Compressed moving picture re-encoding apparatus and compressed moving picture re-encoding method

• US 6,915,018 B2
• Filed: 12/22/2000
• Issued: 07/05/2005
• Est. Priority Date: 12/24/1999
• Status: Active Grant

• Current Assignee: Rakuten Group, Inc.
• Original Assignee: NEC Corporation
• Inventors: Tajime, Junji
• Primary Examiner(s): Mehta, Bhavesh M.
• Assistant Examiner(s): AZARIAN, SEYED H
• Application Number:
  US09/742,113
• Publication Number:
  US 20010006562A1
• Time in Patent Office: 1,656 Days
• Field of Search: 382/232, 382/233, 382/235, 382/236, 382/248, 382/251, 382/253, 382/257, 382/260, 382/263, 382/274, 382/276, 382/277, 382/287, 382/291, 382/294, 382/305, 382/169, 382/250, 382/246, 382/247, 382/244, 382/238, 704/500, 341/61, 375/240.01, 375/240.03, 375/240.23, 375/240.2, 375/240.22, 375/240.15, 375/240.3, 375/224, 375/240.04, 708/203, 345/555, 348/384.1, 348/440, 348/27, 358/426.01, 380/212, 370/521
• US Class Current: 382/251
• CPC Class Codes: H04N 19/115 Selection of the code volume for a coding unit prior to coding
• CPC Class Codes: H04N 19/126 Details of normalisation or weighting functions, e.g. normalisation matrices or variable uniform quantisers
• CPC Class Codes: H04N 19/137 Motion inside a coding unit, e.g. average field, frame or block difference
• CPC Class Codes: H04N 19/14 Coding unit complexity, e.g. amount of activity or edge presence estimation H04N19/146 takes precedence
• CPC Class Codes: H04N 19/149 by estimating the code amount by means of a model, e.g. mathematical model or statistical model
• CPC Class Codes: H04N 19/15 by monitoring actual compressed data size at the memory before deciding storage at the transmission buffer
• CPC Class Codes: H04N 19/172 the region being a picture, frame or field
• CPC Class Codes: H04N 19/176 the region being a block, e.g. a macroblock
• CPC Class Codes: H04N 19/40 using video transcoding, i.e. partial or full decoding of a coded input stream followed by re-encoding of the decoded output stream
• CPC Class Codes: H04N 19/61 in combination with predictive coding
• CPC Class Codes: H04N 19/91 Entropy coding, e.g. variable length coding [VLC] or arithmetic coding

Abstract

To reduce a processing delay when re-encoding compressed moving pictures, and provide a compressed moving picture re-encoding apparatus with higher picture quality. Complexity measure computing unit computes respective complexity measures in two or more kinds of prescribed predetermined periods or numbers of pictures, using either or both of a quantizer step size and a number of bits of an input compressed moving picture stream. Also, picture group quantizer step size computing unit outputs a particular complexity measure from a plurality of complexity measures, and quantizer step size adjusting unit computes the quantizer step size using a pre-set average bit rate and the output complexity measure. Moreover, a quantizer step size selector that adjusts the quantizer step size every particular period according to a difference (excess or deficiency) between a target number of bits and an actual number of bits, computes the quantizer step size that is used in re-encoding, and performs rate control by taking the quantizer step size and the quantizer step size in the input compressed moving picture stream as input, and outputting the quantizer step size that is used in actual re-encoding. In this way, re-encoding is performed with a variable bit rate, and a compressed moving picture stream whose bit rate has been changed is output.

Claims

1. A compressed moving picture re-encoding apparatus comprising:

means to receive an input compressed moving picture stream, generated by a compression-encoding of moving picture data, as an input signal;

means for receiving said a pre-set average bit rate;

means for computing a quantizer step size that is to be in a re-encoding of said input compressed moving picture stream that would have said pre-set average bit rate;

means for inputting said computed quantizer step size and a quantizer step size in said input compressed moving picture stream and outputting a quantizer step size that is used in actual re-encoding;

means to perform said re-encoding at said pre-set average bit rate and at a variable bit rate; and

means to output said compressed moving picture stream whose bit rate has been changed.

44. The compressed moving picture re-encoding apparatus according to claim 1, wherein a minimum value is set for said quantizer step size that is used in re-encoding.

2. A compressed moving picture re-encoding apparatus comprising:

means to receive an input compressed moving picture stream, generated by a compression-encoding of moving picture data, as an input signal;

means for receiving said a pre-set average bit rate;

means for computing a quantizer step size that is used in a re-encoding of said input compressed moving picture stream that would have said pre-set average bit rate;

means for inputting said computed quantizer step size and a quantizer step size in said input compressed moving picture stream and outputting a quantizer step size that is used in actual re-encoding;

means for selecting a larger quantizer step size from said quantizer step size that is used in re-encoding and said quantizer step size in the input compressed moving picture stream;

means to perform said re-encoding at said pre-set average bit rate and at variable bit rate; and

means to output said compressed moving picture stream whose bit rate has been changed.

3. A compressed moving picture re-encoding apparatus comprising:

means to receive an input compressed moving picture stream, generated by a compression-encoding of moving picture data, as an input signal;

means for receiving a pre-set average bit rate;

means for computing a quantizer step size that is used in said re-encoding;

means for inputting said computed quantizer step size and a quantizer step size in said input compressed moving picture stream and outputting a quantizer step size that is used in actual re-encoding;

means for applying weighting, according to image characteristics, to the quantizer step size that is used in said re-encoding, and adjusting that quantizer step size;

means to perform said re-encoding at said pre-set average bit rate and at a variable bit rate; and

means to output said compressed moving picture stream whose bit rate has been changed.

4. A compressed moving picture re-encoding apparatus that has an input compressed moving picture stream, generated by a compression-encoding of moving picture data, as an input signal, performs re-encoding at a pre-set average bit rate and at a variable bit rate, and has an output compressed moving picture stream whose bit rate has been changed as an output signal, said compressed moving picture re-encoding apparatus comprising:

means for computing a quantizer step size that is used in said re-encoding;

means for inputting said computed quantizer step size and a quantizer step size in said input compressed moving picture stream and outputting a quantizer step size that is used in actual re-encoding;

means for applying weighting, according to image characteristics, to the quantizer step size that is used in said re-encoding, and adjusting that quantizer step size; and

means for computing a ratio of a complexity measure in a prescribed period or number of pictures to a complexity measure of an object of re-encoding, using either or both of the quantizer step size and a number of bits of said input compressed moving picture stream, performing weighting of said quantizer step size, and adjusting that quantizer step size.

5. A compressed moving picture re-encoding apparatus that has an input compressed moving picture stream, generated by a compression-encoding of moving picture data, as an input signal, performs re-encoding at a pre-set average bit rate and at a variable bit rate, and has an output compressed moving picture stream whose bit rate has been changed as an output signal, said compressed moving picture re-encoding apparatus comprising:

means for computing a quantizer step size that is used in said re-encoding;

means for inputting said computed quantizer step size and a quantizer step size in said input compressed moving picture stream and outputting a quantizer step size that is used in actual re-encoding; and

means for computing respective complexity measures in two or more kinds of prescribed periods or numbers of pictures, using either or both of the quantizer step size and the number of bits of said input compressed moving picture stream.

6. A compressed moving picture re-encoding apparatus that has an input compressed moving picture stream, generated by a compression-encoding of moving picture data, as an input signal, performs re-encoding at a pre-set average bit rate and at a variable bit rate, and has an output compressed moving picture stream whose bit rate has been changed as an output signal, said compressed moving picture re-encoding apparatus comprising:

means for computing a quantizer step size that is used in said re-encoding;

means for inputting said computed quantizer step size and a quantizer step size in said input compressed moving picture stream and outputting a quantizer step size that is used in actual re-encoding;

means for computing respective complexity measures in two or more kinds of prescribed periods or numbers of pictures, using either or both of the quantizer step size and a number of bits of said input compressed moving picture stream;

means for outputting a prescribed complexity measure from said complexity measures;

means for computing the quantizer step size using said pre-set average bit rate and said output complexity measure;

means for computing an average of respective quantizer step sizes every prescribed period or number of pictures, according to an encoding prediction mode of said input compressed moving picture stream, using the quantizer step size of said input compressed moving picture stream; and

means for computing an addition value for each encoding prediction mode, using said quantizer step size and said average quantizer step size, and computing an addition quantizer step size in which an addition value has been added to said input compressed moving picture stream quantizer step size,

wherein said addition quantizer step size is adjusted every prescribed period according to the difference (excess or deficiency) between a target number of bits and an actual number of bits, to give the quantizer step size that is used in re-encoding.

7. A compressed moving picture re-encoding apparatus that has an input compressed moving picture stream, generated by a compression-encoding of moving picture data, as an input signal, performs re-encoding at a pre-set average bit rate and at a variable bit rate, and has an output compressed moving picture stream whose bit rate has been changed as an output signal, said compressed moving picture re-encoding apparatus comprising:

means for computing a quantizer step size that is used in said re-encoding;

means for inputting said computed quantizer step size and a quantizer step size in said input compressed moving picture stream and outputting a quantizer step size that is used in actual re-encoding;

means for computing, by using a maximum bit rate among set bit rates and either or both of the quantizer step size and a number of bits of said input compressed moving picture stream, the maximum bit rate quantizer step size at said maximum bit rate; and

means for taking said maximum bit rate quantizer step size and the quantizer step size that is used in said re-encoding as input, and outputting the quantizer step size that is used in re-encoding.

42. The compressed moving picture re-encoding apparatus according to claim 7, wherein a threshold setting is made for a prescribed plurality of quantizer step sizes with respect to an addition quantizer step size.

8. A compressed moving picture re-encoding apparatus that has an input compressed moving picture stream, generated by a compression-encoding of moving picture data, as an input signal, performs re-encoding at a pre-set average bit rate and at a variable bit rate, and has an output compressed moving picture stream whose bit rate has been changed as an output signal, said compressed moving picture re-encoding apparatus comprising:

means for computing a quantizer step size that is used in said re-encoding;

means for inputting said computed quantizer step size and a quantizer step size in said input compressed moving picture stream and outputting a quantizer step size that is used in actual re-encoding;

means for computing respective complexity measures in two or more kinds of prescribed predetermined periods or numbers of pictures, using either or both of the quantizer step size and a number of bits in either of said input compressed moving picture stream or a re-encoded compressed moving picture stream; and

means for outputting a prescribed complexity measure from said complexity measures.

9. A compressed moving picture re-encoding apparatus that has an input compressed moving picture stream, generated by a compression-encoding of moving picture data, as an input signal, performs re-encoding at a pre-set average bit rate and at a variable bit rate, and has an output compressed moving picture stream whose bit rate has been changed as an output signal, said compressed moving picture re-encoding apparatus comprising:

means for computing a quantizer step size that is used in said re-encoding;

means for inputting said computed quantizer step size and a quantizer step size in said input compressed moving picture stream and outputting a quantizer step size that is used in actual re-encoding;

means for computing respective complexity measures in two or more kinds of prescribed predetermined periods or numbers of pictures, using either or both of the quantizer step size and a number of bits in either of said input compressed moving picture stream or a re-encoded compressed moving picture stream;

means for outputting a prescribed complexity measure from a plurality of said complexity measures; and

means for computing the quantizer step size using said pre-set average bit rate and said output complexity measure,

wherein said quantizer step size is adjusted every prescribed period according to a difference between a target number of bits and an actual number of bits, to give the quantizer step size that is used in said re-encoding.

20. The compressed moving picture re-encoding apparatus according to claim 9, further comprising:

means for applying weighting, according to image characteristics, to the quantizer step size of said input compressed moving picture stream used in said complexity measure computation, and adjusting that quantizer step size.

31. The compressed moving picture re-encoding apparatus according to claim 9, further comprising:

means for applying weighting, according to image characteristics, to the quantizer step size of said input compressed moving picture stream used in said complexity measure computation, and adjusting that quantizer step size; and

means for computing a ratio of respective complexity measures in a prescribed period or number of pictures to complexity measure of an object of re-encoding, using either or both of the quantizer step size and the number of bits of said input compressed moving picture stream, performing weighting of said quantizer step size, and adjusting that quantizer step size.

10. A compressed moving picture re-encoding apparatus that has an input compressed moving picture stream, generated by a compression-encoding of moving picture data, as an input signal, performs re-encoding at a pre-set average bit rate and at a variable bit rate, and has an output compressed moving picture stream whose bit rate has been changed as an output signal, said compressed moving picture re-encoding apparatus comprising:

means for computing a quantizer step size that is used in said re-encoding;

means for inputting said computed quantizer step size and a quantizer step size in said input compressed moving picture stream and outputting a quantizer step size that is used in actual re-encoding;

means for selecting a larger quantizer step size from said quantizer step size that is used in re-encoding and said quantizer step size in the input compressed moving picture stream;

means for computing respective complexity measures in two or more kinds of prescribed predetermined periods or numbers of pictures, using either or both of the quantizer step size and a number of bits in either of said input compressed moving picture stream or a re-encoded compressed moving picture stream;

means for outputting a prescribed complexity measure from a plurality of said complexity measures; and

means for computing said quantizer step size using said pre-set average bit rate and said output complexity measure;

wherein said quantizer step size is adjusted every prescribed period according to a difference between a target number of bits and an actual number of bits, to give the quantizer step size that is used in said re-encoding.

21. The compressed moving picture re-encoding apparatus according to claim 10, further comprising:

means for applying weighting, according to image characteristics, to the quantizer step size of said input compressed moving picture stream used in said complexity measure computation, and adjusting that quantizer step size.

32. The compressed moving picture re-encoding apparatus according to claim 10, further comprising:

means for applying weighting, according to image characteristics, to the quantizer step size of said input compressed moving picture stream used in said complexity measure computation, and adjusting that quantizer step size; and

means for computing a ratio of respective complexity measures in a prescribed period or number of pictures to a complexity measure of an object of re-encoding, using either or both of the quantizer step size and the number of bits of said input compressed moving picture stream, performing weighting of said quantizer step size, and adjusting that quantizer step size.

11. A compressed moving picture re-encoding apparatus that has an input compressed moving picture stream, generated by a compression-encoding of moving picture data, as an input signal, performs re-encoding at a pre-set average bit rate and at a variable bit rate, and has an output compressed moving picture stream whose bit rate has been changed as an output signal, said compressed moving picture re-encoding apparatus comprising:

means for computing a quantizer step size that is used in said re-encoding;

means for inputting said computed quantizer step size and a quantizer step size in said input compressed moving picture stream and outputting a quantizer step size that is used in actual re-encoding;

means for computing respective complexity measures in two or more kinds of prescribed predetermined periods or numbers of pictures, using either or both of the quantizer step size and a number of bits in either of said input compressed moving picture stream or a re-encoded compressed moving picture stream;

means for outputting a prescribed complexity measure from a plurality of said complexity measures; and

means for computing the quantizer step size using said pre-set average bit rate and said output complexity measure,

wherein said quantizer step size is adjusted every prescribed period according to a difference between a target number of bits and an actual number of bits, to give the quantizer step size that is used in said re-encoding, and

pictures from a picture re-encoded at a start of re-encoding to a picture immediately preceding that for which re-encoding is currently being performed, or a plurality of pictures including one image encoded within a frame, are used as a plurality of pictures used as said prescribed period or number of pictures.

22. The compressed moving picture re-encoding apparatus according to claim 11, further comprising:

means for applying weighting, according to image characteristics, to the quantizer step size of said input compressed moving picture stream used in said complexity measure computation, and adjusting that quantizer step size.

33. The compressed moving picture re-encoding apparatus according to claim 11, further comprising:

means for applying weighting, according to image characteristics, to the quantizer step size of said input compressed moving picture stream used in said complexity measure computation, and adjusting that quantizer step size; and

means for computing a ratio of respective complexity measures in a prescribed period or number of pictures to a complexity measure of an object of re-encoding, using either or both of the quantizer step size and the number of bits of said input compressed moving picture stream, performing weighting of said quantizer step size, and adjusting that quantizer step size.

12. A compressed moving picture re-encoding apparatus that has an input compressed moving picture stream, generated by a compression-encoding of moving picture data, as an input signal, performs re-encoding at a pre-set average bit rate and at a variable bit rate, and has an output compressed moving picture stream whose bit rate has been changed as an output signal, said compressed moving picture re-encoding apparatus comprising:

means for computing a quantizer step size that is used in said re-encoding;

means for inputting said computed quantizer step size and a quantizer step size in said input compressed moving picture stream and outputting a quantizer step size that is used in actual re-encoding;

means for computing respective complexity measures in two or more kinds of prescribed predetermined periods or numbers of pictures, using either or both of the quantizer step size and a number of bits in either of said input compressed moving picture stream or a re-enencoded compressed moving picture stream;

means for outputting a prescribed complexity measure from a plurality of said complexity measures; and

means for computing said quantizer step size using said pre-set average bit rate and said output complexity measure,

wherein said quantizer step size is adjusted every prescribed period according to a difference between a target number of bits and an actual number of bits, to give the quantizer step size that is used in said recording, and

pictures from a picture re-encoded at a start of re-encoding to a picture immediately preceding that for which re-encoding is currently being performed, or a plurality of pictures including one image re-encoded within a frame, are used as a plurality of pictures used as said prescribed period or number of pictures.

23. The compressed moving picture re-encoding apparatus according to claim 12, further comprising:

means for applying weighting, according to image characteristics, to the quantizer step size of said input compressed moving picture stream used in said complexity measure computation, and adjusting that quantizer step size.

34. The compressed moving picture re-encoding apparatus according to claim 12, further comprising:

means for applying weighting, according to image characteristics, to the quantizer step size of said input compressed moving picture stream used in said complexity measure computation, and adjusting that quantizer step size; and

means for computing a ratio of respective complexity measures in a prescribed period or number of pictures to a complexity measure of an object of re-encoding, using either or both of the quantizer step size and the number of bits of said input compressed moving picture stream, performing weighting of said quantizer step size, and adjusting that quantizer step size.

13. A compressed moving picture re-encoding apparatus that has an input compressed moving picture stream, generated by a compression-encoding of moving picture data, as an input signal, performs re-encoding at a pre-set average bit rate and at a variable bit rate, and has an output compressed moving picture stream whose bit rate has been changed as an output signal, said compressed moving picture re-encoding apparatus comprising:

means for computing a quantizer step size that is used in said re-encoding;

means for inputting said computed quantizer step size and a quantizer step size in said input compressed moving picture stream and outputting a quantizer step size that is used in actual re-encoding;

means for computing respective complexity measures in two or more kinds of prescribed predetermined periods or numbers of pictures, using either or both of the quantizer step size and a number of bits in either of said input compressed moving picture stream or a re-encoded compressed moving picture stream;

means for outputting a prescribed complexity measure from a plurality of said complexity measures; and

means for computing said quantizer step size using said pre-set average bit rate and said output complexity measure,

wherein said quantizer step size is adjusted every prescribed period according to a difference between a target number of bits and an actual number of bits, to give the quantizer step size that is used in said re-encoding, and

a group of blocks into which a picture is divided is used for said prescribed period for adjusting a base quantizer step size according to excess or deficiency with respect to said target number of bits.

24. The compressed moving picture re-encoding apparatus according to claim 13, further comprising:

means for applying weighting, according to image characteristics, to the quantizer step size of said input compressed moving picture stream used in said complexity measure computation, and adjusting that quantizer step size.

35. The compressed moving picture re-encoding apparatus according to claim 13, further comprising:

means for applying weighting, according to image characteristics, to the quantizer step size of said input compressed moving picture stream used in said complexity measure computation, and adjusting that quantizer step size; and

means for computing a ratio of respective complexity measures in a prescribed period or number of pictures to a complexity measure of an object of re-encoding, using either or both of the quantizer step size and a number of bits of said input compressed moving picture stream, performing weighting of said quantizer step size, and adjusting that quantizer step size.

14. A compressed moving picture re-encoding apparatus that has an input compressed moving picture stream, generated by a compression-encoding of moving picture data, as an input signal, performs re-encoding at a pre-set average bit rate and at a variable bit rate, and, has an output compressed moving picture stream whose bit rate has been changed as an output signal, said compressed moving picture re-encoding apparatus comprising:

means for computing a quantizer step size that is used in said re-encoding;

means for inputting said computed quantizer step size and a quantizer step size in said input compressed moving picture stream and outputting a quantizer step size that is used in actual re-encoding;

means for selecting a larger quantizer step size from said quantizer step size that is used in re-encoding and said quantizer step size in the input compressed moving picture stream;

means for computing respective complexity measures in two or more kinds of prescribed predetermined periods or numbers of pictures, using either or both of the quantizer step size and a number of bits in either of said input compressed moving picture stream or a re-encoded compressed moving picture stream;

means for outputting a prescribed complexity measure from a plurality of said complexity measures; and

means for computing said quantizer step size using said pre-set average bit rate and said output complexity measure,

wherein said quantizer step size is adjusted every prescribed period according to a difference between a target number of bits and an actual number of bits, to give the quantizer step size that is used in said re-encoding, and

a group of blocks into which a picture is divided is used for said prescribed period for adjusting a base quantizer step size according to excess or deficiency with respect to said target number of bits.

25. The compressed moving picture re-encoding apparatus according to claim 14, further comprising:

means for applying weighting, according to image characteristics, to the quantizer step size of said input compressed moving picture stream used in said complexity measure computation, and adjusting that quantizer step size.

36. The compressed moving picture re-encoding apparatus according to claim 14, further comprising:

means for applying weighting, according to image characteristics, to the quantizer step size of said input compressed moving picture stream used in said complexity measure computation, and adjusting that quantizer step size; and

means for computing a ratio of respective complexity measures in a prescribed period or number of pictures to a complexity measure of an object of re-encoding, using either or both of the quantizer step size and the number of bits of said input compressed moving picture stream, performing weighting of said quantizer step size, and adjusting that quantizer step size.

15. A compressed moving picture re-encoding apparatus that has an input compressed moving picture stream, generated by a compression-encoding of moving picture data, as an input signal, performs re-encoding at a pre-set average bit rate and at a variable bit rate, and has an output compressed moving picture stream whose bit rate has been changed as an output signal, said compressed moving picture re-encoding apparatus comprising:

means for computing a quantizer step size that is used in said re-encoding;

means for inputting said computed quantizer step size and a quantizer step size in said input compressed moving picture stream and outputting a quantizer step size that is used in actual re-encoding;

means for selecting a larger quantizer step size from said quantizer step size that is used in re-encoding and said quantizer step size in the input compressed moving picture stream;

means for computing respective complexity measures in two or more kinds of prescribed predetermined periods or numbers of pictures, using either or both of the quantizer step size and a number of bits in either of said input compressed moving picture stream or a re-encoded compressed moving picture stream;

means for outputting a prescribed complexity measure from a plurality of said complexity measures; and

means for computing said quantizer step size using said pre-set average bit rate and said output complexity measure,

wherein said quantizer step size is adjusted every prescribed period according to a difference between a target number of bits and an actual number of bits, to give the quantizer step size that is used in said re-encoding,

wherein a group of blocks into which a picture is divided is used for said prescribed period for adjusting a base quantizer step size according to excess or deficiency with respect to said target number of bits and pictures from a picture re-encoded at a start of re-encoding to a picture immediately preceding that for which re-encoding is currently being performed, or a plurality of pictures including one image encoded within a frame, are used as a plurality of pictures used as said prescribed period or number of pictures.

26. The compressed moving picture re-encoding apparatus according to claim 15, further comprising:

means for applying weighting, according to image characteristics, to the quantizer step size of said input compressed moving picture stream used in said complexity measure computation, and adjusting that quantizer step size.

37. The compressed moving picture re-encoding apparatus according to claim 15, further comprising:

means for applying weighting, according to image characteristics, to the quantizer step size of said input compressed moving picture stream used in said complexity measure computation, and adjusting that quantizer step size; and

means for computing a ratio of respective complexity measures in a prescribed period or number of pictures to a complexity measure of an object of re-encoding, using either or both of the quantizer step size and the number of bits of said input compressed moving picture stream, performing weighting of said quantizer step size, and adjusting that quantizer step size.

16. A compressed moving picture re-encoding apparatus that has an input compressed moving picture stream, generated by a compression-encoding of moving picture data, as an input signal, performs re-encoding at a pre-set average bit rate and at a variable bit rate, and has an output compressed moving picture stream whose bit rate has been changed as an output signal, said compressed moving picture re-encoding apparatus comprising:

means for computing a quantizer step size that is used in said re-encoding;

means for inputting said computed quantizer step size and a quantizer step size in said input compressed moving picture stream and outputting a quantizer step size that is used in actual re-encoding;

means for computing respective complexity measures in two or more kinds of prescribed predetermined periods or numbers of pictures, using either or both of the quantizer step size and a number of bits in either of said input compressed moving picture stream or a re-encoded compressed moving picture stream;

means for outputting a prescribed complexity measure from a plurality of said complexity measures; and

means for computing said quantizer step size using said pre-set average bit rate and said output complexity measure,

wherein said quantizer step size is adjusted every prescribed period according to a difference between a target number of bits and an actual number of bits, to give the quantizer step size that is used in said re-encoding,

a group of blocks into which a picture is divided is used for said prescribed period for adjusting a base quantizer step size according to excess or deficiency with respect to said target number of bits, and

pictures from a picture re-encoded at a start of re-encoding to a picture immediately preceding that for which re-encoding is currently being performed, or a plurality of pictures including one image re-encoded within a frame, are used as a plurality of pictures used as said prescribed period or number of pictures.

27. The compressed moving picture re-encoding apparatus according to claim 16, further comprising:

means for applying weighting, according to image characteristics, to the quantizer step size of said input compressed moving picture stream used in said complexity measure computation, and adjusting that quantizer step size.

38. The compressed moving picture re-encoding apparatus according to claim 16, further comprising:

means for applying weighting, according to image characteristics, to the quantizer step size of said input compressed moving picture stream used in said complexity measure computation, and adjusting that quantizer step size; and

means for computing a ratio of respective complexity measures in a prescribed period or number of pictures to a complexity measure of an object of re-encoding, using either or both of the quantizer step size and the number of bits of said input compressed moving picture stream, performing weighting of said quantizer step size, and adjusting that quantizer step size.

17. A compressed moving picture re-encoding apparatus that has an input compressed moving picture stream, generated by a compression-encoding of moving picture data, as an input signal, performs re-encoding at a pre-set average bit rate and at a variable bit rate, and has an output compressed moving picture stream whose bit rate has been changed as an output signal, said compressed moving picture re-encoding apparatus comprising:

means for computing a quantizer step size that is used in said re-encoding;

means for inputting said computed quantizer step size and a quantizer step size in said input compressed moving picture stream and outputting a quantizer step size that is used in actual re-encoding;

means for computing respective complexity measures in two or more kinds of prescribed predetermined periods or numbers of pictures, using either or both of the quantizer step size and a number of bits in either of said input compressed moving picture stream or a re-encoded compressed moving picture stream;

means for outputting a prescribed complexity measure from a plurality of said complexity measures;

means for computing said quantizer step size using said pre-set average bit rate and said output complexity measure, wherein said quantizer step size is adjusted every prescribed period according to the difference between the target number of bits and the actual number of bits, to give the quantizer step size that is used in said re-encoding; and

means for selecting a minimum complexity measure among said plurality of complexity measures.

28. The compressed moving picture re-encoding apparatus according to claim 17, further comprising:

means for applying weighting, according to image characteristics, to the quantizer step size of said input compressed moving picture stream used in said complexity measure computation, and adjusting that quantizer step size.

39. The compressed moving picture re-encoding apparatus according to claim 17, further comprising:

means for applying weighting, according to image characteristics, to the quantizer step size of said input compressed moving picture stream used in said complexity measure computation, and adjusting that quantizer step size; and

means for computing a ratio of respective complexity measures in a prescribed period or number of pictures to a complexity measure of an object of re-encoding, using either or both of the quantizer step size and the number of bits of said input compressed moving picture stream, performing weighting of said quantizer step size, and adjusting that quantizer step size.

18. A compressed moving picture re-encoding apparatus that has an input compressed moving picture stream, generated by a compression-encoding of moving picture data, as an input signal, performs re-encoding at a pre-set average bit rate and at a variable bit rate, and has an output compressed moving picture stream whose bit rate has been changed as an output signal, said compressed moving picture re-encoding apparatus comprising:

means for computing a quantizer step size that is used in said re-encoding;

means for inputting said computed quantizer step size and a quantizer step size in said input compressed moving picture stream and outputting a quantizer step size that is used in actual re-encoding;

means for selecting a larger quantizer step size from said quantizer step size that is used in re-encoding and said quantizer step size in the input compressed moving picture stream;

means for computing respective complexity measures in two or more kinds of prescribed predetermined periods or numbers of pictures, using either or both of the quantizer step size and a number of bits in either of said input compressed moving picture stream or a re-encoded compressed moving picture stream;

means for outputting a prescribed complexity measure from a plurality of said complexity measures;

means for computing said quantizer step size using said pre-set average bit rate and said output complexity measure, wherein said quantizer step size is adjusted every prescribed period according to the difference between the target number of bits and the actual number of bits, to give the quantizer step size that is used in said re-encoding; and

means for selecting a minimum complexity measure among said plurality of complexity measures.

29. The compressed moving picture re-encoding apparatus according to claim 18, further comprising:

means for applying weighting, according to image characteristics, to the quantizer step size of said input compressed moving picture stream used in said complexity measure computation, and adjusting that quantizer step size.

40. The compressed moving picture re-encoding apparatus according to claim 18, further comprising:

means for applying weighting, according to image characteristics, to the quantizer step size of said input compressed moving picture stream used in said complexity measure computation, and adjusting that quantizer step size; and

means for computing a ratio of respective complexity measures in a prescribed period or number of pictures to a complexity measure of an object of re-encoding, using either or both of the quantizer step size and the number of bits of said input compressed moving picture stream, performing weighting of said quantizer step size, and adjusting that quantizer step size.

19. A compressed moving picture re-encoding apparatus that has an input compressed moving picture stream, generated by a compression-encoding of moving picture data, as an input signal, performs re-encoding at a pre-set average bit rate and at a variable bit rate, and has an output compressed moving picture stream whose bit rate has been changed as an output signal, said compressed moving picture re-encoding apparatus comprising:

means for computing a quantizer step size that is used in said re-encoding;

means for inputting said computed quantizer step size and a quantizer step size in said input compressed moving picture stream and outputting a quantizer step size that is used in actual re-encoding;

means for selecting a larger quantizer step size from said quantizer step size that is used in re-encoding and said quantizer step size in the input compressed moving picture stream;

means for computing respective complexity measures in two or more kinds of prescribed predetermined periods or numbers of pictures, using either or both of the quantizer step size and a number of bits in either of said input compressed moving picture stream or a re-encoded compressed moving picture stream, wherein pictures from a picture re-encoded at the start of re-encoding to a picture immediately preceding that for which re-encoding is currently being performed, or a plurality of pictures including one image encoded within a frame, are used as a plurality of pictures used as said prescribed period or number of pictures;

means for outputting a prescribed complexity measure from a plurality of said complexity measures;

means for computing said quantizer step size using said pre-set average bit rate and said output complexity measure, wherein said quantizer step size is adjusted every prescribed period according to the difference between the target number of bits and the actual number of bits, to give the quantizer step size that is used in said re-encoding; and

means for selecting a minimum complexity measure among said plurality of complexity measures.

30. The compressed moving picture re-encoding apparatus according to claim 19, further comprising:

means for applying weighting, according to image characteristics, to the quantizer step size of said input compressed moving picture stream used in said complexity measure computation, and adjusting that quantizer step size.

41. The compressed moving picture re-encoding apparatus according to claim 19, further comprising:

means for applying weighting, according to image characteristics, to the quantizer step size of said input compressed moving picture stream used in said complexity measure computation, and adjusting that quantizer step size; and

means for computing a ratio of respective complexity measures in a prescribed period or number of pictures to a complexity measure of an object of re-encoding, using either or both of the quantizer step size and the number of bits of said input compressed moving picture stream, performing weighting of said quantizer step size, and adjusting that quantizer step size.

43. A compressed moving picture re-encoding apparatus that has an input compressed moving picture stream, generated by a compression encoding of moving picture data, as an input signal, performs re-encoding at a pre-set average bit rate and at a variable bit rate, and has an output compressed moving picture stream whose bit rate has been changed as an output signal, said compressed moving picture re-encoding apparatus comprising:

means for computing a quantizer step size that is used in said re-encoding;

means for inputting said computed quantizer step size and a quantizer step size in said input compressed moving picture stream and outputting a quantizer step size that is used in actual re-encoding;

means for computing, by using a maximum bit rate among set bit rates and either or both of the quantizer step size and a number of bits of said input compressed moving picture stream, a maximum bit rate quantizer step size at said maximum bit rate; and

means for taking said maximum bit rate quantizer step size and the quantizer step size that is used in said re-encoding as input, and outputting the quantizer step size that is used in re-encoding,

said means for computing the maximum bit rate quantizer step size comprises a rate control that satisfies a ratio of an input bit stream bit rate to said maximum bit rate with respect to a number of bits in a prescribed period or number of pictures of said input compressed moving picture stream.

45. A compressed moving picture re-encoding method comprising:

receiving a value for a pre-set average bit rate at which a compressed moving picture stream is to be re-encoded;

receiving a compressed moving picture stream that has been generated by a compression-encoding of moving picture data;

computing a quantizer step size that is used in said re-encoding;

inputting said computed quantizer step size and a quantizer step size in said input compressed moving picture stream and outputting a quantizer step size that is used in actual re-encoding;

performing a re-encoding of said compressed moving picture stream at said received pre-set average bit rate; and

outputting said re-encoded compressed moving picture stream.

46. A compressed moving picture re-encoding method comprising:

receiving a value for a pre-set average bit rate at which a compressed moving picture stream is to be re-encoded;

receiving a compressed moving picture stream that has been generated by a compression-encoding of moving picture data;

computing a quantizer step size that is used in said re-encoding;

inputting said computed quantizer step size and a quantizer step size in said input compressed moving picture stream and outputting a quantizer step size that is used in actual re-encoding;

selecting a larger quantizer step size from said quantizer step size that is used in re-encoding and said quantizer step size in the input compressed moving picture stream;

performing a re-encoding of said compressed moving picture stream at said received pre-set average bit rate; and

outputting said re-encoded compressed moving picture stream.

47. A compressed moving picture re-encoding method that has an input compressed moving picture stream, generated by a compression-encoding of moving picture data, as an input signal, performs re-encoding at a pre-set average bit rate and at a variable bit rate, and has an output compressed moving picture stream whose bit rate has been changed as an output signal, said compressed moving picture re-encoding method comprising:

computing a quantizer step size that is used in said re-encoding;

inputting said computed quantizer step size and a quantizer step size in said input compressed moving picture stream and outputting a quantizer step size that is used in actual re-encoding;

computing respective complexity measures in two or more kinds of prescribed predetermined periods or numbers of pictures, using either or both of the quantizer step size and a number of bits in either of said input compressed moving picture stream or a re-encoded compressed moving picture stream;

outputting a prescribed complexity measure from a plurality of said complexity measures; and

computing said quantizer step size using said pre-set average bit rate and said output complexity measure,

wherein said quantizer step size is adjusted every prescribed period according to a difference between a target number of bits and an actual number of bits, to give the quantizer step size that is used in said re-encoding.

48. A compressed moving picture re-encoding method that has an input compressed moving picture stream, generated by a compression-encoding of moving picture data, as an input signal, performs re-encoding at a pre-set average bit rate and at a variable bit rate, and has an output compressed moving picture stream whose bit rate has been changed as an output signal, said compressed moving picture re-encoding method comprising:

computing a quantizer step size that is used in said re-encoding;

inputting said computed quantizer step size and a quantizer step size in said input compressed moving picture stream and outputting a quantizer step size that is used in actual re-encoding;

selecting a larger quantizer step size from said quantizer step size that is used in re-encoding and said quantizer step size in the input compressed moving picture stream;

computing respective complexity measures in two or more kinds of prescribed predetermined periods or numbers of pictures, using either or both of the quantizer step size and a number of bits in either of said input compressed moving picture stream or said re-encoded compressed moving picture stream;

outputting a prescribed complexity measure from a plurality of said complexity measures; and

computing said quantizer step size using said pre-set average bit rate and said output complexity measure;

wherein said quantizer step size is adjusted every prescribed period according to a difference between a target number of bits and an actual number of bits, to give the quantizer step size that is used in said re-encoding.