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cl_aware(3dm)							 cl_aware(3dm)

NAME    [Toc]    [Back]

     cl_aware, CLaware - Aware Audio Schemes in	the Compression	Library

SYNOPSIS    [Toc]    [Back]

     #include <dmedia/cl.h>

DESCRIPTION    [Toc]    [Back]

     This man page describes the Aware audio compression algorithms that are
     installed in the Compression Library (CL).	 Two Aware schemes are
     currently supported.

     1.	CL_MPEG1_AUDIO_AWARE  The ISO/MPEG-audio standard algorithm
			      with layers I and	II.

     2.	CL_MULTIRATE_AWARE    The Aware-proprietary MultiRate I
			      lossless or low-distortion algorithm.

     Each scheme is accessed through the standard CL API, described in
     CLintro(3dm).  Listed below are the parameters that may be	used with
     these two codecs.	Note that parameters described in cl_mpeg1(3dm)	are
     currently not supported for CL_MPEG1_AUDIO_AWARE.

     The following general CL parameters are useful for	the Aware codecs.

     CL_FORMAT    [Toc]    [Back]
	  Indicates the	format of the components of the	original uncompressed
	  audio.  Default is CL_FORMAT_STEREO_INTERLEAVED, legal alternative

     CL_BITS_PER_COMPONENT    [Toc]    [Back]
	  Informs the scheme of	the width of the audio samples (assumed	to
	  be linear two's complement).	Currently, the only supported value
	  is 16.

     CL_FRAME_RATE    [Toc]    [Back]
	  Tells	the scheme the sampling	rate of	the uncompressed audio.
	  Default is 44100.0 Hz.  Legal	values for the MPEG algorithm are
	  32000.0, 44100.0, and	48000.0	Hz.  Legal values for the MultiRate
	  algorithm are	8000.0,	11025.0, 16000.0, 22050.0, 32000.0, 44100.0,
	  and 48000.0 Hz.

     CL_COMPRESSION_RATIO    [Toc]    [Back]
	  A read-only parameter.

     CL_EXACT_COMPRESSION_RATIO    [Toc]    [Back]
	  A read-only parameter.  It is	true if	CL_COMPRESSION_RATIO is
	  exact, and false if the ratio	is a worst-case	estimate.

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cl_aware(3dm)							 cl_aware(3dm)

     CL_FRAMES_PER_CHUNK    [Toc]    [Back]
	  A read-only parameter.  This is the number of	audio frames which
	  are compressed at one	time by	the scheme.  The data that are passed
	  to clCompress	should be in multiples of this size.

     CL_FRAME_TYPE    [Toc]    [Back]
	  A read-only parameter.  Indicates the	status of the next frame to be
	  processed is either CL_KEYFRAME (i.e.	the first frame	in a compressed
	  chunk) or CL_PREDICTED (all other alignments).  This should always be
	  CL_KEYFRAME if the CL_FRAMES_PER_CHUNK parameter is followed.	 Note
	  that this definition is somewhat different than the general usage
	  given	in CLintro(3dm).

     CL_SPEED    [Toc]    [Back]
	  The CL_SPEED parameter takes values from 1.0 to 100.0.  It has no
	  effect during	compression.  During decompression, it controls	the
	  computational	complexity by controlling several factors:
	  sample rate decimation, combining of stereo channels,	filter shape
	  (MPEG	only), and lossy_decode	(MultiRate only).

	  The user of this parameter should be advised that changing it	may
	  cause	the sampling rate, total number	of sample frames available,
	  and sample frames per	compressed chunk to be changed.

	  After	modifying this parameter, the values of	CL_FRAME_RATE and
	  CL_FRAMES_PER_CHUNK should be	queried	for their new values.

     These parameters are specific to the Aware	codecs.

     CL_AWARE_CHANNEL_POLICY    [Toc]    [Back]
	  Selects the treatment	of stereo signals.

	  CL_AWARE_STEREO	indicates that the channels are	part of	a
				single multi-channel signal.

	  CL_AWARE_JOINT_STEREO	stereo redundancy exploited by coding high
				frequency subbands together.  Not supported
				under MultiRate	algorithm.

	  CL_AWARE_INDEPENDENT	the channels are unrelated and coded
				separately; e.g. multilingual sound tracks.

	  Note that any	of these options are equivalent	for single channel

     CL_AWARE_BITRATE_POLICY    [Toc]    [Back]
	  Provides for different modes of bit assignment:

	  CL_AWARE_FIXED_RATE  (MPEG only) A fixed bitrate is used to code
			       all of the channels.  This is the default for

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cl_aware(3dm)							 cl_aware(3dm)

			       MPEG audio.  See	CL_AWARE_BITRATE_TARGET.

	  CL_AWARE_CONST_QUAL  bitrate allowed to vary to satisfy MPEG
			       psychoacoustic model or MultiRate data
			       requirements (90+dB).  This is the default
			       for the MultiRate algorithm.  See

	  CL_AWARE_LOSSLESS    (MultiRate only)	The data is coded losslessly.

     CL_AWARE_NOISE_MARGIN    [Toc]    [Back]
	  Used in conjunction with CL_AWARE_CONST_QUAL.	 Provides for
	  specification	of the noise-to-mask ratio in MPEG psychoaccoustics:
	  Zero yields a	theoretic psychoacoustic imperceptible compression.
	  Positive values provide more compression and noise becomes audible.
	  Negative values cause	less compression and less perceptible noise.

	  For MultiRate, sets the noise-floor at -90 dB	below the signal level.
	  This is the only valid MultiRate setting at this time.

     CL_AWARE_BITRATE_TARGET    [Toc]    [Back]
	  (MPEG	only) Used in conjunction with CL_AWARE_FIXED_RATE.
	  Determines the output	data rate in bits per second.  The allowed
	  values are:

	  MPEG layer I:
	  32000, 64000,	96000, 128000, 160000, 192000, 224000
	  256000, 228000, 320000, 352000, 384000, 416000, 448000

	  MPEG layer II:
	  32000, 48000,	56000, 64000, 80000, 96000, 112000, 128000,
	  160000, 192000, 224000, 256000, 320000, 384000

     CL_AWARE_LAYER    [Toc]    [Back]
	  (MPEG	only) Selects the MPEG layer. Default is
	  CL_AWARE_MPEG_LAYER_II for layer II, other legal value is
	  CL_AWARE_MPEG_LAYER_I	for layer I.

NOTES    [Toc]    [Back]

     Aware compression is also accessible through the Audio File Library.  For
     more information see AFaware(3dm).

     In	order to use these schemes, a NetLS license needs to be	obtained from

     Aware, Inc.
     One Memorial Drive
     Cambridge,	MA 02142 USA

     phone:  (617) 577-1700
     fax:    (617) 577-1710
     e-mail: sales@aware.com

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cl_aware(3dm)							 cl_aware(3dm)

SEE ALSO    [Toc]    [Back]

     mpeg(4), CLintro(3dm), cl_mpeg1(3dm), aware(5), AFaware(3dm)

									PPPPaaaaggggeeee 4444
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