bool findInt32(uint32_t key, int32_t *value)函数 =>个人理解！

最近应用工作原因在看Android多媒体框架的源码！看到了AwesomePlayer.cpp源码！发现有很多 bool findInt32(uint32_t key, int32_t *value);类似的代码！看不懂什么意思！现在豁然开朗！也是个人理解！假设！猜测！做个笔记！

AwesomePlayer.cpp里面有如下函数：
            int32_t displayWidth, displayHeight;
            bool success = meta->findInt32(kKeyDisplayWidth, &displayWidth/*输出参数*/);
            if (success) {
                success = meta->findInt32(kKeyDisplayHeight, &displayHeight/*输出参数*/);
            }
            if (success) {
                mDisplayWidth = displayWidth;
                mDisplayHeight = displayHeight;
            }

1）有以上得出个人理解：kKeyDisplayWidth、kKeyDisplayHeight是个"键",它对应的有个值!findInt32就是找到对应的值赋值给displayWidth, displayHeight；

2）在源码搜索kKeyDisplayWidth、kKeyDisplayHeight果然搜到键值对应enum在MetaData.h源码里：

// The following keys map to int32_t data unless indicated otherwise.
enum {
    kKeyMIMEType          = 'mime',  // cstring
    kKeyWidth             = 'widt',  // int32_t, image pixel
    kKeyHeight            = 'heig',  // int32_t, image pixel
    kKeyDisplayWidth      = 'dWid',  // int32_t, display/presentation
    kKeyDisplayHeight     = 'dHgt',  // int32_t, display/presentation

    // a rectangle, if absent assumed to be (0, 0, width - 1, height - 1)
    kKeyCropRect          = 'crop',

    kKeyRotation          = 'rotA',  // int32_t (angle in degrees)
    kKeyIFramesInterval   = 'ifiv',  // int32_t
    kKeyStride            = 'strd',  // int32_t
    kKeySliceHeight       = 'slht',  // int32_t
    kKeyChannelCount      = '#chn',  // int32_t
    kKeySampleRate        = 'srte',  // int32_t (audio sampling rate Hz)
    kKeyFrameRate         = 'frmR',  // int32_t (video frame rate fps)
    kKeyBitRate           = 'brte',  // int32_t (bps)
    kKeyESDS              = 'esds',  // raw data
    kKey***CC              = 'avcc',  // raw data
#ifdef OMAP_ENHANCEMENT
    kKeyHdr               = 'hdrd',  // raw data
    kKeySARIdc            = 'sari',  // Sample aspect ratio of the luma samples (int32_t)
    kKeySARWidth          = 'sarw',  // Sample aspect ratio width (int32_t)
    kKeySARHeight         = 'sarh',  // Sample aspect ratio height (int32_t)
#endif
    kKeyD263              = 'd263',  // raw data
    kKeyVorbisInfo        = 'vinf',  // raw data
    kKeyVorbisBooks       = 'vboo',  // raw data
    kKeyWantsNALFragments = 'NALf',
    kKeyIsSyncFrame       = 'sync',  // int32_t (bool)
    kKeyIsCodecConfig     = 'conf',  // int32_t (bool)
    kKeyTime              = 'time',  // int64_t (usecs)
    kKeyDecodingTime      = 'decT',  // int64_t (decoding timestamp in usecs)
    kKeyNTPTime           = 'ntpT',  // uint64_t (ntp-timestamp)
    kKeyTargetTime        = 'tarT',  // int64_t (usecs)
    kKeyDriftTime         = 'dftT',  // int64_t (usecs)
    kKeyAnchorTime        = 'ancT',  // int64_t (usecs)
    kKeyDuration          = 'dura',  // int64_t (usecs)
    kKeyColorFormat       = 'colf',
    kKeyPlatformPrivate   = 'priv',  // pointer
    kKeyDecoderComponent  = 'decC',  // cstring
    kKeyBufferID          = 'bfID',
    kKeyMaxInputSize      = 'inpS',
    kKeyThumbnailTime     = 'thbT',  // int64_t (usecs)
    kKeyTrackID           = 'trID',
    kKeyIsDRM             = 'idrm',  // int32_t (bool)

    kKeyAlbum             = 'albu',  // cstring
    kKeyArtist            = 'arti',  // cstring
    kKeyAlbumArtist       = 'aart',  // cstring
    kKeyComposer          = 'comp',  // cstring
    kKeyGenre             = 'genr',  // cstring
    kKeyTitle             = 'titl',  // cstring
    kKeyYear              = 'year',  // cstring
    kKeyAlbumArt          = 'albA',  // compressed image data
    kKeyAlbumArtMIME      = 'alAM',  // cstring
    kKeyAuthor            = 'auth',  // cstring
    kKeyCDTrackNumber     = 'cdtr',  // cstring
    kKeyDiscNumber        = 'dnum',  // cstring
    kKeyDate              = 'date',  // cstring
    kKeyWriter            = 'writ',  // cstring
    kKeyCompilation       = 'cpil',  // cstring
    kKeyLocation          = 'loc ',  // cstring
    kKeyTimeScale         = 'tmsl',  // int32_t

    // video profile and level
    kKeyVideoProfile      = 'vprf',  // int32_t
    kKeyVideoLevel        = 'vlev',  // int32_t

    // Set this key to enable authoring files in 64-bit offset
    kKey64BitFileOffset   = 'fobt',  // int32_t (bool)
    kKey2ByteNalLength    = '2NAL',  // int32_t (bool)

    // Identify the file output format for authoring
    // Please see <media/mediarecorder.h> for the supported
    // file output formats.
    kKeyFileType          = 'ftyp',  // int32_t

    // Track authoring progress status
    // kKeyTrackTimeStatus is used to track progress in elapsed time
    kKeyTrackTimeStatus   = 'tktm',  // int64_t

    kKeyNotRealTime       = 'ntrt',  // bool (int32_t)

    // Ogg files can be tagged to be automatically looping...
    kKeyAutoLoop          = 'autL',  // bool (int32_t)

    kKeyValidSamples      = 'valD',  // int32_t

    kKeyIsUnreadable      = 'unre',  // bool (int32_t)

    // An indication that a video buffer has been rendered.
    kKeyRendered          = 'rend',  // bool (int32_t)

    // The language code for this media
    kKeyMediaLanguage     = 'lang',  // cstring

    // To store the timed text format data
    kKeyTextFormatData    = 'text',  // raw data

    kKeyRequiresSecureBuffers = 'secu',  // bool (int32_t)
#ifdef OMAP_ENHANCEMENT_S3D
    kKeyS3DLayout         = 's3dl',
#endif
#ifdef OMAP_ENHANCEMENT
    kKeyBufferLayout      = 'lout',
    kKeyVideoFPS          = 'vfps', // int32_t
#endif
};

enum {
    kTypeESDS        = 'esds',
    kType***CC        = 'avcc',
#ifdef OMAP_ENHANCEMENT
    kTypeHdr         = 'hdrd',
#endif
    kTypeD263        = 'd263',
};

具体这些键值什么意思有待进一步分析！