Re: Audio synch issues with CBS HD

I've had the same experience. I personally feel that the decision to
independently compress the video and audio and then maintain their synch was
a short-sighted one. Using an "interleaved" audio/video format with inherent
time synchronization like DV tape for example does impart a penalty in
storage, but makes the whole process of presentation so much more reliable
in terms of lip synch. In a world where storage costs drop by a factor of
two or more each year, and transmission rates increase in much the same
manner per dollar, then the design choice to separate the two streams for
compression gains seems unfortunate. Getting movie film to use the same
approach in the last century took a similar path until eventually the film
and sound track were unified.

Smarty


"hac" <redacted@xxxxxxxxxxxx> wrote in message
news:pan.2005.09.23.02.53.20.79183@xxxxxxxxxxxxxxx
> On Thu, 22 Sep 2005 18:23:49 -0400, Smarty wrote:
>
>> Unfortunately, in the design of current digital TV systems, the audio
>> and video signals are independently compressed using two entirely
>> different methods, then mixed / muxed together with some time stamps to
>> allow the receiver to get things back into synch.
>>
>> This bifurcation of the data can and often is corrupted by DVD authoring
>> programs, retransmission of the signal by local broadcasters, and video
>> editing, compositing, or studio switching equipment. We are still
>> witnessing the infancy of the HDTV broadcast industry with a lot of
>> glitches and problems.
>>
> I've run into this while editing HDTV captures, and converting them to
> formats that will fit on a DVD-R (the largest storage format on my HTPC).
>
> Some software grabs the first time stamps, calculates the difference
> between the audio and video, and assumes that the delay will stay the
> same.
>
> That's a bad assumption. It may stay the same for a long period. But it
> may change at any time. Once the system starts ignoring the the incoming
> timestamps, then the timing is lost for everything downstream.
>
> -- hac
>


.

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