參數(shù)資料
型號(hào)： MT9123AP
廠商： Mitel Networks Corporation
英文描述： CMOS Dual Voice Echo Canceller
中文描述： CMOS雙語(yǔ)音回聲消除器
文件頁(yè)數(shù)： 7/32頁(yè)
文件大小： 191K
代理商： MT9123AP
Preliminary Information
MT9123
8-51
NLPTHR
(hex)
= hex(NLPTHR
(dec)
* 32768)
where 0 < NLPTHR
(dec)
< 1
The comfort noise injection can be disabled by
setting the INJDis bit to 1 in Control Register 1.
It should be noted that the NLPTHR is valid and the
comfort noise injection is active only when the NLP is
enabled.
Narrow Band Signal Detector (NBSD)
Single or dual frequency tones (e.g. DTMF tones)
present in the reference input (Rin) of the echo
canceller for a prolonged period of time may cause
the adaptive filter to diverge. The Narrow Band
Signal Detector (NBSD) is designed to prevent this
divergence by detecting single or dual tones of
arbitrary frequency, phase, and amplitude. When
narrow band signals are detected, the adaptation
process is halted but the echo canceller continues to
cancel echo.
Controllerless Mode
The NBSD is always active and automatically
disables the filter adaptation process when narrow
band signals are detected.
Controller Mode
The NBSD can be disabled by setting the NBDis bit
to 1 in Control Register 2.
Offset Null Filter
Adaptive filters in general do not operate properly
when a DC offset is present on either the reference
signal (Rin) or the echo composite signal (Sin). To
remove
the
DC
component,
incorporates Offset Null filters in both Rin and Sin
inputs.
the
MT9123
Controllerless Mode
The Offset Null filters are always active.
Controller Mode
The offset null filters can be disabled by setting the
HPFDis bit to 1 in Control Register 2.
Echo Canceller Functional States
Each echo canceller has four functional states: Mute,
Bypass, Disable Adaptation and Enable Adaptation.
Mute:
The Mute state forces the echo canceller to
transmit quiet code and halts the filter adaptation
process.
In Normal configuration, the PCM output data on
Rout is replaced with the quiet code according to
the following table.
In Back-to-Back configuration, both echo cancellers
are combined to implement a full duplex echo
canceller. Therefore muting Echo Canceller A
causes quiet code to be transmitted on Rout, while
muting Echo Canceller B causes quiet code to be
transmitted on Sout.
In Extended Delay configuration, both echo
cancellers are cascaded to make one 128ms echo
canceller. In this configuration, muting Echo
Canceller A causes quiet code to be transmitted on
Rout.
Bypass:
The Bypass state directly transfers PCM codes from
Rin to Rout and from Sin to Sout. When Bypass state
is selected, the adaptive filter coefficients are reset
to zero.
Disable Adaptation:
When the Disable Adaptation state is selected, the
adaptive filter coefficients are frozen at their current
value. In this state, the adaptation process is halted
however the MT9123 continues to cancel echo.
Enable Adaptation:
In Enable Adaptation state, the adaptive filter
coefficients are continually updated. This allows
the echo canceller to model the echo return path
characteristics in order to cancel echo. This is the
normal operating state.
Controllerless Mode
The four functional states can be selected via S1,
S2, S3, and S4 pins as shown in the following table.
LINEAR
16 bits
2’s
complement
SIGN/
-Law
A-Law
MAGNITUDE
CCITT (G.711)
μ
-Law
A-Law
+Zero
(quiet code)
0000h
80h
FFh
D5h
Table 1 - Quiet PCM Code Assignment
相關(guān)PDF資料
PDF描述
MT9125AE CMOS Dual ADPCM Transcoder
MT9125AP CMOS Dual ADPCM Transcoder
MT9126AE CMOS Quad ADPCM Transcoder
MT9126AS CMOS Quad ADPCM Transcoder
MT9126 Quad ADPCM Transcoder(四ADPCM編解碼器)
相關(guān)代理商/技術(shù)參數(shù)
參數(shù)描述
MT9123AP1 制造商:Microsemi Corporation 功能描述:ECHO Canceller Chip 2-CH G.165/G.711 With Tone Detection 28-Pin PLCC Tube 制造商:Microsemi Corporation 功能描述:ECHO CANCELLER CHIP 2CH G.165/G.711 W/OUT TONE DETECTION 28P - Rail/Tube 制造商:MICROSEMI CONSUMER MEDICAL PRODUCT GROUP 功能描述:IC ECHO CANCELLER DUAL 28PLCC 制造商:Microsemi Corporation 功能描述:IC ECHO CANCELLER DUAL 28PLCC
MT9123APR1 制造商:Microsemi Corporation 功能描述:ECHO CANCELLER CHIP 2CH G.165/G.711 W/OUT TONE DETECTION 28P - Tape and Reel 制造商:Zarlink Semiconductor Inc 功能描述:ECHO CANCELLER CHIP 2CH G.165/G.711 W/OUT TONE DETECTION 28P - Tape and Reel
MT9125 制造商:MITEL 制造商全稱:Mitel Networks Corporation 功能描述:CMOS Dual ADPCM Transcoder
MT9125AE 制造商:MITEL 制造商全稱:Mitel Networks Corporation 功能描述:CMOS Dual ADPCM Transcoder
MT9125AP 制造商:MITEL 制造商全稱:Mitel Networks Corporation 功能描述:CMOS Dual ADPCM Transcoder
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