ML7204-003 datasheet(45/214 Pages) LAPIS

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FEDL7204-003-02

ML7204-003

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B-2. G.729.A

 G.711 (-law and A-law) switching control (20 ms frame mode)

Figure 27 Speech CODEC Coding Format Switching Control Method on the

Receive Side G.729.A

G.711 <20 ms frame mode>

 G.729.A operation (before switching)

Operates according to the contents described in  Operation and  Error processing in Figure 19 G.729A

receive buffer method at single-channel operation (20 ms/frame mode).

 Switching processing

Switch the Speech CODEC coding format from G729.A to G.711 within the valid MCU write period

according to the setting in the Speech CODEC selection register on the receive side (RX_SCSEL[1:0]).

When receive data is written from the MCU in the frame from which the switching of the Speech CODEC

coding format has been detected, the LSI internal section performs decoding processing for the data of 10 ms

in the next frame. When receive data is not written from the MCU, the frame loss compensation processing

(BFI) that is specified in G.729.A is performed in the next frame; however, a receive error (RXERR_CH =

“1”) does not occur.

If a receive error occurred before this frame, that receive error is cleared to “0” at termination of this frame.

To avoid sudden transition from a voice state to a silent state, the function that gradually attenuates decoding

output (fade-out function) operates.

(Note)

If the coding format is switched outside of the valid MCU write period, the G.729.A

 G.711 switching

processing may be delayed by one frame. Therefore, check whether the receive request is for the receive

data encoded in the G.729.A or encoded in the G.711 by referencing the receive Speech CODEC operation

mode notification flag (RX_SCFLAG) when requesting reception due to the fall of FR1B.

 G.711 operation (after switching)

Operates according to the operation that is effective on and after the third receive request that is described in

 Operation and  Error processing in Figure 21 G.711 (

-law and A-law) receive buffer control method at

single-channel operation (20 ms/ frame mode).

To avoid a sudden transition from a silent state to a voice state, the function that gradually amplifies the

initial decoded output that was initially written from the MCU (fade-in function) operates.

FR1B

(Pin output)

MCU write

Valid write section

Speech

CODEC

DEC

OUT

20 ms

WE_SC7

R5(G.729.A)

R3(G.729.A)

Fade-out function valid period (*1)



G.729.A operation (before switching)



Switching processing



G.711 operation (after switching)

FR1

INTB

(Pin output)

Valid write section

MCU write

FR1B

(Pin output)

20 msec

WE_SC9

WE_SC11

WE_SC15

(*1) Fade-in/fade-out function valid period: Approx. 15 ms

FR1

INTB

(Pin output)

Silent

R11(G.711)

R9(G.711)

R11(G.711)

DEC

OUT

PLC_EN=1

PLC_EN=0

Speech

CODEC

G.729.A

G.711

Receive SC coding

format setting

RX_SCSEL[1:0]

G.729.A

G.711

Receive SC operation

mode notification

RX_SCFLAG

Approx. 20 ms

Silent

R9(G.711)

Approx. 23.75 ms

Fade-in function valid period (*1)

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