Method and device for retrieving data in low-power
A method and device for retrieving data in low-power is provided. More specifically, it relates to a method and device for minimizing power consumption while retrieving the continuous media data from a disk drive for the purpose of real-time playback. The data reproducing device reproduces multimedia data by a determined playback strategy after it computes power consumption values according to various playback strategies and retrieves data from a storage medium by a playback strategy having the least power consumption by means of comparing respective power consumption values.
1. A method for responding data in low-power, comprising the steps of:
computing a first power consumption according to Normal playback strategy and a second power consumption according to Full Buffering playback strategy before starting the reproduction of data;
determining a playback strategy having the least power consumption, by means of comparing the first power consumption according to the Normal playback strategy with the second power consumption according to the Full Buffering playback strategy;
retrieving data from a storage medium corresponding to the determined playback strategy; and
reproducing the retrieved data by the determined playback strategy only,
wherein the Normal playback strategy includes a start-up mode, a read mode, an idle mode, and a finish mode, and the Full Buffering playback strategy includes a start-up mode, a read node, and a finish mode.
2. The method of claim 1 , wherein the Full Buffering playback strategy in order to retrieve data from a storage medium in a round on a data reproducing device having a buffer, comprises the steps of:
a) performing a preceding operation for retrieving data when a reproducing command is inputted;
b) retrieving data from the storage medium;
c) sending the retrieved data to the buffer;
d) stopping retrieving data when the buffer becomes full;
e) executing spin down;
f) stopping rotating of a motor while the data filling the buffer are reproduced; and
g) requesting the reproducing command when the buffer becomes empty.
3. The method of claim 1 , wherein the Full Buffering playback strategy in order to retrieve data from a storage medium in a round on a data reproducing device having a buffer group comprising a plurality of buffers, comprises the steps of:
a) performing a preceding operation for retrieving data when a reproducing command is inputted;
b) retrieving data from the storage medium;
c) sending the retrieved data to a first buffer selected from the buffer group while the first buffer becomes full;
d) sending the retrieved data subsequently to any other buffer from the buffer group while the data filling the first buffer are reproduced;
e) executing spin down if all of buffers in the buffer group become full;
f) stopping rotating of a motor white an arbitrary buffer in the buffer group becomes empty; and
g) requesting the reproducing command when the arbitrary buffer in the buffer group becomes empty.
4. The method of claim 1 , wherein the first power consumption is computed by the formula as defined below:
P
N
=
P
s
+
P
f
+
α
(
B
*
R
-
r
+
Lr
-
B
r
)
where P N is power consumption according to the Normal playback strategy, P s is power consumption in the start-up mode, P f is power consumption in the finish mode, α is power consumption rate in the read mode, B* is buffer size, R is the maximum transfer rate from the storage medium, r is playback rate from the buffer, L is playback length, and B is data size retrieved during a round.
5. The method of claim 1 , wherein the second power consumption is computed by the formula as defined below:
P
P
=
Lr
B
*
R
R
-
r
E
(
P
s
+
P
f
+
α
B
*
R
-
r
)
+
(
P
s
+
P
f
+
αT
p
′
)
EI
where P p is power consumption according to the Full Buffering playback strategy, P s is power consumption in the start-up mode, P f is power consumption in the finish mode, α is power consumption rate in the read mode, B* is buffer size, R is the maximum transfer rate from the storage medium, r is playback rate from the buffer, L is playback length, T′ p is the length of active mode in the last round, and I is an index function which is 0if the surplus equals zero (0) when L by length of a round but 1 other wise.
6. The method of claim 2 , wherein, the data size retrieved from the storage medium during the round, B, in the step b) is computed by the formula as defined below:
B
=
{
T
p
ER
,
if
T
p
D
B
*
R
-
r
B
*
R
-
r
R
+
(
T
p
-
B
*
R
-
r
)
r
,
otherwise
where T P is the length of active mode in each round, R is to maximum transfer rate from the storage medium, r is playback rate from the buffer, and B* is buffer size.
7. The method of claim 3 , wherein, the data size retrieved front the storage medium during the round, B, in the step b) is computed by the formula as defined below:
B
=
{
T
p
E
R
,
if
T
p
D
B
*
R
-
r
B
*
R
-
r
R
+
(
T
p
-
B
*
R
-
r
)
r
,
otherwise
where T p is the length of active mode in each round, R is the maximum transfer rate from the storage medium, r is playback rate from the buffer, and B* is buffer size.
8. The method of claim 6 , wherein the data size retrieved during a single round B is greater than the minimum data size retrieved during a round capable of being reproduced in low-power, B min computed by the formula as defined below;
B
min
=
(
R
-
r
)
s
r
s
[
T
s
+
T
f
]
R
-
2
r
where R is the maximum transfer rate from the storage medium, r is playback rate from the buffer, T s is the length of star-up mode in each round, and T f is the length of finish mode in each round.
9. The method of claim 2 , further comprising the step of determining whether or not to merge a last round with any preceding round in a plurality of rounds.
10. The method of claim 3 , further comprising the step of determining whether or not to merge a last round with any preceding round in a plurality of rounds.
11. The method of claim 9 , wherein the result of determining whether or not to merge the last round in a plurality of rounds with its preceding round is indicated by the si P* of and computed by the formula as defined below:
P
*
=
P
s
+
P
f
+
α
B
1
R
-
α
B
1
r
where B 1 is the number of remaining data blocks retrieved in the last round.
12. The method of claim 11 , wherein the number of remaining data blocks retrieved in the last round, B 1 , is computed by the formula as defined below:
B
1
=
L
r
-
N
B
*
R
-
r
R
where L is playback length, r is playback rate from the buffer, N is the number of rounds of the same length B* is buffer size, and R is the maximum transfer rate from the storage medium.
13. The method of claim 9 , wherein the step of determining whether or not to merge the last round with any preceding round in a plurality of rounds, comprises the steps of;
counting the number of preceding rounds from the last round;
computing the split data size by means of dividing the data size retrieved during a round by the number of preceding rounds; and
retrieving data from the storage medium by merging the split amount of data with the preceding rounds, respectively.
14. A device for reproducing data in low-power, comprising;
a reading part for reading data from a storage medium;
a buffer for temporarily storing the data received from said reading part; and
an output part for reproducing the data stored in said buffer according to predetermined playback rate,
wherein said reading part reads the data from the storage medium according to a method comprising:
computing a first power consumption according to Normal playback strategy and a second power consumption according to Full Buffering playback strategy before starting the reproduction of data;
determining a playback strategy having the least power consumption, by means of comparing the first power consumption according to the Normal playback strategy with the second power consumption according to the Full Buffering playback strategy;
retrieving data from a storage medium corresponding to the determined playback strategy; and
reproducing the retrieved data by the determined playback strategy only,
wherein the Normal playback strategy includes a start-up mode, a read mode, an idle mode, and a finish mode, and the Full Buffering playback strategy includes a start-up mode, a read mode, and a finish mode.
15. A method for reproducing data stored in a storage medium in low-power, comprising the steps of:
a) performing a preceding operation for retrieving data when a reproducing command is inputted;
b) retrieving data from the storage medium;
e) sending the retrieved data to a buffer;
d) stopping the retrieving of data when the buffer becomes full;
e) executing spin down;
f) stopping rotating of a motor while the data filling the buffer are reproduced;
g) requesting the reproducing command when the buffer becomes empty; and
h) repeating steps a)–g) by the number of rounds when a plurality of rounds exist,
wherein in Full Buffering playback strategy as the method for reproducing data further comprises determining whether or not to merge the last round with any preceding round in a plurality of rounds.
16. The method of claim 15 , wherein the data size retrieved B, in the step b) is computed by the formula as defined below:
B
=
{
T
p
E
R
,
if
T
p
D
B
*
R
-
r
B
*
R
-
r
R
+
(
T
p
-
B
*
R
-
r
)
r
,
otherwise
where T p is the length of active mode in each round, R is the maximum transfer rate from the storage medium, r is playback rate from the buffer, and B* is buffer size.
17. The method of claim 16 , wherein the data size retrieved during a single round, B is greater than the minimum data size retrieved during a round capable of being reproduced in low-power, B min computed by the formula as defined below:
B
min
=
(
R
-
r
)
s
r
s
[
T
s
+
T
f
]
R
-
2
r
where R is the maximum transfer rate from the storage medium, r is playback rate from the buffer, B* is buffer size, T s is the length of start-up mode in each round, and T f is the length of finish mode in each round.
18. The method of claim 15 , wherein the power consumption according to the method for reproducing data is computed by the formula as defined below:
P
p
=
L
r
B
*
R
R
-
r
E
(
P
s
+
P
f
+
α
B
*
R
-
r
)
+
(
P
s
+
P
f
+
α
T
p
′
)
E
I
where P p is power consumption according to Full Buffering playback strategy, P s is power consumption in start-up mode, P f is power consumption in finish mode, α is power consumption rate in read mode, B* is buffer size, R is the maximum transfer rate from the storage medium, r is playback rate from the buffer, L is playback length, T′ p is the length of active mode in the last round, and I is an index function that is 0 if the surplus equals zero (0) when L is divided by length of a round but 1 otherwise.
19. The method of claim 15 wherein the result of determining whether or not to merge the last round in a plurality of rounds with its preceding round is indicated by the sign of P* and computed by the formula as defined below:
P
*
=
P
s
+
P
f
+
α
B
1
R
-
α
B
1
r
where B 1 is the number of remaining data blocks retrieved in the last round.
20. The method of claim 19 , wherein the number of remaining data blocks retrieved in the last round, B 1 , is computed by the formula as defined below:
B
1
=
L
r
-
N
B
*
R
-
r
R
where L is playback length r is playback rate from the buffer, N is the number of rounds of the same length, B* size, and R is the maximum transfer rate from the storage medium.
21. The method of claim 15 , wherein the step of determining whether or not to merge the last round with any preceding round in a plurality of rounds, comprises the steps of;
counting the number of preceding rounds from the last round;
computing the split data size by means of dividing the data size retrieved during a round by the number of preceding rounds; and
retrieving data from the storage medium by merging the split amount of data with the preceding rounds, respectively.
22. The method of claim 15 , wherein the method for reproducing data removes an idle mode by means of setting a time-out value as zero.
23. A device for reproducing data in low-power, comprising:
a reading part for reading data from a storage medium;
a buffer for temporarily storing the data received from said reading part; and
an output part for reproducing the data stored in said buffer according to a predetermined playback rate,
wherein said reading part reads the data from the storage medium according to a method comprising;
a) performing a preceding operation for retrieving data when a reproducing command is inputted;
b) retrieving data from the storage medium;
c) sending the retrieved data to a buffer;
d) stopping the retrieving of data when the buffer becomes full;
e) executing spin down;
f) stopping rotating of a motor while the data filling the buffer are reproduced;
g) requesting the reproducing command when the buffer becomes empty; and
h) repeating steps a)–g) by the number of rounds when a plurality of rounds exist,
wherein Full Buffering playback strategy as the method for reproducing data further comprises the step of determining whether or not to merge the last round with any preceding round in a plurality of rounds.