6 Example solution
06.113GPPSubstitution and muting of lost frames for full rate speech channelsTS
For guidance, an example solution is given.
The first lost speech frame is replaced at the speech decoder input by the previous good speech frame. Normal decoding is then performed.
The muting procedure to be used in the case of subsequent lost speech frames or for comfort noise frames following the second lost SID frame is as follows:
The pseudo‑logarithmic encoded block amplitude Xmaxcr (GSM 06.10 [2]), coded on the interval from 0 to 63, is decreased with a constant value d=4 in each frame, down to the lowest possible value. Consequently, Xmaxcr will be reduced gradually, and the output muted after a maximum of 320 ms. The grid position parameters are chosen randomly between 0 and 3 during this time.
For subsequent unusable frames, after the frame where Xmaxcr reached the lowest possible value, "silence frames" are passed from the RX DTX handler to the speech decoder to guarantee a low output level under all conditions. The silence frame is defined in table 1.
Table 1: Encoded parameters (GSM 06.10) of the silence frame
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Log area ratio 1 = 42 |
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Log area ratio 2 = 39 |
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Log area ratio 3 = 21 |
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Log area ratio 4 = 10 |
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Log area ratio 5 = 9 |
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Log area ratio 6 = 4 |
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Log area ratio 7 = 3 |
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Log area ratio 8 = 2 |
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LTP gain = 0 |
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LTP lag = 40 |
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Grid position = 1 |
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Block amplitude = 0 |
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RPE pulse no. 1 = 3 |
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RPE pulse no. 2 = 4 |
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RPE pulse no. 3 = 3 |
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RPE pulse no. 4 = 4 |
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RPE pulse no. 5 = 4 |
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‑ repeated for each subsegment |
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RPE pulse no. 6 = 3 |
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RPE pulse no. 7 = 3 |
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RPE pulse no. 8 = 3 |
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RPE pulse no. 9 = 3 |
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RPE pulse no. 10 = 4 |
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RPE pulse no. 11 = 4 |
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RPE pulse no. 12 = 3 |
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RPE pulse no. 13 = 3 _ |
Annex A (informative):
Change Request History
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Change history |
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SMG No. |
TDoc. No. |
CR. No. |
Clause affected |
New version |
Subject/Comments |
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SMG#07 |
4.0.4 |
ETSI Publication |
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SMG#20 |
5.0.1 |
Release 1996 version |
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SMG#27 |
6.0.0 |
Release 1997 version |
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SMG#28 |
6.0.1 |
ETSI Publication |
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SMG#29 |
7.0.0 |
Specification version 6.0.0 upgrade to Release 1998 version 7.0.0 |
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7.0.1 |
Version update for Publication |
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SMG#31 |
8.0.0 |
Release 1999 version |
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8.0.1 |
Update to Version 8.0.1 for Publication |
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