Method for fast macroblock mode decision based on motion cost of variable block size
A method for fast macroblock mode decision is disclosed. The method includes: (A) determining if a motion cost at the origin (0, 0) or a prediction motion vector (PMV) for a 4n*4n macroblock is smaller than a first threshold; (B) if the motion cost is smaller than the first threshold, determining a macroblock mode as 4n*4n and ending the method; (C) if the motion cost is not smaller than the first threshold, using an adaptive diversity search strategy to perform motion estimation on four 2n*2n blocks associated with the 4n*4n macroblock; (D) determining if all motion costs of the four 2n*2n blocks in step (C) are smaller than a second threshold; and (E) if step (D) determines that the motion costs of the four 2n*2n blocks are smaller than the second threshold, determining the macroblock mode as 2n*2n and ending the method.
1. A method for fast macroblock mode decision, which is used in a frame encoder meeting H.264/MPEG-4 video coding standard, the method comprising:
(A) calculating a motion cost at the origin (0, 0) or a prediction motion vector (PMV) for a 4n*4n macroblock;
(B) deciding a macroblock mode as 4n*4n if the motion cost calculated in step (A) is smaller than a first threshold and ending the method;
(C) using an adaptive diversity search strategy to perform motion estimation on four 2n*2n blocks associated with the 4n*4n macroblock if the motion cost calculated in step (A) is greater than or equal to the first threshold;
(D) calculating all motion costs of the four 2n*2n blocks;
(E) deciding the macroblock mode as 2n*2n if the motion costs of the four 2n*2n blocks calculated in step (D) are smaller than a second threshold;
(F) using a motion vector merge to perform the motion estimation on two 4n*2n blocks and two 2n*4n blocks associated with the 4n*4n macroblock when step (E) decides that any of the motion costs of the four 2n*2n blocks is greater than or equal to the second threshold;
(G) calculating a total motion cost of the two 4n*2n blocks and a total motion cost of the two 2n*4n blocks; and
(H) executing a sub-macroblock mode decision step when the two total motion costs calculated in step (0) are greater than the total motion cost of the four 2n*2n blocks,
wherein step (H) further comprises:
(H1) using a motion vector splitting to perform the motion estimation on two 2n*n blocks and two n*2n blocks associated with one of the four 2n*2n blocks,
(H2) calculating a total motion cost of the two 2n*n blocks and a total motion cost of the two n*2n blocks,
(H3) deciding the macroblock mode as 2n*2n when the total motion cost of the two 2n*n blocks and the total motion cost of the two n*2n blocks calculated in step (H2) are greater than the motion cost of the 2n*2n block, and
(H4) returning to step (H1) for execution until the four 2n*2n blocks are processed completely.
2. The method as claimed in claim 1 , further comprising:
(I) using the motion vector merge to perform the motion estimation on the 4n*4n macroblock if either the total motion cost of the two 4n*2n blocks or the total motion cost of the two 2n*4n blocks calculated in step (G) is smaller than or equal to the total motion cost of the four 2n*2n blocks; and
(J) selecting one with a minimum motion cost from the 4n*4n macroblock, the two 4n*2n blocks and the 2n*4n blocks as the macroblock mode, and ending the method.
3. The method as claimed in claim 1 , further comprises:
(H5) using the motion vector splitting to perform the motion estimation on four n*n blocks associated with one of the four 2n*2n blocks if either the total motion cost of the two 2n*n blocks or the total motion cost of the two n*2n blocks calculated in step (112) is smaller than or equal to the motion cost of the 2n*2n block;
(H6) selecting one with a minimum motion cost from the four n*n blocks, the two 2n*n blocks and the two n*2n blocks as the macroblock mode; and
(H7) returning to step (H1) for execution until the four 2n*2n blocks are processed completely.
4. The method as claimed in claim 1 , wherein n is a positive integer.
5. The method as claimed in claim 1 , wherein n equals to four.
6. The method as claimed in claim 1 , wherein the motion cost is represented by an equation J(m,λ motion )=SAD(s,c(m))+λ motion ·R(m−p), where m(m x , m y ) T indicates a motion vector (MV), p=(p x , p y ) T indicates a prediction motion vector (PMV), R(m−p) is a motion vector information, and λ motion =(0.85·2 QP/3 ) 1/2 that is a correction factor.
7. The method as claimed in claim 1 , wherein the first threshold is represented by an equation
TH
16
*
16
=
min
i
∈
{
i
❘
1
≤
i
≤
20
,
MBi
with
mode
16
*
16
}
[
cost
(
MBi
)
]
+
Δ
TH
16
*
16
.
8. The method as claimed in claim 7 , wherein ΔTH 16*16 =600.
9. The method as claimed in claim 1 , wherein the second threshold is represented by an equation
TH
8
*
8
=
min
i
∈
{
i
1
≤
i
≤
20
,
Sub
-
MBi
with
mode
8
*
8
}
[
cost
(
Sub
-
MBi
)
]
+
Δ
TH
8
*
8
.
10. The method as claimed in claim 9 , wherein ΔTH 8*8 =150.
11. The method as claimed in claim 1 , wherein in step (B), a motion vector of the macroblock is the origin (0, 0) or the prediction motion vector.
12. The method as claimed in claim 1 , wherein in step (E), a motion vector of the macroblock is a motion vector obtained by the adaptive diversity search strategy.
13. A method for fast macroblock mode decision, which is used in a frame encoder meeting H.264/MPEG-4 video coding standard, the method comprising:
(A) determining if a motion cost at the origin (0, 0) or a prediction motion vector (PMV) for a 4n*4n macroblock is smaller than a first threshold;
(B) if the motion cost is smaller than the first threshold, deciding a macroblock mode as 4n*4n and ending the method;
(C) if the motion cost is greater than or equal to the first threshold, using an adaptive diversity search strategy to perform motion estimation on four 2n*2n blocks associated with the 4n*4n macroblock;
(D) determining if all motion costs of the four 2n*2n blocks in step (C) are smaller than a second threshold;
(E) if step (D) decides that the motion costs of the four 2n*2n blocks are smaller than the second threshold, choosing the macroblock mode as 2n*2n and ending the method;
(F) when step (D) decides that any of the motion costs of the four 2n*2n blocks is greater than or equal to the second threshold, using a motion vector merge to perform the motion estimation on two 4n*2n blocks and two 2n*4n blocks associated with the 4n*4n macroblock;
(G) determining if a total motion cost of the two 4n*2n blocks and a total motion cost of the two 2n*4n blocks are greater than a total motion cost of the four 2n*2n blocks; and
(H) when step (G) decides that the two total motion costs are greater than the total motion cost of the four 2n*2n blocks, executing a sub-macroblock mode decision step which contains,
wherein step (H) further comprises:
(H1) using a motion vector splitting to perform the motion estimation on two 2n*n blocks and two n*2n blocks associated with one of the four 2n*2n blocks,
(H2) determining if a total motion cost of the two 2n*n blocks and a total motion cost of the two n*2n blocks are greater than a motion cost of the 2n*2n block,
(H3) when sty (H2) decides that the total motion cost of the two 2n*n blocks and the total motion cost of the two n*2n blocks are greater than the motion cost of the 2n*2n block, choosing the macroblock mode as 2n*2n, and
(H4) returning to step (H1) for execution until the four 2n*2n blocks are processed completely.
14. The method as claimed in claim 13 , further comprising:
(I) if step (G) decides that either the total motion cost of the two 4n*2n blocks or the total motion cost of the two 2n*4n blocks is smaller than or equal to the total motion cost of the four 2n*2n blocks, using the motion vector merge to perform the motion estimation on the 4n*4n macroblock; and
(J) selecting one with a minimum motion cost from the 4n*4n macroblock, the two 4n*2n blocks and the 2n*4n blocks as the macroblock mode, and ending the method.
15. The method as claimed in claim 13 , further comprises:
(H5) if step (H2) decides that either the total motion cost of the two 2n*n blocks or the total motion cost of the two n*2n blocks is smaller than or equal to the motion cost of the 2n*2n block, using the motion vector splitting to perform the motion estimation on four n*n blocks associated with one of the four 2n*2n blocks;
(H6) selecting one with a minimum motion cost from the four n*n blocks, the two 2n*n blocks and the two n*2n blocks as the macroblock mode; and
(H7) returning to step (H1) for execution until the four 2n*2n blocks are processed completely.
16. The method as claimed in claim 13 , wherein the motion cost is represented by an equation J(m,λ motion )=SAD(s,c(m))+λ motion ·R(m−p), where m(m x , m y ) T indicates a motion vector (MV), p=(p x , p y ) T indicates a prediction motion vector (PMV), R(m−p) is a motion vector information, and λ motion =(0.85·2 QP/3 ) 1/2 that is a correction factor.
17. The method as claimed in claim 13 , wherein the first threshold is represented by an equation
TH
16
*
16
=
min
i
∈
{
i
1
≤
i
≤
20
,
MBi
with
mode
16
*
16
}
[
cost
(
MBi
)
]
+
Δ
TH
16
*
16
.
18. The method as claimed in claim 17 , wherein ΔTH 16*16 =600.
19. The method as claimed in claim 13 , wherein the second threshold is represented by an equation
TH
8
*
8
=
min
i
∈
{
i
1
≤
i
≤
20
,
Sub
-
MBi
with
mode
8
*
8
}
[
cost
(
Sub
-
MBi
)
]
+
Δ
TH
8
*
8
.
20. The method as claimed in claim 19 , wherein ΔTH 8*8 =150.