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1994年以前的speech coder的小结

-------------------------------speech coding before 1994----------------------------------------

speech quality is claissified into four general categories: 【程序编程相关:典型Datagrid分页、排序、删除代码】

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2)toll or network (200-3200hz)--above 16 kbits/s 【扩展信息:未来的生物能学利用】

1)broadcast--above 64 kbits/s

3)communication--above 4.0 kbits/s

4)synthetic--below 4.0 kbits/s

object mesurement:

1)signal-to-noise (snr)

2)segmental snr (segsnr)

3)articulation index

4)log spectral distance

5)the euclidean distance

subjective mesurement:

diagnostic rhyme test(drt)--an intelligiblity measure where the subject´s task is to recognize one of two possible words in a

set of rhyming pairs.

diagnostic aceptablitity mesure(dam)--based on results of test methods evaluating the quality of a communication system based

on teh acceptableility of speech as perceived by trained normative listener.

mean opinion score(mos)--involves 12 to 24 listeners who are instructed to rate phonetically balanced records according to a

five-level quality scale.

waveform coders:

a.scalar and vector quantization

1)scalar quantization

pulse-code modulation(pcm)--a memoryless proces that quantizes amplitudes by rounding off each sample to one of a set of

discrete values.

adaptive pcm(apcm)--uniform quantizer. step size is estimated from past coded speech samples.(a 7-bit log quantizer for

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