FreeCalypso > hg > gsm-codec-lib
view libtwamr/inv_sqrt.h @ 477:4c9222d95647
libtwamr encoder: always emit frame->mode = mode;
In the original implementation of amr_encode_frame(), the 'mode' member
of the output struct was set to 0xFF if the output frame type is TX_NO_DATA.
This design was made to mimic the mode field (16-bit word) being set to
0xFFFF (or -1) in 3GPP test sequence format - but nothing actually depends
on this struct member being set in any way, and amr_frame_to_tseq()
generates the needed 0xFFFF on its own, based on frame->type being equal
to TX_NO_DATA.
It is simpler and more efficient to always set frame->mode to the actual
encoding mode in amr_encode_frame(), and this new behavior has already
been documented in doc/AMR-library-API description in anticipation of
the present change.
| author | Mychaela Falconia <falcon@freecalypso.org> |
|---|---|
| date | Sat, 18 May 2024 22:30:42 +0000 |
| parents | 54f6bc41ed10 |
| children |
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/* ******************************************************************************** * * GSM AMR-NB speech codec R98 Version 7.6.0 December 12, 2001 * R99 Version 3.3.0 * REL-4 Version 4.1.0 * ******************************************************************************** * * File : inv_sqrt.h * Purpose : Computes 1/sqrt(L_x), where L_x is positive. * : If L_x is negative or zero, the result is * : 1 (3fff ffff). * Description : The function 1/sqrt(L_x) is approximated by a table * : and linear interpolation. The inverse square root is * : computed using the following steps: * 1- Normalization of L_x. * 2- If (30-exponent) is even then shift right once. * 3- exponent = (30-exponent)/2 +1 * 4- i = bit25-b31 of L_x; 16<=i<=63 because of normalization. * 5- a = bit10-b24 * 6- i -=16 * 7- L_y = table[i]<<16 - (table[i] - table[i+1]) * a * 2 * 8- L_y >>= exponent * ******************************************************************************** */ #ifndef inv_sqrt_h #define inv_sqrt_h "$Id $" /* ******************************************************************************** * INCLUDE FILES ******************************************************************************** */ #include "typedef.h" /* ******************************************************************************** * DEFINITION OF DATA TYPES ******************************************************************************** */ /* ******************************************************************************** * DECLARATION OF PROTOTYPES ******************************************************************************** */ Word32 Inv_sqrt ( /* (o) : output value (range: 0<=val<1) */ Word32 L_x /* (i) : input value (range: 0<=val<=7fffffff) */ ); #endif