1. Field of the Invention
The present invention relates to image processing performed to protect a copyright for an image, and the like.
2. Related Background Art
Recently, the standardization of motion image encoding techniques has been advanced rapidly. And encoding standards, such as MPEG-1, MPEG-2, H.261 and H.263 (these encoding systems are specifically accepted as international standards by ISO (International Organization for Standardization) and ITU (International Telecommunication Union)), have now been established. Further, work is progressing on MPEG-4, a new international standard that is intended to be a general-purpose, next-generation multimedia encoding standard that can be used in many fields, such as computers, broadcasting and communication. Image digitization has also been advanced by the encoding technique, and the storage and communication of motion image data have been markedly improved.
For example, with MPEG-4, a motion image scene at a specific moment is regarded as an aggregate of objects, such as a “person”, a “car”, a “background”, “music” and “video”, which are the components of the scene, and an appropriate encoding process is performed for each object to efficiently encode all the motion image data.
According to a multi-object encoding technique such as MPEG-4, a frame for a scene is expressed by combining individual objects that have been encoded and compressed. Therefore, object data obtained from specific MPEG-4 data can be re-used with different MPEG-4 data, so that another frame can be easily expressed.
As the above described digital encoding standards have spread, the contents business has strongly expressed the problem they represent for the provision of copyright protection. That is, if the standards do not satisfactorily ensure adequate copyright protection, safe and superior contents can not be provided.
For MPEG-4 this is a very serious problem. This is so because, as is described above, with MPEG-4 it is possible to encode and to operate/process data for individual objects. Therefore, since the use of the multi-object encoding system MPEG-4 permits the seamless reuse of individual objects, it is natural for requests to be made that protection be provided for the intellectual property represented by an object. And if the target is a person, it is natural that protection be sought for the right of portrait.
To protect a copyright for a portion of a motion image, a method is available for temporarily halting the decoding of the motion image to prevent the reproduction of a part of it. According to this method, while taking into account the right of portrait and the copyright for the motion image, the decoding of a portion related to them is halted until that portion has been passed, at which time the decoding is resumed.
With this method, however, the following problem is encountered.
The encoding system for using interframe correlation is generally employed to encode motion images. In the previously mentioned, well-known encoding systems H.261 and H.263, and MPEG-1, 2 and 4, basically, the preceding frame, or both the preceding and the succeeding frames, are referred to along the time axis, and motion compensation is performed to encode motion images.
Data reproduction provided by H.261 or H.263 is shown in FIG. 1. I* denotes a frame for intraframe encoding, and P* denotes a frame for interframe encoding. In FIG. 1, Time is the direction in which time elapses, and in Security, a period during which the decoding process is halted is represented as a black block. Code represents the arrangement of screens in the order in which encoded, and Display represents the arrangement of screens in the order in which displayed.
Suppose that the decoding of the encoded data for frames P4 to P9 is halted to apply the protection (Security) provided for an intellectual property (e.g., a copyright). The decoding of motion images is halted at data P3, and images are not again displayed until the decoding is resumed. Since the writing of encoded data to a buffer is also halted at the same time, the encoded data from P4 to P9 are abandoned. Therefore, when the image protection time has ended and the decoding is resumed, data P9, which originally should have been referred to by data P10, have already been abandoned, so that data P10 and the following data can not be normally decoded. As a result, until frame I1, for which intraframe encoding is performed, is decoded, in an interval extending from P10 to P13, the images in the frames are deteriorated, or the decoding process is halted.
MPEG-1, 2, and 4 also employ bidirectional motion compensation, whereby motion along the time axis is predicted from preceding and succeeding frames.
The data reproduction provided by MPEG-1, 2, and 4 is shown in FIG. 2. B* denotes frames for bidirectional (two-way) interframe encoding. In FIG. 2, Time is the direction in which time elapses, and in Security, a period during which the decoding process is halted is represented as a black block. Code represents the arrangement of screens in the order in which encoding is performed, and Display represents the arrangement of screens in the order in which of displayed. For the frames B, the order in which pictures are encoded differs from the order for the original pictures.
Suppose that the decoding for encoded data from B10 to P3 is halted to protect an intellectual property (e.g., a copyright). Since motion compensation is not correctly performed, as in FIG. 1, the images in frames B30 and B31, or B40 and B41, are not correctly decoded, and the images in the frames are deteriorated, or the decoding process is halted.