12339 2011-03-19 03:53:09 +0000 We should mention that UAs may use a different clock than the wall clock for defining the rate of time in the media timeline, specifically so that they are allowed to use the soundcard clock to ensure reliable audio playback. 2011-08-04 05:02:01 +0000 1 1 1 Unclassified HTML WG LC1 HTML5 spec unspecified Other other RESOLVED FIXED http://www.whatwg.org/specs/web-apps/current-work/#media-timeline P3 normal --- 1 contributor ian ian mike philipj public-html-admin public-html-wg-issue-tracking singer public-html-bugzilla oldest_to_newest 46832 0 contributor 2011-03-19 03:53:09 +0000 Specification: http://www.whatwg.org/specs/web-apps/current-work/complete.html Section: http://www.whatwg.org/specs/web-apps/current-work/#media-timeline Comment: We should mention that UAs may use a different clock than the wall clock for defining the rate of time in the media timeline, specifically so that they are allowed to use the soundcard clock to ensure reliable audio playback. Posted from: 76.102.14.57 by ian@hixie.ch User agent: Mozilla/5.0 (Macintosh; U; Intel Mac OS X 10_6_6; en-US) AppleWebKit/534.16 (KHTML, like Gecko) Chrome/10.0.648.133 Safari/534.16 46858 1 singer 2011-03-20 10:26:43 +0000 I don't think that the HTML5 spec. requires that the time-of-day clock be used for clocking media out, only that as the TOD clock progresses, playback also progresses. I agree, it's normal to use the audio clock as the base clock for media, not time-of-day. This is a media-specific playout issue that we shouldn't get into. (People writing streaming specs have to; we don't.) 46877 2 ian 2011-03-21 09:08:55 +0000 Actually the spec currently uses the term "wall clock" to define the rate of playback. My plan is just to change it to say you can use any clock; I agree that we shouldn't get into it any more than that. 46878 3 philipj 2011-03-21 09:53:09 +0000 Just be careful to assume that the sound card actually has a monotonically increasing global clock which can be queried independently of any audio streams. In actuality the sound card has a ring buffer and it's (hopefully) possible to query approximately which sample in that ring buffer is in the DAC right now. So, just be a bit vague and it'll be fine. 47255 4 ian 2011-04-08 07:00:29 +0000 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: Accepted Change Description: see diff given below Rationale: Concurred with reporter's comments. 47256 5 contributor 2011-04-08 07:01:28 +0000 Checked in as WHATWG revision r5976. Check-in comment: Allow non-wall-clock clocks for media playback, since in practice UAs sync things to the soundcard's ring buffer, or similar, to avoid stuttering. http://html5.org/tools/web-apps-tracker?from=5975&to=5976 52498 6 mike 2011-08-04 05:02:01 +0000 mass-moved component to LC1