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Retrieves an IMediaSamplebuffer suitable for passing across the connection.
virtual HRESULT GetDeliveryBuffer( IMediaSample ** ppSample , REFERENCE_TIME * pStartTime , REFERENCE_TIME * pEndTime , DWORD dwFlags );
Parameters
- ppSample
- IMediaSamplebuffer to be provided.
- pStartTime
- Start time of the media sample (optional and can be NULL).
- pEndTime
- Stop time of the media sample (optional and can be NULL).
- dwFlags
- The following flags are supported.
AM_GBF_NOTASYNCPOINT Dynamic format changes are not allowed on this buffer because it is not a key frame. AM_GBF_PREVFRAMESKIPPED Buffer returned will not be filled with data contiguous with any previous data sent. Return Values
Returns E_NOINTERFACE if an allocator is not found; otherwise, returns the value returned from calling the IMemAllocator::GetBuffermethod.
Remarks
The pin object must lock itself before calling this member function; otherwise, the filter graph could disconnect this pin from the input pin midway through the process. If the filter has no worker threads, the lock is best applied on the IMemInputPin::Receivecall; otherwise, it should be done when the worker thread is ready to deliver the sample.
This call can block; therefore, to avoid deadlocking with an IMediaFilter::Stopcommand, a two-tier locking scheme (such as that implemented in CTransformFilter) is required. Only the second-level lock is acquired here. The IBaseFilterbase class implementation of IMediaFilter::Stopfirst gets the first-level lock and then calls IMemAllocator::Decommiton the allocator. This has the effect of making GetDeliveryBufferreturn with a failure code. The Stopmember function then gets the second-level lock and completes the command by calling Inactivefor this pin.
No lock is needed when calling CBaseOutputPin::GetDeliveryBufferwhen passing on samples using a worker thread. In this case, the CBaseFilter::Stopbase class implementation acquires its filter-level lock and just calls IMemAllocator::Decommiton the allocator, at which point the worker thread is freed up to listen for a command to stop.
You must release the sample yourself after this function. If the connected input pin needs to hold on to the sample beyond the function, it will add the reference for the sample itself through IUnknown::AddRef. You must release this one and call CBaseOutputPin::GetDeliveryBufferfor the next. (You cannot reuse it directly.)