Audio in HMTL5 video works fine in Safari on iOS 10.3.1 on iPhone, though it doesn't in standalone web apps (same html code & video file). Video play is fine. Just no sound.
There are a few other related discussions in the past, eg, Why HTML5 video doesn't play in IOS 8 WebApp(webview)?. I tested on iOS 10 using the html provided by that post.
Not sure whether it is a new bug introduced in iOS 10, or a bug that has never been fixed by Apple since earlier versions. Does anyone experience this issue? Are there any workarounds? Thanks in advance.