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78c89228
编写于
3月 12, 2015
作者:
N
Niels Möller
提交者:
Diego Biurrun
3月 12, 2015
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dca: Document the permuted order in the lfe_fir_64 and lfe_fir_128 tables
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b97f427f
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1
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1 changed file
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27 addition
and
1 deletion
+27
-1
libavcodec/dcadata.c
libavcodec/dcadata.c
+27
-1
未找到文件。
libavcodec/dcadata.c
浏览文件 @
78c89228
...
...
@@ -7295,7 +7295,21 @@ DECLARE_ALIGNED(16, const float, ff_dca_fir_32bands_nonperfect)[512] = {
+
1.390191784E-007
};
/* pre-scale lfe fir coefficients */
/* pre-scale lfe fir coefficients
*
* Permuted compared to table D.8 in the spec. First, the table in the
* spec has twice the number of coefficients, but they are reflected,
* T[i] = T[511 - i]. Furthermore, the indices are permuted, so that
*
* lfe_fir_64[8 * k + j] = T[64 * j + k]
*
* for 0 <= k < 32 and 0 <= j < 8. (This corresponds to adding a
* leading zero to the 8-bit index, and rotating it right by 3 bits
* as a 9-bit field). Values with j >= 4 can be reflected, as
*
* lfe_fir_64[8 * k + j] = T[64 * (7 - j) + (63 - k)]
*
* so all values in T get included. */
#define SCALE(c) ((c) / (256.0f * 32768.0f))
DECLARE_ALIGNED
(
16
,
const
float
,
ff_dca_lfe_fir_64
)[
256
]
=
{
SCALE
(
2.658434386830777e-4
),
SCALE
(
9.029330685734748e-3
),
...
...
@@ -7428,6 +7442,18 @@ DECLARE_ALIGNED(16, const float, ff_dca_lfe_fir_64)[256] = {
SCALE
(
3.165979683399200e-2
),
SCALE
(
1.527829794213176e-3
),
};
/* Permuted compared to table D.8 in the spec. First, the table in the
* spec has twice the number of coefficients, but they are reflected,
* T[i] = T[511 - i]. Furthermore, the indices are permuted, so that
*
* lfe_fir_128[4 * k + j] = T[128 * j + k]
*
* for 0 <= k < 64 and 0 <= j < 4. Values with j >= 2 can be
* reflected, as
*
* lfe_fir_128[4 * k + j] = T[128 * (3 - j) + (127 - k)]
*
* so all values in T get included. */
DECLARE_ALIGNED
(
16
,
const
float
,
ff_dca_lfe_fir_128
)[
256
]
=
{
SCALE
(
0
.
0005316
8571
),
SCALE
(
0
.
15878495574
),
SCALE
(
0
.
68603444099
),
SCALE
(
0
.
15492856503
),
SCALE
(
0
.
0001635
8691
),
SCALE
(
0
.
16269733012
),
SCALE
(
0
.
68591803312
),
SCALE
(
0
.
15112841129
),
...
...
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