Android5.1 MediaScanner
2015-10-07 19:46
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前言
MediaScanner是Android系统中针对媒体文件的扫描过程,将储存空间中的媒体文件通过扫描的方式遍历并存储在数据库中,然后通过MediaProvider提供接口使用,在Android多媒体中占有很重要的位置。源码位置
packages\providers\mediaproviderframeworks\base\media\java\android\media
frameworks\av\media\libmedia
frameworks\base\media\jni
frameworks\av\media\libstagefright
扫描过程
MediaScannerReceiver.java (packages\providers\mediaprovider\src\com\android\providers\media)MediaScannerReceiver继承BroadcastReceiver,在AndroidManifest.xml静态注册
[code] <receiver android:name="MediaScannerReceiver"> <intent-filter> <action android:name="android.intent.action.BOOT_COMPLETED" /> </intent-filter> <intent-filter> <action android:name="android.intent.action.MEDIA_MOUNTED" /> <data android:scheme="file" /> </intent-filter> <intent-filter> <action android:name="android.intent.action.MEDIA_UNMOUNTED" /> <data android:scheme="file" /> </intent-filter> <intent-filter> <action android:name="android.intent.action.MEDIA_SCANNER_SCAN_FILE" /> <data android:scheme="file" /> </intent-filter> </receiver>
可以看到,当接收到
1. android.intent.action.BOOT_COMPLETED
2. android.intent.action.MEDIA_MOUNTED
3. android.intent.action.MEDIA_UNMOUNTED
4. android.intent.action.MEDIA_SCANNER_SCAN_FILE
广播的时候,MediaScannerReceiver中的onReceiver()方法将会执行
[code]public void onReceive(Context context, Intent intent) { final String action = intent.getAction(); final Uri uri = intent.getData(); if (Intent.ACTION_BOOT_COMPLETED.equals(action)) { // Scan both internal and external storage scan(context, MediaProvider.INTERNAL_VOLUME); scan(context, MediaProvider.EXTERNAL_VOLUME); } else { if (uri.getScheme().equals("file")) { // handle intents related to external storage String path = uri.getPath(); String externalStoragePath = Environment.getExternalStorageDirectory().getPath(); String legacyPath = Environment.getLegacyExternalStorageDirectory().getPath(); try { path = new File(path).getCanonicalPath(); } catch (IOException e) { Log.e(TAG, "couldn't canonicalize " + path); return; } if (path.startsWith(legacyPath)) { path = externalStoragePath + path.substring(legacyPath.length()); } Log.d(TAG, "action: " + action + " path: " + path); if (Intent.ACTION_MEDIA_MOUNTED.equals(action)) { // scan whenever any volume is mounted scan(context, MediaProvider.EXTERNAL_VOLUME); } else if (Intent.ACTION_MEDIA_SCANNER_SCAN_FILE.equals(action) && path != null && path.startsWith(externalStoragePath + "/")) { scanFile(context, path); } } } }
onReceiver方法中,会执行到scan()或者是scanFile()方法,一个是针对整个卷,一个是针对具体的文件,从传入的参数可以看出眉目,scan传入的是卷名,scanFile传入的是文件路径。通过接收广播启动扫描,然而不管是scan还是scanFile都是以startService的方式启动MediaScannerService。
[code] private void scan(Context context, String volume) { Bundle args = new Bundle(); args.putString("volume", volume); context.startService( new Intent(context, MediaScannerService.class).putExtras(args)); } private void scanFile(Context context, String path) { Bundle args = new Bundle(); args.putString("filepath", path); context.startService( new Intent(context, MediaScannerService.class).putExtras(args)); }
分别传入卷名或者文件路径。
MediaScannerService.java (packages\providers\mediaprovider\src\com\android\providers\media)
MediaScannerService看下AndroidManifest.xml文件中定义
[code] <service android:name="MediaScannerService" android:exported="true"> <intent-filter> <action android:name="android.media.IMediaScannerService" /> </intent-filter> </service>
继承Service,实现Runnable接口,首先执行onCreate()方法
[code] public void onCreate() { PowerManager pm = (PowerManager)getSystemService(Context.POWER_SERVICE); mWakeLock = pm.newWakeLock(PowerManager.PARTIAL_WAKE_LOCK, TAG); StorageManager storageManager = (StorageManager)getSystemService(Context.STORAGE_SERVICE); mExternalStoragePaths = storageManager.getVolumePaths(); // Start up the thread running the service. Note that we create a // separate thread because the service normally runs in the process's // main thread, which we don't want to block. Thread thr = new Thread(null, this, "MediaScannerService"); thr.start(); }
这里会单独启动一个线程来处理,然后走到onStartCommand()
[code] public int onStartCommand(Intent intent, int flags, int startId) { while (mServiceHandler == null) { synchronized (this) { try { wait(100); } catch (InterruptedException e) { } } } if (intent == null) { Log.e(TAG, "Intent is null in onStartCommand: ", new NullPointerException()); return Service.START_NOT_STICKY; } Message msg = mServiceHandler.obtainMessage(); msg.arg1 = startId; msg.obj = intent.getExtras(); mServiceHandler.sendMessage(msg); // Try again later if we are killed before we can finish scanning. return Service.START_REDELIVER_INTENT; }
这里先等待mServiceHandler创建完成,然后通过handler message机制传递消息给handler处理,这里的mServiceHandler创建过程是在run()方法中
[code] public void run() { // reduce priority below other background threads to avoid interfering // with other services at boot time. Process.setThreadPriority(Process.THREAD_PRIORITY_BACKGROUND + Process.THREAD_PRIORITY_LESS_F***ORABLE); Looper.prepare(); mServiceLooper = Looper.myLooper(); mServiceHandler = new ServiceHandler(); Looper.loop(); }
由于这个是单独的线程,无法保证在发送消息的时候,handler已经创建完成,所以需要等待handler的创建
看下这个处理消息的handler
[code] private final class ServiceHandler extends Handler { @Override public void handleMessage(Message msg) { Bundle arguments = (Bundle) msg.obj; String filePath = arguments.getString("filepath"); try { if (filePath != null) { IBinder binder = arguments.getIBinder("listener"); IMediaScannerListener listener = (binder == null ? null : IMediaScannerListener.Stub.asInterface(binder)); Uri uri = null; try { uri = scanFile(filePath, arguments.getString("mimetype")); } catch (Exception e) { Log.e(TAG, "Exception scanning file", e); } if (listener != null) { listener.scanCompleted(filePath, uri); } } else { String volume = arguments.getString("volume"); String[] directories = null; if (MediaProvider.INTERNAL_VOLUME.equals(volume)) { // scan internal media storage directories = new String[] { Environment.getRootDirectory() + "/media", Environment.getOemDirectory() + "/media", }; } else if (MediaProvider.EXTERNAL_VOLUME.equals(volume)) { // scan external storage volumes directories = mExternalStoragePaths; } if (directories != null) { if (false) Log.d(TAG, "start scanning volume " + volume + ": " + Arrays.toString(directories)); scan(directories, volume); if (false) Log.d(TAG, "done scanning volume " + volume); } } } catch (Exception e) { Log.e(TAG, "Exception in handleMessage", e); } stopSelf(msg.arg1); } };
分别执行scan和scanFile方法
[code] private void scan(String[] directories, String volumeName) { Uri uri = Uri.parse("file://" + directories[0]); // don't sleep while scanning mWakeLock.acquire(); try { ContentValues values = new ContentValues(); values.put(MediaStore.MEDIA_SCANNER_VOLUME, volumeName); Uri scanUri = getContentResolver().insert(MediaStore.getMediaScannerUri(), values); sendBroadcast(new Intent(Intent.ACTION_MEDIA_SCANNER_STARTED, uri)); try { if (volumeName.equals(MediaProvider.EXTERNAL_VOLUME)) { openDatabase(volumeName); } MediaScanner scanner = createMediaScanner(); scanner.scanDirectories(directories, volumeName); } catch (Exception e) { Log.e(TAG, "exception in MediaScanner.scan()", e); } getContentResolver().delete(scanUri, null, null); } finally { sendBroadcast(new Intent(Intent.ACTION_MEDIA_SCANNER_FINISHED, uri)); mWakeLock.release(); } }
[code] private Uri scanFile(String path, String mimeType) { String volumeName = MediaProvider.EXTERNAL_VOLUME; openDatabase(volumeName); MediaScanner scanner = createMediaScanner(); try { // make sure the file path is in canonical form String canonicalPath = new File(path).getCanonicalPath(); return scanner.scanSingleFile(canonicalPath, volumeName, mimeType); } catch (Exception e) { Log.e(TAG, "bad path " + path + " in scanFile()", e); return null; } }
两者都是会通过createMediaScanner创建MediaScanner对象,然后通过scanDirectories或者scanSingleFile来对卷或者文件进行扫描,下面我们就只针对scanDirectories进行分析。
MediaScanner.java (base\media\java\android\media)
[code] public void scanDirectories(String[] directories, String volumeName) { try { long start = System.currentTimeMillis(); initialize(volumeName);//初始化数据库中的一些内容 prescan(null, true); //预扫描 long prescan = System.currentTimeMillis(); //计算预扫描时间 if (ENABLE_BULK_INSERTS) { // create MediaInserter for bulk inserts mMediaInserter = new MediaInserter(mMediaProvider, mPackageName, 500); } for (int i = 0; i < directories.length; i++) { processDirectory(directories[i], mClient); //扫描目录 } if (ENABLE_BULK_INSERTS) { // flush remaining inserts mMediaInserter.flushAll(); mMediaInserter = null; } long scan = System.currentTimeMillis(); postscan(directories); long end = System.currentTimeMillis(); if (false) { Log.d(TAG, " prescan time: " + (prescan - start) + "ms\n"); Log.d(TAG, " scan time: " + (scan - prescan) + "ms\n"); Log.d(TAG, "postscan time: " + (end - scan) + "ms\n"); Log.d(TAG, " total time: " + (end - start) + "ms\n"); } } catch (SQLException e) { // this might happen if the SD card is removed while the media scanner is running Log.e(TAG, "SQLException in MediaScanner.scan()", e); } catch (UnsupportedOperationException e) { // this might happen if the SD card is removed while the media scanner is running Log.e(TAG, "UnsupportedOperationException in MediaScanner.scan()", e); } catch (RemoteException e) { Log.e(TAG, "RemoteException in MediaScanner.scan()", e); } finally { releaseResources(); } }
这里面比较重要的几个内容,一个是prescan,一个是processDirectory
先看看prescan
[code] Uri limitUri = mFilesUri.buildUpon().appendQueryParameter("limit", "1000").build(); //查询条数为1000条 mWasEmptyPriorToScan = true; while (true) { selectionArgs[0] = "" + lastId; if (c != null) { c.close(); c = null; } c = mMediaProvider.query(mPackageName, limitUri, FILES_PRESCAN_PROJECTION, where, selectionArgs, MediaStore.Files.FileColumns._ID, null); if (c == null) { break; } int num = c.getCount(); if (num == 0) { break; } mWasEmptyPriorToScan = false; while (c.moveToNext()) { long rowId = c.getLong(FILES_PRESCAN_ID_COLUMN_INDEX); String path = c.getString(FILES_PRESCAN_PATH_COLUMN_INDEX); int format = c.getInt(FILES_PRESCAN_FORMAT_COLUMN_INDEX); long lastModified = c.getLong(FILES_PRESCAN_DATE_MODIFIED_COLUMN_INDEX); lastId = rowId; //查询id,路径,格式和最后修改时间 // Only consider entries with absolute path names. // This allows storing URIs in the database without the // media scanner removing them. if (path != null && path.startsWith("/")) { boolean exists = false; try { exists = Os.access(path, android.system.OsConstants.F_OK); } catch (ErrnoException e1) { } ...... } } } } }
这里主要就是注意下最后修改时间,后面扫描的过程中应该会用到。
再看下processDirectory,native方法
android_media_MediaScanner.cpp (base\media\jni)
[code]static void android_media_MediaScanner_processDirectory( JNIEnv *env, jobject thiz, jstring path, jobject client) { ALOGV("processDirectory"); MediaScanner *mp = getNativeScanner_l(env, thiz); if (mp == NULL) { jniThrowException(env, kRunTimeException, "No scanner available"); return; } if (path == NULL) { jniThrowException(env, kIllegalArgumentException, NULL); return; } const char *pathStr = env->GetStringUTFChars(path, NULL); if (pathStr == NULL) { // Out of memory return; } MyMediaScannerClient myClient(env, client); MediaScanResult result = mp->processDirectory(pathStr, myClient); if (result == MEDIA_SCAN_RESULT_ERROR) { ALOGE("An error occurred while scanning directory '%s'.", pathStr); } env->ReleaseStringUTFChars(path, pathStr); }
从MediaScanner.java一直跟过来,忘记了MediaScanner.java中有一个比较重要的内容
[code] static { System.loadLibrary("media_jni"); native_init(); }
这里加载libmedia_jni.so即上面会用到的android_media_MediaScanner.cpp就是存在于这个so中,
[code]private static native final void native_init();
[code]static void android_media_MediaScanner_native_init(JNIEnv *env) { ALOGV("native_init"); jclass clazz = env->FindClass(kClassMediaScanner); //这里指的是static const char* const kClassMediaScanner ="android/media/MediaScanner";也就是后面会用到的MediaScanner.cpp if (clazz == NULL) { return; } fields.context = env->GetFieldID(clazz, "mNativeContext", "J"); if (fields.context == NULL) { return; } }
在创建MediaScanner对象的过程中
[code] public MediaScanner(Context c) { native_setup(); mContext = c; mPackageName = c.getPackageName(); mBitmapOptions.inSampleSize = 1; mBitmapOptions.inJustDecodeBounds = true; setDefaultRingtoneFileNames(); mExternalStoragePath = Environment.getExternalStorageDirectory().getAbsolutePath(); mExternalIsEmulated = Environment.isExternalStorageEmulated(); //mClient.testGenreNameConverter(); } ...... private native final void native_setup();//native方法
[code]static void android_media_MediaScanner_native_setup(JNIEnv *env, jobject thiz) { ALOGV("native_setup"); MediaScanner *mp = new StagefrightMediaScanner;//这里采用的是StagefrightMediaScanner if (mp == NULL) { jniThrowException(env, kRunTimeException, "Out of memory"); return; } env->SetLongField(thiz, fields.context, (jlong)mp);//set操作一下,后面会用到 }
再回到processDirectory方法中来,
MediaScanner *mp = getNativeScanner_l(env, thiz);拿到MediaScaner的cpp对象
MyMediaScannerClient myClient(env, client); //创建MyMediaScannerClient对象,而这里传入的client是MediaScanner.java中的MyMediaScannerClient对象
MediaScanResult result = mp->processDirectory(pathStr, myClient);
//执行processDirectory方法,传入myClient对象
这样传来传去无非就是想保存下当前的java侧的一个client,后面会有妙用?
StagefrightMediaScanner继承MediaScanner,没有实现processDirectory方法,使用的是父类中的方法
[code]MediaScanResult MediaScanner::processDirectory( const char *path, MediaScannerClient &client) { ...... MediaScanResult result = doProcessDirectory(pathBuffer, pathRemaining, client, false); free(pathBuffer); return result; }
[code]MediaScanResult MediaScanner::doProcessDirectory( char *path, int pathRemaining, MediaScannerClient &client, bool noMedia) { ...... while ((entry = readdir(dir))) { if (doProcessDirectoryEntry(path, pathRemaining, client, noMedia, entry, fileSpot) == MEDIA_SCAN_RESULT_ERROR) { result = MEDIA_SCAN_RESULT_ERROR; break; } } }
[code]MediaScanResult MediaScanner::doProcessDirectoryEntry( char *path, int pathRemaining, MediaScannerClient &client, bool noMedia, struct dirent* entry, char* fileSpot) { ...... if (type == DT_DIR) { //如果是目录,继续遍历子节点 bool childNoMedia = noMedia; // set noMedia flag on directories with a name that starts with '.' // for example, the Mac ".Trashes" directory if (name[0] == '.') childNoMedia = true; // report the directory to the client if (stat(path, &statbuf) == 0) { status_t status = client.scanFile(path, statbuf.st_mtime, 0, true /*isDirectory*/, childNoMedia); if (status) { return MEDIA_SCAN_RESULT_ERROR; } } // and now process its contents strcat(fileSpot, "/"); MediaScanResult result = doProcessDirectory(path, pathRemaining - nameLength - 1, client, childNoMedia); if (result == MEDIA_SCAN_RESULT_ERROR) { return MEDIA_SCAN_RESULT_ERROR; } } else if (type == DT_REG) { //如果是普通文件,执行scanFile操作 stat(path, &statbuf); status_t status = client.scanFile(path, statbuf.st_mtime, statbuf.st_size, false /*isDirectory*/, noMedia); ...... }
这里注意一下,使用的client就是之前传入的参数,最终会调用会MediaScanner.java中MyMediaScannerClient中的scanFile方法
[code] public void scanFile(String path, long lastModified, long fileSize, boolean isDirectory, boolean noMedia) { // This is the callback funtion from native codes. // Log.v(TAG, "scanFile: "+path); doScanFile(path, null, lastModified, fileSize, isDirectory, false, noMedia); }
[code] public Uri doScanFile(String path, String mimeType, long lastModified, long fileSize, boolean isDirectory, boolean scanAlways, boolean noMedia) { ...... try { FileEntry entry = beginFile(path, mimeType, lastModified, fileSize, isDirectory, noMedia); //beginFile创建FileEntry ...... // rescan for metadata if file was modified since last scan if (entry != null && (entry.mLastModifiedChanged || scanAlways)) { if (noMedia) { result = endFile(entry, false, false, false, false, false); } else { ...... // we only extract metadata for audio and video files if (isaudio || isvideo) { processFile(path, mimeType, this);//处理音频视频文件 } if (isimage) { processImageFile(path);//处理图片文件 } result = endFile(entry, ringtones, notifications, alarms, music, podcasts); } ...... }
下面看下音频文件的处理
processFile(path, mimeType, this),注意这里传入的参数有路径和mimetype
[code]private native void processFile(String path, String mimeType, MediaScannerClient client);
跟到android_media_MediaScanner.cpp
[code]MyMediaScannerClient myClient(env, client); MediaScanResult result = mp->processFile(pathStr, mimeTypeStr, myClient);
然后跟到
StagefrightMediaScanner.cpp (av\include\media\stagefright)
[code]MediaScanResult StagefrightMediaScanner::processFile( const char *path, const char *mimeType, MediaScannerClient &client) { ALOGV("processFile '%s'.", path); client.setLocale(locale()); client.beginFile(); MediaScanResult result = processFileInternal(path, mimeType, client); client.endFile(); return result; }
[code]MediaScanResult StagefrightMediaScanner::processFileInternal( const char *path, const char * /* mimeType */, MediaScannerClient &client) { ...... sp<MediaMetadataRetriever> mRetriever(new MediaMetadataRetriever); //创建解析实例 int fd = open(path, O_RDONLY | O_LARGEFILE); status_t status; if (fd < 0) { //设置数据源 // couldn't open it locally, maybe the media server can? status = mRetriever->setDataSource(NULL /* httpService */, path); } else { status = mRetriever->setDataSource(fd, 0, 0x7ffffffffffffffL); close(fd); } ...... const char *value; if ((value = mRetriever->extractMetadata(//解析元数据 METADATA_KEY_MIMETYPE)) != NULL) { status = client.setMimeType(value); if (status) { return MEDIA_SCAN_RESULT_ERROR; } } struct KeyMap { const char *tag; int key; }; static const KeyMap kKeyMap[] = { { "tracknumber", METADATA_KEY_CD_TRACK_NUMBER }, { "discnumber", METADATA_KEY_DISC_NUMBER }, { "album", METADATA_KEY_ALBUM }, { "artist", METADATA_KEY_ARTIST }, { "albumartist", METADATA_KEY_ALBUMARTIST }, { "composer", METADATA_KEY_COMPOSER }, { "genre", METADATA_KEY_GENRE }, { "title", METADATA_KEY_TITLE }, { "year", METADATA_KEY_YEAR }, { "duration", METADATA_KEY_DURATION }, { "writer", METADATA_KEY_WRITER }, { "compilation", METADATA_KEY_COMPILATION }, { "isdrm", METADATA_KEY_IS_DRM }, { "width", METADATA_KEY_VIDEO_WIDTH }, { "height", METADATA_KEY_VIDEO_HEIGHT }, }; static const size_t kNumEntries = sizeof(kKeyMap) / sizeof(kKeyMap[0]); for (size_t i = 0; i < kNumEntries; ++i) { const char *value; if ((value = mRetriever->extractMetadata(kKeyMap[i].key)) != NULL) { status = client.addStringTag(kKeyMap[i].tag, value); if (status != OK) { return MEDIA_SCAN_RESULT_ERROR; } } } return MEDIA_SCAN_RESULT_OK; }
这里创建的MediaMetadataRetriever并不是MediaMetadataRetriver本身,而是一个之类,StagefrightMetadataRetriver,中间有一个过程,我们来看下。
[code]MediaMetadataRetriever::MediaMetadataRetriever() { ALOGV("constructor"); const sp<IMediaPlayerService>& service(getService()); if (service == 0) { ALOGE("failed to obtain MediaMetadataRetrieverService"); return; } sp<IMediaMetadataRetriever> retriever(service->createMetadataRetriever()); //创建元数据解析对象 if (retriever == 0) { ALOGE("failed to create IMediaMetadataRetriever object from server"); } mRetriever = retriever;//赋值给mRetriver }
这里的service是MediaPlayerService,这里使用的代理,实现直接看MediaPlayerService.cpp中的函数
[code]sp<IMediaMetadataRetriever> MediaPlayerService::createMetadataRetriever() { pid_t pid = IPCThreadState::self()->getCallingPid(); sp<MetadataRetrieverClient> retriever = new MetadataRetrieverClient(pid); //这里创建了MetadataRetrieverClient对象 ALOGV("Create new media retriever from pid %d", pid); return retriever; }
MetadataRetrieverClient.cpp (av\media\libmediaplayerservice)
[code]MetadataRetrieverClient::MetadataRetrieverClient(pid_t pid) { ALOGV("MetadataRetrieverClient constructor pid(%d)", pid); mPid = pid; mThumbnail = NULL; mAlbumArt = NULL; mRetriever = NULL; }
显然上面创建的东西只是一个空壳,继续往下看
在processFileInternal函数中setDataSource函数中同样会跟到
[code]status_t MetadataRetrieverClient::setDataSource(int fd, int64_t offset, int64_t length) { ...... player_type playerType = MediaPlayerFactory::getPlayerType(NULL /* client */, fd, offset, length); //获取playertype方便后面选择对应的元数据解析器 ALOGV("player type = %d", playerType); sp<MediaMetadataRetrieverBase> p = createRetriever(playerType);//创建实际的metadataretriver if (p == NULL) { ::close(fd); return NO_INIT; } status_t status = p->setDataSource(fd, offset, length); if (status == NO_ERROR) mRetriever = p; ::close(fd); return status; }
[code]static sp<MediaMetadataRetrieverBase> createRetriever(player_type playerType) { sp<MediaMetadataRetrieverBase> p; switch (playerType) { case STAGEFRIGHT_PLAYER: case NU_PLAYER: { p = new StagefrightMetadataRetriever;//这里才是我们实际使用的MedadataRetriver break; } case SONIVOX_PLAYER: ALOGV("create midi metadata retriever"); p = new MidiMetadataRetriever(); break; default: // TODO: // support for TEST_PLAYER ALOGE("player type %d is not supported", playerType); break; } if (p == NULL) { ALOGE("failed to create a retriever object"); } return p; }
StagefrightMetadataRetriever.cpp (av\media\libstagefright)
那么然后执行setDataSouce()
[code]// Warning caller retains ownership of the filedescriptor! Dup it if necessary. status_t StagefrightMetadataRetriever::setDataSource( int fd, int64_t offset, int64_t length) { ...... mExtractor = MediaExtractor::Create(mSource);//创建媒体解析器 ...... }
setDataSouce()有两个方法,传入的参数不用,另外一个是针对在线媒体的
然后就是创建媒体解析器
MediaExtractor.cpp (av\media\libstagefright)
[code]sp<MediaExtractor> MediaExtractor::Create( const sp<DataSource> &source, const char *mime) { ...... //如果Mimetype为null,匹配出最符合的mimetype if (mime == NULL) { float confidence; if (!source->sniff(&tmp, &confidence, &meta)) { ALOGV("FAILED to autodetect media content."); return NULL; } mime = tmp.string(); ALOGV("Autodetected media content as '%s' with confidence %.2f", mime, confidence); } ...... MediaExtractor *ret = NULL; //不同的mimetype对应不同的extractor if (!strcasecmp(mime, MEDIA_MIMETYPE_CONTAINER_MPEG4) || !strcasecmp(mime, "audio/mp4")) { ret = new MPEG4Extractor(source); } else if (!strcasecmp(mime, MEDIA_MIMETYPE_AUDIO_MPEG)) { ret = new MP3Extractor(source, meta); } else if (!strcasecmp(mime, MEDIA_MIMETYPE_AUDIO_AMR_NB) || !strcasecmp(mime, MEDIA_MIMETYPE_AUDIO_AMR_WB)) { ret = new AMRExtractor(source); } else if (!strcasecmp(mime, MEDIA_MIMETYPE_AUDIO_FLAC)) { ret = new FLACExtractor(source); } else if (!strcasecmp(mime, MEDIA_MIMETYPE_CONTAINER_W***)) { ret = new W***Extractor(source); } else if (!strcasecmp(mime, MEDIA_MIMETYPE_CONTAINER_OGG)) { ret = new OggExtractor(source); } else if (!strcasecmp(mime, MEDIA_MIMETYPE_CONTAINER_MATROSKA)) { ret = new MatroskaExtractor(source); } else if (!strcasecmp(mime, MEDIA_MIMETYPE_CONTAINER_MPEG2TS)) { ret = new MPEG2TSExtractor(source); } else if (!strcasecmp(mime, MEDIA_MIMETYPE_CONTAINER_WVM)) { // Return now. WVExtractor should not have the DrmFlag set in the block below. return new WVMExtractor(source); } else if (!strcasecmp(mime, MEDIA_MIMETYPE_AUDIO_AAC_ADTS)) { ret = new AACExtractor(source, meta); } else if (!strcasecmp(mime, MEDIA_MIMETYPE_CONTAINER_MPEG2PS)) { ret = new MPEG2PSExtractor(source); } if (ret != NULL) { if (isDrm) { ret->setDrmFlag(true); } else { ret->setDrmFlag(false); } } return ret; }
针对mimetype为空的情况
DataSource.cpp (av\media\libstagefright)
[code]bool DataSource::sniff( String8 *mimeType, float *confidence, sp<AMessage> *meta) { *mimeType = "";//mimetype *confidence = 0.0f;//可信度 meta->clear(); { Mutex::Autolock autoLock(gSnifferMutex); if (!gSniffersRegistered) {//如果没有嗅探器直接return return false; } } for (List<SnifferFunc>::iterator it = gSniffers.begin(); it != gSniffers.end(); ++it) { String8 newMimeType; float newConfidence; sp<AMessage> newMeta; if ((*it)(this, &newMimeType, &newConfidence, &newMeta)) { if (newConfidence > *confidence) { *mimeType = newMimeType; *confidence = newConfidence; *meta = newMeta; } } } //遍历所有的嗅探器,找到可信度最高的 return *confidence > 0.0; }
到这里对应的mimetype和extractor都明确了,再回到StagefrightMediaScanner.cpp中processFileInternal函数,执行完了setDataSouce,执行extractMetadata,依然是跟到StagefrightMetadataRetriver.cpp中
[code]const char *StagefrightMetadataRetriever::extractMetadata(int keyCode) { if (mExtractor == NULL) { return NULL; } if (!mParsedMetaData) { parseMetaData();//如果没有解析,就解析一下 mParsedMetaData = true;//标识一下,已经解析过了 } ssize_t index = mMetaData.indexOfKey(keyCode); if (index < 0) { return NULL; } return mMetaData.valueAt(index).string();//如果解析过就直接放回对应的内容即可 }
再看下parseMetaData函数,这个函数比较长,主要看下一部分
[code] static const Map kMap[] = { { kKeyMIMEType, METADATA_KEY_MIMETYPE, NULL }, { kKeyCDTrackNumber, METADATA_KEY_CD_TRACK_NUMBER, "tracknumber" }, { kKeyDiscNumber, METADATA_KEY_DISC_NUMBER, "discnumber" }, { kKeyAlbum, METADATA_KEY_ALBUM, "album" }, { kKeyArtist, METADATA_KEY_ARTIST, "artist" }, { kKeyAlbumArtist, METADATA_KEY_ALBUMARTIST, "albumartist" }, { kKeyAuthor, METADATA_KEY_AUTHOR, NULL }, { kKeyComposer, METADATA_KEY_COMPOSER, "composer" }, { kKeyDate, METADATA_KEY_DATE, NULL }, { kKeyGenre, METADATA_KEY_GENRE, "genre" }, { kKeyTitle, METADATA_KEY_TITLE, "title" }, { kKeyYear, METADATA_KEY_YEAR, "year" }, { kKeyWriter, METADATA_KEY_WRITER, "writer" }, { kKeyCompilation, METADATA_KEY_COMPILATION, "compilation" }, { kKeyLocation, METADATA_KEY_LOCATION, NULL }, }; static const size_t kNumMapEntries = sizeof(kMap) / sizeof(kMap[0]); //创建字符集探测器,这个内容是L版本新加的内容 CharacterEncodingDetector *detector = new CharacterEncodingDetector(); for (size_t i = 0; i < kNumMapEntries; ++i) { const char *value; if (meta->findCString(kMap[i].from, &value)) { if (kMap[i].name) { // add to charset detector detector->addTag(kMap[i].name, value);//加入探测器 } else { // directly add to output list mMetaData.add(kMap[i].to, String8(value)); } } } detector->detectAndConvert();//探测器中执行字符集的探测和转换 int size = detector->size(); if (size) { for (int i = 0; i < size; i++) { const char *name; const char *value; detector->getTag(i, &name, &value); for (size_t j = 0; j < kNumMapEntries; ++j) { if (kMap[j].name && !strcmp(kMap[j].name, name)) { mMetaData.add(kMap[j].to, String8(value));//最后的数据保存 } } } }
此函数中其他的内容也是解析一些其他的元数据报保存下来。
再回到processFileInternal中,在解析完元数据之后
[code] for (size_t i = 0; i < kNumEntries; ++i) { const char *value; if ((value = mRetriever->extractMetadata(kKeyMap[i].key)) != NULL) { status = client.addStringTag(kKeyMap[i].tag, value); if (status != OK) { return MEDIA_SCAN_RESULT_ERROR; } } }
将数据一个一个通过client的addStringTag往上传递,跟下此过程
MediaScannerClient.cpp (av\media\libmedia)
[code]status_t MediaScannerClient::addStringTag(const char* name, const char* value) { handleStringTag(name, value); return OK; }
最后会回到MediaScanner.java中的handleStringTag()
[code] public void handleStringTag(String name, String value) { if (name.equalsIgnoreCase("title") || name.startsWith("title;")) { // Don't trim() here, to preserve the special \001 character // used to force sorting. The media provider will trim() before // inserting the title in to the database. mTitle = value; } else if (name.equalsIgnoreCase("artist") || name.startsWith("artist;")) { mArtist = value.trim(); } else if (name.equalsIgnoreCase("albumartist") || name.startsWith("albumartist;") || name.equalsIgnoreCase("band") || name.startsWith("band;")) { mAlbumArtist = value.trim(); } else if (name.equalsIgnoreCase("album") || name.startsWith("album;")) { mAlbum = value.trim(); } else if (name.equalsIgnoreCase("composer") || name.startsWith("composer;")) { mComposer = value.trim(); } else if (mProcessGenres && (name.equalsIgnoreCase("genre") || name.startsWith("genre;"))) { mGenre = getGenreName(value); } else if (name.equalsIgnoreCase("year") || name.startsWith("year;")) { mYear = parseSubstring(value, 0, 0); } else if (name.equalsIgnoreCase("tracknumber") || name.startsWith("tracknumber;")) { // track number might be of the form "2/12" // we just read the number before the slash int num = parseSubstring(value, 0, 0); mTrack = (mTrack / 1000) * 1000 + num; } else if (name.equalsIgnoreCase("discnumber") || name.equals("set") || name.startsWith("set;")) { // set number might be of the form "1/3" // we just read the number before the slash int num = parseSubstring(value, 0, 0); mTrack = (num * 1000) + (mTrack % 1000); } else if (name.equalsIgnoreCase("duration")) { mDuration = parseSubstring(value, 0, 0); } else if (name.equalsIgnoreCase("writer") || name.startsWith("writer;")) { mWriter = value.trim(); } else if (name.equalsIgnoreCase("compilation")) { mCompilation = parseSubstring(value, 0, 0); } else if (name.equalsIgnoreCase("isdrm")) { mIsDrm = (parseSubstring(value, 0, 0) == 1); } else if (name.equalsIgnoreCase("width")) { mWidth = parseSubstring(value, 0, 0); } else if (name.equalsIgnoreCase("height")) { mHeight = parseSubstring(value, 0, 0); } else { //Log.v(TAG, "unknown tag: " + name + " (" + mProcessGenres + ")"); } }
对应的数据已经被传递到了Java侧,剩下的就比较好处理了
本文只是跟了一条大致的代码流程,先到此,后续有可能还要更新一下。
本文中代码使用的是Android5.1原始代码,欢迎大家留言交流。
版权声明:本文为博主原创文章,未经博主允许不得转载。
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