[whatwg] HTML5 video: frame accuracy / SMPTE

Silvia Pfeiffer silviapfeiffer1 at gmail.com
Fri Jan 21 13:57:24 PST 2011

On Sat, Jan 22, 2011 at 8:50 AM, Roger Hågensen <rescator at emsai.net> wrote:
> On 2011-01-21 22:04, Philip Jägenstedt wrote:
>> Concretely: Add seek(time, flags) where flags defaults to nothing.
>> Accurate seeking would be done via seek(time, "accurate") or some such.
>> Setting currentTime is left as is and doesn't set any flags.
> Hmm. I think the default (nothing) should be synonymous with "best-effort"
> (or "best") and leave it to the browser/os/codec/format/etc. as to what
> "best effort" actually is.
> While "accurate" means as accurate as technically possible, even if it means
> increased resource use. I can see online video editing, subtitle syncing,
> closed caption syncing, and audio syncing being key usage examples of that.
> And maybe a "simple" flag for when keyframe or second seeking and similar is
> good enough, preferring lower resource seeking.
> So "best" ("" default) and "accurate" and "simple", that covers most uses
> right?

Not really. I think "simple" needs to be more specific. If the browser
is able to do frame accurate seeking and the author wants to do
frame-accurate seeking, then it should be possible to get the two
together, both on keyframe boundaries and actual frame boundaries
closest to a given time.

So, I think what might make sense is:
* the default is best effort
* ACCURATE is time-accurate seeking
* FRAME is frame-accurate seeking, so to the previous frame boundary start
* KEYFRAME is keyframe-accurate seeking, so to the previous keyframe


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