[whatwg] Video : Slow motion, fast forward effects

Silvia Pfeiffer silviapfeiffer1 at gmail.com
Tue Oct 14 11:37:52 PDT 2008

On Wed, Oct 15, 2008 at 5:28 AM, Peter Kasting <pkasting at google.com> wrote:
> On Tue, Oct 14, 2008 at 8:00 AM, Eric Carlson <eric.carlson at apple.com>
> wrote:
>>  Some media formats and/or engines may not support reverse playback, but I
>> think it is a mistake for the spec to mandate this behavior. Why is reverse
>> playback different from other situations described in the spec where
>> different UAs/ media formats will result in different behavior, eg. pitch
>> adjusted audio, negotiation with a server to achieve the appropriate
>> playback rate, etc?
>>  I think the current sentence that talks about audio playback rate:
>>  When the playbackRate is so low or so high that the user agent cannot
>> play audio usefully, the corresponding audio must not play.
>> could be modified to include reverse playback as well:
>>  When the playbackRate is such that the user agent cannot play audio
>> usefully (eg. too low, too high, negative when the format or engine does not
>> support reverse playback), the corresponding audio must not play.
> Agree wholeheartedly.
> Mandating silence during reverse playback seems bizarre in the abstract,
> unnecessary if authors have a way to mute, and potentially detrimental to
> future applications which may _want_ to be able to do this in a controlled
> fashion (e.g. a virtual turntable application).
> PK

Also in the case of a caption/subtitle authoring application: being
able to scrub through the audio forwards/backwards is a very important
means for captioners to identify the time points to start/end a
caption segment. I disagree with mandating silence and would rather
deal with an intermediate inconsistent browser landscape for lack of
the audio scrubbing feature in some browsers.


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