diff --git a/codec/api/svc/codec_api.h b/codec/api/svc/codec_api.h
index 4793f51d..628ed8f0 100644
--- a/codec/api/svc/codec_api.h
+++ b/codec/api/svc/codec_api.h
@@ -36,36 +36,43 @@
 #include "codec_app_def.h"
 #include "codec_def.h"
 
+#if defined(_WIN32) || defined(__cdecl)
+#define EXTAPI __cdecl
+#else
+#define EXTAPI
+#endif
+
+#ifdef __cplusplus
 class ISVCEncoder {
  public:
   /*
    * return: CM_RETURN: 0 - success; otherwise - failed;
    */
-  virtual int Initialize (SVCEncodingParam* pParam, const INIT_TYPE kiInitType = INIT_TYPE_PARAMETER_BASED) = 0;
-  virtual int Initialize2 (void* pParam, const INIT_TYPE kiInitType = INIT_TYPE_CONFIG_BASED) = 0;
+  virtual int EXTAPI Initialize (SVCEncodingParam* pParam, const INIT_TYPE kiInitType = INIT_TYPE_PARAMETER_BASED) = 0;
+  virtual int EXTAPI Initialize2 (void* pParam, const INIT_TYPE kiInitType = INIT_TYPE_CONFIG_BASED) = 0;
 
-  virtual int Uninitialize() = 0;
+  virtual int EXTAPI Uninitialize() = 0;
 
   /*
    * return: EVideoFrameType [IDR: videoFrameTypeIDR; P: videoFrameTypeP; ERROR: videoFrameTypeInvalid]
    */
-  virtual int EncodeFrame (const unsigned char* kpSrc, SFrameBSInfo* pBsInfo) = 0;
-  virtual int EncodeFrame2 (const SSourcePicture**   kppSrcPicList, int nSrcPicNum, SFrameBSInfo* pBsInfo) = 0;
+  virtual int EXTAPI EncodeFrame (const unsigned char* kpSrc, SFrameBSInfo* pBsInfo) = 0;
+  virtual int EXTAPI EncodeFrame2 (const SSourcePicture**   kppSrcPicList, int nSrcPicNum, SFrameBSInfo* pBsInfo) = 0;
 
   /*
    * return: 0 - success; otherwise - failed;
    */
-  virtual int EncodeParameterSets (SFrameBSInfo* pBsInfo) = 0;
+  virtual int EXTAPI EncodeParameterSets (SFrameBSInfo* pBsInfo) = 0;
 
   /*
    * return: 0 - success; otherwise - failed;
    */
-  virtual int PauseFrame (const unsigned char* kpSrc, SFrameBSInfo* pBsInfo) = 0;
+  virtual int EXTAPI PauseFrame (const unsigned char* kpSrc, SFrameBSInfo* pBsInfo) = 0;
 
   /*
    * return: 0 - success; otherwise - failed;
    */
-  virtual int ForceIntraFrame (bool bIDR) = 0;
+  virtual int EXTAPI ForceIntraFrame (bool bIDR) = 0;
 
   /************************************************************************
    * InDataFormat, IDRInterval, SVC Encode Param, Frame Rate, Bitrate,..
@@ -73,58 +80,118 @@ class ISVCEncoder {
   /*
    * return: CM_RETURN: 0 - success; otherwise - failed;
    */
-  virtual int SetOption (ENCODER_OPTION eOptionId, void* pOption) = 0;
-  virtual int GetOption (ENCODER_OPTION eOptionId, void* pOption) = 0;
+  virtual int EXTAPI SetOption (ENCODER_OPTION eOptionId, void* pOption) = 0;
+  virtual int EXTAPI GetOption (ENCODER_OPTION eOptionId, void* pOption) = 0;
 };
 
 class ISVCDecoder {
  public:
-  virtual long Initialize (void* pParam, const INIT_TYPE iInitType) = 0;
-  virtual long Uninitialize() = 0;
+  virtual long EXTAPI Initialize (void* pParam, const INIT_TYPE iInitType) = 0;
+  virtual long EXTAPI Uninitialize() = 0;
 
-  virtual DECODING_STATE DecodeFrame (const unsigned char* pSrc,
-                                      const int iSrcLen,
-                                      unsigned char** ppDst,
-                                      int* pStride,
-                                      int& iWidth,
-                                      int& iHeight) = 0;
+  virtual DECODING_STATE EXTAPI DecodeFrame (const unsigned char* pSrc,
+                                             const int iSrcLen,
+                                             unsigned char** ppDst,
+                                             int* pStride,
+                                             int& iWidth,
+                                             int& iHeight) = 0;
 
   /*
    *  src must be 4 byte aligned,   recommend 16 byte aligned.    the available src size must be multiple of 4.
    */
-  virtual DECODING_STATE DecodeFrame2 (const unsigned char* pSrc,
-                                      const int iSrcLen,
-                                      void** ppDst,
-                                      SBufferInfo* pDstInfo) = 0;
+  virtual DECODING_STATE EXTAPI DecodeFrame2 (const unsigned char* pSrc,
+                                              const int iSrcLen,
+                                              void** ppDst,
+                                              SBufferInfo* pDstInfo) = 0;
 
   /*
    *  src must be 4 byte aligned,   recommend 16 byte aligned.    the available src size must be multiple of 4.
    *  this API does not work for now!! This is for future use to support non-I420 color format output.
    */
-  virtual DECODING_STATE DecodeFrameEx (const unsigned char* pSrc,
-                                        const int iSrcLen,
-                                        unsigned char* pDst,
-                                        int iDstStride,
-                                        int& iDstLen,
-                                        int& iWidth,
-                                        int& iHeight,
-                                        int& iColorFormat) = 0;
+  virtual DECODING_STATE EXTAPI DecodeFrameEx (const unsigned char* pSrc,
+                                               const int iSrcLen,
+                                               unsigned char* pDst,
+                                               int iDstStride,
+                                               int& iDstLen,
+                                               int& iWidth,
+                                               int& iHeight,
+                                               int& iColorFormat) = 0;
 
   /*************************************************************************
    * OutDataFormat
    *************************************************************************/
-  virtual long SetOption (DECODER_OPTION eOptionId, void* pOption) = 0;
-  virtual long GetOption (DECODER_OPTION eOptionId, void* pOption) = 0;
+  virtual long EXTAPI SetOption (DECODER_OPTION eOptionId, void* pOption) = 0;
+  virtual long EXTAPI GetOption (DECODER_OPTION eOptionId, void* pOption) = 0;
 };
 
 
 extern "C"
 {
+#else
+
+typedef struct ISVCEncoderVtbl ISVCEncoderVtbl;
+typedef const ISVCEncoderVtbl* ISVCEncoder;
+struct ISVCEncoderVtbl {
+
+  int (*Initialize) (ISVCEncoder*, SVCEncodingParam* pParam, const INIT_TYPE kiInitType);
+  int (*Initialize2) (ISVCEncoder*, void* pParam, const INIT_TYPE kiInitType);
+
+  int (*Uninitialize) (ISVCEncoder*);
+
+  int (*EncodeFrame) (ISVCEncoder*, const unsigned char* kpSrc, SFrameBSInfo* pBsInfo);
+  int (*EncodeFrame2) (ISVCEncoder*, const SSourcePicture**   kppSrcPicList, int nSrcPicNum, SFrameBSInfo* pBsInfo);
+
+  int (*EncodeParameterSets) (ISVCEncoder*, SFrameBSInfo* pBsInfo);
+
+  int (*PauseFrame) (ISVCEncoder*, const unsigned char* kpSrc, SFrameBSInfo* pBsInfo);
+
+  int (*ForceIntraFrame) (ISVCEncoder*, bool bIDR);
+
+  int (*SetOption) (ISVCEncoder*, ENCODER_OPTION eOptionId, void* pOption);
+  int (*GetOption) (ISVCEncoder*, ENCODER_OPTION eOptionId, void* pOption);
+};
+
+typedef struct ISVCDecoderVtbl ISVCDecoderVtbl;
+typedef const ISVCDecoderVtbl* ISVCDecoder;
+struct ISVCDecoderVtbl {
+  long (*Initialize) (ISVCDecoder*, void* pParam, const INIT_TYPE iInitType);
+  long (*Uninitialize) (ISVCDecoder*);
+
+  DECODING_STATE (*DecodeFrame) (ISVCDecoder*, const unsigned char* pSrc,
+                                 const int iSrcLen,
+                                 unsigned char** ppDst,
+                                 int* pStride,
+                                 int* iWidth,
+                                 int* iHeight);
+
+  DECODING_STATE (*DecodeFrame2) (ISVCDecoder*, const unsigned char* pSrc,
+                                  const int iSrcLen,
+                                  void** ppDst,
+                                  SBufferInfo* pDstInfo);
+
+  DECODING_STATE (*DecodeFrameEx) (ISVCDecoder*, const unsigned char* pSrc,
+                                   const int iSrcLen,
+                                   unsigned char* pDst,
+                                   int iDstStride,
+                                   int* iDstLen,
+                                   int* iWidth,
+                                   int* iHeight,
+                                   int* iColorFormat);
+
+  long (*SetOption) (ISVCDecoder*, DECODER_OPTION eOptionId, void* pOption);
+  long (*GetOption) (ISVCDecoder*, DECODER_OPTION eOptionId, void* pOption);
+};
+#endif
+
+
   int  CreateSVCEncoder (ISVCEncoder** ppEncoder);
   void DestroySVCEncoder (ISVCEncoder* pEncoder);
 
   long CreateDecoder (ISVCDecoder** ppDecoder);
   void DestroyDecoder (ISVCDecoder* pDecoder);
+
+#ifdef __cplusplus
 }
+#endif
 
 #endif//WELS_VIDEO_CODEC_SVC_API_H__
diff --git a/codec/decoder/plus/inc/welsDecoderExt.h b/codec/decoder/plus/inc/welsDecoderExt.h
index 230adfea..4fea2e2d 100644
--- a/codec/decoder/plus/inc/welsDecoderExt.h
+++ b/codec/decoder/plus/inc/welsDecoderExt.h
@@ -59,8 +59,8 @@ class CWelsDecoder : public ISVCDecoder {
 CWelsDecoder (void_t);
 virtual ~CWelsDecoder();
 
-virtual long Initialize (void_t* pParam, const INIT_TYPE keInitType);
-virtual long Uninitialize();
+virtual long EXTAPI Initialize (void_t* pParam, const INIT_TYPE keInitType);
+virtual long EXTAPI Uninitialize();
 
 /***************************************************************************
 *	Description:
@@ -74,28 +74,28 @@ virtual long Uninitialize();
 *
 *	return: if decode frame success return 0, otherwise corresponding error returned.
 ***************************************************************************/
-virtual DECODING_STATE DecodeFrame (const unsigned char* kpSrc,
-                                    const int kiSrcLen,
-                                    unsigned char** ppDst,
-                                    int* pStride,
-                                    int& iWidth,
-                                    int& iHeight);
+virtual DECODING_STATE EXTAPI DecodeFrame (const unsigned char* kpSrc,
+                                           const int kiSrcLen,
+                                           unsigned char** ppDst,
+                                           int* pStride,
+                                           int& iWidth,
+                                           int& iHeight);
 
-virtual DECODING_STATE DecodeFrame2 (const unsigned char* kpSrc,
-                                    const int kiSrcLen,
-                                    void_t** ppDst,
-                                    SBufferInfo* pDstInfo);
-virtual DECODING_STATE DecodeFrameEx (const unsigned char* kpSrc,
-                                      const int kiSrcLen,
-                                      unsigned char* pDst,
-                                      int iDstStride,
-                                      int& iDstLen,
-                                      int& iWidth,
-                                      int& iHeight,
-                                      int& color_format);
+virtual DECODING_STATE EXTAPI DecodeFrame2 (const unsigned char* kpSrc,
+                                            const int kiSrcLen,
+                                            void_t** ppDst,
+                                            SBufferInfo* pDstInfo);
+virtual DECODING_STATE EXTAPI DecodeFrameEx (const unsigned char* kpSrc,
+                                             const int kiSrcLen,
+                                             unsigned char* pDst,
+                                             int iDstStride,
+                                             int& iDstLen,
+                                             int& iWidth,
+                                             int& iHeight,
+                                             int& color_format);
 
-virtual long SetOption (DECODER_OPTION eOptID, void_t* pOption);
-virtual long GetOption (DECODER_OPTION eOptID, void_t* pOption);
+virtual long EXTAPI SetOption (DECODER_OPTION eOptID, void_t* pOption);
+virtual long EXTAPI GetOption (DECODER_OPTION eOptID, void_t* pOption);
 
  private:
 PWelsDecoderContext 				m_pDecContext;
diff --git a/codec/encoder/plus/inc/welsEncoderExt.h b/codec/encoder/plus/inc/welsEncoderExt.h
index b7bcea3b..23cc29bf 100644
--- a/codec/encoder/plus/inc/welsEncoderExt.h
+++ b/codec/encoder/plus/inc/welsEncoderExt.h
@@ -65,31 +65,31 @@ class CWelsH264SVCEncoder : public ISVCEncoder {
   /*
    * return: CM_RETURN: 0 - success; otherwise - failed;
    */
-  virtual int Initialize (SVCEncodingParam* argv, const INIT_TYPE init_type);
-  virtual int Initialize2 (void* argv, const INIT_TYPE init_type);
+  virtual int EXTAPI Initialize (SVCEncodingParam* argv, const INIT_TYPE init_type);
+  virtual int EXTAPI Initialize2 (void* argv, const INIT_TYPE init_type);
 
-  virtual int Uninitialize();
+  virtual int EXTAPI Uninitialize();
 
   /*
    * return: EVideoFrameType [IDR: videoFrameTypeIDR; P: videoFrameTypeP; ERROR: videoFrameTypeInvalid]
    */
-  virtual int EncodeFrame (const unsigned char* kpSrc, SFrameBSInfo* pBsInfo);
-  virtual int EncodeFrame2 (const SSourcePicture** kppSrcPicList, int nSrcPicNum, SFrameBSInfo* pBsInfo);
+  virtual int EXTAPI EncodeFrame (const unsigned char* kpSrc, SFrameBSInfo* pBsInfo);
+  virtual int EXTAPI EncodeFrame2 (const SSourcePicture** kppSrcPicList, int nSrcPicNum, SFrameBSInfo* pBsInfo);
 
   /*
    * return: 0 - success; otherwise - failed;
    */
-  virtual int EncodeParameterSets (SFrameBSInfo* pBsInfo);
+  virtual int EXTAPI EncodeParameterSets (SFrameBSInfo* pBsInfo);
 
   /*
    * return: 0 - success; otherwise - failed;
    */
-  virtual int PauseFrame (const unsigned char* pSrc, SFrameBSInfo* pBsInfo);
+  virtual int EXTAPI PauseFrame (const unsigned char* pSrc, SFrameBSInfo* pBsInfo);
 
   /*
    * return: 0 - success; otherwise - failed;
    */
-  virtual int ForceIntraFrame (bool bIDR);
+  virtual int EXTAPI ForceIntraFrame (bool bIDR);
 
   /************************************************************************
    * InDataFormat, IDRInterval, SVC Encode Param, Frame Rate, Bitrate,..
@@ -97,8 +97,8 @@ class CWelsH264SVCEncoder : public ISVCEncoder {
   /*
    * return: CM_RETURN: 0 - success; otherwise - failed;
    */
-  virtual int SetOption (ENCODER_OPTION opt_id, void* option);
-  virtual int GetOption (ENCODER_OPTION opt_id, void* option);
+  virtual int EXTAPI SetOption (ENCODER_OPTION opt_id, void* option);
+  virtual int EXTAPI GetOption (ENCODER_OPTION opt_id, void* option);
 
  private:
   sWelsEncCtx*	m_pEncContext;