Platform: Rockchip
OS: Android 6.0
Kernel: 3.10.92

開機動畫的退出是靠property即
#define EXIT_PROP_NAME "service.bootanim.exit"
來判斷的，見函式checkExit()
BootAnimation.cpp

void BootAnimation::checkExit() {
    if(mShutdown){
        return ;
    }

    // Allow surface flinger to gracefully request shutdown
    char
 
 value[PROPERTY_VALUE_MAX];
    property_get(EXIT_PROP_NAME, value, "0");
    int exitnow = atoi(value);
    if (exitnow) {
        requestExit();
        if (mAudioPlayer != NULL) {
            mAudioPlayer->requestExit();
        }
    }
}

而設定個property的地方是在
SurfaceFlinger.cpp

void SurfaceFlinger::bootFinished()
{
    const
 
 nsecs_t now = systemTime();
    const nsecs_t duration = now - mBootTime;
    ALOGI("Boot is finished (%ld ms)", long(ns2ms(duration)) );
    mBootFinished = true;

    // wait patiently for the window manager death
    const String16 name("window");
    sp<IBinder> window(defaultServiceManager()->getService(name));
    if
 
 (window != 0) {
        window->linkToDeath(static_cast<IBinder::DeathRecipient*>(this));
    }

    // stop boot animation
    // formerly we would just kill the process, but we now ask it to exit so it
    // can choose where to stop the animation.
    property_set("service.bootanim.exit", "1");
}

當顯示模組boot完成後，會呼叫
property_set("service.bootanim.exit", "1");
告訴bootanimation模組退出動畫顯示。

所以從開機動畫開始顯示到SurfaceFlinger boot完成，這個時間就是視訊最少時間。
驗證測試大概在30s左右。