aifccompress(1)
aifccompress - compress the audio data in an AIFF-C file
As shipped in IRIX 6.5.7. Unchanged since IRIX 6.5.
NAME aifccompress - compress the audio data in an AIFF-C file SYNOPSIS aifccompress [-v] [-c algorithm] [options] infile.aifc outfile.aifc DESCRIPTION aifccompress is a command-line program which reads an AIFF-C digital audio input file, and copies the header information and sample data to a compressed AIFF-C digital audio output file. The output file will contain copies of all the AIFF-C chunks in the original input file. The chunks may not appear in exactly the same order as in the original file. aiffccompress offers compression algorithms which are supported by the SGI audio file library. They are selected with the -c option. Be sure to audition to the results before deleting the original sound file. Note that a signal will degrade with each compression/decompression cycle. Sound files may have already been subjected to multiple lossy compressions before they reach your hands. Your next compression may degrade the signal intolerably. Keep in mind that signal processing operations such as frequency equalization and reverberation that modify frequency or phase characteristics may expose the previously masked (inaudible) heavily quantized portions of the compressed signal when the significant but mildly quantized portions of the signal are removed or relatively attenuated. none No compression. This is the default. g722 CCITT G.722 ADPCM 4:1 compression recommended for 16-kHz, 16- bit mono or stereo data. The compression algorithm currently cannot handle more than two channels. This algorithm is lossy. ulaw CCITT G.711 mu-law 2:1 compression recommended for 8-kHz, 16- bit (mono or multichannel) data. This algorithm is lossy. alaw CCITT G.711 A-law 2:1 compression recommended for 8-kHz, 16-bit (mono or multichannel) data. This algorithm is lossy. awmpeg1 MPEG-1 audio layer 1. Supports single or dual channel 16-bit input at 32 kHz, 44.1 kHz, or 48 kHz. This algorithm is lossy. awmpeg2 MPEG-1 audio layer 2. Supports single or dual channel 16-bit input at 32 kHz, 44.1 kHz, or 48 kHz. This algorithm is lossy. awmulti Aware MultiRate near-lossless compression typically yielding compression ratios from 2:1 to 4:1. Supported for single or dual channel, 16 bit input at 8, 11.025, 16, 22.05, 32, 44.1, or 48 kHz. This algorithm is lossy. awlsls Aware MultiRate true lossless compression typically yielding compression ratios from 1.5:1 to 3:1. Supported for single or dual channel, 16 bit input at 8, 11.025, 16, 22.05, 32, 44.1, or 48 kHz. This algorithm is lossless. The MPEG and Aware MultiRate algorithms take the following additional options: -aw_chanpol chooses how multiple channels should be treated: stereo (default for MultiRate) indicates that the channels are part of a single multi- channel signal. This includes 4-channel, etc.; joint (default for MPEG) indicates that the algorithm may attempt to exploit redundancy between channels for greater coding gain; Not valid for MultiRate. indep indicates that the separate channels are unrelated and should be processed separately, such as multilingual sound tracks. Note that all of these settings are equivalent for single channel input. -aw_targ specifies the desired bitrate for all channels of compressed data, in bits per second. The following is a list of valid bitrates for MPEG. Layer 1: 32000, 64000, 96000, 128000, 160000, 192000, 224000, 256000, 288000, 320000, 352000, 384000, 416000, and 448000. Layer 2: 32000, 48000, 56000, 64000, 80000, 96000, 112000, 128000, 160000, 192000, 224000, 256000, 320000, and 384000. Default value is 192 kbps / channel for layer 1 and 128 kbps / channel for layer 2. This parameter is not used for Aware's MultiRate algorithm. -aw_bitpol Provides for different modes of bit assignment: The valid values depend on the algorithm, as indicated below. MPEG: fixed (default) Fixed bitrate per second. The Compression ratio is determined by value of -aw_targ. constqual Bitrate is driven by the psychoacoustic model. Enough bits are assigned so that a constant Mask to Noise ratio is attained. See -aw_nmr. Aware MultiRate: constqual Enough bits are assigned so that the signal is 90+ dB above the quantization noise. Compression ratios are typically between 2.5:1 and 4:1. lossless Enough bits are assigned to provide for perfect reconstruction. Compression ratios are typically between 2:1 and 3:1. -aw_nmr Not used in the Aware MultiRrate algorithm. For MPEG with - aw_bitpol constqual sets the constant quality mode noise-to- mask ratio in dB. 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. with no errors, aifccompress returns 0. If there is an error, aifccompress returns 1. If invoked with no arguments, aifccompress displays help. If the -v verbose option is specified, aifccompress periodically prints messages as sample data is copied from the input file to the output file. The AIFF and AIFF-C file format specifications are published by Apple Computer Inc. AUTHOR Silicon Graphics Inc. SEE ALSO playaifc(1), recordaifc(1), aiff2aifc(1), aifcdecompress(1), aifcresample(1), dmconvert(1), mediaconvert(1), MPEG(4), Aware(5) AIFF-C File Format Specification AFintro(3A), Introduction to the Audio File Library