I was asked an interesting question on Thursday after I showed my HTML5 video demo. Q: If you use playbackrate to fast forward video does the property have a max value setting? Reading through the W3C spec I couldn’t find anything specific.
Although the following paragraph seems to suggest that the rate can be set to whatever, but if it is too high then audio should be muted.
[playbackRate](http://dev.w3.org/html5/spec/#dom-media-playbackrate) is negative (playback is backwards), any corresponding audio must be muted. When the
[playbackRate](http://dev.w3.org/html5/spec/#dom-media-playbackrate) is so low or so high that the user agent cannot play audio usefully, the corresponding audio must also be muted. If the
[playbackRate](http://dev.w3.org/html5/spec/#dom-media-playbackrate) is not 1.0, the user agent may apply pitch adjustments to the audio as necessary to render it faithfully.”
I tried this in IE9 and set the Playbackrate to 20000 (document.getElementById("mVideo").playbackRate = 20000)
IE9 seemed to fast-forward the video to a watchable but very fast speed, there was no notable difference between setting it at 20 and 20000. So I am assuming there is a max setting somewhere.
So in answer to the question. Nothing bad will happen in the current IE9 beta but at this point I don’t know for sure if their is a Max value setting somewhere (I will find out and update)