[wdmaudiodev] Re: One Audio Driver Problem

  • From: "Sam Tertzakian" <sam@xxxxxxxxxxx>
  • To: <wdmaudiodev@xxxxxxxxxxxxx>
  • Date: Sat, 29 Jan 2005 07:16:17 -0800

When you say "serious delay" do you mean that the audio is out of sync with
the video?


One of the filters use KxProxy which uses very small buffers. That is
probably the one that works well.


The other filter uses the WaveAPI and uses big buffers. So what happens is
that the video starts playing immediately while it takes a short time for
audio buffer to fill up.


If you are capturing audio/video to a file, it should not be a problem as
both streams are time stamped. But if you are previewing audio/video, then
it can be a problem to use the WaveAPI filter since the WaveAPI buffers are
so large. And, you cannot time stamp the audio/video preview stream because
then the video renderer will cause the video to start and stop.


If you are using GraphEdit to build the graph, there is no solution (that I
know of). But, if you write a program using direct show (basically doing the
same thing as GraphEdit), you can use the WaveAPI filter and you change the
buffer size that it uses in the program. I have done this before and it
works great.but, right now I cannot remember the exact details. If you need
to know, let me know and I will post the information. From what I remember,
there is no sample in the DDK that shows this. But the functions are
documented somewhere.I just cannot remember the com interface name right


I may have posted an answer similar to this in this forum, but I am not


From: wdmaudiodev-bounce@xxxxxxxxxxxxx
[mailto:wdmaudiodev-bounce@xxxxxxxxxxxxx] On Behalf Of ???
Sent: Saturday, January 29, 2005 7:01 AM
To: wdmaudiodev@xxxxxxxxxxxxx
Subject: [wdmaudiodev] One Audio Driver Problem


Dear All:


I am developing an audio driver which is based on Streaming Minidriver

When I use the filter within "WDM Streaming Capture Devices" category, the
audio stream (44100MHz) is listened well.

However, when I use the filter of "Audio Capture Sources" folder, there is a
serious delay (1 ~ 2 secs) which is happened.

I don't know what's happened in this delay.

The filter within "Audio Capture Sources" folder is a virtual filter, right?

Why can't the MasterClock be offered from DirectShow manager for this

Can you help me to solve this problem?


Best Regards,



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