[whatwg] Video : Slow motion, fast forward effects
singer at apple.com
Thu Aug 7 12:08:38 PDT 2008
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....
>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
>Given that codecs are often highly optimized for forward playback the
>cost in memory can be excessive to go the other way. Could there be a
>possibility to say 'reverse playback not supported'?
Indeed, on I/P/B video, showing all the frames is also painful.
I think that the spec. should say that degraded playback (e.g. I
frames only) or no playback (non-reversed audio) may occur...
More information about the whatwg