dmMPEG1AudioHeaderGetBlockBytes(3dm)	  dmMPEG1AudioHeaderGetBlockBytes(3dm)

NAME    [Toc]    [Back]

     dmMPEG1AudioHeaderGetBlockBytes - gets expected length in bytes of	any
     compressed	data block.

SYNOPSIS    [Toc]    [Back]

     #include <dmedia/dmedia.h>
     #include <dmedia/dm_audioutil.h>

     DMstatus dmMPEG1AudioHeaderGetBlockBytes(DMMPEG1audiodecoder decoder,
					 unsigned char *cmpData,
					 int *blockSize)

PARAMETER    [Toc]    [Back]

     decoder   DMMPEG1audiodecoder structure, created by
	       dmMPEG1AudioDecoderCreate(3dm), specifies and stores the	signal
	       processing parameters.  It describes the	kind of	decompression
	       to perform, and holds the between-block state of	the
	       decompressor.  It is initially generated	by calls to
	       dmMPEG1AudioDecoderCreate(3dm) and
	       dmMPEG1AudioDecoderSetParams(3dm).
	       dmMPEG1AudioHeaderGetBlockBytes modifies	DMMPEG1audiodecoder
	       structure to reflect the	header on the compressed data block if
	       one is found; decoder parameters	may then subsequenly be
	       queried using dmMPEG1AudioDecoderSetParams(3dm) to determine
	       the decoding parameters of the encoded bytes.


     cmpData   points to a block of data bytes presumed	to constitute the
	       compressed data stream.


     blockSize pointer to an integer return value; indicates the expected
	       length in bytes of any compressed data block starting from the
	       header that was found. If no valid header was found zero	is
	       returned.  This may be useful number of bytes to	queue up for
	       calls to	dmMPEG1AudioDecode(3dm).  The largest compressed data
	       block possible under MPEG1 audio	layer 1	is 672 bytes (32kHz
	       sampling	rate, 448 kbps data rate, 38 sample frames per block)
	       and under layer 2 it is 1728 bytes (32kHz sampling rate,	384
	       kbps data rate, 1152 sample frames per block) --	???.

RETURNED VALUE    [Toc]    [Back]

     Returns DM_FAILURE	or DM_SUCCESS.

DESCRIPTION    [Toc]    [Back]

     dmMPEG1AudioHeaderGetBlockBytes(3dm) extracts information from a
     compressed	data stream without going so far as to decompress the data.




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dmMPEG1AudioHeaderGetBlockBytes(3dm)	  dmMPEG1AudioHeaderGetBlockBytes(3dm)

NOTE    [Toc]    [Back]

SEE ALSO
     dmMPEG1AudioDecoderCreate(3dm), dmMPEG1AudioDecoderSetParams(3dm),
     dmMPEG1AudioDecoderGetParams(3dm),	dmMPEG1AudioDecode(3dm).


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