Android 13 - Media框架（26）- MPEG4Extractor

static bool AdjustChannelsAndRate(uint32_t fourcc, uint32_t *channels, uint32_t *rate) {
    if (!strcasecmp(MEDIA_MIMETYPE_AUDIO_AMR_NB, FourCC2MIME(fourcc))) {
        // AMR NB audio is always mono, 8kHz
        *channels = 1;
        *rate = 8000;
        return true;
    } else if (!strcasecmp(MEDIA_MIMETYPE_AUDIO_AMR_WB, FourCC2MIME(fourcc))) {
        // AMR WB audio is always mono, 16kHz
        *channels = 1;
        *rate = 16000;
        return true;
    }
    return false;
}

MPEG4Extractor::MPEG4Extractor(DataSourceHelper *source, const char *mime)
    : mMoofOffset(0),
      mMoofFound(false),
      mMdatFound(false),
      mDataSource(source),
      mInitCheck(NO_INIT),
      mHeaderTimescale(0),
      mIsQT(false),
      mIsHeif(false),
      mHasMoovBox(false),
      mPreferHeif(mime != NULL && !strcasecmp(mime, MEDIA_MIMETYPE_CONTAINER_HEIF)),
      mIsAvif(false),
      mFirstTrack(NULL),
      mLastTrack(NULL) {
    ALOGV("mime=%s, mPreferHeif=%d", mime, mPreferHeif);
    mFileMetaData = AMediaFormat_new();
}

MPEG4Extractor::~MPEG4Extractor() {
    Track *track = mFirstTrack;
    while (track) {
        Track *next = track->next;

        delete track;
        track = next;
    }
    mFirstTrack = mLastTrack = NULL;

    for (size_t i = 0; i < mPssh.size(); i++) {
        delete [] mPssh[i].data;
    }
    mPssh.clear();

    delete mDataSource;
    AMediaFormat_delete(mFileMetaData);
}

uint32_t MPEG4Extractor::flags() const {
    return CAN_PAUSE |
            ((mMoofOffset == 0 || mSidxEntries.size() != 0) ?
                    (CAN_SEEK_BACKWARD | CAN_SEEK_FORWARD | CAN_SEEK) : 0);
}

media_status_t MPEG4Extractor::getMetaData(AMediaFormat *meta) {
    status_t err;
    if ((err = readMetaData()) != OK) {
        return AMEDIA_ERROR_UNKNOWN;
    }
    AMediaFormat_copy(meta, mFileMetaData);
    return AMEDIA_OK;
}

size_t MPEG4Extractor::countTracks() {
    status_t err;
    if ((err = readMetaData()) != OK) {
        ALOGV("MPEG4Extractor::countTracks: no tracks");
        return 0;
    }

    size_t n = 0;
    Track *track = mFirstTrack;
    while (track) {
        ++n;
        track = track->next;
    }

    ALOGV("MPEG4Extractor::countTracks: %zu tracks", n);
    return n;
}