文件列表:

lpc_burg_filter.m (482, 2008-08-25)
lpc_burg_filter_opt65.dll (24576, 2008-08-25)
lpc_burg_filter_opt.m (154, 2008-08-25)
lpc_burg_filter_opt.mexw32 (25088, 2008-08-25)
muquant.m (757, 2010-07-05)
quant.m (517, 2008-08-25)
adpcm.m (2909, 2008-08-25)
entropy.m (672, 2010-07-07)
lpc_burg.m (967, 2008-08-25)

The ADPCM package is a flexible simulation tool for an adaptive differential encoder and decoder with backward predictor adaptation. It uses an LP-based (Burg) adaptive predictor and a nonuniform quantizer with mu transfer function. It generates the encoded bitstream and estimates the efficiency of a Huffman code for the compressed sequence. The main function is adpcm. The typical command is: pred.order = 1; quant.steps = 16; quant.mu = 20; s = adpcm(x,pred,quant); this will return a structure s with encoded data (it takes few minutes to compute). The first three lines set up compression parameters. These may have different values, affecting the obtained compression ratio and the distortion. To get the idea on the compression gain, type: entropy(s.data) To decode the audio and listen to it, type: y = adpcm(s); Try different settings of the encoder and quantizer, observe, how the audio quality and the entropy depend on these settings. To measure the speech quality call: snr(x,y)

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