This is an archived snapshot of W3C's public bugzilla bug tracker, decommissioned in April 2019. Please see the home page for more details.
It is unclear what happens when defaultPlaybackRate is set to a negative value. It is also unclear what happens to audio. Presumably this depends on the codec, but the specification ought to at least have some kind of note to that effect. It is also not clear whether pitching will be normalized or not. See also: http://krijnhoetmer.nl/irc-logs/whatwg/20091126#l-703
defaultPlaybackRate has no effect directly, except that it can influence playbackRate. Regarding playbackRate, the spec says "When the playbackRate is negative (playback is backwards), any corresponding audio must be muted. When the 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 is not 1.0, the user agent may apply pitch adjustments to the audio as necessary to render it faithfully.", which seems to answer all the questions you asked. EDITOR'S RESPONSE: This is an Editor's Response to your comment. If you are satisfied with this response, please change the state of this bug to CLOSED. If you have additional information and would like the editor to reconsider, please reopen this bug. If you would like to escalate the issue to the full HTML Working Group, please add the TrackerRequest keyword to this bug, and suggest title and text for the tracker issue; or you may create a tracker issue yourself, if you are able to do so. For more details, see this document: http://dev.w3.org/html5/decision-policy/decision-policy.html Status: Rejected Change Description: no spec change Rationale: Marking "Rejected" since the spec already answers this as far as I can tell.