apple music杜比音效
看到介绍说iPhone7以后的机型都支持杜比音效，为何iPhone8plus直接外放没有显示杜比音效的图标呢，使用耳机时会有，但切换到外放就没有了。
iPhone 8 Plus, iOS 14
参考 https://support.apple.com/zh-cn/HT212182
Supported songs automatically play in Dolby Atmos when you're listening with:
- AirPods Pro or AirPods Max with spatial audio turned on. Go to Control Center, touch and hold the volume button, then tap Spatial Audio.
- AirPods
- BeatsX, Beats Solo3 Wireless, Beats Studio3, Powerbeats3 Wireless, Beats Flex, Powerbeats Pro, or Beats Solo Pro
- The built-in speakers on an iPhone XR or later (except iPhone SE), iPad Pro 12.9-inch (3rd generation or later), iPad Pro 11-inch, iPad (6th generation or later), iPad Air (3rd generation or later), or iPad mini (5th generation)
使用 iPhone 内建扬声器听杜比全景声需要 iPhone XR 及更新机型（iPhone SE 除外）