diff --git a/dlls/qcap/vfwcapture.c b/dlls/qcap/vfwcapture.c
index 3b66bea..8316ddc 100644
--- a/dlls/qcap/vfwcapture.c
+++ b/dlls/qcap/vfwcapture.c
@@ -669,30 +669,38 @@
     return 1;
 }
 
+static HRESULT WINAPI VfwPin_DecideBufferSize(IPin *iface, IMemAllocator *pAlloc, ALLOCATOR_PROPERTIES *ppropInputRequest)
+{
+    ALLOCATOR_PROPERTIES actual;
+
+    /* What we put here doesn't matter, the
+       driver function should override it then commit */
+    if (!ppropInputRequest->cBuffers)
+        ppropInputRequest->cBuffers = 3;
+    if (!ppropInputRequest->cbBuffer)
+        ppropInputRequest->cbBuffer = 230400;
+    if (!ppropInputRequest->cbAlign)
+        ppropInputRequest->cbAlign = 1;
+
+    return IMemAllocator_SetProperties(pAlloc, ppropInputRequest, &actual);
+}
+
 static HRESULT
 VfwPin_Construct( IBaseFilter * pBaseFilter, LPCRITICAL_SECTION pCritSec,
                   IPin ** ppPin )
 {
     static const WCHAR wszOutputPinName[] = { 'O','u','t','p','u','t',0 };
-    ALLOCATOR_PROPERTIES ap;
     PIN_INFO piOutput;
     HRESULT hr;
 
     ppPin = NULL;
 
-    /* What we put here doesn't matter, the
-       driver function should override it then commit */
-    ap.cBuffers = 3;
-    ap.cbBuffer = 230400;
-    ap.cbAlign = 1;
-    ap.cbPrefix = 0;
-
     piOutput.dir = PINDIR_OUTPUT;
     piOutput.pFilter = pBaseFilter;
     lstrcpyW(piOutput.achName, wszOutputPinName);
     ObjectRefCount(TRUE);
 
-    hr = BaseOutputPin_Construct(&VfwPin_Vtbl, sizeof(VfwPinImpl), &piOutput, &ap, NULL, pCritSec, ppPin);
+    hr = BaseOutputPin_Construct(&VfwPin_Vtbl, sizeof(VfwPinImpl), &piOutput, VfwPin_DecideBufferSize, NULL, pCritSec, ppPin);
 
     if (SUCCEEDED(hr))
     {
diff --git a/dlls/quartz/acmwrapper.c b/dlls/quartz/acmwrapper.c
index 3fdb320..66ae6c6 100644
--- a/dlls/quartz/acmwrapper.c
+++ b/dlls/quartz/acmwrapper.c
@@ -264,8 +264,6 @@
         {
             This->has = drv;
 
-            /* Update buffer size of media samples in output */
-            ((BaseOutputPin*)This->tf.ppPins[1])->allocProps.cbBuffer = This->pWfOut->nAvgBytesPerSec / 2;
             TRACE("Connection accepted\n");
             return S_OK;
         }
@@ -294,8 +292,6 @@
     {
         This->has = drv;
 
-        /* Update buffer size of media samples in output */
-        ((BaseOutputPin*)This->tf.ppPins[1])->allocProps.cbBuffer = This->pWfOut->nAvgBytesPerSec / 2;
         TRACE("Connection accepted\n");
         return S_OK;
     }
@@ -323,7 +319,25 @@
     return S_OK;
 }
 
+static HRESULT WINAPI ACMWrapper_DecideBufferSize(TransformFilter *tf, IMemAllocator *pAlloc, ALLOCATOR_PROPERTIES *ppropInputRequest)
+{
+    ACMWrapperImpl *pACM = (ACMWrapperImpl*)tf;
+    ALLOCATOR_PROPERTIES actual;
+
+    if (!ppropInputRequest->cbAlign)
+        ppropInputRequest->cbAlign = 1;
+
+    if (ppropInputRequest->cbBuffer < pACM->pWfOut->nAvgBytesPerSec / 2)
+            ppropInputRequest->cbBuffer = pACM->pWfOut->nAvgBytesPerSec / 2;
+
+    if (!ppropInputRequest->cBuffers)
+        ppropInputRequest->cBuffers = 1;
+
+    return IMemAllocator_SetProperties(pAlloc, ppropInputRequest, &actual);
+}
+
 static const TransformFilterFuncTable ACMWrapper_FuncsTable = {
+    ACMWrapper_DecideBufferSize,
     NULL,
     ACMWrapper_Receive,
     NULL,
diff --git a/dlls/quartz/avidec.c b/dlls/quartz/avidec.c
index 1b51f46..b2419ea 100644
--- a/dlls/quartz/avidec.c
+++ b/dlls/quartz/avidec.c
@@ -279,11 +279,6 @@
 
     TRACE("(%p)\n", This);
 
-    if (dir == PINDIR_INPUT)
-    {
-        /* Update buffer size of media samples in output */
-        ((BaseOutputPin*)This->tf.ppPins[1])->allocProps.cbBuffer = This->pBihOut->biSizeImage;
-    }
     return S_OK;
 }
 
@@ -310,7 +305,25 @@
     return S_OK;
 }
 
+static HRESULT WINAPI AVIDec_DecideBufferSize(TransformFilter *tf, IMemAllocator *pAlloc, ALLOCATOR_PROPERTIES *ppropInputRequest)
+{
+    AVIDecImpl *pAVI = (AVIDecImpl*)tf;
+    ALLOCATOR_PROPERTIES actual;
+
+    if (!ppropInputRequest->cbAlign)
+        ppropInputRequest->cbAlign = 1;
+
+    if (ppropInputRequest->cbBuffer < pAVI->pBihOut->biSizeImage)
+            ppropInputRequest->cbBuffer = pAVI->pBihOut->biSizeImage;
+
+    if (!ppropInputRequest->cBuffers)
+        ppropInputRequest->cBuffers = 1;
+
+    return IMemAllocator_SetProperties(pAlloc, ppropInputRequest, &actual);
+}
+
 static const TransformFilterFuncTable AVIDec_FuncsTable = {
+    AVIDec_DecideBufferSize,
     AVIDec_StartStreaming,
     AVIDec_Receive,
     AVIDec_StopStreaming,
diff --git a/dlls/quartz/filesource.c b/dlls/quartz/filesource.c
index d36c0d0..c1e9ae5 100644
--- a/dlls/quartz/filesource.c
+++ b/dlls/quartz/filesource.c
@@ -656,6 +656,7 @@
     BaseOutputPin pin;
     const struct IAsyncReaderVtbl * lpVtblAR;
 
+    ALLOCATOR_PROPERTIES allocProps;
     HANDLE hFile;
     BOOL bFlushing;
     /* Why would you need more? Every sample has its own handle */
@@ -814,6 +815,24 @@
     return hr;
 }
 
+static HRESULT WINAPI FileAsyncReaderPin_DecideBufferSize(IPin *iface, IMemAllocator *pAlloc, ALLOCATOR_PROPERTIES *ppropInputRequest)
+{
+    FileAsyncReader *This = (FileAsyncReader *)iface;
+    ALLOCATOR_PROPERTIES actual;
+
+    if (ppropInputRequest->cbAlign && ppropInputRequest->cbAlign != This->allocProps.cbAlign)
+        FIXME("Requested Buffer cbAlign mismatch %i,%i\n",This->allocProps.cbAlign, ppropInputRequest->cbAlign);
+    if (ppropInputRequest->cbPrefix)
+        FIXME("Requested Buffer cbPrefix mismatch %i,%i\n",This->allocProps.cbPrefix, ppropInputRequest->cbPrefix);
+    if (ppropInputRequest->cbBuffer)
+        FIXME("Requested Buffer cbBuffer mismatch %i,%i\n",This->allocProps.cbBuffer, ppropInputRequest->cbBuffer);
+    if (ppropInputRequest->cBuffers)
+        FIXME("Requested Buffer cBuffers mismatch %i,%i\n",This->allocProps.cBuffers, ppropInputRequest->cBuffers);
+
+    return IMemAllocator_SetProperties(pAlloc, &This->allocProps, &actual);
+}
+
+
 static HRESULT FileAsyncReader_Construct(HANDLE hFile, IBaseFilter * pBaseFilter, LPCRITICAL_SECTION pCritSec, IPin ** ppPin)
 {
     PIN_INFO piOutput;
@@ -823,7 +842,7 @@
     piOutput.dir = PINDIR_OUTPUT;
     piOutput.pFilter = pBaseFilter;
     strcpyW(piOutput.achName, wszOutputPinName);
-    hr = BaseOutputPin_Construct(&FileAsyncReaderPin_Vtbl, sizeof(FileAsyncReader), &piOutput, NULL, FileAsyncReaderPin_AttemptConnection, pCritSec, ppPin);
+    hr = BaseOutputPin_Construct(&FileAsyncReaderPin_Vtbl, sizeof(FileAsyncReader), &piOutput, FileAsyncReaderPin_DecideBufferSize, FileAsyncReaderPin_AttemptConnection, pCritSec, ppPin);
 
     if (SUCCEEDED(hr))
     {
@@ -933,7 +952,7 @@
                     This->handle_list[This->samples + 1 + x] = This->handle_list[x];
             }
             This->handle_list[This->samples] = CreateEventW(NULL, 1, 0, NULL);
-            This->pin.allocProps = *pProps;
+            This->allocProps = *pProps;
         }
         else
         {
diff --git a/dlls/quartz/parser.c b/dlls/quartz/parser.c
index efa68f6..6574dfa 100644
--- a/dlls/quartz/parser.c
+++ b/dlls/quartz/parser.c
@@ -43,6 +43,7 @@
 static HRESULT WINAPI Parser_ChangeStart(IMediaSeeking *iface);
 static HRESULT WINAPI Parser_ChangeStop(IMediaSeeking *iface);
 static HRESULT WINAPI Parser_ChangeRate(IMediaSeeking *iface);
+static HRESULT WINAPI Parser_OutputPin_DecideBufferSize(IPin *iface, IMemAllocator *pAlloc, ALLOCATOR_PROPERTIES *ppropInputRequest);
 
 static inline ParserImpl *impl_from_IMediaSeeking( IMediaSeeking *iface )
 {
@@ -411,7 +412,7 @@
     This->ppPins = CoTaskMemAlloc((This->cStreams + 2) * sizeof(IPin *));
     memcpy(This->ppPins, ppOldPins, (This->cStreams + 1) * sizeof(IPin *));
 
-    hr = BaseOutputPin_Construct(&Parser_OutputPin_Vtbl, sizeof(Parser_OutputPin), piOutput, props, NULL, &This->filter.csFilter, This->ppPins + (This->cStreams + 1));
+    hr = BaseOutputPin_Construct(&Parser_OutputPin_Vtbl, sizeof(Parser_OutputPin), piOutput, Parser_OutputPin_DecideBufferSize, NULL, &This->filter.csFilter, This->ppPins + (This->cStreams + 1));
 
     if (SUCCEEDED(hr))
     {
@@ -423,6 +424,7 @@
 
         pin->pin.pin.pinInfo.pFilter = (LPVOID)This;
         pin->pin.custom_allocator = 1;
+        pin->allocProps = *props;
         This->cStreams++;
         BaseFilterImpl_IncrementPinVersion((IBaseFilter*)This);
         CoTaskMemFree(ppOldPins);
@@ -528,6 +530,23 @@
     SourceSeekingImpl_GetPreroll
 };
 
+static HRESULT WINAPI Parser_OutputPin_DecideBufferSize(IPin *iface, IMemAllocator *pAlloc, ALLOCATOR_PROPERTIES *ppropInputRequest)
+{
+    Parser_OutputPin *This = (Parser_OutputPin *)iface;
+    ALLOCATOR_PROPERTIES actual;
+
+    if (ppropInputRequest->cbAlign && ppropInputRequest->cbAlign != This->allocProps.cbAlign)
+        FIXME("Requested Buffer cbAlign mismatch %i,%i\n",This->allocProps.cbAlign, ppropInputRequest->cbAlign);
+    if (ppropInputRequest->cbPrefix)
+        FIXME("Requested Buffer cbPrefix mismatch %i,%i\n",This->allocProps.cbPrefix, ppropInputRequest->cbPrefix);
+    if (ppropInputRequest->cbBuffer)
+        FIXME("Requested Buffer cbBuffer mismatch %i,%i\n",This->allocProps.cbBuffer, ppropInputRequest->cbBuffer);
+    if (ppropInputRequest->cBuffers)
+        FIXME("Requested Buffer cBuffers mismatch %i,%i\n",This->allocProps.cBuffers, ppropInputRequest->cBuffers);
+
+    return IMemAllocator_SetProperties(pAlloc, &This->allocProps, &actual);
+}
+
 static HRESULT WINAPI Parser_OutputPin_GetMediaType(IPin *iface, int iPosition, AM_MEDIA_TYPE *pmt)
 {
     Parser_OutputPin *This = (Parser_OutputPin *)iface;
diff --git a/dlls/quartz/parser.h b/dlls/quartz/parser.h
index 3103c19..06ca757 100644
--- a/dlls/quartz/parser.h
+++ b/dlls/quartz/parser.h
@@ -45,6 +45,7 @@
 
     AM_MEDIA_TYPE * pmt;
     LONGLONG dwSamplesProcessed;
+    ALLOCATOR_PROPERTIES allocProps;
 } Parser_OutputPin;
 
 extern HRESULT Parser_AddPin(ParserImpl * This, const PIN_INFO * piOutput, ALLOCATOR_PROPERTIES * props, const AM_MEDIA_TYPE * amt);
diff --git a/dlls/strmbase/pin.c b/dlls/strmbase/pin.c
index 3c3d753..089cfe4 100644
--- a/dlls/strmbase/pin.c
+++ b/dlls/strmbase/pin.c
@@ -721,6 +721,48 @@
     return hr;
 }
 
+HRESULT WINAPI BaseOutputPinImpl_InitAllocator(BaseOutputPin *This, IMemAllocator **pMemAlloc)
+{
+    return CoCreateInstance(&CLSID_MemoryAllocator, NULL, CLSCTX_INPROC_SERVER, &IID_IMemAllocator, (LPVOID*)pMemAlloc);
+}
+
+HRESULT WINAPI BaseOutputPinImpl_DecideAllocator(BaseOutputPin *This, IMemInputPin *pPin, IMemAllocator **pAlloc)
+{
+    HRESULT hr;
+
+    if (!This->custom_allocator)
+    {
+        hr = IMemInputPin_GetAllocator(pPin, pAlloc);
+
+        if (hr == VFW_E_NO_ALLOCATOR)
+            /* Input pin provides no allocator, use standard memory allocator */
+            hr = BaseOutputPinImpl_InitAllocator(This, pAlloc);
+
+        if (SUCCEEDED(hr))
+        {
+            ALLOCATOR_PROPERTIES rProps;
+            ZeroMemory(&rProps, sizeof(ALLOCATOR_PROPERTIES));
+
+            IMemInputPin_GetAllocatorRequirements(pPin, &rProps);
+            hr = This->pDecideBufferSize((IPin*)This, *pAlloc, &rProps);
+        }
+
+        if (SUCCEEDED(hr))
+            hr = IMemInputPin_NotifyAllocator(pPin, *pAlloc, This->readonly);
+    }
+    else
+    {
+        pAlloc = NULL;
+
+        if (This->alloc)
+            hr = IMemInputPin_NotifyAllocator(pPin, This->alloc, This->readonly);
+        else
+            hr = VFW_E_NO_ALLOCATOR;
+    }
+
+    return hr;
+}
+
 /*** The Construct functions ***/
 
 /* Function called as a helper to IPin_Connect */
@@ -730,7 +772,6 @@
     BaseOutputPin *This = (BaseOutputPin *)iface;
     HRESULT hr;
     IMemAllocator * pMemAlloc = NULL;
-    ALLOCATOR_PROPERTIES actual; /* FIXME: should we put the actual props back in to This? */
 
     TRACE("(%p, %p)\n", pReceivePin, pmt);
     dump_AM_MEDIA_TYPE(pmt);
@@ -750,32 +791,12 @@
         This->pMemInputPin = NULL;
         hr = IPin_QueryInterface(pReceivePin, &IID_IMemInputPin, (LPVOID)&This->pMemInputPin);
 
-        if (SUCCEEDED(hr) && !This->custom_allocator)
+        if (SUCCEEDED(hr))
         {
-            hr = IMemInputPin_GetAllocator(This->pMemInputPin, &pMemAlloc);
-
-            if (hr == VFW_E_NO_ALLOCATOR)
-                /* Input pin provides no allocator, use standard memory allocator */
-                hr = CoCreateInstance(&CLSID_MemoryAllocator, NULL, CLSCTX_INPROC_SERVER, &IID_IMemAllocator, (LPVOID*)&pMemAlloc);
-
-            if (SUCCEEDED(hr))
-                hr = IMemAllocator_SetProperties(pMemAlloc, &This->allocProps, &actual);
-
-            if (SUCCEEDED(hr))
-                hr = IMemInputPin_NotifyAllocator(This->pMemInputPin, pMemAlloc, This->readonly);
-
+            hr = BaseOutputPinImpl_DecideAllocator(This, This->pMemInputPin, &pMemAlloc);
             if (pMemAlloc)
                 IMemAllocator_Release(pMemAlloc);
         }
-        else if (SUCCEEDED(hr))
-        {
-            if (This->alloc)
-            {
-                hr = IMemInputPin_NotifyAllocator(This->pMemInputPin, This->alloc, This->readonly);
-            }
-            else
-                hr = VFW_E_NO_ALLOCATOR;
-        }
 
         /* break connection if we couldn't get the allocator */
         if (FAILED(hr))
@@ -800,7 +821,7 @@
 }
 
 static HRESULT OutputPin_Init(const IPinVtbl *OutputPin_Vtbl, const PIN_INFO *
-pPinInfo, const ALLOCATOR_PROPERTIES * props, BasePin_AttemptConnection pConnectProc, LPCRITICAL_SECTION pCritSec,
+pPinInfo, BaseOutputPin_DecideBufferSize pBufferProc, BasePin_AttemptConnection pConnectProc, LPCRITICAL_SECTION pCritSec,
 BaseOutputPin * pPinImpl)
 {
     TRACE("\n");
@@ -819,25 +840,19 @@
         pPinImpl->pAttemptConnection = pConnectProc;
     else
         pPinImpl->pAttemptConnection = OutputPin_AttemptConnection;
+
+    pPinImpl->pDecideBufferSize = pBufferProc;
     /* If custom_allocator is set, you will need to specify an allocator
      * in the alloc member of the struct before an output pin can connect
      */
     pPinImpl->custom_allocator = 0;
     pPinImpl->alloc = NULL;
     pPinImpl->readonly = FALSE;
-    if (props)
-    {
-        pPinImpl->allocProps = *props;
-        if (pPinImpl->allocProps.cbAlign == 0)
-            pPinImpl->allocProps.cbAlign = 1;
-    }
-    else
-        ZeroMemory(&pPinImpl->allocProps, sizeof(pPinImpl->allocProps));
 
     return S_OK;
 }
 
-HRESULT WINAPI BaseOutputPin_Construct(const IPinVtbl *OutputPin_Vtbl, LONG outputpin_size, const PIN_INFO * pPinInfo, ALLOCATOR_PROPERTIES *props, BasePin_AttemptConnection pConnectProc, LPCRITICAL_SECTION pCritSec, IPin ** ppPin)
+HRESULT WINAPI BaseOutputPin_Construct(const IPinVtbl *OutputPin_Vtbl, LONG outputpin_size, const PIN_INFO * pPinInfo, BaseOutputPin_DecideBufferSize pBufferProc, BasePin_AttemptConnection pConnectProc, LPCRITICAL_SECTION pCritSec, IPin ** ppPin)
 {
     BaseOutputPin * pPinImpl;
 
@@ -856,7 +871,7 @@
     if (!pPinImpl)
         return E_OUTOFMEMORY;
 
-    if (SUCCEEDED(OutputPin_Init(OutputPin_Vtbl, pPinInfo, props, pConnectProc, pCritSec, pPinImpl)))
+    if (SUCCEEDED(OutputPin_Init(OutputPin_Vtbl, pPinInfo, pBufferProc, pConnectProc, pCritSec, pPinImpl)))
     {
         *ppPin = (IPin *)(&pPinImpl->pin.lpVtbl);
         return S_OK;
diff --git a/dlls/strmbase/transform.c b/dlls/strmbase/transform.c
index 54f4aac..19d2025 100644
--- a/dlls/strmbase/transform.c
+++ b/dlls/strmbase/transform.c
@@ -103,6 +103,13 @@
     return S_FALSE;
 }
 
+static HRESULT WINAPI TransformFilter_Output_DecideBufferSize(IPin *iface, IMemAllocator *pAlloc, ALLOCATOR_PROPERTIES *ppropInputRequest)
+{
+    BasePin *This = (BasePin *)iface;
+    TransformFilter *pTransformFilter = (TransformFilter *)This->pinInfo.pFilter;
+    return pTransformFilter->pFuncsTable->pfnDecideBufferSize(pTransformFilter, pAlloc, ppropInputRequest);
+}
+
 static IPin* WINAPI TransformFilter_GetPin(IBaseFilter *iface, int pos)
 {
     TransformFilter *This = (TransformFilter *)iface;
@@ -148,13 +155,7 @@
 
     if (SUCCEEDED(hr))
     {
-        ALLOCATOR_PROPERTIES props;
-        props.cbAlign = 1;
-        props.cbPrefix = 0;
-        props.cbBuffer = 0; /* Will be updated at connection time */
-        props.cBuffers = 1;
-
-        hr = BaseOutputPin_Construct(&TransformFilter_OutputPin_Vtbl, sizeof(BaseOutputPin), &piOutput, &props, NULL, &pTransformFilter->filter.csFilter, &pTransformFilter->ppPins[1]);
+        hr = BaseOutputPin_Construct(&TransformFilter_OutputPin_Vtbl, sizeof(BaseOutputPin), &piOutput, TransformFilter_Output_DecideBufferSize, NULL, &pTransformFilter->filter.csFilter, &pTransformFilter->ppPins[1]);
 
         if (FAILED(hr))
             ERR("Cannot create output pin (%x)\n", hr);
diff --git a/include/wine/strmbase.h b/include/wine/strmbase.h
index be28c91..ffc7d2d 100644
--- a/include/wine/strmbase.h
+++ b/include/wine/strmbase.h
@@ -28,6 +28,7 @@
 typedef LONG (WINAPI *BasePin_GetMediaTypeVersion)(IPin* iface);
 typedef HRESULT (WINAPI *BasePin_AttemptConnection)(IPin *iface, IPin *pReceivePin, const AM_MEDIA_TYPE *pmt);
 typedef HRESULT (WINAPI *BasePin_CheckMediaType)(IPin *iface, const AM_MEDIA_TYPE *pmt);
+typedef HRESULT (WINAPI *BaseOutputPin_DecideBufferSize)(IPin *iface, IMemAllocator *pAlloc, ALLOCATOR_PROPERTIES *ppropInputRequest);
 
 typedef IPin* (WINAPI *BaseFilter_GetPin)(IBaseFilter* iface, int iPosition);
 typedef LONG (WINAPI *BaseFilter_GetPinCount)(IBaseFilter* iface);
@@ -58,10 +59,10 @@
 
 	IMemInputPin * pMemInputPin;
 	BasePin_AttemptConnection pAttemptConnection;
+	BaseOutputPin_DecideBufferSize pDecideBufferSize;
 	BOOL custom_allocator;
 	IMemAllocator *alloc;
 	BOOL readonly;
-	ALLOCATOR_PROPERTIES allocProps;
 } BaseOutputPin;
 
 typedef struct BaseInputPin
@@ -110,7 +111,10 @@
 HRESULT WINAPI BaseOutputPinImpl_BreakConnect(BaseOutputPin * This);
 HRESULT WINAPI BaseOutputPinImpl_Active(BaseOutputPin * This);
 HRESULT WINAPI BaseOutputPinImpl_Inactive(BaseOutputPin * This);
-HRESULT WINAPI BaseOutputPin_Construct(const IPinVtbl *OutputPin_Vtbl, LONG outputpin_size, const PIN_INFO * pPinInfo, ALLOCATOR_PROPERTIES *props, BasePin_AttemptConnection pConnectProc, LPCRITICAL_SECTION pCritSec, IPin ** ppPin);
+HRESULT WINAPI BaseOutputPinImpl_InitAllocator(BaseOutputPin *This, IMemAllocator **pMemAlloc);
+HRESULT WINAPI BaseOutputPinImpl_DecideAllocator(BaseOutputPin *This, IMemInputPin *pPin, IMemAllocator **pAlloc);
+
+HRESULT WINAPI BaseOutputPin_Construct(const IPinVtbl *OutputPin_Vtbl, LONG outputpin_size, const PIN_INFO * pPinInfo, BaseOutputPin_DecideBufferSize pBufferProc, BasePin_AttemptConnection pConnectProc, LPCRITICAL_SECTION pCritSec, IPin ** ppPin);
 
 /* Base Input Pin */
 HRESULT WINAPI BaseInputPinImpl_QueryInterface(IPin * iface, REFIID riid, LPVOID * ppv);
@@ -171,6 +175,7 @@
 	const struct TransformFilterFuncTable * pFuncsTable;
 } TransformFilter;
 
+typedef HRESULT (WINAPI *TransformFilter_DecideBufferSize) (TransformFilter *iface, IMemAllocator *pAlloc, ALLOCATOR_PROPERTIES *ppropInputRequest);
 typedef HRESULT (WINAPI *TransformFilter_StartStreaming) (TransformFilter *iface);
 typedef HRESULT (WINAPI *TransformFilter_StopStreaming) (TransformFilter *iface);
 typedef HRESULT (WINAPI *TransformFilter_Receive) (TransformFilter* iface, IMediaSample* pIn);
@@ -185,6 +190,7 @@
 REFERENCE_TIME tStart, REFERENCE_TIME tStop, double dRate);
 
 typedef struct TransformFilterFuncTable {
+    TransformFilter_DecideBufferSize pfnDecideBufferSize;
     TransformFilter_StartStreaming pfnStartStreaming;
     TransformFilter_Receive pfnReceive;
     TransformFilter_StopStreaming pfnStopStreaming;