Sharp Kabushiki Kaisha Corporation

Nippon Telegraph and Telephone Corporation

Toshihiro Uota

Osamu Nakamura

Hirotaka Nakano

Jiro Nakabayashi

Tsuneaki Iwano

A correction characteristic storage portion stores coordinates (Xp,Yp) of a break point P and curve approximation range widths Wa and Wb. A basic broken line coefficient calculation portion calculates a coefficient Cfor a straight line OP and a coefficient Cfor a straight line PP'. An auxiliary straight line coefficient calculation portion obtains division points P and Q at which to divide two line segments AP and PB in the proportion in which a curve approximation range is divided by input data X, and calculates a coefficient Cfor an auxiliary straight line PQ. A range determination portion determines whether the input data lies within the curve approximation range. A coefficient selection portion and a primary expression calculation portion perform either correction based on the basic broken line or correction based on the auxiliary straight line according to the determination.

Digital gamma correction circuit and digital gamma correction method

A digital gamma correction circuit includes: a data setting portion for setting set data including a section width Wand coordinates (Xp,Yp) of a break point P; a coefficient calculation portion for calculating coefficients for straight-line equations representing a broken baseline including a break point and three predetermined approximate line segments for defining a gamma correction broken line approximating an ideal gamma correction curve, the approximate line segments gradually varying in slope in the vicinity of the break point; arithmetic portions for performing arithmetic operations based on the coefficients to subject input data to gamma correction; and a result selection portion for making a suitable selection from among results for the arithmetic operations. Thus, it is possible to obtain a gamma correction broken line approximating an ideal gamma correction curve, and achieve a smooth correction characteristic with a small number of data items.

Throughput of data transmission is improved by efficiently retransmitting a requested frame between two terminals directly connected each other in a packetized data transmission system. Data is transmitted in frames, each of which is constructed of a flag sequence field for delimiting a frame, a forward information field including a number for identifying a frame, a backward information field containing a history of frame-numbers of correctly received frames, an information field including user data of a fixed length and a code for error-detection field for detecting an error of the received frame. With a frame correctly received, a receiving terminal updates a history of correctly received frame-numbers and sets it in a backward information field of a frame to be transmitted to a transmitting terminal. With a frame incorrectly received, history information for a precedent correct frame is set the backward information field of the frame.

Data transmission system and method utilizing history information corresponding to correctly received frames

A connection control equipment can connect a plurality of calls originating from a terminal to a private side terminal by identifying the calling terminal. Each of the user terminals sets a calling number and a calling sub-address or a user-to-user information for identifying the terminal in a call-setting message. A switching system of the connection control equipment receives the call-setting message and stores the calling number and the calling sub-address or the user-to-user information of the message, and connects the call to a private side terminal with which the same user terminal issuing the just received call is communicating. The switching system can connect calls from the same user terminal to the same private terminal, allowing for any user terminal to freely transmit a plurality of calls without considering how to access a host computer.

Growing community of inventors

Nara, Japan

Toshihiro Uota