[whatwg] Video : Slow motion, fast forward effects

Dave Singer singer at apple.com
Thu Aug 7 12:16:21 PDT 2008

At 12:11  -0700 7/08/08, Jonas Sicking wrote:
>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 yet
>>>>>  > support it.
>>>>>  So can I assume HTML5 spec also allow playbackRate  to be negative value.
>>>>>  ie to support go backward at various speed....
>>>>  Yes.
>>>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'm sorry if I wasn't clear:  I agree.  If you want your 
implementation to shine, or be used heavily for audio scrubbing, or 
something, go ahead and implement.  But it should not be required. 
("For extra credit")
David Singer

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