CDaddcallback(3dm)					    CDaddcallback(3dm)

NAME    [Toc]    [Back]

     CDaddcallback - set a callback for	the CD audio data parser

SYNOPSIS    [Toc]    [Back]

     #include <sys/types.h>
     #include <dmedia/cdaudio.h>

     void CDaddcallback(CDPARSER* cdp, CDDATATYPES type,
		    CDCALLBACKFUNC func, void* arg)

PARAMETERS    [Toc]    [Back]

     cdp    A pointer to the target CDPARSER.

     type   The	type of	callback being set.  CDDATATYPES is an enumerated type
	    defined in cdaudio.h containing the	following values:  cd_audio,
	    cd_pnum, cd_index, cd_ptime, cd_atime, cd_catalog, cd_ident,
	    cd_control.

     func   A pointer to the function to be called.

     arg    A user supplied argument that is passed to the callback function.

DESCRIPTION    [Toc]    [Back]

     CDaddcallback(3dm)	adds a callback	for the	specified parser.  The parser
     has callbacks for eight different types of	data in	the digital audio data
     stream corresponding to the enumerated types listed above.	 When data of
     a particular type changes in the data stream from the disc, the parser
     invokes the corresponding callback	passing	it a pointer to	the data.  The
     cd_audio callback is an exception to this.	 It is called for every
     recorded frame regardless of whether the data changed.

     The callback is called as follows

	      func(void* arg, CDDATATYPES type,	void* data);


     arg is the	user supplied argument provided	as the fourth parameter	to
     CDaddcallback(3dm). type is the particular	type of	callback.  It is
     passed so that a single function could be used for	all eight callbacks.
     data is the data returned for this	type of	callback.  The argument	is
     cast to void*.  Each type of callback returns a different kind of data.
     An	explanation of the callback types and data structures passed to	them
     is	given below.  See cdframe(4) for a detailed description	of each	type
     of	data in	the digital audio data stream.

   cd_audio
     This is the audio data.  The data argument	in this	case is	really a
     short* pointing at	an array containing the	byte-swapped and, if
     necessary,	de-emphasized audio data ready to hand to ALwritesamps(3dm).
     If	you use	this callback you will want to change the handling of floating
     point underflow exceptions	to achieve acceptable performance.  Put	the
     following lines of	code in	your program:



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CDaddcallback(3dm)					    CDaddcallback(3dm)



	      #include <sigfpe.h>

	      sigfpe_[_UNDERFL].repls =	_ZERO;
	      handle_sigfpes(_ON, _EN_UNDERFL, NULL, _ABORT_ON_ERROR, NULL);


     See CDintro(3dm) for a complete explanation.

   cd_pnum
     This is the number	of the current program (aka track).  The data type in
     this case is a pointer to a struct	cdprognum defined in cdaudio.h as
     follows:

	      typedef struct cdprognum {
		  int value;		      /* Program converted to integer */
		  struct cdpackedbcd bcd;     /* Program in BCD	digits */
	      }	CDPROGNUM;


     Program number AA (program	number not currently valid) is represented in
     the converted value by 0xaaa.  Program number BB (lead-in)	is represented
     by	0xbbb and program number EE (lead-out) is represented by 0xeee.

   cd_index
     This is the index number of the current subdivision within	the program.
     The data type in this case	is a pointer to	a struct cdprognum as
     described above.

   cd_ptime
     This is the time into the current program.	 The data type is a pointer to
     a struct cdtimecode defined in cdaudio.h as follows:

	      struct cdtimecode	{
		  unchar mhi:4,	mlo:4;
		  unchar shi:4,	slo:4;
		  unchar fhi:4,	flo:4;
	      }	ptime;


   cd_atime
     This is the time since the	start of the disc (absolute time).  The	data
     type is a pointer to a struct cdtimecode as described above.

   cd_catalog
     This is the catalog number	of the CD.  The	data type is a char* pointing
     to	an array of 13 bytes.  Each byte contains 1 BCD	digit in its least
     significant nibble.

   cd_ident
     This is the ISRC identification number of the recording.  The data	type
     is	a pointer to a struct cdident defined in cdaudio.h as follows:




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CDaddcallback(3dm)					    CDaddcallback(3dm)



	      struct cdident {
		  unchar country[2];
		  unchar owner[3];
		  unchar year[2];
		  unchar serial[5];
	      }	ident;


     country and owner are encoded in the six-bit code converted by
     CDsbtoa(3dm). year	and serial are BCD digits.

   cd_control
     This is for the control bits from the CD subcode data.  The data type is
     unchar* pointing at a single byte.	 The bits in this byte include copy
     protect and preemphasis on	or off.

SEE ALSO    [Toc]    [Back]

     Cdintro(3dm), CDseekblock(3dm), CDseektrack(3dm), CDclose(3dm),
     CDcreateparser(3dm), CDopen(3dm), CDparseframe(3dm), CDreadda(3dm),
     CDseek(3dm), CDremovecallback(3dm), CDresetparser(3dm), cdframe(4),
     sigfpe(3C)

AUTHOR    [Toc]    [Back]

     Roger Chickering, Mark Callow


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