2 * WMA compatible decoder
3 * Copyright (c) 2002 The FFmpeg Project.
5 * This library is free software; you can redistribute it and/or
6 * modify it under the terms of the GNU Lesser General Public
7 * License as published by the Free Software Foundation; either
8 * version 2 of the License, or (at your option) any later version.
10 * This library is distributed in the hope that it will be useful,
11 * but WITHOUT ANY WARRANTY; without even the implied warranty of
12 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13 * Lesser General Public License for more details.
15 * You should have received a copy of the GNU Lesser General Public
16 * License along with this library; if not, write to the Free Software
17 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
24 /*these are the sin and cos rotations used by the MDCT*/
26 /*accessed too infrequently to give much speedup in IRAM*/
28 int32_t *tcosarray
[5], *tsinarray
[5];
29 int32_t tcos0
[1024], tcos1
[512], tcos2
[256], tcos3
[128], tcos4
[64];
30 int32_t tsin0
[1024], tsin1
[512], tsin2
[256], tsin3
[128], tsin4
[64];
32 uint16_t revtab0
[1024];
35 * init MDCT or IMDCT computation.
37 int ff_mdct_init(MDCTContext
*s
, int nbits
, int inverse
)
41 memset(s
, 0, sizeof(*s
));
42 n
= 1 << nbits
; /* nbits ranges from 12 to 8 inclusive */
46 s
->tcos
= tcosarray
[12-nbits
];
47 s
->tsin
= tsinarray
[12-nbits
];
50 int32_t ip
= itofix32(i
) + 0x2000;
53 /*I can't remember why this works, but it seems
54 to agree for ~24 bits, maybe more!*/
55 s
->tsin
[i
] = - fsincos(ip
<<16, &(s
->tcos
[i
]));
59 (&s
->fft
)->nbits
= nbits
-2;
60 (&s
->fft
)->inverse
= inverse
;
67 * Compute inverse MDCT of size N = 2^nbits
68 * @param output N samples
69 * @param input N/2 samples
70 * @param tmp N/2 samples
72 void ff_imdct_calc(MDCTContext
*s
,
76 int k
, n8
, n4
, n2
, n
, j
,scale
;
77 const int32_t *tcos
= s
->tcos
;
78 const int32_t *tsin
= s
->tsin
;
79 const int32_t *in1
, *in2
;
80 FFTComplex
*z1
= (FFTComplex
*)output
;
81 FFTComplex
*z2
= (FFTComplex
*)input
;
82 int revtabshift
= 12 - s
->nbits
;
94 for(k
= 0; k
< n4
; k
++)
96 j
=revtab0
[k
<<revtabshift
];
97 CMUL(&z1
[j
].re
, &z1
[j
].im
, *in2
, *in1
, tcos
[k
], tsin
[k
]);
102 scale
= fft_calc_unscaled(&s
->fft
, z1
);
104 /* post rotation + reordering */
105 for(k
= 0; k
< n4
; k
++)
107 CMUL(&z2
[k
].re
, &z2
[k
].im
, (z1
[k
].re
), (z1
[k
].im
), tcos
[k
], tsin
[k
]);
110 for(k
= 0; k
< n8
; k
++)
112 int32_t r1
,r2
,r3
,r4
,r1n
,r2n
,r3n
;
123 output
[n2
-1-2*k
] = r1
;
126 output
[n2
-1-2*k
-1] = r2n
;
128 output
[n2
+ 2*k
]= r3n
;
129 output
[n
-1- 2*k
]= r3n
;
131 output
[n2
+ 2*k
+1]= r4
;
132 output
[n
-2 - 2 * k
] = r4
;
138 int mdct_init_global(void)
142 /* although seemingly degenerate, these cannot actually be merged together without
143 a substantial increase in error which is unjustified by the tiny memory savings*/
145 tcosarray
[0] = tcos0
; tcosarray
[1] = tcos1
; tcosarray
[2] = tcos2
; tcosarray
[3] = tcos3
;tcosarray
[4] = tcos4
;
146 tsinarray
[0] = tsin0
; tsinarray
[1] = tsin1
; tsinarray
[2] = tsin2
; tsinarray
[3] = tsin3
;tsinarray
[4] = tsin4
;
148 /* init the MDCT bit reverse table here rather then in fft_init */
150 for(i
=0;i
<1024;i
++) /*hard coded to a 2048 bit rotation*/
151 { /*smaller sizes can reuse the largest*/
155 m
|= ((i
>> j
) & 1) << (10-j
-1);