Abstract: A digital data reproducing apparatus and method which allows reproduction for a long period of time without deterioration in picture quality. Data are reproduced from an optical disk by a pickup and are transferred to and stored in a ring buffer memory. Data read from the ring buffer memory are transferred to and stored into a video code buffer of an encoder section. The data stored in the video code buffer are encoded in the encoder section and displayed on a display. A track jump judging circuit produces a track jumping instruction to cause the pickup to track jump back to a preceding track when the amount of data stored in the ring buffer memory reaches a predetermined value.

Abstract: A system for transmitting still picture data between a first still picture transmitter with a display device and a keyboard disposed on one panel, and a second still picture transmitter with a display device and a keyboard disposed separately. The second still picture transmitter comprises memory means for storing a plurality of still picture files with individual file names, and transfer means for transmitting or receiving the still pictures and the file names. The first still picture transmitter further comprises control means for reading out the data of the file names from the memory means via the transfer means of the second still picture transmitter.

Abstract: Data multiplexing and demultiplexing apparatus for respectively timeshare-multiplexing a plurality of data signals and demultiplexing the timeshared-multiplexed data signals. The multiplexing apparatus includes a plurality of code buffers each respectively receiving one of the data signals, a control circuit for generating switching and header control signals, a switching circuit responsive to the switching control signal for successively retrieving each of the data signals from the code buffers and for grouping the retrieved data signals so as to form respective packets of data and for generating one or more packs of data from the packets of data each having a fixed data length, and a header adding circuit responsive to the header control signal for respectively adding a packet header and a pack header to each packet and pack.