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Re: Audio Looping issue on Vista
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Re: Audio Looping issue on Vista

I am sorry about that information.It behaves the same way in XP as
well,i.e, there is the same issue while looping.Sorry about that

Thanks for all the help,

On 9/26/07, Praveen K <email@hidden> wrote:
> Hi Daniel,
> Thanks for all the information.But I wonder how  the the same 1 second
> audio file plays back well while looping in Windows XP with QT player
> and  does'nt on Vista.Any suggestions?
> Thanks again
> Praveen
> On 9/26/07, Daniel Steinberg <email@hidden> wrote:
> > At 11:21 AM +0530 9/26/07, Praveen K wrote:
> > >I am playing back an audiofile(A Wav file) looping continuously using
> > >QuickTime Player on Windows Vista.I find that the initial portion of
> > >the audio is clipped when it loops.Could someone tell me the reason
> > >for this.Is it a bug in QuickTime or does'nt QuickTime support Vista
> > >as yet
> > >
> > >Thanks and Regards
> > >Praveen
> >
> > Do you have any reason to believe that this behavior is substantially
> > different from how it works on Windows XP?
> >
> > When QuickTime reaches a loop point in a movie, a SetTime is
> > internally generated to jump back to the loop point.  The timebase
> > runs continuously through this action, and the video display tends to
> > be fairly smooth across this transition.  However, the audio queue is
> > flushed and audio data starting at the new position is transmitted.
> >
> > For reasons having to do with the stability of the DirectSound audio
> > data callbacks, we have a fairly deep safety buffer for queuing audio
> > samples...nearly a half a second (as opposed to a small fraction of
> > that in MacOS).  In order to keep audio and video in sync, this means
> > that the first half-second of audio at the loop point is silent while
> > the newly queued samples move through the safety buffer.   This
> > doesn't happen on the initial play, or when you jump to a new
> > position in the file, because we delay the start of video to line up
> > with the playback of the first audio sample.
> >
> > We already have a bug request to improve this behavior by queuing
> > audio around the loop point, but the behavior for now, on Windows
> > platforms, is pretty much what you've observed.  Application writers
> > that would prefer to hear all the audio data, rather than preserve
> > the forward motion of the timeline, may manage the looping manually
> > by setting a timebase callback for the loop endpoint, and issuing a
> > Stop/SetTime/Start sequence to restart at the loop start.
> >
> > Daniel Steinberg
> > QuickTime Engineering
> >
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 >Audio Looping issue on Vista (From: "Praveen K" <email@hidden>)
 >Re: Audio Looping issue on Vista (From: "Praveen K" <email@hidden>)

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