[wdmaudiodev] Re: How to adjust lip-sync for WaveCyclic driver using GetPosition()

  • From: Tim Roberts <timr@xxxxxxxxx>
  • To: "wdmaudiodev@xxxxxxxxxxxxx" <wdmaudiodev@xxxxxxxxxxxxx>
  • Date: Fri, 7 Jun 2013 16:45:27 -0700

Philip Gruebele wrote:
> According to MS docs, GetPosition() should start incrementing when in 
> the RUN state.  ... this means that after entering KS_RUN state, 
> GetPosition() should return 0 for about 60ms, and only then start to 
> increment (since the hardware is not outputting the sample data for the 
> first 60 ms).

GetPosition needs to increase always, so I think you will have to have
it start at -60ms.

However, I'm not convinced this will help lip synch.  Applications
usually do not do their audio/video syncing based on the absolute value
of the time.  Instead, they use relative time from the first sample. 
For that, you could start GetPosition at 30 minutes and it wouldn't make
a difference.

60ms is a LOT of latency.  Why is it so high?

-- 
Tim Roberts, timr@xxxxxxxxx
Providenza & Boekelheide, Inc.

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