aifcresample(1) aifcresample(1) NAME aifcresample - perform sampling rate conversion on an AIFF-C file SYNOPSIS aifcresample [options] -rate rate infile.aifc outfile.aifc OPTIONS -rate rate specifies the sampling rate for the output file outfile.aifc. The value rate must be one of the following (sample frames per second): 8000 11025 16000 22050 32000 44100 48000 The sampling rate specified for the output file must be different from the sampling rate of the input file. -dynamic decibels specifies the minimum attenuation (in decibels) of the alias/image artifacts generated by the sampling rate conversion. The loss in dynamic range due to the rate conversion process will be no worse than this value. The value for decibels must be one of: 78, 96, or 120. Default value is 96. A higher value for decibels gives higher quality rate conversion. -taper bandwidth specifies the percentage of the final bandwidth tapered off. A smaller percentage of tapered bandwidth corresponds to a greater high frequency content. Conversions to low sampling rates should use higher values for bandwidth. The value for bandwidth must be chosen from: 1, 10, or 20. Default value is 10. A lower value for bandwidth gives higher quality rate conversion. -verbose causes the program to print out messages periodically which indicate how much of the data in the original file has been converted. DESCRIPTION aifcresample is a command-line program which reads an AIFF-C (or AIFF) digital audio input file, converts the audio data to new sampling rate, and writes out a new AIFF-C file containing the resampled data. aifcresample uses high-quality rate conversion algorithms with linear phase filters to perform resampling between any two of the following rates: 8000, 11025, 16000, 22050, 32000, 44100, 48000 sample frames per second (or Hz). The speed of the rate conversion algorithm depends on the values specified for bandwidth, decibels, and the original and new sampling rates. If the input AIFF-C file parses correctly, and the output file is written with no errors, aifcresample returns 0. If there is an error, aifcresample returns 1. The AIFF-C file format specification is published by Apple Computer Inc. NOTES Files converted using decibels set to 96 and bandwidth set to 10 will sound most excellent. For the highest quality conversion algorithm, however, you can set decibels to 120 and bandwidth to 1. By decreasing decibels and increasing bandwidth, you increase the speed of the rate conversion at a loss of high frequency response. The following table shows the relationships between the bandwidth parameter, and the pass band ripple: bandwidth % final passband parameter bandwidth ripple tapered 20 20% +/- 0.05 dB 10 10% +/- 0.05 dB 1 1% +/- 0.0005 dB BUGS Due to convolution remnants at the beginning of the output file's audio data, there may be some inaccuracy in rescaled loop points or markers. The leading convolution remnant may displace some valid audio data at the end of the file. The magnitude of this inaccuracy depends on the rate conversion bandwidth parameters and input and output sampling rates. aifcresample simply multiplies existing loop points by the ratio output/input sampling rate. AUTHOR Gints Klimanis and Scott Porter, Silicon Graphics Inc. SEE ALSO playaifc(1), recordaifc(1), aifc2aiff(1), aifccompress(1), aifcdecompress(1), dmconvert(1), mediaconvert(1) AIFF-C File Format Specification Page 3