On stuttering audio in quartz/DirectShow

[Alex Villací­s Lasso]

Upon checking the source code of dlls/quartz I found out about the 
method SetSyncSource defined in the IBaseFilter interface:

dsoundrender.c:static HRESULT WINAPI 
DSoundRender_SetSyncSource(IBaseFilter * iface, IReferenceClock *pClock)
filesource.c:static HRESULT WINAPI AsyncReader_SetSyncSource(IBaseFilter 
* iface, IReferenceClock *pClock)
filtergraph.c:static HRESULT WINAPI 
MediaFilter_SetSyncSource(IMediaFilter *iface, IReferenceClock *pClock)
parser.c:static HRESULT WINAPI Parser_SetSyncSource(IBaseFilter * iface, 
IReferenceClock *pClock)
transform.c:static HRESULT WINAPI 
TransformFilter_SetSyncSource(IBaseFilter * iface, IReferenceClock *pClock)
videorenderer.c:static HRESULT WINAPI 
VideoRenderer_SetSyncSource(IBaseFilter * iface, IReferenceClock *pClock)

In particular, I see the following two things about sync sources:
1) I see no effort on part of filtergraph.c to add a sync source when 
simply asked to render a file
2) Even if it did, current implementation of videorenderer.c does 
nothing with its sync source

So I have a couple of questions:
1) Am I right to assume that a sync source might be used to synchronize 
and (if necessary) drop frames at the videorenderer in order to maintain 
synchronization and avoid stuttering?
2) Could the sttutering really be solved by implementing the using and 
passing of a synchronization source (systemclock.c) in file rendering? 
If so, then the migration to DirectDraw would become just an 
optimization to increase the frame rate.

Alex Villacís Lasso

-- 
perl -e '$x=2.4;print sprintf("%.0f + %.0f = %.0f\n",$x,$x,$x+$x);'