[whatwg] Video : Slow motion, fast forward effects
smfr at mac.com
Thu Aug 7 15:52:17 PDT 2008
On Aug 7, 2008, at 12:23 PM, Charles Iliya Krempeaux wrote:
> On Thu, Aug 7, 2008 at 12:11 PM, Jonas Sicking <jonas at sicking.cc>
> Dave Singer wrote:
> At 20:10 +1200 7/08/08, Chris Double wrote:
> On Thu, Aug 7, 2008 at 6:20 PM, Ian Hickson <ian at hixie.ch> wrote:
> On Thu, 7 Aug 2008, Biju Gm at il wrote:
> On Thu, Aug 7, 2008 at 1:49 AM, Ian Hickson <ian at hixie.ch> wrote:
> > playbackRate is the right way to do it, but maybe Firefox doesn't
> > support it.
> So can I assume HTML5 spec also allow playbackRate to be negative
> ie to support go backward at various speed....
> Would you expect the audio to be played backwards too?
> I think that's extra credit and optional. As you say, even with
> audio coded in independent frames you have to flip the samples,
> which is a pain. For audio with forward dependencies, correct
> decoding means decoding forwards and then flipping whole chunks of
> timeline (though AAC doesn't suffer too badly if you don't do this,
> by the way).
> Honestly, this seems useless enough that the spec should just say
> that when playback is less than 0 sound should be turned off. I'd
> hate to see engineers working on this just because "the spec says it
> should work that way".
> I don't think turning sound off is a good idea.
> This feature would be used to implement "scrubing". Like what you
> see in Non-Linear Editors... for making movies, etc. (I.e.,
> grabbing the "position handle" of the player, and moving it forwards
> and backwards through the video, and varying speeds, to find what
> you are looking for.)
> In those types of applications, the audio is on. And it is
> important for usability, for the video editor to hear the sound.
But those applications are not naïvely playing the sound at the
current playback rate; they are grabbing little snippets of audio
samples from the current playhead position, and playing them at normal
rate. I don't think the spec should go into this much detail about
what happens to audio when rate != 1.
-------------- next part --------------
An HTML attachment was scrubbed...
More information about the whatwg