Television – Bandwidth reduction system
Patent
1997-09-08
1999-09-07
Britton, Howard
Television
Bandwidth reduction system
348 14, 455 383, 455574, H04N 712, H04M 1100
Patent
active
059494840
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a multimedia communication terminal apparatus having a plurality of encoding modes with different power consumption. In the present invention, a change in the encoding mode indicates a change of a terminal state in which a transmitted encoding bit stream is changed even when the same input information source (e.g., images inputted to a camera, sounds inputted to a microphone, etc.) is supplied to a terminal. Moreover, according to the present invention, a terminal for executing a communication of single information such as sounds or the like also is included in the multimedia communication terminal.
BACKGROUND ART
Multimedia communication terminals which can perform digital image communication have been popularized really. As a main factor for putting digital image communication into a practice, there can be enumerated a progress of image information compression technique (image coding technique) in addition to the development of electronic device technique. Image encoding technique is a technique for compressing image information having an information amount 1000 times as large as that of audio information to the level such that image information can be transmitted/stored. When a digital image communication using image encoding techniques is carried out, a terminal on the transmission side encodes (compresses), transforms inputted image information into an encoded bit stream, and transmits the encoded bit stream. A terminal on the reception side obtains a decoded image by decoding a received bit stream. At that time, in order to correctly carry out the communication, terminals located on both ends of the channel have to use a common image encoding system. To this end, as an international standard, there are now determined standard image encoding systems such as H. 261, MPEG1 or MPEG2. It is expected that much more standard image encoding systems will be determined from now on in accordance with new applications such as a wireless image communication.
Most of image communication terminals that were already commercially available on the market are wired image communication terminals connected to an ISDN network line or the like. However, it is expected that wireless image communication terminals which can provide similar functions will become widespread in the future wireless networks. The wireless communication terminal is featured in its portability, and it is customary that the wireless communication terminal uses a storage battery as its electric power source. However, an amount of an electric power that a light-weight storage battery used by the portable terminal can supply is limited so that a power consumption of a terminal has to be suppressed in order to prolong a continuous communication time. Also, since a surveillance system or the like uses a large number of terminals, even when a storage battery is not in use, it is important to suppress the power consumption. While the saving of the electric power becomes an important condition depending on applications as described above, an image encoding algorithm having a high information compression ratio has a large amount of calculations, and a power consumption tends to increase. In general, it is a first object for the image encoding to increase an information compression ratio, and a problem of a power consumption is not regarded as being important. However, in the future in which terminals for multimedia communication will become widespread and the problem of the power consumption that has been regarded as being unimportant will hold an important position in the design and development of apparatus.
In order to save an electric power of commercially-available portable apparatus, notebook-type (laptop) computers had created some devices. Main power-saving functions of Macintosh Power Book 18C manufactured by Apple Computer Inc., USA are as follows: backlight of a liquid-crystal display is automatically darkened; level, an alarm message is displayed on a display; during a predetermined period of tim
REFERENCES:
patent: 5485504 (1996-01-01), Ohnsorge
patent: 5491507 (1996-02-01), Umezawa
International Telecommunication Union, ITU-T Recommendation H.261, Previously "CCITT Recommendation"), "Line Transmission of Non-Telephone Signals", "Video Codec for Audiovisual Services at p .times. 64 kbits", Mar. 1993.
ISO/IEC 11172-2: 1993 (E).
ISO/IEC 13818-2: 1995 (E).
Fujii Yukio
Maruyama Masanori
Nagata Minoru
Nakaya Yuichiro
Britton Howard
Hitachi , Ltd.
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