dmMPEG1AudioDecoderGetParams man page on IRIX

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dmMPEG1AudioEncoderSetParams(3dm)	     dmMPEG1AudioEncoderSetParams(3dm)

NAME
     dmMPEG1AudioEncoderSetParams, dmMPEG1AudioDecoderSetParams,
     dmMPEG1AudioEncoderGetParams, dmMPEG1AudioDecoderGetParams - set and
     query MPEG1 audio encoder/decoder parameter values.

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

     DMstatus dmMPEG1AudioEncoderSetParams(DMMPEG1audioencoder encoder,
				   DMparams *params)
     DMstatus dmMPEG1AudioDecoderSetParams(DMMPEG1audiodecoder decoder,
				   DMparams *params)
     DMstatus dmMPEG1AudioEncoderGetParams(DMMPEG1audioencoder encoder,
				   DMparams *params)
     DMstatus dmMPEG1AudioDecoderGetParams(DMMPEG1audiodecoder decoder,
				   DMparams *params)

PARAMETER
     encoder  DMMPEG1audioencoder structure, created by
	      dmMPEG1AudioEncoderCreate(3dm).

     decoder  DMMPEG1audiodecoder structure, created by
	      dmMPEG1AudioDecoderCreate(3dm).

     params   List of parameters for specification.

RETURNED VALUE
     Returns DM_SUCCESS or DM_FAILURE.

DESCRIPTION
     dmMPEG1AudioEncoderSetParams(3dm) or dmMPEG1AudioDecoderSetParams(3dm)
     sets MPEG1 audio encoder or decoder parameters to user defined values
     with params.  These values will overwrite the default values set by
     dmMPEG1AudioEncoderCreate(3dm) or dmMPEG1AudioDecoderSetParams(3dm).
     *params can be NULL, then default values will be used.  Unrecognized
     parameters are ignored.  dmMPEG1AudioEncoderSetParams(3dm) or
     dmMPEG1AudioDecoderSetParams(3dm) also initializes necessary filter
     coefficients for encoder/decoder so it has to be used before calling
     dmMPEG1AudioEncode(3dm) or dmMPEG1AudioDecode(3dm). For decoder, user
     defined parameters usually should be obtained first by using
     dmMPEG1AudioHeaderGetParams(3dm) from compressed data header.
     dmMPEG1AudioEncoderGetParams(3dm) or dmMPEG1AudioDecoderGetParams(3dm)
     obtains MPEG1 audio encoder or decoder parameters.

									Page 1

dmMPEG1AudioEncoderSetParams(3dm)	     dmMPEG1AudioEncoderSetParams(3dm)

     The set of parameters for params are, defined in dmedia/dm_audioutil.h
     and dmedia/dm_params.h are as follows

     Parameters for MPEG1 audio encoder and decoder:

     DM_AUDIO_RATE
     input/output sampling rate parameter (rate given in Hz).  The
     corresponding values for the rates are doubles. 32000, 44100 (default),
     and 48000 Hz are supported.

     DM_AUDIO_FORMAT
	  DM_AUDIO_TWOS_COMPLEMENT
     indicates the format of each input/ouput audio sample.
     DM_AUDIO_TWOS_COMPLEMENT is the only value supported.

     DM_AUDIO_WIDTH
	  DM_AUDIO_WIDTH_16
     indicates the width of each input/ouput audio sample.  DM_AUDIO_WIDTH_16
     is the only value supported.

     DM_AUDIO_CHANNELS
     passes the number of channels in the input/output audio data. Integer 1
     or 2 (default) are the only values supported.

     DM_MPEG1_AUDIO_LAYER
	  DM_MPEG1_AUDIO_LAYER1
	  DM_MPEG1_AUDIO_LAYER2	 (default)
     a flag specifying the basic algorithm to be used.

     DM_AUDIO_CHANNEL_POLICY
	  DM_AUDIO_STEREO
	  DM_AUDIO_JOINT_STEREO	 (default)
	  DM_AUDIO_INDEPENDENT
     chooses how multiple channels should be treaed.
     DM_AUDIO_STEREO indicates that the channels are part of a single
     multichannel signal. This includes quadrophonic, etc.;
     DM_AUDIO_JOINT_STEREO indicates that the algorithm may attempt to exploit
     redundancy between channels for greater coding gain;
     DM_AUDIO_INDEPENDENT indicates that the separate channels are unrelated
     and should be processed separately, such as multilingual sound tracks.

     DM_AUDIO_BITRATE
     specifies the desired bitrate for the compressed data, in bits per
     second. Note that for some schemes such as MPEG's maxrate this is treated
     as an upper limit, whereas for MPEG's fixrate, this is strictly achieved
     as a constant rate. The following is a list of valid bitrates for MPEG1

									Page 2

dmMPEG1AudioEncoderSetParams(3dm)	     dmMPEG1AudioEncoderSetParams(3dm)

     audio:
     Layer 1: 32000, 64000, 96000, 128000, 160000, 192000, 224000, 256000
     (default), 288000, 320000, 352000, 384000, 416000, and 448000.
     Layer 2: 32000, 48000, 56000, 64000, 80000, 96000, 112000, 128000,
     160000, 192000, 224000, 256000 (default), 320000, and 384000.

     Parameters for MPEG1 audio encoder only:

     DM_MPEG1_AUDIO_PSYCHOMODEL
	  DM_MPEG1_AUDIO_PSYCHOMODEL1
	  DM_MPEG1_AUDIO_PSYCHOMODEL2
     selects which psychoacoustic model is used to calculate the safe masking
     thresholds for quantizing noise (the basis of the compression).  The
     psychoacoustic model determines when quantization noise may be safely
     hidden below signal components.  The

     DM_MPEG1_AUDIO_PSYCHOMODEL1_ALPHA
     specifies possible float value for MPEG1 audio psychoacoustic model's
     alpha parameter (only for model 1).  Valid value is within (0.0, 2.0].
     Default is 2.0.

     DM_MPEG1_AUDIO_BITRATE_POLICY
	  DM_MPEG1_AUDIO_FIXRATE	(default)
	  DM_MPEG1_AUDIO_CONSTANT_QUALITY
     is a flag to select variants for interpreting DM_AUDIO_BIT_RATE.

     DM_MPEG1_AUDIO_CONST_QUAL_NMR
     The argument is the desired mask to noise ratio in dB. Possible float
     value for this parameter is within (-13.0, 13.0]. Default is 0.0.
     Positive (negative) values will make quantization noise more (less)
     audible and result in smaller (larger) compressed files.

     Parameters for MPEG1 audio decoder only:

     DM_MPEG1_AUDIO_DECIMATION_SCALE
	  DM_MPEG1_AUDIO_BANDWIDTH_FULL (default)
	  DM_MPEG1_AUDIO_BANDWIDTH_HALF
	  DM_MPEG1_AUDIO_BANDWIDTH_QUARTER
     specifies the decimation factor applied to reduced complexity of
     decoding. A value of fraction of DM_MPEG1_AUDIO_BANDWIDTH_HALF or
     DM_MPEG1_AUDIO_BANDWIDTH_QUARTER indicates that the resynthesized stream
     should be at one-half or one- quaner of the nominal sampling rate.	 A
     value of DM_MPEG1_AUDIO_BANDWIDTH_FULL results in normal behavior.

									Page 3

dmMPEG1AudioEncoderSetParams(3dm)	     dmMPEG1AudioEncoderSetParams(3dm)

     DM_MPEG1_AUDIO_SCALE_FILTERSHAPE
	  DM_MPEG1_AUDIO_DEFAULT_FILTER (default)
	  DM_MPEG1_AUDIO_FILTER_SHAPE1
	  DM_MPEG1_AUDIO_FILTER_SHAPE2
     specifies the filter shape applied to reduced complexity of decoding.   A
     value of DM_MPEG1_AUDIO_BANDWIDTH_FULL results in normal behavior.

     DM_MPEG1_AUDIO_COMBINE_CHANS_FLAG
     integer, default value is 0; if set to 1, it overwrites the JOINT_STEREO
     mode and force decoder to produce single channel output.

     Parameters for MPEG1 audio query only, using
     dmMPEG1AudioEncoderGetParams(3dm) or dmMPEG1AudioDecoderGetParams(3dm):

     DM_AUDIO_CODEC_FRAMES_PER_BLOCK
     specifies how many sample frames (integer) are put into each compressed
     data block.  For each call to dmMPEG1AudioEncode(3dm), this many new
     sample frames must be provided; each call to dmMPEG1AudioDecode(3dm),
     will return this many new sample frames.

     DM_AUDIO_CODEC_MAX_BYTES_PER_BLOCK
     indicates the maximum number of bytes (integer) that will comprise a
     compressed data block (representing frames per block sample frames). For
     compression, this is the size of the output buffer that must be provided
     to dmMPEG1AudioEncode(3dm); for decompression, this is the number of
     compressed bytes that must be queued up for dmMPEG1AudioDecode(3dm) to
     look at. Note that any particular block can be smaller than this; both
     dmMPEG1AudioEncode(3dm) and dmMPEG1AudioDecode(3dm) return the actual
     byte-size of the given block.

     DM_AUDIO_CODEC_FILTER_DELAY
     This is the number of sample fames (integer) of delay introduced in
     compression and decompression processing.	These numbers are usually
     different for compression versus decompression.  This is caused by filter
     operations that convolve a N past input samples with a filter M-
     coefficient array to create N+M-1 output samples.	The filtered signal
     contains more samples than the unfiltered signal. the output signal is
     offset by DM_AUDIO_CODEC_FILTER_DELAY samples from the first sample thus
     omits the last DM_AUDIO_CODEC_FILTER_DELAY samples from the output file.

NOTE
SEE ALSO
     dmMPEG1AudioEncoderCreate(3dm), dmMPEG1AudioEncode(3dm),
     dmMPEG1AudioDecoderCreate(3dm), dmMPEG1AudioDecode(3dm).

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