System for transmitting compressed data if compression ratio is at least preset ratio and pre-compressed data if compression ratio is less than preset ratio

• US 5,805,932 A
• Filed: 02/13/1996
• Issued: 09/08/1998
• Est. Priority Date: 04/22/1994
• Status: Expired due to Term

• Current Assignee: Sony Corporation (Sony Group Corp.)
• Original Assignee: Sony Corporation (Sony Group Corp.)
• Inventors: Kawashima, Tetsuji, Inokuchi, Tatsuya
• Primary Examiner(s): Lee, Thomas C.
• Assistant Examiner(s): Chen, Anderson I.
• Application Number:
  US08/564,144
• Time in Patent Office: 938 Days
• Field of Search: 395/888, 395/427, 395/438, 360/48, 361/260.8
• US Class Current: 710/68
• CPC Class Codes: H03M 7/3088 employing the use of a dictionary, e.g. LZ78
• CPC Class Codes: H03M 7/48 alternating with other codes during the code conversion process, e.g. run-length coding being performed only as long as sufficientlylong runs of digits of the same kind are present

Abstract

A difference/compression ratio calculating means 76 in a data processing means 71 of a data transmitting apparatus according to the present invention calculates an actual difference and an actual compression ratio based on the data length of pre-compression data received from a data source 2 through pre-compression data receiving means 74 and the data length of compressed data outputted from a data compression circuit 67. If the actual difference is equal to or greater than a preset difference α and the actual compression ratio is equal to and greater than a preset compression ratio β, then the compressed data is transmitted to a data destination 3 through a transfer request data output means 79. Otherwise, the pre-compression data is transmitted to the data destination 3. With this arrangement, it is possible to prevent a phenomenon in which the size of compressed data which occupies a storage area in the data destination 3 is substantially the same as the size of uncompressed data which occupies the storage area, and also to avoid wasteful data expansion in the data destination 3.

Claims

1. An apparatus for transmitting data, comprising:

pre-compression data holding means for holding pre-compression data;

data compressing means for compressing the pre-compression data held by the pre-compression data holding means;

compressed data holding means for holding compressed data from the data compressing means;

decision means for determining data to be transmitted, based on data lengths of the pre-compression data and the compressed data and a preset condition; and

data transmitting means for transmitting either one of the pre-compression data held by the pre-compression data holding means and the compressed data held by the compressed data holding means, based upon decision results from the decision means, wherein the decision means carries out a decision process based on an actual compression ratio of the data length of the pre-compression data to the data length of the compressed data and a preset compression ratio outputs decision results indicating the data to be transmitted as the compressed data if the actual compression ratio is at least the preset compression ratio, and outputs decision results indicating the data to be transmitted as the pre-compression data if the actual compression ratio is smaller than the preset compression ratio.

2. An apparatus according to claim 1, wherein the decision means carries out a decision process based on an actual difference between the data lengths of the pre-compression data and the compressed data and a preset difference, outputs decision results indicating the data to be transmitted as the compressed data if the actual difference is at least the preset difference, and output decision results indicating the data to be transmitted as the pre-compression data if the actual difference is smaller than the preset difference.

3. An apparatus according to claim 1, wherein the decision means outputs decision results indicating the data to be transmitted as the compressed data if an actual difference between the data lengths of the pre-compression data and the compressed data is at least a preset difference and also if an actual compression ratio of the data length of the pre-compression data to the data length of the compressed data is at least a preset compression ratio, and outputs decision results indicating the data to be transmitted as the pre-compression data otherwise.

4. An apparatus according to claim 1, wherein the decision means determines whether an actual compression ratio of the data length of the pre-compression data to the data length of the compressed data satisfies either one of two preset conditions, outputs decision results indicating the data to be transmitted as the pre-compression data if the actual compression ratio satisfies one of the two conditions, and outputs decision results indicating the data to be transmitted as the compressed data if the actual compression ratio satisfies the other of the two conditions.

5. An apparatus according to claim 4, wherein the one of the two conditions is 0<

the actual compression ratio ε

<

β

(β

-1) and the other of the two conditions is the actual compression ratio ε

≦

β

(β

-1) where β

is a compression ratio to be expected when the pre-compression data is compressed.

6. An apparatus according to claim 2, further comprising preset value changing means for changing the preset compression ratio or the preset difference and the preset compression ratio and the preset difference to optional values.

7. An apparatus according to claim 1, wherein the pre-compression data comprises data supplied from an external source.

8. An apparatus according to claim 1, wherein the data transmitting means transmits the pre-compression data or the compressed data to data recording means for recording data on a recording medium.

9. An apparatus for transmitting data, comprising:

pre-compression data holding means for holding pre-compression data;

data compressing means for compressing the pre-compression data held by the pre-compression data holding means in units of a predetermined data length;

compressed data holding means for holding compressed data from the data compressing means;

decision means for determining data to be transmitted, based on a data length of partial compresses data produced by compressing a portion of the pre-compression data with the data compressing means, a data length of the portion of the pre-compression data, and a preset condition; and

data transmitting means for transmitting either one of the pre-compression data held by the pre-compression data holding means and the compressed data held by the compressed data holding means, based upon decision results from the decision means, wherein the decision means carries out a decision process based on a predicted compression ratio of the data length of the portion of the pre-compression data to the data length of the partial compressed data, and a preset compression ratio, outputs decision results indicating the data to be transmitted as the compressed data if the predicted compression ratio is at least the preset compression ratio, and outputs decision results indicating the data to be transmitted as the pre-compression data if the predicted compression ratio is smaller than the preset compression ratio.

10. An apparatus according to claim 9, further comprising data deleting means for successively deleting the pre-compression data compressed by the data compressing means.

11. An apparatus according to claim 9, wherein the data compressing means stops compressing the pre-compression data after the portion of the pre-compression data is compressed when the decision results from the decision means indicate the data to be transmitted as the pre-compression data.

12. An apparatus according to claim 9, further comprising weighting means for weighting the predicted compression ratio depending on the type of data.

13. An apparatus according to claim 9, further comprising preset value changing means for changing the preset compression ratio to an optional value.

14. An apparatus according to claim 9, wherein the pre-compression data comprises data supplied from an external source.

15. An apparatus according to claim 9, wherein the data transmitting means transmits the pre-compression data or the compressed data to data recording means for recording data on a recording medium.

16. A method for transmitting data, comprising the steps of:

determining data to be transmitted, based on a data length of a pre-compression data which is held, a data length of compressed data produced by compressing the pre-compression data and a preset condition; and

transmitting either one of the pre-compression data and the compressed data based upon decision results, wherein the step of determining is carried out based on an actual compression ratio of the data length of the pre-compression data to the data length of the compressed data and a preset compression ratio, and wherein the compressed data is transmitted if the actual compression ratio is at least the preset compression ratio, and the pre-compression data is transmitted if the actual compression ratio is smaller than the preset compression ratio.

17. A method according to claim 16, wherein the step of determining is carried out based on an actual difference between the data lengths of the pre-compression data and the compressed data and a preset difference, and wherein the compressed data is transmitted if the actual difference is at least the preset difference, and the pre-compression data is transmitted if the actual difference is smaller than the preset difference.

18. A method according to claim 16, wherein the the compressed data is transmitted if the decision results indicate that an actual difference between the data lengths of the pre-compression data and the compressed data is at least a preset difference and also that an actual compression ratio of the data length of the pre-compression data to the data length of the compressed data is at least a preset compression ratio, and the pre-compression data is transmitted otherwise.

19. A method according to claim 16, wherein the step of determining is carried out depending on whether an actual compression ratio of the data length of the pre-compression data to the data length of the compressed data satisfies either one of two preset conditions, and wherein the pre-compression data is transmitted if the actual compression ratio satisfies one of the two conditions, and the compressed data is transmitted if the actual compression ratio satisfies the other of the two conditions.

20. A method according to claim 19, wherein the one of the two conditions is 0<

the actual compression ratio ε

<

β

(β

-1) and the other of the two conditions is the actual compression ratio ε

≧

β

(β

-1) where β

is a compression ratio to be expected when the pre-compression data is compressed.

21. A method according to claim 17, wherein the preset compression ratio or the preset difference and the preset compression ratio and the preset difference can be changed to optional values.

22. A method according to claim 16, wherein the pre-compression data comprises data supplied from an external source.

23. A method according to claim 16, wherein the pre-compression data or the compressed data is transmitted to data recording means for recording data on a recording medium.

24. A method for transmitting data, comprising the steps of:

determining data to be transmitted, based on a data length of partial compressed data which is produced by compressing a portion of pre-compression data which is held, a data length of the portion of the pre-compression data, and a preset condition; and

transmitting either one of the pre-compression data and the compressed data based upon decision results, wherein the step of determining is carried out based on a predicted compression ratio of the data length of the portion of the pre-compression data to the data length of the partial compressed data, and a preset compression ratio, and wherein the compressed data is transmitted if the predicted compression ratio is at least the preset compression ratio, and the pre-compression data is transmitted if the Predicted compression ratio is smaller than the preset compression ratio.

25. A method according to claim 24, wherein the compressed portion of the pre-compression data is successively deleted.

26. A method according to claim 24, wherein the pre-compression data is not compressed after the portion of the pre-compression data is compressed when the decision results indicate that the data to be transmitted is the pre-compression data.

27. A method according to claim 24, wherein the predicted compression ratio is weighted depending on the type of data.

28. A method according to claim 24, wherein the preset compression ratio can be changed to an optional value.

29. A method according to claim 24, wherein the pre-compression data comprises data supplied from an external source.

30. A method according to claim 24, wherein the pre-compression data or the compressed data is transmitted to data recording means for recording data on a recording medium.