请问一下在dsp中u-law,具体一点,
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请问一下在dsp中u-law,具体一点,
请问一下在dsp中u-law,具体一点,
请问一下在dsp中u-law,具体一点,
A-law and u-law are companding schemes used in telephone network to get more dynamics to the 8 bit samples that is available with linear coding.
the u-LAW used in North America and Japan,and the A-LAW used in Europe and the rest of the world and international routes
U-LAW和A-LAW主要应用于通信网中TC单元的DSP芯片,是实现基于8bit的TDM时隙的语音数据编解码的算法,目前主要作GSM基站系统BSS和NSS核心网之间1:4的带宽转换,两种算法实现的作用基本相同,只不过u-law主要应用于美国和日本,a-law主要应用于欧洲以及世界其他国家.
以下是两种算法的算式,具体想了解的话可以去查阅相关的资料.
u-law definition
u-LAW (pronounced mu-LAW) is
sgn(m) ( |m |) |m |
y= ------- ln( 1+ u|--|) |--| =< 1
ln(1+u) ( |mp|) |mp|
Another definition for mu-law I have seen
ln(1+255 |x|)
output = sgn(x) ---------------------
ln(1+255)
x = normalized input ( between -1 and 1)
255 = compression parameter
sgn(x) = sign (+/-) of x
a-law definition
A-LAW is
| A (m ) |m | 1
| ------- (--) |--| =< -
| 1+ln A (mp) |mp| A
y=|
| sgn(m) ( |m |) 1 |m |
| ------ ( 1+ ln A|--|) - =< |--| =< 1
| 1+ln A ( |mp|) A |mp|
Values of u=100 and 255,A=87.6,mp is the Peak message value,m is the current quantised message value.(The formulae get simpler if you substitute x for m/mp and sgn(x) for sgn(m); then -1