Object Signatures

Standard PJMEDIA object signatures. More...

Macros
#define	PJMEDIA_SIGNATURE(a, b, c, d)   PJMEDIA_FOURCC(d,c,b,a)
#define	PJMEDIA_SIG_CLASS_CODEC(b, c, d)   PJMEDIA_SIGNATURE('C',b,c,d)
#define	PJMEDIA_SIG_IS_CLASS_CODEC(sig)   ((sig) >> 24 == 'C')
#define	PJMEDIA_SIG_CLASS_AUD_CODEC(c, d)   PJMEDIA_SIG_CLASS_CODEC('A',c,d)
#define	PJMEDIA_SIG_IS_CLASS_AUD_CODEC(s)   ((s)>>24=='C' && (((s)>>16)&0xff)=='A')
#define	PJMEDIA_SIG_CLASS_VID_CODEC(c, d)   PJMEDIA_SIG_CLASS_CODEC('V',c,d)
#define	PJMEDIA_SIG_IS_CLASS_VID_CODEC(sig)   ((s)>>24=='C' && (((s)>>16)&0xff)=='V')
#define	PJMEDIA_SIG_VID_CODEC_FFMPEG   PJMEDIA_SIG_CLASS_VID_CODEC('F','F')
#define	PJMEDIA_SIG_CLASS_PORT(b, c, d)   PJMEDIA_SIGNATURE('P',b,c,d)
#define	PJMEDIA_SIG_IS_CLASS_PORT(sig)   ((sig) >> 24 == 'P')
#define	PJMEDIA_SIG_CLASS_PORT_AUD(c, d)   PJMEDIA_SIG_CLASS_PORT('A',c,d)
#define	PJMEDIA_SIG_IS_CLASS_PORT_AUD(s)   ((s)>>24=='P' && (((s)>>16)&0xff)=='A')
#define	PJMEDIA_SIG_PORT_BIDIR   PJMEDIA_SIG_CLASS_PORT_AUD('B','D')
#define	PJMEDIA_SIG_PORT_CONF   PJMEDIA_SIG_CLASS_PORT_AUD('C','F')
#define	PJMEDIA_SIG_PORT_CONF_PASV   PJMEDIA_SIG_CLASS_PORT_AUD('C','P')
#define	PJMEDIA_SIG_PORT_CONF_SWITCH   PJMEDIA_SIG_CLASS_PORT_AUD('C','S')
#define	PJMEDIA_SIG_PORT_ECHO   PJMEDIA_SIG_CLASS_PORT_AUD('E','C')
#define	PJMEDIA_SIG_PORT_MEM_CAPTURE   PJMEDIA_SIG_CLASS_PORT_AUD('M','C')
#define	PJMEDIA_SIG_PORT_MEM_PLAYER   PJMEDIA_SIG_CLASS_PORT_AUD('M','P')
#define	PJMEDIA_SIG_PORT_NULL   PJMEDIA_SIG_CLASS_PORT_AUD('N','U')
#define	PJMEDIA_SIG_PORT_RESAMPLE   PJMEDIA_SIG_CLASS_PORT_AUD('R','E')
#define	PJMEDIA_SIG_PORT_SPLIT_COMB   PJMEDIA_SIG_CLASS_PORT_AUD('S','C')
#define	PJMEDIA_SIG_PORT_SPLIT_COMB_P   PJMEDIA_SIG_CLASS_PORT_AUD('S','P')
#define	PJMEDIA_SIG_PORT_STEREO   PJMEDIA_SIG_CLASS_PORT_AUD('S','R')
#define	PJMEDIA_SIG_PORT_STREAM   PJMEDIA_SIG_CLASS_PORT_AUD('S','T')
#define	PJMEDIA_SIG_PORT_TONEGEN   PJMEDIA_SIG_CLASS_PORT_AUD('T','O')
#define	PJMEDIA_SIG_PORT_WAV_PLAYER   PJMEDIA_SIG_CLASS_PORT_AUD('W','P')
#define	PJMEDIA_SIG_PORT_WAV_PLAYLIST   PJMEDIA_SIG_CLASS_PORT_AUD('W','Y')
#define	PJMEDIA_SIG_PORT_WAV_WRITER   PJMEDIA_SIG_CLASS_PORT_AUD('W','W')
#define	PJMEDIA_SIG_CLASS_PORT_VID(c, d)   PJMEDIA_SIG_CLASS_PORT('V',c,d)
#define	PJMEDIA_SIG_IS_CLASS_PORT_VID(s)   ((s)>>24=='P' && (((s)>>16)&0xff)=='V')
#define	PJMEDIA_SIG_PORT_VID_AVI_PLAYER   PJMEDIA_SIG_CLASS_PORT_VID('A','V')
#define	PJMEDIA_SIG_PORT_VID_STREAM   PJMEDIA_SIG_CLASS_PORT_VID('S','T')
#define	PJMEDIA_SIG_PORT_VID_TEE   PJMEDIA_SIG_CLASS_PORT_VID('T','E')
#define	PJMEDIA_SIG_CLASS_VID_DEV(c, d)   PJMEDIA_SIGNATURE('V','D',c,d)
#define	PJMEDIA_SIG_IS_CLASS_VID_DEV(s)   ((s)>>24=='V' && (((s)>>16)&0xff)=='D')
#define	PJMEDIA_SIG_VID_DEV_COLORBAR   PJMEDIA_SIG_CLASS_VID_DEV('C','B')
#define	PJMEDIA_SIG_VID_DEV_SDL   PJMEDIA_SIG_CLASS_VID_DEV('S','D')
#define	PJMEDIA_SIG_VID_DEV_V4L2   PJMEDIA_SIG_CLASS_VID_DEV('V','2')
#define	PJMEDIA_SIG_VID_DEV_DSHOW   PJMEDIA_SIG_CLASS_VID_DEV('D','S')
#define	PJMEDIA_SIG_VID_DEV_QT   PJMEDIA_SIG_CLASS_VID_DEV('Q','T')
#define	PJMEDIA_SIG_VID_DEV_IOS   PJMEDIA_SIG_CLASS_VID_DEV('I','P')
#define	PJMEDIA_SIG_CLASS_VID_OTHER(c, d)   PJMEDIA_SIGNATURE('V','O',c,d)
#define	PJMEDIA_SIG_IS_CLASS_VID_OTHER(s)   ((s)>>24=='V' && (((s)>>16)&0xff)=='O')
#define	PJMEDIA_SIG_VID_CONF   PJMEDIA_SIG_CLASS_VID_OTHER('C','F')
#define	PJMEDIA_SIG_VID_PORT   PJMEDIA_SIG_CLASS_VID_OTHER('P','O')
#define	PJMEDIA_SIG_CLASS_APP(b, c, d)   PJMEDIA_SIGNATURE('A',b,c,d)
#define	PJMEDIA_SIG_IS_CLASS_APP(s)   ((s)>>24=='A')

Typedefs
typedef pj_uint32_t	pjmedia_obj_sig

Functions
const char *	pjmedia_sig_name (pjmedia_obj_sig sig, char buf[])

Detailed Description

Object signature is a 32-bit integral value similar to FOURCC to help identify PJMEDIA objects such as media ports, transports, codecs, etc. There are several uses of this signature, for example a media port can use the port object signature to verify that the given port instance is the one that it created, and a receiver of Event Framework can use the signature of the publisher to know which object emitted the event.

The 32-bit value of an object signature is generated by the following macro:

  #define PJMEDIA_SIGNATURE(a,b,c,d)   (a<<24 | b<<16 | c<<8 | d)
* 

The following convention is used to maintain order to the signature values so that application can make use of it more effectively, and to avoid conflict between the values themselves. For each object type or class, a specific prefix will be assigned as signature, and a macro is created to build a signature for such object:

   Class               Signature  Signature creation and test macros
   ---------------------------------------------------------------
   Codec               Cxxx       PJMEDIA_SIG_CLASS_CODEC(b,c,d)
                                  PJMEDIA_SIG_IS_CLASS_CODEC(sig)

   Audio codec         CAxx       PJMEDIA_SIG_CLASS_AUD_CODEC(c,d)
                                  PJMEDIA_SIG_IS_CLASS_AUD_CODEC(sig)

   Video codec         CVxx       PJMEDIA_SIG_CLASS_VID_CODEC(c,d)
                                  PJMEDIA_SIG_IS_CLASS_VID_CODEC(sig)

   Media port          Pxxx       PJMEDIA_SIG_CLASS_PORT(b,c,d)
                                  PJMEDIA_SIG_IS_CLASS_PORT(sig)

   Audio media port    PAxx       PJMEDIA_SIG_CLASS_PORT_AUD(c,d)
                                  PJMEDIA_SIG_IS_CLASS_PORT_AUD(sig)

   Video media port    PVxx       PJMEDIA_SIG_CLASS_PORT_VID(c,d)
                                  PJMEDIA_SIG_IS_CLASS_PORT_VID(sig)

   Video device        VDxx       PJMEDIA_SIG_CLASS_VID_DEV(c,d)
                                  PJMEDIA_SIG_IS_CLASS_VID_DEV(sig)

   Video other         VOxx       PJMEDIA_SIG_CLASS_VID_OTHER(c,d)
                                  PJMEDIA_SIG_IS_CLASS_VID_OTHER(sig)

   Application object  Axxx       PJMEDIA_SIG_CLASS_APP(b,c,d)
                                  PJMEDIA_SIG_IS_CLASS_APP(sig)

* 

In addition, signatures created in application code should have lowercase letters to avoid conflict with built-in objects.

Macro Definition Documentation

PJMEDIA_SIGNATURE

#define PJMEDIA_SIGNATURE	(		a,
			b,
			c,
			d
	)		PJMEDIA_FOURCC(d,c,b,a)

Macro to generate signature from four ASCII letters.

PJMEDIA_SIG_PORT_VID_AVI_PLAYER

#define PJMEDIA_SIG_PORT_VID_AVI_PLAYER   PJMEDIA_SIG_CLASS_PORT_VID('A','V')

AVI player signature.

Typedef Documentation

pjmedia_obj_sig

typedef pj_uint32_t pjmedia_obj_sig

Type to store object signature.

Function Documentation

pjmedia_sig_name()

const char * pjmedia_sig_name	(	pjmedia_obj_sig	sig,
		char	buf[]
	)

A utility function to convert signature to four letters string.

Parameters

sig	The signature value.
buf	Buffer to store the string, which MUST be at least five bytes long.

Returns

The string.

References PJ_INLINE, and pjmedia_fourcc_name().