Motion video signal processing for recording or reproducing – Local trick play processing – With randomly accessible medium
Reexamination Certificate
1998-10-22
2003-11-25
Tran, Thai (Department: 2615)
Motion video signal processing for recording or reproducing
Local trick play processing
With randomly accessible medium
C386S349000, C348S558000
Reexamination Certificate
active
06654541
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an image signal data structure, an image coding method, and an image decoding method. More particularly, the invention relates to an image signal data structure which includes reproduction timing data relating to the timing of reproduction including decoding and image display for each of frames as components of an image, generation (coding) of a coded image signal including the reproduction timing data, and decoding of the coded image signal.
Further, the present invention relates to an image coding apparatus for generating the coded image signal, an image decoding apparatus performing the above-described decoding, a data storage medium containing a coded image signal of the above-described data structure, and a data storage medium containing an image processing program for implementing the above-described coding and decoding by using a computer.
BACKGROUND OF THE INVENTION
In recent years, we have greeted the age of multimedia in which audio, video and other data 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 objects of multimedia. Generally, “multimedia” means to represent, not only characters, but also diagrams, speeches, and especially images simultaneously in relation with each other. In order to handle the conventional information media as the objects of multimedia, it is necessary to convert the information of the media into a digital format.
When the data quantity of each information medium described above is estimated as a quantity of digital data, in the case of characters, the data quantity for each character is 1~2 byte. However, in the case of speech, the data quantity is 64 kbits per second (quality for telecommunication) and, in the case of moving picture, it is more than 100 Mbits per second (quality for current television broadcasting). Thus, in the information media such as televisions, it is not practical to process such massive data as it is in a digital format. For example, 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 an image of a television camera as it is by the ISDN.
As a result, data compression technologies are demanded. In the case of visual telephones, a moving picture compression technology standardized as H.261 by ITU-T (International Telecommunication Union-Telecommunication Sector) is employed. Further, according to a data compression technology of MPEG1, it is possible to record image data, together with audio data, in an ordinary music CD (compact disk).
MPEG (Moving Picture Experts Group) is an international standard relating to a technology for compressing and expanding an image signal corresponding to a moving picture, and MPEG1 is a standard for compressing moving picture data to 1.5 Mbps, i.e., compressing data of a television signal to about 1/100. Since the transmission rate to which MPEG1 is directed is limited to about 1.5 Mbps, MPEG2 capable of compressing moving picture data to 2~15 Mbps has been standardized to meet the demand for higher image quality.
In the image signal compression and expansiochnologies according to MPEG1 and MPEG2 which have already been put to practical use, only a fixed frame rate is basically employed, namely, intervals between image display timings of the respective frames are regular. As a result, there are only several kinds of frame rates, and in MPEG2 a frame rate designated by a flag (frame rate code) which is transmitted with coded data is selected from plural frame rates (frame rate values) with reference to a table shown in FIG.
13
.
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). MPEG4 enables coding and signal operation in object units, and realizes new functions required in the age of multimedia. MPEG4 enables coding and signal operation in object units, and realizes new functions required in the age of multimedia. MPEG4 has originally aimed at standardization of image processing at a low bit rate, but the object of the standardization is now extended to more versatile image processing including high-bit-rate image processing adaptable to an interlaced image.
Also in MPEG4, when a table similar to the table for MPEG2 (refer to
FIG. 13
) is added at the beginning of a video object layer (corresponding to a video sequence of MPEG2), frame rates can be expressed according to the table. In MPEG4, however, since image signals in a broad range from an image signal of a low bit rate to a high-quality image signal of a high bit rate are processed, the number of frame rates required is out of count. Therefore, it is difficult to perform decision of frame rates by the use of a table.
As a result, MPEG4 employs a data structure including frame display time data inserted in each frame in order to deal with almost uncountable number of fixed frame rates and, furthermore, to process an image having variable intervals of image display timings or decoding timings of the respective frames.
FIG. 14
shows a data structure of a conventional coded image signal
200
.
The coded image signal
200
corresponds to one image (in MPEG4, a series of frames constituting an image corresponding to one object) and includes a header H at the beginning. The header H is followed by code sequences Sa
0
, Sa
1
, Sa
2
, . . . , San corresponding to frames F(
0
), F(
1
), F(
2
), . . . , F(n), respectively, which code sequences are arranged according to priority for transmission (transmission order). Here, “n” is the number indicating the transmission order of data of each frame in the frame sequence corresponding to one image, and n of the head frame is 0.
In this example, at the beginnings of the code sequences Sa
0
, Sa
1
, Sa
2
, . . . , San of the respective frames, display time data Dt
0
, Dt
1
, Dt
2
, . . . , Dtn indicating the display timings of the frames are arranged. The respective display time data are followed by coded image data Cg
0
, Cg
1
, Cg
2
, . . . , Cgn.
Since each of the display time data indicates a time relative to a reference time, the quantity of data required for expressing this display time, i.e., the bit number of the display time data, increases as the number of the frames constituting the image increases.
Further, at the decoding end of the coded image signal, according to the display time data Dt
0
~Dtn inserted in the code sequences Sa
0
~San corresponding to the respective frames, image display of each frame is carried out at the time indicated by the display time data.
FIG. 15
shows the transmission order and the display order of the coded image data corresponding to each frame in the series of frames. As described above, “n” indicates the transmission order, and “n′”, indicates the display order (n′ of the head frame is 0). Further, frames F(n) (F(
0
)~F(
18
)) are arranged based on the order of frames in the data structure shown in
FIG. 14
(transmission order). The frames F(n) arranged in the transmission order are rearranged according to the display order of the frames as shown by arrows in
FIG. 15
, resulting in frames F′(n′) (F′(
0
)~F′(
18
)) arranged in the display order. Accordingly, a frame F(n) and a frame F′(n′) related to each other with an arrow are identical. For example, the frames F(
0
), F(
1
), F(
2
), and F(
3
) are identical to the frames F′(
0
), F′(
3
), F′(
1
), and F′(
2
), respectively.
Amongst the frames F(n) (F(
0
)~F(
18
)) arranged in the transmission order, the frames F(
0
) and F(
13
) are I (Intra-picture) frames (hereinafter also referred to as I-VOP), the frames F(
1
), F(
4
), F(
7
), F(
10
), and F(
16
) are P (Predictive-picture) frames (hereinafter also referred to as P-VOP), and the frames F(
2
), F(
3
), F(
5
), F(
6
Boon Choong Seng
Kadono Shinya
Nishi Takahiro
Chieu Po-lin
Matsushita Eletric Industrial Co., Ltd.
Tran Thai
Wenderoth , Lind & Ponack, L.L.P.
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