cl_aware(3dm)
cl_aware, CLaware - Aware Audio Schemes in the Compression Library
As shipped in IRIX 6.5.5. Unchanged since IRIX 6.5.
NAME cl_aware, CLaware - Aware Audio Schemes in the Compression Library SYNOPSIS #include <dmedia/cl.h> DESCRIPTION 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. PARAMETERS : GENERAL CL The following general CL parameters are useful for the Aware codecs. CL_FORMAT Indicates the format of the components of the original uncompressed audio. Default is CL_FORMAT_STEREO_INTERLEAVED, legal alternative is CL_FORMAT_MONO. CL_BITS_PER_COMPONENT 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 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 A read-only parameter. CL_EXACT_COMPRESSION_RATIO A read-only parameter. It is true if CL_COMPRESSION_RATIO is exact, and false if the ratio is a worst-case estimate. CL_FRAMES_PER_CHUNK 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 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 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. PARAMETERS : AWARE These parameters are specific to the Aware codecs. CL_AWARE_CHANNEL_POLICY 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 signals. CL_AWARE_BITRATE_POLICY 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 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_NOISE_MARGIN. CL_AWARE_LOSSLESS (MultiRate only) The data is coded losslessly. CL_AWARE_NOISE_MARGIN 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 (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 (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 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 SEE ALSO mpeg(4), CLintro(3dm), cl_mpeg1(3dm), aware(5), AFaware(3dm)