What to do in FillBuffer in a source filter if there is no data available?

Question

If you look at the docs for FillBuffer, it can return S_OK (prefer this to the equivalent NOERROR) or S_FALSE.

 

You cannot return S_OK unless you have provided a valid sample in the parameter pSample .

 

You can return S_FALSE if you are at the end of the stream but not to indicate that you do not have a sample ready.

 

I provided the information on the loop above but here it is in code:

 

 

Code Snippet

while (true) {

{

CAutoLock lock(&m_lock); // shared CCritSec with function in other thread that gets the sample data

hr = CheckForNewSample(pSample); // return VFW_S_STATE_INTERMEDIATE when a sample is not ready, S_OK for a sample is provided in pSample and S_FALSE when end of stream is detected

if (hr != VFW_S_STATE_INTERMEDIATE)

return hr;

 

}

::Sleep(1); // adjust the sleep value to suit your needs

}

 

 

 

Hello,

I'm in the case where my source filter doesn't have (yet) any sample to push. But I don't know what to do in FillBuffer():
- I can't return S_OK since no sample is produced
- I can't return S_FALSE since it is not an end of stream
- I can't do a Sleep() until I have samples to produce, since it blocks the video rendering window.

I'm stuck.

Do you have any idea?

Thanks.

Answer 1

You block in FillBuffer until you have samples to push.  Yes, it blocks the rendering window.  Your source filter can send the EC_BUFFERING_DATA events to let the application know that you are buffering.

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www.chrisnet.net

Answer 2

Hi Chris,

Thanks for your answer and your split.

Answer 3

Hi!
I overloaded the DoProcessingLoop function and then I have FillBuffer return 99 (I sometimes have frames that i process but i don't want them to be displayed). 

In DoProcessingLoop, if hr == 99, I skip the

 

hr=Deliver(pSample);

and just do

pSample->Release();

and everything continues fine.
Mechi