Der Internet Explorer 11 unterstützt AAC:
https://html5test.com/compare/browser/ie-11.html
Ob er aber 96kbps AAC+ automatisch nimmt (falls vorhanden) keine Ahnung und Ich nutze den IE nicht.
[7] AAC is only supported in the MP4 container. To avoid patent issues, support for MPEG 4 and AAC is not built directly into Firefox. Instead it relies on support from the OS or hardware (the hardware also needs to be able to support the profile used to encode the video, in the case of MP4). Firefox supports these formats on the following platforms: Windows Vista+ since Firefox 22.0, Android since Firefox 20.0, Firefox OS since Firefox 15.0, Linux since Firefox 26.0 (relies on GStreamer codecs) and OS X 10.7 since Firefox 35.0.
https://developer.mozilla.org/en-US/docs/Web/HTML/Supported_media_formats
Beim FF ist Pustekuchen mit nem 96kbps AAC+ Stream angesagt!