fractional powers of two used for requantization and joint stereo decoding root_table[3 + x] = 2^(x/4) */
| 353 | root_table[3 + x] = 2^(x/4) |
| 354 | */ |
| 355 | static inline mad_fixed_t root_table(int i) |
| 356 | { |
| 357 | static mad_fixed_t const root_table_val[7] PROGMEM = { |
| 358 | MAD_F(0x09837f05) /* 2^(-3/4) == 0.59460355750136 */, |
| 359 | MAD_F(0x0b504f33) /* 2^(-2/4) == 0.70710678118655 */, |
| 360 | MAD_F(0x0d744fcd) /* 2^(-1/4) == 0.84089641525371 */, |
| 361 | MAD_F(0x10000000) /* 2^( 0/4) == 1.00000000000000 */, |
| 362 | MAD_F(0x1306fe0a) /* 2^(+1/4) == 1.18920711500272 */, |
| 363 | MAD_F(0x16a09e66) /* 2^(+2/4) == 1.41421356237310 */, |
| 364 | MAD_F(0x1ae89f99) /* 2^(+3/4) == 1.68179283050743 */ |
| 365 | }; |
| 366 | volatile uint32_t a = *(uint32_t*)&root_table_val[i]; |
| 367 | return *(mad_fixed_t*)&a; |
| 368 | } |
| 369 | /* |
| 370 | coefficients for aliasing reduction |
| 371 | derived from Table B.9 of ISO/IEC 11172-3 |
no outgoing calls
no test coverage detected