroup(SP_DEFAULT),
mProxy(NULL)
{
(void)set(inputSource, sampleRate, format, channelMask, frameCount, cbf, user,
notificationFrames, false /*threadCanCallJava*/, sessionId, transferType, flags,
uid, pid, pAttributes, selectedDeviceId,
selectedMicDirection, microphoneFieldDimension);
}
可以看到具体实现就是set，这样就直接看set就可以了：
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)
{
switch (transferType) { // 传入的transfer是default，其余case可以先忽略
case TRANSFER_DEFAULT:
if (cbf == NULL || threadCanCallJava) {
transferType = TRANSFER_SYNC;
} else {
transferType = TRANSFER_CALLBACK;
}
break;
case TRANSFER_CALLBACK:
if (cbf == NULL) {
ALOGE("%s(): Transfer type TRANSFER_CALLBACK but cbf == NULL", __func__);
status = BAD_VALUE;
goto exit;
}
break;
case TRANSFER_OBTAIN:
case TRANSFER_SYNC:
break;
default:
ALOGE("%s(): Invalid transfer type %d", __func__, transferType);
status = BAD_VALUE;
goto exit;
}
mTransfer = transferType;
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;
if (cbf != NULL) {
mAudioRecordThread = new AudioRecordThread(*this); // 回调线程，这样采集好数据后，可以主动回调调用方
mAudioRecordThread->run("AudioRecord", ANDROID_PRIORITY_AUDIO);
// thread begins in paused state, and will not reference us until start()
}
// create the IAudioRecord
{
AutoMutex lock(mLock);
status = createRecord_l(0 /*epoch*/, mOpPackageName); // 创建record
}
}
可以看到set里面关键的就是createRecord_l，可以猜想到接下来就会和AudioFlinger交互，让AudioFlinger创建对应的Record，并且会拿到该Record的binder proxy, 下面看下代码：
// must be called with mLock held
status_t AudioRecord::createRecord_l(const Modulo<uint32_t> &epoch, const String16& opPackageName)
{
const int64_t beginNs = systemTime();
const sp<IAudioFlinger>& audioFlinger = AudioSystem::get_audio_flinger();
IAudioFlinger::CreateRecordInput input;
IAudioFlinger::CreateRecordOutput output;
audio_session_t originalSessionId;
sp<media::IAudioRecord> record;
void *iMemPointer;
audio_track_cblk_t* cblk;
status_t status;
static const int32_t kMaxCreateAttempts = 3;
int32_t remainingAttempts = kMaxCreateAttempts;
// mFlags (not mOrigFlags) is modified depending on whether fast request is accepted.
// After fast request is denied, we will request again if IAudioRecord is re-created.
// Now that we have a reference to an I/O handle and have not yet handed it off to AudioFlinger,
// we must release it ourselves if anything goes wrong.
// Client can only express a preference for FAST. Server will perform additional tests.
if (mFlags & AUDIO_INPUT_FLAG_FAST) {
bool useCaseAllowed =
// any of these use cases:
// use case 1: callback transfer mode
(mTransfer == TRANSFER_CALLBACK) ||
// use case 2: blocking read mode
// The default buffer capacity at 48 kHz is 2048 frames, or ~42.6 ms.
// That's enough for double-buffering with our standard 20 ms rule of thumb for
// the minimum period of a non-SCHED_FIFO thread.
// This is needed so that AAudio apps can do a low latency non-blocking read from a
// callback running with SCHED_FIFO.
(mTransfer == TRANSFER_SYNC) ||
// use case 3: obtain/release mode
(mTransfer == TRANSFER_OBTAIN);
if (!useCaseAllowed) {
ALOGD("%s(%d): AUDIO_INPUT_FLAG_FAST denied, incompatible transfer = %s",
__func__, mPortId,
convertTransferToText(mTransfer));
mFlags = (audio_input_flags_t) (mFlags & ~(AUDIO_INPUT_FLAG_FAST |
AUDIO_INPUT_FLAG_RAW));
}
}
input.attr = mAttributes;
input.config.sample_rate = mSampleRate;
input.config.channel_mask = mChannelMask;
input.config.format = mFormat;
input.clientInfo.clientUid = mClientUid;
input.clientInfo.clientPid = mClientPid;
input.clientInfo.clientTid = -1;
if (mFlags & AUDIO_INPUT_FLAG_FAST) {
if (mAudioRecordThread != 0) {
input.clientInfo.clientTid = mAudioRecordThread->getTid();
}
}
input.opPackageName = opPackageName;
input.riid = mTracker->getRiid();
input.flags = mFlags;
// The notification frame count is the period between callbacks, as suggested by the client
// but moderated by the server. For record, the calculations are done entirely on server side.
input.frameCount = mReqFrameCount;
input.notificationFrameCount = mNotificationFramesReq;
input.selectedDeviceId = mSelectedDeviceId;
input.sessionId = mSessionId;
originalSessionId = mSessionId;
do {
record = audioFlinger->createRecord(input, output, &status); // 创建record
if (status == NO_ERROR) {
break;
}
if (status != FAILED_TRANSACTION || --remainingAttempts <= 0) {
ALOGE("%s(%d): AudioFlinger could not create record track, status: %d",
__func__, mPortId, status);
goto exit;
}
// FAILED_TRANSACTION happens under very specific conditions causing a state mismatch
// between audio policy manager and audio flinger during the input stream open sequence
// and can be recovered by retrying.
// Leave time for race condition to clear before retrying and randomize delay
// to reduce the probability of concurrent retries in locked steps.
usleep((20 + rand() % 30) * 10000);
} while (1);
ALOG_ASSERT(record != 0);
// AudioFlinger now owns the reference to the I/O handle,
// so we are no longer responsible for releasing it.
mAwaitBoost = false;
if (output.flags & AUDIO_INPUT_FLAG_FAST) {
ALOGI("%s(%d): AUDIO_INPUT_FLAG_FAST successful; frameCount %zu -> %zu",
__func__, mPortId,
mReqFrameCount, output.frameCount);
mAwaitBoost = true;
}
mFlags = output.flags;
mRoutedDeviceId = output.selectedDeviceId;
mSessionId = output.sessionId;
mSampleRate = output.sampleRate;
if (output.cblk == 0) {
ALOGE("%s(%d): Could not get control block", __func__, mPortId);
status = NO_INIT;
goto exit;
}
// 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).
iMemPointer = output.cblk ->unsecurePointer(); // 获取共享内存
if (iMemPointer == NULL) {
ALOGE("%s(%d): Could not get control block pointer", __func__, mPortId);
status = NO_INIT;
goto exit;
}
cblk = static_cast<audio_track_cblk_t*>(iMemPointer);
// 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;
// note that output.frameCount is the (possibly revised) value of mReqFrameCount
if (output.frameCount < mReqFrameCount || (mReqFrameCount == 0 && output.frameCount == 0)) {
ALOGW("%s(%d): Requested frameCount %zu but received frameCount %zu",
__func__, output.portId,
mReqFrameCount, output.frameCount);
}
// Make sure that application is notified with sufficient margin before overrun.
// The computation is done on server side.
if (mNotificationFramesReq > 0 && output.notificationFrameCount != mNotificationFramesReq) {
ALOGW("%s(%d): Server adjusted notificationFrames from %u to %zu for frameCount %zu",
__func__, output.portId,
mNotificationFramesReq, output.notificationFrameCount, output.frameCount);
}
mNotificationFramesAct = (uint32_t)output.notificationFrameCount;
//mInput != input includes the case where mInput == AUDIO_IO_HANDLE_NONE for first creation
if (mDeviceCallback != 0) {
if (mInput != AUDIO_IO_HANDLE_NONE) {
AudioSystem::removeAudioDeviceCallback(this, mInput, mPortId);
}
AudioSystem::addAudioDeviceCallback(this, output.inputId, output.portId);
}
mPortId = output.portId;
// We retain a copy of the I/O handle, but don't own the reference
mInput = output.inputId;
mRefreshRemaining = true;
mFrameCount = output.frameCount;
// If IAudioRecord is re-created, don't let the requested frameCount
// decrease. This can confuse clients that cache frameCount().
if (mFrameCount > mReqFrameCount) {
mReqFrameCount = mFrameCount;
}
// update proxy
mProxy = new AudioRecordClientProxy(cblk, buffers, mFrameCount, mFrameSize); // 共享内存proxy
mProxy->setEpoch(epoch);
mProxy->setMinimum(mNotificationFramesAct);
mDeathNotifier = new DeathNotifier(this);
IInterface::asBinder(mAudioRecord)->linkToDeath(mDeathNotifier, this);
exit:
mStatus = status;
// sp<IAudioTrack> track destructor will cause releaseOutput() to be called by AudioFlinger
return status;
}
可以看到这里面果然主要做了上面猜想的2件事，接下来主要看下调用AudioFlinger创建Record，在看之前可以继续猜想下在AudioFlinger中需要做哪些事情，当前可以想到的应该有以下几件：
- 创建一个Record结构，并创建可以跨进城共享的内存
- 将该Record和一个线程关联，这样这个线程可以一直loop，并调用hal层的采集接口进行采集
- 把这个Record结构包装成一个binder，这样调用方可以直接操作该Record
加下来就继续看代码验证下猜想吧
// ----------------------------------------------------------------------------
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;
output.cblk.clear();
output.buffers.clear();
output.inputId = AUDIO_IO_HANDLE_NONE;
bool updatePid = (input.clientInfo.clientPid == -1);
const uid_t callingUid = IPCThreadState::self()->getCallingUid();
uid_t clientUid = input.clientInfo.clientUid;
if (!isAudioServerOrMediaServerUid(callingUid)) {
ALOGW_IF(clientUid != callingUid,
"%s uid %d tried to pass itself off as %d",
__FUNCTION__, callingUid, clientUid);
clientUid = callingUid;
updatePid = true;
}
pid_t clientPid = input.clientInfo.clientPid;
const pid_t callingPid = IPCThreadState::self()->getCallingPid();
if (updatePid) {
ALOGW_IF(clientPid != -1 && clientPid != callingPid,
"%s uid %d pid %d tried to pass itself off as pid %d",
__func__, callingUid, callingPid, clientPid);
clientPid = callingPid;
}
// we don't yet support anything other than linear PCM
if (!audio_is_valid_format(input.config.format) || !audio_is_linear_pcm(input.config.format)) {
ALOGE("createRecord() invalid format %#x", input.config.format);
lStatus = BAD_VALUE;
goto Exit;
}
// further channel mask checks are performed by createRecordTrack_l()
if (!audio_is_input_channel(input.config.channel_mask)) {
ALOGE("createRecord() invalid channel mask %#x", input.config.channel_mask);
lStatus = BAD_VALUE;
goto Exit;
}
if (sessionId == AUDIO_SESSION_ALLOCATE) {
sessionId = (audio_session_t) newAudioUniqueId(AUDIO_UNIQUE_ID_USE_SESSION);
} else if (audio_unique_id_get_use(sessionId) != AUDIO_UNIQUE_ID_USE_SESSION) {
lStatus = BAD_VALUE;
goto Exit;
}
output.sessionId = sessionId;
output.selectedDeviceId = input.selectedDeviceId;
output.flags = input.flags;
client = registerPid(clientPid); //创建共享内存
// Not a conventional loop, but a retry loop for at most two iterations total.
// Try first maybe with FAST flag then try again without FAST flag if that fails.
// Exits loop via break on no error of got exit on error
// The sp<> references will be dropped when re-entering scope.
// The lack of indentation is deliberate, to reduce code churn and ease merges.
for (;;) {
// release previously opened input if retrying.
if (output.inputId != AUDIO_IO_HANDLE_NONE) {
recordTrack.clear();
AudioSystem::releaseInput(portId);
output.inputId = AUDIO_IO_HANDLE_NONE;
output.selectedDeviceId = input.selectedDeviceId;
portId = AUDIO_PORT_HANDLE_NONE;
}
lStatus = AudioSystem::getInputForAttr(&input.attr, &output.inputId, // 调用hal层获取属性信息
input.riid,
sessionId,
// FIXME compare to AudioTrack
clientPid,
clientUid,
input.opPackageName,
&input.config,
output.flags, &output.selectedDeviceId, &portId);
if (lStatus != NO_ERROR) {
ALOGE("createRecord() getInputForAttr return error %d", lStatus);
goto Exit;
}
{
Mutex::Autolock _l(mLock);
RecordThread *thread = checkRecordThread_l(output.inputId); // 获取采集线程，验证猜想2
if (thread == NULL) {
ALOGW("createRecord() checkRecordThread_l failed, input handle %d", output.inputId);
lStatus = FAILED_TRANSACTION;
goto Exit;
}
ALOGV("createRecord() lSessionId: %d input %d", sessionId, output.inputId);
output.sampleRate = input.config.sample_rate;
output.frameCount = input.frameCount;
output.notificationFrameCount = input.notificationFrameCount;
recordTrack = thread->createRecordTrack_l(client, input.attr, &output.sampleRate, // 在采集线程中创建Record，验证猜想1
input.config.format, input.config.channel_mask,
&output.frameCount, sessionId,
&output.notificationFrameCount,
callingPid, clientUid, &output.flags,
input.clientInfo.clientTid,
&lStatus, portId,
input.opPackageName);
LOG_ALWAYS_FATAL_IF((lStatus == NO_ERROR) && (recordTrack == 0));
// lStatus == BAD_TYPE means FAST flag was rejected: request a new input from
// audio policy manager without FAST constraint
if (lStatus == BAD_TYPE) {
continue;
}
if (lStatus != NO_ERROR) {
goto Exit;
}
// Check if one effect chain was awaiting for an AudioRecord to be created on this
// session and move it to this thread.
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(); // 返回匿名共享内存操作符
output.portId = portId;
// return handle to client
recordHandle = new RecordHandle(recordTrack); // 包装成binder， 证明了猜想3
Exit:
if (lStatus != NO_ERROR) {
// remove local strong reference to Client before deleting the RecordTrack so that the
// Client destructor is called by the TrackBase destructor with mClientLock held
// Don't hold mClientLock when releasing the reference on the track as the
// destructor will acquire it.
{
Mutex::Autolock _cl(mClientLock);
client.clear();
}
recordTrack.clear();
if (output.inputId != AUDIO_IO_HANDLE_NONE) {
AudioSystem::releaseInput(portId);
}
}
*status = lStatus;
return recordHandle;
}
当前会有2个采集线程，一个是 RecordThread， 一个是MmapCaptureThread，从字面就可以理解这两个线程的区别，接下来直接看创建Record:
// RecordThread::createRecordTrack_l() must be called with AudioFlinger::mLock held
sp<AudioFlinger::RecordThread::RecordTrack> AudioFlinger::RecordThread::createRecordTrack_l(
const sp<AudioFlinger::Client>& client,
const audio_attributes_t& attr,
uint32_t *pSampleRate,
audio_format_t format,
audio_channel_mask_t channelMask,
size_t *pFrameCount,
audio_session_t sessionId,
size_t *pNotificationFrameCount,
pid_t creatorPid,
uid_t uid,
audio_input_flags_t *flags,
pid_t tid,
status_t *status,
audio_port_handle_t portId,
const String16& opPackageName)
{
size_t frameCount = *pFrameCount;
size_t notificationFrameCount = *pNotificationFrameCount;
sp<RecordTrack> track;
status_t lStatus;
audio_input_flags_t inputFlags = mInput->flags;
audio_input_flags_t requestedFlags = *flags;
uint32_t sampleRate;
lStatus = initCheck();
if (*pSampleRate == 0) {
*pSampleRate = mSampleRate;
}
sampleRate = *pSampleRate;
// special case for FAST flag considered OK if fast capture is present
if (hasFastCapture()) {
inputFlags = (audio_input_flags_t)(inputFlags | AUDIO_INPUT_FLAG_FAST);
}
// Check if requested flags are compatible with input stream flags
if ((*flags & inputFlags) != *flags) {
ALOGW("createRecordTrack_l(): mismatch between requested flags (%08x) and"
" input flags (%08x)",
*flags, inputFlags);
*flags = (audio_input_flags_t)(*flags & inputFlags);
}
// client expresses a preference for FAST, but we get the final say
if (*flags & AUDIO_INPUT_FLAG_FAST) {
if (
// we formerly checked for a callback handler (non-0 tid),
// but that is no longer required for TRANSFER_OBTAIN mode
//
// Frame count is not specified (0), or is less than or equal the pipe depth.
// It is OK to provide a higher capacity than requested.
// We will force it to mPipeFramesP2 below.
(frameCount <= mPipeFramesP2) &&
// PCM data
audio_is_linear_pcm(format) &&
// hardware format
(format == mFormat) &&
// hardware channel mask
(channelMask == mChannelMask) &&
// hardware sample rate
(sampleRate == mSampleRate) &&
// record thread has an associated fast capture
hasFastCapture() &&
// there are sufficient fast track slots available
mFastTrackAvail
) {
// check compatibility with audio effects.
Mutex::Autolock _l(mLock);
// Do not accept FAST flag if the session has software effects
sp<EffectChain> chain = getEffectChain_l(sessionId);
if (chain != 0) {
audio_input_flags_t old = *flags;
chain->checkInputFlagCompatibility(flags);
if (old != *flags) {
ALOGV("%p AUDIO_INPUT_FLAGS denied by effect old=%#x new=%#x",
this, (int)old, (int)*flags);
}
}
ALOGV_IF((*flags & AUDIO_INPUT_FLAG_FAST) != 0,
"%p AUDIO_INPUT_FLAG_FAST accepted: frameCount=%zu mFrameCount=%zu",
this, frameCount, mFrameCount);
} else {
ALOGV("%p AUDIO_INPUT_FLAG_FAST denied: frameCount=%zu mFrameCount=%zu mPipeFramesP2=%zu "
"format=%#x isLinear=%d mFormat=%#x channelMask=%#x sampleRate=%u mSampleRate=%u "
"hasFastCapture=%d tid=%d mFastTrackAvail=%d",
this, frameCount, mFrameCount, mPipeFramesP2,
format, audio_is_linear_pcm(format), mFormat, channelMask, sampleRate, mSampleRate,
hasFastCapture(), tid, mFastTrackAvail);
*flags = (audio_input_flags_t)(*flags & ~AUDIO_INPUT_FLAG_FAST);
}
}
// If FAST or RAW flags were corrected, ask caller to request new input from audio policy
if ((*flags & AUDIO_INPUT_FLAG_FAST) !=
(requestedFlags & AUDIO_INPUT_FLAG_FAST)) {
*flags = (audio_input_flags_t) (*flags & ~(AUDIO_INPUT_FLAG_FAST | AUDIO_INPUT_FLAG_RAW));
lStatus = BAD_TYPE;
goto Exit;
}
// compute track buffer size in frames, and suggest the notification frame count
if (*flags & AUDIO_INPUT_FLAG_FAST) {
// fast track: frame count is exactly the pipe depth
frameCount = mPipeFramesP2;
// ignore requested notificationFrames, and always notify exactly once every HAL buffer
notificationFrameCount = mFrameCount;
} else {
// not fast track: max notification period is resampled equivalent of one HAL buffer time
// or 20 ms if there is a fast capture
// TODO This could be a roundupRatio inline, and const
size_t maxNotificationFrames = ((int64_t) (hasFastCapture() ? mSampleRate/50 : mFrameCount)
* sampleRate + mSampleRate - 1) / mSampleRate;
// minimum number of notification periods is at least kMinNotifications,
// and at least kMinMs rounded up to a whole notification period (minNotificationsByMs)
static const size_t kMinNotifications = 3;
static const uint32_t kMinMs = 30;
// TODO This could be a roundupRatio inline
const size_t minFramesByMs = (sampleRate * kMinMs + 1000 - 1) / 1000;
// TODO This could be a roundupRatio inline
const size_t minNotificationsByMs = (minFramesByMs + maxNotificationFrames - 1) /
maxNotificationFrames;
const size_t minFrameCount = maxNotificationFrames *
max(kMinNotifications, minNotificationsByMs);
frameCount = max(frameCount, minFrameCount);
if (notificationFrameCount == 0 || notificationFrameCount > maxNotificationFrames) {
notificationFrameCount = maxNotificationFrames;
}
}
*pFrameCount = frameCount;
*pNotificationFrameCount = notificationFrameCount;
{ // scope for mLock
Mutex::Autolock _l(mLock);
track = new RecordTrack(this, client, attr, sampleRate, // 创建Record
format, channelMask, frameCount,
nullptr /* buffer */, (size_t)0 /* bufferSize */, sessionId, creatorPid, uid,
*flags, TrackBase::TYPE_DEFAULT, opPackageName, portId);
lStatus = track->initCheck();
if (lStatus != NO_ERROR) {
ALOGE("createRecordTrack_l() initCheck failed %d; no control block?", lStatus);
// track must be cleared from the caller as the caller has the AF lock
goto Exit;
}
mTracks.add(track); // 将Record加入到列表中
if ((*flags & AUDIO_INPUT_FLAG_FAST) && (tid != -1)) {
pid_t callingPid = IPCThreadState::self()->getCallingPid();
// we don't have CAP_SYS_NICE, nor do we want to have it as it's too powerful,
// so ask activity manager to do this on our behalf
sendPrioConfigEvent_l(callingPid, tid, kPriorityAudioApp, true /*forApp*/);
}
}
lStatus = NO_ERROR;
Exit:
*status = lStatus;
return track;
}
看到这儿，可以看出来AudioFlinger管理Record的模式如下：
image.png
接下来继续看下RecordTrack的创建：
// RecordTrack constructor must be called with AudioFlinger::mLock and ThreadBase::mLock held
AudioFlinger::RecordThread::RecordTrack::RecordTrack(
RecordThread *thread,
const sp<Client>& client,
const audio_attributes_t& attr,
uint32_t sampleRate,
audio_format_t format,
audio_channel_mask_t channelMask,
size_t frameCount,
void *buffer,
size_t bufferSize,
audio_session_t sessionId,
pid_t creatorPid,
uid_t uid,
audio_input_flags_t flags,
track_type type,
const String16& opPackageName,
audio_port_handle_t portId)
: TrackBase(thread, client, attr, sampleRate, format,
channelMask, frameCount, buffer, bufferSize, sessionId,
creatorPid, uid, false /*isOut*/,
(type == TYPE_DEFAULT) ?
((flags & AUDIO_INPUT_FLAG_FAST) ? ALLOC_PIPE : ALLOC_CBLK) :
((buffer == NULL) ? ALLOC_LOCAL : ALLOC_NONE),
type, portId,
std::string(AMEDIAMETRICS_KEY_PREFIX_AUDIO_RECORD) + std::to_string(portId)),
mOverflow(false),
mFramesToDrop(0),
mResamplerBufferProvider(NULL), // initialize in case of early constructor exit
mRecordBufferConverter(NULL),
mFlags(flags),
mSilenced(false),
mOpRecordAudioMonitor(OpRecordAudioMonitor::createIfNeeded(uid, attr, opPackageName))
{
if (mCblk == NULL) {
return;
}
if (!isDirect()) {
mRecordBufferConverter = new RecordBufferConverter(
thread->mChannelMask, thread->mFormat, thread->mSampleRate,
channelMask, format, sampleRate);
// Check if the RecordBufferConverter construction was successful.
// If not, don't continue with construction.
//
// NOTE: It would be extremely rare that the record track cannot be created
// for the current device, but a pending or future device change would make
// the record track configuration valid.
if (mRecordBufferConverter->initCheck() != NO_ERROR) {
ALOGE("%s(%d): RecordTrack unable to create record buffer converter", __func__, mId);
return;
}
}
mServerProxy = new AudioRecordServerProxy(mCblk, mBuffer, frameCount,
mFrameSize, !isExternalTrack());
mResamplerBufferProvider = new ResamplerBufferProvider(this);
if (flags & AUDIO_INPUT_FLAG_FAST) {
ALOG_ASSERT(thread->mFastTrackAvail);
thread->mFastTrackAvail = false;
} else {
// TODO: only Normal Record has timestamps (Fast Record does not).
mServerLatencySupported = checkServerLatencySupported(mFormat, flags);
}
#ifdef TEE_SINK
mTee.setId(std::string("_") + std::to_string(mThreadIoHandle)
+ "_" + std::to_string(mId)
+ "_R");
#endif
// Once this item is logged by the server, the client can add properties.
mTrackMetrics.logConstructor(creatorPid, uid);
}
这儿应该会感觉比较熟悉了，共享内存的构造依旧是在TrackBase里面，毕竟采集和播放都需要一个共享内存，这块就可以抽象出来了：
AudioFlinger::ThreadBase::TrackBase::TrackBase(
ThreadBase *thread,
const sp<Client>& client,
const audio_attributes_t& attr,
uint32_t sampleRate,
audio_format_t format,
audio_channel_mask_t channelMask,
size_t frameCount,
void *buffer,
size_t bufferSize,
audio_session_t sessionId,
pid_t creatorPid,
uid_t clientUid,
bool isOut,
alloc_type alloc,
track_type type,
audio_port_handle_t portId,
std::string metricsId)
: RefBase(),
mThread(thread),
mClient(client),
mCblk(NULL),
// mBuffer, mBufferSize
mState(IDLE),
mAttr(attr),
mSampleRate(sampleRate),
mFormat(format),
mChannelMask(channelMask),
mChannelCount(isOut ?
audio_channel_count_from_out_mask(channelMask) :
audio_channel_count_from_in_mask(channelMask)),
mFrameSize(audio_has_proportional_frames(format) ?
mChannelCount * audio_bytes_per_sample(format) : sizeof(int8_t)),
mFrameCount(frameCount),
mSessionId(sessionId),
mIsOut(isOut),
mId(android_atomic_inc(&nextTrackId)),
mTerminated(false),
mType(type),
mThreadIoHandle(thread ? thread->id() : AUDIO_IO_HANDLE_NONE),
mPortId(portId),
mIsInvalid(false),
mTrackMetrics(std::move(metricsId), isOut),
mCreatorPid(creatorPid)
{
const uid_t callingUid = IPCThreadState::self()->getCallingUid();
mUid = clientUid;
size_t minBufferSize = buffer == NULL ? roundup(frameCount) : frameCount;
// check overflow when computing bufferSize due to multiplication by mFrameSize.
if (minBufferSize < frameCount // roundup rounds down for values above UINT_MAX / 2
|| mFrameSize == 0 // format needs to be correct
|| minBufferSize > SIZE_MAX / mFrameSize) {
android_errorWriteLog(0x534e4554, "34749571");
return;
}
minBufferSize *= mFrameSize;
if (buffer == nullptr) {
bufferSize = minBufferSize; // allocated here.
} else if (minBufferSize > bufferSize) {
android_errorWriteLog(0x534e4554, "38340117");
return;
}
size_t size = sizeof(audio_track_cblk_t);
if (buffer == NULL && alloc == ALLOC_CBLK) {
// check overflow when computing allocation size for streaming tracks.
if (size > SIZE_MAX - bufferSize) {
android_errorWriteLog(0x534e4554, "34749571");
return;
}
size += bufferSize;
}
if (client != 0) {
mCblkMemory = client->heap()->allocate(size); // 分配共享内存，client携带了创建的共享内存信息
if (mCblkMemory == 0 ||
(mCblk = static_cast<audio_track_cblk_t *>(mCblkMemory->unsecurePointer())) == NULL) {
ALOGE("%s(%d): not enough memory for AudioTrack size=%zu", __func__, mId, size);
client->heap()->dump("AudioTrack");
mCblkMemory.clear();
return;
}
} else {
mCblk = (audio_track_cblk_t *) malloc(size);
if (mCblk == NULL) {
ALOGE("%s(%d): not enough memory for AudioTrack size=%zu", __func__, mId, size);
return;
}
}
// construct the shared structure in-place.
if (mCblk != NULL) {
new(mCblk) audio_track_cblk_t();
switch (alloc) {
case ALLOC_READONLY: {
const sp<MemoryDealer> roHeap(thread->readOnlyHeap());
if (roHeap == 0 ||
(mBufferMemory = roHeap->allocate(bufferSize)) == 0 ||
(mBuffer = mBufferMemory->unsecurePointer()) == NULL) {
ALOGE("%s(%d): not enough memory for read-only buffer size=%zu",
__func__, mId, bufferSize);
if (roHeap != 0) {
roHeap->dump("buffer");
}
mCblkMemory.clear();
mBufferMemory.clear();
return;
}
memset(mBuffer, 0, bufferSize);
} break;
case ALLOC_PIPE:
mBufferMemory = thread->pipeMemory();
// mBuffer is the virtual address as seen from current process (mediaserver),
// and should normally be coming from mBufferMemory->unsecurePointer().
// However in this case the TrackBase does not reference the buffer directly.
// It should references the buffer via the pipe.
// Therefore, to detect incorrect usage of the buffer, we set mBuffer to NULL.
mBuffer = NULL;
bufferSize = 0;
break;
case ALLOC_CBLK:
// clear all buffers
if (buffer == NULL) {
mBuffer = (char*)mCblk + sizeof(audio_track_cblk_t);
memset(mBuffer, 0, bufferSize);
} else {
mBuffer = buffer;
#if 0
mCblk->mFlags = CBLK_FORCEREADY; // FIXME hack, need to fix the track ready logic
#endif
}
break;
case ALLOC_LOCAL:
mBuffer = calloc(1, bufferSize);
break;
case ALLOC_NONE:
mBuffer = buffer;
break;
default:
LOG_ALWAYS_FATAL("%s(%d): invalid allocation type: %d", __func__, mId, (int)alloc);
}
mBufferSize = bufferSize;
#ifdef TEE_SINK
mTee.set(sampleRate, mChannelCount, format, NBAIO_Tee::TEE_FLAG_TRACK);
#endif
}
}
这儿再次回顾下client:
sp<AudioFlinger::Client> AudioFlinger::registerPid(pid_t pid)
{
Mutex::Autolock _cl(mClientLock);
// If pid is already in the mClients wp<> map, then use that entry
// (for which promote() is always != 0), otherwise create a new entry and Client.
sp<Client> client = mClients.valueFor(pid).promote();
if (client == 0) {
client = new Client(this, pid);
mClients.add(pid, client);
}
return client;
}
AudioFlinger::Client::Client(const sp<AudioFlinger>& audioFlinger, pid_t pid)
: RefBase(),
mAudioFlinger(audioFlinger),
mPid(pid)
{
mMemoryDealer = new MemoryDealer(
audioFlinger->getClientSharedHeapSize(),
(std::string("AudioFlinger::Client(") + std::to_string(pid) + ")").c_str());
}
可以看到内存也是按照pid进行管理的。
接下来再看下如何包装成binder， RecordHandle是支持binder的：
AudioFlinger::RecordHandle::~RecordHandle() {
stop_nonvirtual();
mRecordTrack->destroy();
}
binder::Status AudioFlinger::RecordHandle::start(int /*AudioSystem::sync_event_t*/ event,
int /*audio_session_t*/ triggerSession) {
ALOGV("%s()", __func__);
return binder::Status::fromStatusT(
mRecordTrack->start((AudioSystem::sync_event_t)event, (audio_session_t) triggerSession));
}
binder::Status AudioFlinger::RecordHandle::stop() {
stop_nonvirtual();
return binder::Status::ok();
}
void AudioFlinger::RecordHandle::stop_nonvirtual() {
ALOGV("%s()", __func__);
mRecordTrack->stop();
}
binder::Status AudioFlinger::RecordHandle::getActiveMicrophones(
std::vector<media::MicrophoneInfo>* activeMicrophones) {
ALOGV("%s()", __func__);
return binder::Status::fromStatusT(
mRecordTrack->getActiveMicrophones(activeMicrophones));
}
binder::Status AudioFlinger::RecordHandle::setPreferredMicrophoneDirection(
int /*audio_microphone_direction_t*/ direction) {
ALOGV("%s()", __func__);
return binder::Status::fromStatusT(mRecordTrack->setPreferredMicrophoneDirection(
static_cast<audio_microphone_direction_t>(direction)));
}
binder::Status AudioFlinger::RecordHandle::setPreferredMicrophoneFieldDimension(float zoom) {
ALOGV("%s()", __func__);
return binder::Status::fromStatusT(mRecordTrack->setPreferredMicrophoneFieldDimension(zoom));
}
到了这儿就完成了AudioRecord的创建。
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