如果用户的首选项没有指示另一个轨道在HTML中更合适，那么如何识别要启用的轨道？
如果要为视频提供两个字幕轨道，请使用默认属性标识要启用的轨道。
示例
您可以尝试以下代码来实现轨道的默认属性-
<!DOCTYPE HTML>
<html>
<body>
<video width = "300" height = "200" controls autoplay>
<source src = "/html5/foo.ogg" type = "video/ogg" />
<source src = "/html5/foo.mp4" type = "video/mp4" />
<track src = "subtitles_en.vtt" kind = "subtitles" srclang = "en" label = "English">
<track src = "subtitles_ru.vtt" kind = "subtitles" srclang = "ru" label = "Russia" default>
Your browser does not support the video element.
</video>
</body>
</html>