quartz: Simplify error handling in GetClassMediaFile().

dlls/quartz/filtergraph.c

@@ -1691,11 +1691,10 @@ static HRESULT GetFileSourceFilter(LPCOLESTR pszFileName, IBaseFilter **filter)
     IFileSourceFilter* pSource = NULL;
     IPin * pOutputPin = NULL;
     static const WCHAR wszOutputPinName[] = { 'O','u','t','p','u','t',0 };
+    BOOL ret;
 
     /* Try to find a match without reading the file first */
-    hr = GetClassMediaFile(NULL, pszFileName, NULL, NULL, &clsid);
-
-    if (hr == S_OK)
+    if (get_media_type(NULL, pszFileName, NULL, NULL, &clsid))
         return CreateFilterInstanceAndLoadFile(&clsid, pszFileName, filter);
 
     /* Now create a AyncReader instance, to check for signature bytes in the file */
@@ -1734,10 +1733,10 @@ static HRESULT GetFileSourceFilter(LPCOLESTR pszFileName, IBaseFilter **filter)
     }
 
     /* Try again find a match */
-    hr = GetClassMediaFile(pReader, pszFileName, NULL, NULL, &clsid);
+    ret = get_media_type(pReader, pszFileName, NULL, NULL, &clsid);
     IAsyncReader_Release(pReader);
 
-    if (hr == S_OK)
+    if (ret)
     {
         TRACE("Found source filter %s.\n", debugstr_guid(&clsid));
         /* Release the AsyncReader filter and create the matching one */

dlls/quartz/quartz_private.h

@@ -77,6 +77,6 @@ extern void video_unregister_windowclass(void) DECLSPEC_HIDDEN;
 BOOL CompareMediaTypes(const AM_MEDIA_TYPE * pmt1, const AM_MEDIA_TYPE * pmt2, BOOL bWildcards);
 void dump_AM_MEDIA_TYPE(const AM_MEDIA_TYPE * pmt) DECLSPEC_HIDDEN;
 
-HRESULT GetClassMediaFile(IAsyncReader * pReader, LPCOLESTR pszFileName, GUID * majorType, GUID * minorType, GUID * sourceFilter);
+BOOL get_media_type(IAsyncReader *reader, const WCHAR *filename, GUID *majortype, GUID *subtype, GUID *source_clsid) DECLSPEC_HIDDEN;
 
 #endif /* __QUARTZ_PRIVATE_INCLUDED__ */