WMPTSE API

The WMPTSE API is the interface between the WMPTSE plug-in and its "tag support dll".

A tag support dll give WMPTSE the ability to add support of a tag format in Windows Media Player. With the this "tag support dll" properly installed, files tagged with its format are readable inside WMP.

API

Every WMPTSE API application must export two function (c standard call):

BOOL Read<TagFormat>Tag( LPTSTR lpstrFileFullPath, METATAG * pMetaTag )

BOOL Write<TagFormat>Tag( LPTSTR lpstrFileFullPath, TAGITEM tagiChangedItem )

<TagFormat> will be the name of the corresponding tag format (APE, Vorbis, MPEG4 for example). The complete function names will be search by WMPTSE during the load process.

The boolean return value is important.

For the read function, it tells WMPTSE if the "tag support dll" has find the correct tag format structures (even if they are empty). If the value is TRUE, WMPTSE will stop searching for compatible tag format for this file (yes, a file can be multi-tagged). If the value is FALSE, WMPTSE will continue searching in its compatible tag format list.

For the write function, it tells WMPTSE if the "tag support dll" has correctly write the new value. If this is true, WMPTSE will continue using this "tag support dll" for this filetype. If this value is false, WMPTSE may unload the "tag support dll".

These function types are defined as FP_TAGREAD (read), FP_TAGWRITE (write) in "WMPTSE.h".

Definition

Note : All types and definition are declared in WMPTSE.h. It is simple for developper to include it at first.

For reading purpose, we will expose the necessary structure definition here.

struct stTagItem											
{
	char *	MetaTagWMPKey;	/** the MediaLibrary attribute's name */
	LPTSTR	MetaTagValue;	/** the value to set */
};
#define TAGITEM struct stTagItem		
typedef struct stTagItem * LPTAGITEM;				

struct stMetaTag
{
	UINT	uiNbItems;	/** number of list tags */
	LPTAGITEM tagiItems;	/** pointer to array of pointer to tag items */
};
#define METATAG struct stMetaTag
typedef struct stMetaTag * LPMETATAG;

Example Source Code

In this example, we will add support for a weird tag format : the "Sting fan" format. In fact, every file considered tagged with this format will return "Sting" for every Tag Key. The sign of a true fan :)

Note : We will not create the write function as it is a "read only" tag format.

Let's see the documented code :

/////////////////////////////////////////////////////////////////////////////
//
// StingTagSupport.c : 
//		Handler for Sting tags support
//
// Copyxxx (\C) 200x - 
//	
/////////////////////////////////////////////////////////////////////////////
#define		STING_TAGSUPPORT_C
#include	"StingTagSupport.h"
#undef		STING_TAGSUPPORT_C


#define	STING_FAN_ARTIST	TCHAR( "Sting" )


BOOL FLACTAG_API			ReadStingTag
( 
	LPTSTR					lpstrFileFullPath, 
	METATAG				*	pMetaTag 
) 
{
	UINT						uiFilePathSize;
	LPSTR						lpcFileFullPath;
	LPVOID	lpvTempPtr;
	
	//First we get the filepath length before retrieving it
	uiFilePathSize = WideCharToMultiByte
		(
			CP_ACP,
			0,
			lpstrFileFullPath,
			-1,
			NULL,
			0,
			NULL,
			NULL
		);
	//then we alloc on the process Heap the memory
	lpcFileFullPath = ( LPSTR ) HeapAlloc
		(
			GetProcessHeap(), 
			HEAP_ZERO_MEMORY,
			uiFilePathSize
		);
	//and we retrieve the filepath
	WideCharToMultiByte
	(
		CP_ACP,
		0,
		lpstrFileFullPath,
		-1,
		lpcFileFullPath,
		uiFilePathSize,
		NULL,
		NULL
	); 
	
	//now, we fill the MetaTag structure with start values
	//at start we don't have any Tags..
	pMetaTag->uiNbItems = 0;
	//at start we need to have a "root" TAGITEM table so we alloc it
	pMetaTag->tagiItems = ( LPTAGITEM )HeapAlloc
		( 
			GetProcessHeap(), 
			HEAP_ZERO_MEMORY, 
			sizeof( TAGITEM )
		);
	
	//We will handles just Album Artist (it should be enough for an example)
	//first we resize our previous TAGITEM table
	lpvTempPtr = ( LPTAGITEM )HeapReAlloc
		( 
			GetProcessHeap(), 
			HEAP_ZERO_MEMORY, 
			pMetaTag->tagiItems,
			sizeof( TAGITEM ) * ( pMetaTag->uiNbItems + 1 )
		);
	if( lpvTempPtr == NULL )
	// we handle a worse case scenario
		return FALSE;
	
	//we replace with the new pointer (if it has changed)
	pMetaTag->tagiItems = lpvTempPtr;
	
	//we alloc the new string to store our tag value
	//it will be freed by WMPTSE, so be sure to have it alloced yourself.
	//(no static string...)
	pMetaTag->tagiItems[ pMetaTag->uiNbItems ].MetaTagValue = HeapAlloc
		(
			GetProcessHeap(),
			HEAP_ZERO_MEMORY,
			sizeof( TCHAR ) * ( lstrlen( STING_FAN_ARTIST ) + 1 )
		);
	//we copy the tag value
	lstrcpy( pMetaTag->tagiItems[ pMetaTag->uiNbItems ].MetaTagValue, STING_FAN_ARTIST );
	//we give WMPTSE the right tag Key (it must be a WMP_TAG_ string, see WMPTSE.h)
	pMetaTag->tagiItems[ pMetaTag->uiNbItems ].MetaTagWMPKey = WMP_TAG_ALBUMARTIST;
	//we increase our tagitem number
	pMetaTag->uiNbItems++;
	
	
	//all is finished, we can release the filepath string	
	HeapFree( GetProcessHeap(), 0, lpcFileFullPath );
	
	return TRUE;
}

BOOL FLACTAG_API			WriteFLACTag
( 
	LPTSTR					lpstrFileFullPath, 
	TAGITEM					tagiChangedItem 
)
{
	return TRUE;
}

Installation

To be effective, a "tag support dll" must be correctly installed in WMPTSE.

You have two choice to install a "tag support dll" :

• use the WMPTSE tag support wizard (see WMPTSE - How to add support for a tag format)
• edit the registry yourself :

Note : In this guide, we will not expose the registry editing for complete file type support in Windows (MIME Types, Media Library Support, etc...). Please refer to Microsoft Windows Media Player documentation for this.

On load, WMPTSE browse the HKEY_LOCAL_MACHINE\SOFTWARE\piPOol\WMPTSE registry key.

Each subkey it finds will be consider a <TagFormat> definition.

Inside each subkey (or <TagFormat> definition), WMPTSE browse for file type support.

Each string in HKEY_LOCAL_MACHINE\SOFTWARE\piPOol\WMPTSE\<TagFormat> describe the file type to support (registry string name) and the path to the "tag support dll" to load (registry string value).

After reading all file types definitions, WMPTSE loads each "tag support dll" and try to get the Read<TagFormat>Tag and Write<TagFormat>Tag functions.

For each dll, If one of those two functions doesn't exist, the dll is considered non-WMPTSE API compatible and is unloaded.

It those two functions exist, the dll is registered as a "tag support dll" for the registered file type.