US 7,065,491 B2Granted

Inverse-modified discrete cosine transform and overlap-add method and hardware structure for MPEG layer3 audio signal decoding

AssigneeNational Central University

InventorsTsung-Han Tsai, Ya-Chau Yang

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Abstract

An inverse-modified discrete cosine transform and overlap-add method, and hardware structure for MPEG Layer3 audio signal decoding. In order to have the MPEG Layer3 audio signal decoder have more competitive power in the consumer market, the present invention provides a low cost fast algorithm of the inverse-modified discrete cosine transform and overlap-add, so that the quantity of the operation needed in the decoding process can be significantly reduced to enhance the system performance. Afterwards, according to the fast algorithm, the present invention provides a hardware structure that is suitable for the inverse-modified discrete cosine transform and overlap-add in the MPEG Layer3 decoder. Since the hardware structure of the present invention makes the MPEG Layer3 decoder able to be implemented by the application specific integrated circuit (ASIC), the entire system can fulfill the low cost and high performance requirements.

Claims16

Dependent claims

A method for an inverse-modified discrete cosine transform and overlap-add for MPEG Layer3 audio signal decoding, comprising the steps of:

applying an operation of the inverse-modified discrete cosine transform and overlap-add according to equation (1) to 32 sub-band samples of a compressed audio signal, wherein the equation (1) includes an inverse-modified discrete cosine transform:
x
⁡
(
i
)
=
∑
k
=
0
n
2
-
1
⁢
X
⁡
(
k
)
*
cos
⁢
⁢
(
i
,
k
)
⁢
⁢
0
≤
i
≤
n
4
-
1
⁢
⁢
and
⁢
⁢
n
2
⁢
≤
i
≤
3
⁢
n
4
-
1
Wherein
cos
⁡
(
i
,
k
)
=
cos
⁡
(
π
2
⁢
n
⁢
(
2
⁢
i
+
1
+
n
2
)
⁢
(
2
⁢
k
+
1
)
)
,
for I and k=0 to n−1 and an overlap-add:
Z(i)=x(i)*win(i,p)
⁢
Z
⁢
⁢
(
n
2
-
1
-
i
)
=
-
x
⁡
(
i
)
*
win
⁢
⁢
(
n
2
-
1
-
i
,
p
)
⁢
⁢
0
≤
i
≤
n
4
-
1
⁢
Z(i)=x(i)*win(i,p)
⁢
Z
⁢
⁢
(
n
-
1
-
i
)
=
x
⁡
(
i
)
*
win
⁢
⁢
(
n
-
1
-
i
,
p
)
⁢
⁢
n
2
⁢
≤
i
≤
3
⁢
n
4
-
1
,
where X(k) is the sub-band sample, Z(i) is the sub-band sample after process, when a window type is 0, 1, 3, n equals 36, and when the window type is 2, n equals 12;
providing a dynamic window inverse-modified discrete cosine transform (DWIMDGT) module, wherein a multiplier-adder of the dynamic window inverse-modified discrete cosine transform module processes an operation of the inverse-modified discrete cosine transform, and an operation result of the inverse-modified discrete cosine transform is stored in a register stack of the dynamic window inverse-modified discrete cosine transform module;
and
using the multiplier-adder to operate the overlap-add operation, and an operation result of the overlap-add is stored in a dynamic window inverse-modified discrete cosine transform buffer memory.

187 more elements

A hardware structure of an inverse-modified discrete cosine transform and an overlap-add for MPEG Layer3 audio signal decoding, comprising:

a dynamic window inverse-modified discrete cosine transform module, comprising:
a multiplier-adder, used to calculate the inverse-modified discrete cosine transform and the overlap-add;
and
a register stack, coupled to the multiplier-adder, used to store an operation result of the inverse-modified discrete cosine transform;
and
a dynamic window inverse-modified discrete cosine transform buffer memory, coupled to the dynamic window inverse-modified discrete cosine transform module, used to store an operation result of the overlap-add.

3 more elements

Dependencies are inferred from the claim text.