Pulse or digital communications – Bandwidth reduction or expansion – Television or motion video signal
Reexamination Certificate
2000-02-18
2004-09-28
Diep, Nhon (Department: 2713)
Pulse or digital communications
Bandwidth reduction or expansion
Television or motion video signal
Reexamination Certificate
active
06798837
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention is related to a video coding apparatus and a method thereof for coding a digital compressed video signal having a compression format to obtain a digital coded video signal having the same, or different compression format. More specifically, the present invention is directed to such a video coding apparatus and a video coding method, capable of coding the digital compressed video signal by utilizing information about the compression of this digital compressed video signal.
Recently, digital video signals are widely used in various technical fields, since technical aspects of digital data related to data transfer techniques, data storage techniques, and data process techniques have been developed. Most of these digital video signals are usually compressed so as to reduce coding amounts thereof. There are plural compression formats. However, there is no united compression format. Also, most of these plural compression formats do not own compatibility among these compression formats. As a consequence, there are many difficult cases that a video (picture) which has been compressed by a certain compression format cannot be directly used in a system with employment of another different compression format. Otherwise, even when the same compression format is employed in two systems, there are large differences in coding amounts per unit time (bit rates) between these two systems, since these two systems own different limitations in data transfers and data storage capacitances. Similarly, there are possibilities that a video which has been compressed in one bit rate cannot be utilized in a system which introduces the other bit rate.
Under such a circumstance, various compression format conversion techniques have been researched/developed by which digital video signals compressed in one compression format are converted into digital video signals compressed in another compression format. These conventional compression format converting techniques are known from, for instance, Japanese Laid-open Patent Application No. Hei-10-271494 opened in 1998. This opened conventional technique describes the method for converting the bit streams of the moving pictures having the spatial resolution different from each other. In this bit stream converting method, the moving picture which has been compressed in the MPEG-2 format and owns the high resolution is inputted, whereas the moving picture compressed in the H.263-recommended compression format and owns the low resolution. Then, this conventional converting technique is featured by that since the motion vector of the MPEG-2 formatted bit stream as the input video data is corrected, the corrected motion vector can be utilized as the motion vector of the H.263-formatted bit stream as the output video data.
However, the above-described prior art owns the following problems:
(1). Since the motion vector of the input stream (input bit stream) is utilized irrespective of the magnitude of the motion prediction error caused by the motion vector of the input stream, there are some cases that the input stream is coded based upon such a motion vector having a large motion prediction error. In this case, there is such a possibility that this coding operation may cause a larger prediction error to be produced, resulting in deterioration of image qualities.
(2). Since all of the actual images are decoded and then are re-coded, the errors may be produced in the decoding stage and also the re-coding stage. There is another possibility that these errors may cause the image quality to be deteriorated.
(3). Furthermore, a large number of calculation amount is necessarily required so as to execute the decoding process operation and the re-coding process operation.
SUMMARY OF THE INVENTION
The present invention has been made to solve the above-explained problems, and therefore, has an object to achieve the following aspects:
(1). When a motion vector of an input stream (input bit stream) is reused, deterioration in an image quality is reduced, which is caused by reusing such a motion vector having a large motion prediction error.
(2). Both a decoding operation for an input stream and a re-coding operation for an output stream are deleted, so that deterioration in image qualities which is caused in these process steps is reduced.
(3). Also, a calculation amount required in compression format converting operation is reduced.
Moreover, the present invention owns another object to shorten a process delay required in the compression format converting operation, as compared with that of the conventional compression format converting operation.
To achieve the above-described objects, a video coding method, according to the present invention, is featured such a video coding method for performing either a partial stage of all stages of a decoding process operation with respect of an input stream and for coding the decoded digital moving picture by way of the same, or different compression format as/from the compression format of the input stream to there by produce an output stream corresponding to a digital moving picture under different compression condition, in which the output stream is produced by utilizing added information corresponding to information other than a decoded pixel value of the input stream.
Also, the video coding method is featured by that when the input stream and the output stream own coding modes corresponding to information as to coding methods every subpicture, the coding mode of the output stream is determined based upon a coding mode of the corresponding subpicture of the input stream.
Also, the video coding method is featured by that when the output stream owns a coding mode every picture, the coding mode of the output stream is determined based upon the coding mode of the subpicture contained in the corresponding picture of the input stream.
Also, the video coding method is featured by that the video coding method includes a method for producing/referring to coding mode history information containing information for indicating how many subpictures of the output stream have been continuously inter-coded in the past for plural pictures counted from a picture under being coded; and when a subpicture which is intra-coded while the output stream is compressed is selected from a plurality of subpictures inter-coded in the input stream, the coding mode history information is utilized.
Also, the video coding method is featured by that when both the input stream and the output stream are compressed in the unit of a subpicture by way of a motion-compensatable format, a format of a motion vector of the input stream is changed into a format usable as a motion vector of the output stream, and the format-changed motion vector of the input stream is used as the motion vector of the output stream.
Also, the video coding method is featured by that a starting point for a searching operation is determined based upon a value of a motion vector of an input stream; and a motion vector searching operation is carried out so as to determine a motion vector of an output stream.
Also, the video coding method is featured by that when the motion vector of the input stream is such a motion vector obtained by using a filtering-processed reference image, the motion vector of the output stream is produced by converting the motion vector into a representation obtained by using a reference image to which the filtering process is not performed, and further by converting the converted motion vector into another representation which is obtained by using another filtering-processed reference image different from the reference image of the input stream.
Also, the video coding method is featured by that when the input stream owns both a motion vector every subpicture and subtraction information corresponding to a motion prediction error, a magnitude of the subtraction information is obtained so as to calculate an accurate degree of the motion vector, and a method for utilizing the motion vector of the input stream is changed in response to
Etoh Minoru
Iwasaki Osamu
Komiya Daisaku
Uenoyama Tsutomu
Diep Nhon
Matsushita Electric - Industrial Co., Ltd.
Pearne & Gordon LLP
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