Pulse or digital communications – Bandwidth reduction or expansion – Television or motion video signal
Reexamination Certificate
2000-10-25
2004-06-29
Diep, Nhon (Department: 2613)
Pulse or digital communications
Bandwidth reduction or expansion
Television or motion video signal
Reexamination Certificate
active
06757332
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates a method and an apparatus for video decoding capable of reducing an adverse effect on decoded video by a delay in a stream, which is caused by congestion of a transmission line or retransmission of the stream as a countermeasure against a transmission path error, when transmitting a coded stream obtained by coding video data, through the communication line. Further, the invention relates to a program storage medium containing a video decoding program for implementing the video decoding method by software.
BACKGROUND OF THE INVENTION
In recent years, we have greeted the age of multimedia in which representation media such as audio, video, and the like are integrally handled, and the conventional information media, i.e., means for transmitting information to men, such as newspapers, magazines, televisions, radios, and telephones, have been adopted as the targets of multimedia. Generally, “multimedia” means media representing not only characters but also diagrams, speeches, and especially pictures simultaneously in association with each other. In order to handle the conventional information media as the targets of multimedia, it is necessary to express the information in digital format.
However, when the quantity of data possessed by each of the above-described information media is estimated as the quantity of digital data, audio having quality for telecommunication requires 64 kbits per second while the quantity of data per character is only 1-2 byte. Further, video having quality for present television broadcasting requires more than 100 Mbits per second. So, with respect to the information media such as a telephone and a television, it is not practical to handle such massive data as it is in digital format. Although visual telephones have already been put to practical use by ISDN (Integrated Services Digital Network) having a transmission rate of 64 kbps-1.5 Mbps, it is impossible to transmit video data obtained by a television camera as digital data through ISDN.
So, a data compression technique is demanded. For example, for a visual telephone, a video compression technique such as H.261 or H.263 standard, which have been standardized by ITU-T (International Telecommunication Union—Telecommunication Sector), is employed. Further, according to a data compression technique of MPEG1 standard, it is possible to store video data as well as audio data in an ordinary music CD (compact disk).
MPEG (Moving Picture Experts Group) is an international standard of video data compression, and MPEG1 is a standard for compressing video data to 1.5 Mbps, i.e., data of a television signal to about 1/100. Since the transmission rate of the targets to which MPEG1 is directed is limited to about 1.5 Mbps, MPEG2, which compresses video data to 2~15 Mbps, has been standardized to meet the demands for higher picture quality.
Furthermore, under the existing circumstances, standardization of MPEG4 is now proceeded by the working group for standardization of MPEG1 and MPEG2 (ISO/IEC JTC1/SC29/WG11), and this MPEG4 enables coding and processing of picture data in object units to realize new functions required in the age of multimedia. At the beginning, MPEG4 has aimed at standardization of low-bit-rate coding, but the target of standardization is now extended to more versatile high-bit-rate coding adaptable to an interlace picture.
By the way, a feature of MPEG4 resides in that picture data corresponding to plural picture sequences (objects) are simultaneously coded and transmitted. This scheme enables constitution of one moving picture composed of plural objects. In this scheme, for example, a foreground and a background are handled as different picture sequences (different objects), and the frame frequency, picture quality, bit rate, etc. are separately changed for each picture sequence. Further, when plural picture sequences are arranged in the horizontal or vertical direction on a display area like multi-window, the user can extract or enlarge only his/her favorite picture sequence.
In order to code an object having no shape such as a background, generally employed is a coding method in which only pixel value signals indicating pixel values of the object are coded as picture data, such as MPEG2. On thy other hand, in order to code an object having a shape such as a foreground, employed is a coding method in which not only pixel value signals indicating pixel values of the object but also shape signals indicating the shape of the object are coded as picture data.
Further, in MPEG2 and MPEG4, each picture sequence is coded for each of pictures constituting the picture sequence (it corresponds to a frame in MPEG2, and a VOP in MPEG4), and some of the pictures are subjected to a differential coding process (inter-frame predictive coding) in which difference data between picture data of a picture to be encoded (target picture) and predictive data obtained from picture data of a picture for which coding has already been completed (already-processed picture) are encoded.
However, with respect to an object having a shape, its shape and size vary with time. So, in the coding process based on MPEG4, the coding algorithm for a shape signal and a pixel value signal greatly depends on the shape of the object in the already-processed picture. Therefore, the coding process based on MPEG4 is less resistant to a transmission error of a coded stream and has more difficulty in picture recovery utilizing inter-picture correlation or picture correction by picture processing, as compared with the coding process based on MPEG2 which handles picture data of a picture whose shape and size do not vary. In other words, in a decoding system based on MPEG4, when a transmission error occurs in a coded stream, the quality of decoded picture is considerably degraded.
In MPEG4, as described above, one moving picture is composed of plural picture sequences (objects), and each picture in one moving picture is a frame while each picture in one picture sequence is a VOP (Video Object Plane). When one moving picture is composed of one picture sequence, a frame is equal to a VOP.
Hereinafter, a decoding system adaptable to MPEG4 will be described specifically.
Generally, in a data transmission path (communication line), transmission delay of data occurs due to retransmission of data or the like which is a countermeasure against noise and congestion. Therefore, in a coded stream outputted from a video coding apparatus for coding picture data to output a coded stream or from a video transmission apparatus for transmitting a coded stream, the order of bit streams constituting the coded stream (the order of bit streams at transmission) is different from that when received at the receiving end (the order of bit streams at reception). To be specific, the order of bit streams corresponding to some VOPs in the coded stream at transmission is different from that at reception.
As a countermeasure against this problem, when a coded stream is divided into transmission units called “packets” at the transmitting end, each packet is given a number indicating its turn in the transmission order. Thereby, at the receiving end, VOP data in the received coded stream can be rearranged such that its order becomes equal to that at transmission, on the basis of the number given to each packet.
FIG. 30
is a block diagram for explaining a conventional video decoding apparatus
1000
. The video decoding apparatus
1000
receives coded streams Vin corresponding to plural objects constituting one moving picture, and rearranges VOP data in the coded stream corresponding to each object. Thereafter, the video decoding apparatus
1000
decodes the coded streams Vin, and composites decoded picture data corresponding to the respective objects. Further, at the transmitting end, each VOP data in the coded stream Vin corresponding to each object is given information indicating the time at which the VOP data is to be displayed at the receiving end (VOP display time).
The video decoding apparatus
1000
includes a rearrang
Diep Nhon
Wenderoth , Lind & Ponack, L.L.P.
LandOfFree
Video decoding method, video decoding apparatus, and program... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Video decoding method, video decoding apparatus, and program..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Video decoding method, video decoding apparatus, and program... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3364854