本文重點：stagefrightRecorder.cpp OMXCodec.cpp MPEG4Writer.cpp CameraSource.cpp 之間的調用關係
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最初看的時候，有些地方還是不清楚，關於解碼和文件的讀寫之間的關係不是很瞭解。只是知道底層回調的數據會經過CameraSource.cpp回調，只是知道數據會在OMXCodec.cpp 中完成解碼，只是在MPEG4Writer.cpp 會有讀寫線程和軌跡線程，只是知道在stagefrightRecorder.cpp 中會將OMXCodex.cpp、MPEG4Writer.cpp和CameraSource.cpp 做相互的配合調用。之前一直糾結的是MPEG4Writer.cpp是直接讀CameraSource.cpp 的數據，那和解碼之間又是怎樣的聯繫呢？
是自己知識面不廣，瞭解的不多，讀代碼能力也還得加強。
這次看源碼，總算是理清了上面的疑點。
OMXCodec.cpp 的read函數，直接讀的是CameraSource.cpp 中數據，然後MPEG4Writer.cpp 中的軌跡線程的mSource->read()調用的則是OMXCodec.cpp 中數據。那也就是說，底層數據經過CameraSource.cpp回調的時候，是先經過解碼，然後在將數據寫入文件。
>>>>>>>>這裏直接從stagefrightRecorder.cpp 的start函數開始了，會在start()函數中調用startMPEG4Recording()函數
stagefrightRecorder.cpp
status_t StagefrightRecorder::start()
{
......
switch (mOutputFormat) {
case OUTPUT_FORMAT_DEFAULT:
case OUTPUT_FORMAT_THREE_GPP:
case OUTPUT_FORMAT_MPEG_4:
status = startMPEG4Recording();
......
}
>>>>>>>>在startMPEG4Recording()方法中過，調用的重要方法已經標紅
status_t StagefrightRecorder::startMPEG4Recording()
{
......
status_t err =
setupMPEG4Recording(
mOutputFd, mVideoWidth, mVideoHeight,
mVideoBitRate, &totalBitRate, &mWriter);
sp<MetaData> meta = new MetaData;
setupMPEG4MetaData(startTimeUs, totalBitRate, &meta);
err = mWriter->start(meta.get());
......
}
>>>>>>>>在setupMPEG4Recording()方法中，我們看到 sp<MediaWriter> writer = new MPEG4Writer(outputFd);
這個是完成writer的初始化，那我們現在就知道這個writer是MPEG4Writer了，這個還是蠻重要的。在這個方法中，會調用setupMediaSource(),完成source的初始化，而這個source就是CameraSource，還會繼續調用setupVideoEncoder()方法，完成coder的初始化，而這個coder則是OMXCodex。還得注意下的就是writer->addSource(encoder);
這裏是把解碼的數據交給了writer，這樣MPEG4Writer.cpp和OMXCodec.cpp直接就連續起來了
status_t StagefrightRecorder::setupMPEG4Recording(
......
sp<MediaWriter> *mediaWriter) {
mediaWriter->clear();
sp<MediaWriter> writer = new MPEG4Writer(outputFd);
if (mVideoSource < VIDEO_SOURCE_LIST_END) {
sp<MediaSource> mediaSource;
err = setupMediaSource(&mediaSource);
if (err != OK) {
return err;
}
sp<MediaSource> encoder;
err = setupVideoEncoder(mediaSource, videoBitRate, &encoder);
if (err != OK) {
return err;
}
writer->addSource(encoder);
*totalBitRate += videoBitRate;
}
// Audio source is added at the end if it exists.
// This help make sure that the "recoding" sound is suppressed for
// camcorder applications in the recorded files.
if (!mCaptureTimeLapse && (mAudioSource != AUDIO_SOURCE_CNT)) {
err = setupAudioEncoder(writer);
if (err != OK) return err;
*totalBitRate += mAudioBitRate;
}
if (mInterleaveDurationUs > 0) {
reinterpret_cast<MPEG4Writer *>(writer.get())->
setInterleaveDuration(mInterleaveDurationUs);
}
if (mLongitudex10000 > -3600000 && mLatitudex10000 > -3600000) {
reinterpret_cast<MPEG4Writer *>(writer.get())->
setGeoData(mLatitudex10000, mLongitudex10000);
}
if (mMaxFileDurationUs != 0) {
writer->setMaxFileDuration(mMaxFileDurationUs);
}
if (mMaxFileSizeBytes != 0) {
writer->setMaxFileSize(mMaxFileSizeBytes);
}
mStartTimeOffsetMs = mEncoderProfiles->getStartTimeOffsetMs(mCameraId);
if (mStartTimeOffsetMs > 0) {
reinterpret_cast<MPEG4Writer *>(writer.get())->
setStartTimeOffsetMs(mStartTimeOffsetMs);
}
writer->setListener(mListener);
*mediaWriter = writer;
return OK;
}
>>>>>>>>在setupMediaSource（）方法中是完成了cameraSource的初始化
status_t StagefrightRecorder::setupMediaSource(
sp<MediaSource> *mediaSource) {
if (mVideoSource == VIDEO_SOURCE_DEFAULT
|| mVideoSource == VIDEO_SOURCE_CAMERA) {
sp<CameraSource> cameraSource;
status_t err = setupCameraSource(&cameraSource);
if (err != OK) {
return err;
}
*mediaSource = cameraSource;
} else if (mVideoSource == VIDEO_SOURCE_GRALLOC_BUFFER) {
// If using GRAlloc buffers, setup surfacemediasource.
// Later a handle to that will be passed
// to the client side when queried
status_t err = setupSurfaceMediaSource();
if (err != OK) {
return err;
}
*mediaSource = mSurfaceMediaSource;
} else {
return INVALID_OPERATION;
}
return OK;
}
status_t StagefrightRecorder::setupVideoEncoder(
......
sp<MediaSource> encoder = OMXCodec::Create(
client.interface(), enc_meta,
true /* createEncoder */, cameraSource,
NULL, encoder_flags);
if (encoder == NULL) {
ALOGW("Failed to create the encoder");
// When the encoder fails to be created, we need
// release the camera source due to the camera's lock
// and unlock mechanism.
cameraSource->stop();
return UNKNOWN_ERROR;
}
mVideoSourceNode = cameraSource;
mVideoEncoderOMX = encoder;
*source = encoder;
return OK;
}
-----------------------------
>>>>>上面有說到在stagefrigheRecorder.cpp中有調用到MPEG4Writer.cpp中addSource（）方法 [writer->addSource(encoder);]，而addSource中傳進來的參數是解碼的數據，這樣MPEG4Writer.cpp和OMXCodec.cpp之間就有了聯繫，MPEG4Writer.cpp 讀寫的就是OMXCodec.cpp 中解碼後的數據。
MPEG4Writer.cpp
>>>>>> 在MPEG4Writer.cpp 的addSource（）方法中，注意看下Track *track = new Track(this, source, 1 + mTracks.size()); 我們看到new Track(...,source,...)的時候，是傳進去了source,而這個source，從上面的分析，我們已經知道它是解碼後的數據
status_t MPEG4Writer::addSource(const sp<MediaSource> &source) {
Mutex::Autolock l(mLock);
if (mStarted) {
ALOGE("Attempt to add source AFTER recording is started");
return UNKNOWN_ERROR;
}
// At most 2 tracks can be supported.
if (mTracks.size() >= 2) {
ALOGE("Too many tracks (%d) to add", mTracks.size());
return ERROR_UNSUPPORTED;
}
CHECK(source.get() != NULL);
// A track of type other than video or audio is not supported.
const char *mime;
sp<MetaData> meta = source->getFormat();
CHECK(meta->findCString(kKeyMIMEType, &mime));
bool isAudio = !strncasecmp(mime, "audio/", 6);
bool isVideo = !strncasecmp(mime, "video/", 6);
if (!isAudio && !isVideo) {
ALOGE("Track (%s) other than video or audio is not supported",
mime);
return ERROR_UNSUPPORTED;
}
// At this point, we know the track to be added is either
// video or audio. Thus, we only need to check whether it
// is an audio track or not (if it is not, then it must be
// a video track).
// No more than one video or one audio track is supported.
for (List<Track*>::iterator it = mTracks.begin();
it != mTracks.end(); ++it) {
if ((*it)->isAudio() == isAudio) {
ALOGE("%s track already exists", isAudio? "Audio": "Video");
return ERROR_UNSUPPORTED;
}
}
// This is the first track of either audio or video.
// Go ahead to add the track.
Track *track = new Track(this, source, 1 + mTracks.size()); -------------------------------
mTracks.push_back(track); |
|
|
mHFRRatio = ExtendedUtils::HFR::getHFRRatio(meta); |
|
|
return OK; |
} |
|
MPEG4Writer::Track::Track( --------------------------------------------------------------------------- |
MPEG4Writer *owner, const sp<MediaSource> &source, size_t trackId)
: mOwner(owner),
mMeta(source->getFormat()),
mSource(source),
mDone(false),
mPaused(false),
mResumed(false),
mStarted(false),
mTrackId(trackId),
mTrackDurationUs(0),
mEstimatedTrackSizeBytes(0),
mSamplesHaveSameSize(true),
mStszTableEntries(new ListTableEntries<uint32_t>(1000, 1)),
mStcoTableEntries(new ListTableEntries<uint32_t>(1000, 1)),
mCo64TableEntries(new ListTableEntries<off64_t>(1000, 1)),
mStscTableEntries(new ListTableEntries<uint32_t>(1000, 3)),
mStssTableEntries(new ListTableEntries<uint32_t>(1000, 1)),
mSttsTableEntries(new ListTableEntries<uint32_t>(1000, 2)),
mCttsTableEntries(new ListTableEntries<uint32_t>(1000, 2)),
mCodecSpecificData(NULL),
mCodecSpecificDataSize(0),
mGotAllCodecSpecificData(false),
mReachedEOS(false),
mRotation(0),
mHFRRatio(1) {
getCodecSpecificDataFromInputFormatIfPossible();
const char *mime;
mMeta->findCString(kKeyMIMEType, &mime);
mIsAvc = !strcasecmp(mime, MEDIA_MIMETYPE_VIDEO_AVC);
mIsAudio = !strncasecmp(mime, "audio/", 6);
mIsMPEG4 = !strcasecmp(mime, MEDIA_MIMETYPE_VIDEO_MPEG4) ||
!strcasecmp(mime, MEDIA_MIMETYPE_AUDIO_AAC);
setTimeScale();
}
>>>>>> theradEntry()是軌跡線程真正執行的方法，在這個方法中會通過mSource->read(&buffer)去不斷的讀取數據，那我們想知道，它是read的哪裏的數據，所以就需要找到mSource是在哪裏初始化的，我們搜索下，會發現是在
MPEG4Writer::Track::Track( )
MPEG4Writer *owner, const sp<MediaSource> &source, size_t trackId)
: mOwner(owner),
mSource(source),
這裏進行了初始化。直接看上面，已經連線標出來的方法，就知道，這個source就是解碼後的數據了
status_t MPEG4Writer::Track::threadEntry() {
while (!mDone && (err = mSource->read(&buffer)) == OK) {
......
}
}
--------------------
>>>>>>在上面的分析中，我們知道在stagefrightRecorder.cpp中會完成OMXCodec的初始化，而且在初始化中，就將CameraSource傳進來，這裏只是想說 下面的source就是CameraSource,這樣CameraSource.cpp和OMXCodec.cpp之間就聯繫起來了
OMXCodec.cpp
OMXCodec::OMXCodec(
const sp<IOMX> &omx, IOMX::node_id node,
uint32_t quirks, uint32_t flags,
bool isEncoder,
const char *mime,
const char *componentName,
const sp<MediaSource> &source,
const sp<ANativeWindow> &nativeWindow)
: mOMX(omx),
mOMXLivesLocally(omx->livesLocally(node, getpid())),
mNode(node),
mQuirks(quirks),
mFlags(flags),
mIsEncoder(isEncoder),
mIsVideo(!strncasecmp("video/", mime, 6)),
mMIME(strdup(mime)),
mComponentName(strdup(componentName)),
mSource(source),
mCodecSpecificDataIndex(0),
mState(LOADED),
mInitialBufferSubmit(true),
mSignalledEOS(false),
mNoMoreOutputData(false),
mOutputPortSettingsHaveChanged(false),
mSeekTimeUs(-1),
mSeekMode(ReadOptions::SEEK_CLOSEST_SYNC),
mTargetTimeUs(-1),
mOutputPortSettingsChangedPending(false),
mSkipCutBuffer(NULL),
mLeftOverBuffer(NULL),
mPaused(false),
mNativeWindow(
(!strncmp(componentName, "OMX.google.", 11))
? NULL : nativeWindow),
mNumBFrames(0),
mInSmoothStreamingMode(false),
mOutputCropChanged(false),
mSignalledReadTryAgain(false),
mReturnedRetry(false),
mLastSeekTimeUs(-1),
mLastSeekMode(ReadOptions::SEEK_CLOSEST) {
mPortStatus[kPortIndexInput] = ENABLING;
mPortStatus[kPortIndexOutput] = ENABLING;
setComponentRole();
}
>>>>>>這裏的read（）方法，會被MPEG4Writer.cpp的mSourcr->read()調用，至於解碼的過程，還沒有詳細看
status_t OMXCodec::read(
MediaBuffer **buffer, const ReadOptions *options) {
.......
}