initFromDataSource

status_t NuPlayer::GenericSource::initFromDataSource() {
    sp<IMediaExtractor> extractor;
    sp<DataSource> dataSource;
    {
        Mutex::Autolock _l_d(mDisconnectLock);
        dataSource = mDataSource;
    }
    CHECK(dataSource != NULL);

    mLock.unlock();
    // This might take long time if data source is not reliable.
    extractor = MediaExtractorFactory::Create(dataSource, NULL);

    if (extractor == NULL) {
        ALOGE("initFromDataSource, cannot create extractor!");
        mLock.lock();
        return UNKNOWN_ERROR;
    }

    sp<MetaData> fileMeta = extractor->getMetaData();

    size_t numtracks = extractor->countTracks();
    if (numtracks == 0) {
        ALOGE("initFromDataSource, source has no track!");
        mLock.lock();
        return UNKNOWN_ERROR;
    }

    mLock.lock();
    mFileMeta = fileMeta;
    if (mFileMeta != NULL) {
        int64_t duration;
        if (mFileMeta->findInt64(kKeyDuration, &duration)) {
            mDurationUs = duration;
        }
    }

    int32_t totalBitrate = 0;

    mMimes.clear();

    for (size_t i = 0; i < numtracks; ++i) {
        sp<IMediaSource> track = extractor->getTrack(i);
        if (track == NULL) {
            continue;
        }

        sp<MetaData> meta = extractor->getTrackMetaData(i);
        if (meta == NULL) {
            ALOGE("no metadata for track %zu", i);
            return UNKNOWN_ERROR;
        }

        const char *mime;
        CHECK(meta->findCString(kKeyMIMEType, &mime));

        ALOGV("initFromDataSource track[%zu]: %s", i, mime);

        // Do the string compare immediately with "mime",
        // we can't assume "mime" would stay valid after another
        // extractor operation, some extractors might modify meta
        // during getTrack() and make it invalid.
        if (!strncasecmp(mime, "audio/", 6)) {
            if (mAudioTrack.mSource == NULL) {
                mAudioTrack.mIndex = i;
                mAudioTrack.mSource = track;
                mAudioTrack.mPackets =
                    new AnotherPacketSource(mAudioTrack.mSource->getFormat());

                if (!strcasecmp(mime, MEDIA_MIMETYPE_AUDIO_VORBIS)) {
                    mAudioIsVorbis = true;
                } else {
                    mAudioIsVorbis = false;
                }

                mMimes.add(String8(mime));
            }
        } else if (!strncasecmp(mime, "video/", 6)) {
            if (mVideoTrack.mSource == NULL) {
                mVideoTrack.mIndex = i;
                mVideoTrack.mSource = track;
                mVideoTrack.mPackets =
                    new AnotherPacketSource(mVideoTrack.mSource->getFormat());

                // video always at the beginning
                mMimes.insertAt(String8(mime), 0);
            }
        }

        mSources.push(track);
        int64_t durationUs;
        if (meta->findInt64(kKeyDuration, &durationUs)) {
            if (durationUs > mDurationUs) {
                mDurationUs = durationUs;
            }
        }

        int32_t bitrate;
        if (totalBitrate >= 0 && meta->findInt32(kKeyBitRate, &bitrate)) {
            totalBitrate += bitrate;
        } else {
            totalBitrate = -1;
        }
    }

    ALOGV("initFromDataSource mSources.size(): %zu  mIsSecure: %d  mime[0]: %s", mSources.size(),
            mIsSecure, (mMimes.isEmpty() ? "NONE" : mMimes[0].string()));

    if (mSources.size() == 0) {
        ALOGE("b/23705695");
        return UNKNOWN_ERROR;
    }

    // Modular DRM: The return value doesn't affect source initialization.
    (void)checkDrmInfo();

    mBitrate = totalBitrate;

    return OK;
}

sp<IMediaExtractor> MediaExtractorFactory::Create(
        const sp<DataSource> &source, const char *mime) {
    ALOGV("MediaExtractorFactory::Create %s", mime);

    if (!property_get_bool("media.stagefright.extractremote", true)) {
        // local extractor
        ALOGW("creating media extractor in calling process");
        return CreateFromService(source, mime);
    } else {
        // remote extractor
        ALOGV("get service manager");
        sp<IBinder> binder = defaultServiceManager()->getService(String16("media.extractor"));

        if (binder != 0) {
            sp<IMediaExtractorService> mediaExService(
                    interface_cast<IMediaExtractorService>(binder));
            sp<IMediaExtractor> ex;
            mediaExService->makeExtractor(
                    CreateIDataSourceFromDataSource(source),
                    mime ? std::make_unique<std::string>(mime) : nullptr,
                    &ex);
            return ex;
        } else {
            ALOGE("extractor service not running");
            return NULL;
        }
    }
    return NULL;
}

::android::binder::Status MediaExtractorService::makeExtractor(
        const ::android::sp<::android::IDataSource>& remoteSource,
        const ::std::unique_ptr< ::std::string> &mime,
        ::android::sp<::android::IMediaExtractor>* _aidl_return) {
    ALOGV("@@@ MediaExtractorService::makeExtractor for %s", mime.get()->c_str());

    sp<DataSource> localSource = CreateDataSourceFromIDataSource(remoteSource);

    MediaBuffer::useSharedMemory();
    sp<IMediaExtractor> extractor = MediaExtractorFactory::CreateFromService(
            localSource,
            mime.get() ? mime.get()->c_str() : nullptr);

    ALOGV("extractor service created %p (%s)",
            extractor.get(),
            extractor == nullptr ? "" : extractor->name());

    if (extractor != nullptr) {
        registerMediaExtractor(extractor, localSource, mime.get() ? mime.get()->c_str() : nullptr);
    }
    *_aidl_return = extractor;	//返回创建好的 extractor
    return binder::Status::ok();
}

sp<IMediaExtractor> MediaExtractorFactory::CreateFromService(
        const sp<DataSource> &source, const char *mime) {

    ALOGV("MediaExtractorFactory::CreateFromService %s", mime);

    void *meta = nullptr;
    void *creator = NULL;
    FreeMetaFunc freeMeta = nullptr;
    float confidence;
    sp<ExtractorPlugin> plugin;
    uint32_t creatorVersion = 0;
    creator = sniff(source, &confidence, &meta, &freeMeta, plugin, &creatorVersion);
    if (!creator) {
        ALOGV("FAILED to autodetect media content.");
        return NULL;
    }

    MediaExtractor *ex = nullptr;
    if (creatorVersion == EXTRACTORDEF_VERSION_NDK_V1 ||
            creatorVersion == EXTRACTORDEF_VERSION_NDK_V2) {
        CMediaExtractor *ret = ((CreatorFunc)creator)(source->wrap(), meta);
        if (meta != nullptr && freeMeta != nullptr) {
            freeMeta(meta);
        }
        ex = ret != nullptr ? new MediaExtractorCUnwrapper(ret) : nullptr;
    }

    ALOGV("Created an extractor '%s' with confidence %.2f",
         ex != nullptr ? ex->name() : "<null>", confidence);

    return CreateIMediaExtractorFromMediaExtractor(ex, source, plugin);
}

void *MediaExtractorFactory::sniff(
        const sp<DataSource> &source, float *confidence, void **meta,
        FreeMetaFunc *freeMeta, sp<ExtractorPlugin> &plugin, uint32_t *creatorVersion) {
    *confidence = 0.0f;
    *meta = nullptr;

    std::shared_ptr<std::list<sp<ExtractorPlugin>>> plugins;
    {
        Mutex::Autolock autoLock(gPluginMutex);
        if (!gPluginsRegistered) {
            return NULL;
        }
        plugins = gPlugins;
    }

    void *bestCreator = NULL;
    for (auto it = plugins->begin(); it != plugins->end(); ++it) {
        ALOGV("sniffing %s", (*it)->def.extractor_name);
        float newConfidence;
        void *newMeta = nullptr;
        FreeMetaFunc newFreeMeta = nullptr;

        void *curCreator = NULL;
        if ((*it)->def.def_version == EXTRACTORDEF_VERSION_NDK_V1) {
            curCreator = (void*) (*it)->def.u.v2.sniff(
                    source->wrap(), &newConfidence, &newMeta, &newFreeMeta);
        } else if ((*it)->def.def_version == EXTRACTORDEF_VERSION_NDK_V2) {
            curCreator = (void*) (*it)->def.u.v3.sniff(
                    source->wrap(), &newConfidence, &newMeta, &newFreeMeta);
        }

        if (curCreator) {
            if (newConfidence > *confidence) {
                *confidence = newConfidence;
                if (*meta != nullptr && *freeMeta != nullptr) {
                    (*freeMeta)(*meta);
                }
                *meta = newMeta;
                *freeMeta = newFreeMeta;
                plugin = *it;
                bestCreator = curCreator;
                *creatorVersion = (*it)->def.def_version;
            } else {
                if (newMeta != nullptr && newFreeMeta != nullptr) {
                    newFreeMeta(newMeta);
                }
            }
        }
    }

    return bestCreator;
}