The disclosure relates to a television titling apparatus which is substantially the same as a conventional television titling apparatus designed for left-to-right character presentation, but includes a novel subsystem and method which can be utilized to effect display of characters from right-to-left for languages which so require. Reverse image stroke representations are stored in a stroke generator. An auxiliary storage is provided for storing a scanline of stroke bits from the stroke generator. Scanlines of stroke bits are read out of the auxiliary storage in reverse order from the order in which they were read in; i.e., on a last-in-first-out basis. Preferably, the auxiliary storage includes first and second stores which are alternately operable to read in and read out successive scanlines of stroke bits so that one scanline of stroke bits is being read out while the next scanline of stroke bits is being read in.
The video memory of a CRT display system is split into an application video memory and a CRT memory. The two memories are interconnected by logic means for manipulating primary and secondary texts whose characters proceed in directions which are different from each other. The character codes are applied to the application video memory. The logic manipulates the code in accordance with the rules of the primary and secondary languages and provides data to the CRT video memory for driving a CRT controller.
A cathode ray tube display system and method having bidirectional line scanning are disclosed. Bidirectional line scanning is achieved by scanning each odd numbered scan line from left to right and each even numbered scan line from right to left, thereby avoiding the necessity for retrace, or flyback. In order to avoid loss of intelligibility in displaying the video information received from a conventional source providing video information written only from left to right, as is conventional, the received video information is stored in memory by scan lines with each odd numbered line being read out in the same order as stored in memory and each even numbered line being read out in reverse order as stored in memory. Timed control is provided for processing of the video information and display thereof with bidirectional scanning, and geometric error correction is provided for both the horizontal and vertical scan generators.
In a display apparatus equipped with a plurality of frame memories for keeping data to be used for display on a display section and an output logic for outputting the display data on the frame memories to the display section, for effective use to various CAD/CAM graphic applications, a switching operation for connection of the frame memories to the output logic is selectively effected through a software among a mode for connecting one of the frame memories to the output logic, a double-buffer mode for switching two of the frame memories at the timing of vertical retrace intervals and a mode for switching the plurality of frame memories at the timing of horizontal retrace intervals.
Pixel representations for each of a plurality of superimposed (or splitscreen) display portions are accumulated in a band buffer prior to being transferred to the display. The actual pixel representations are made available to the band buffer from an image memory, with addresses provided by a display list memory. This system minimizes the need for buffering and high speed storage to service the video, by addressing first the display list memory, then in turn using the content of the display list memory to address the image storage, and then in turn using the content of the image storage as the actual pixel representations for accumulation in the band buffer. Two band buffers operate alternatively. The current band buffer is feeding a band of pixel representations to the video shift register while the next band buffer is accumulating the pixel representations of the subsequent video display band. The band buffer accumulates actual pixel representations equivalent to the related band of the display. The pixel representations sent to the band buffer from image memory are gated by controls which ensure that the proper pixel prevails in the case of a composite display made up of a primary display with a secondary display which might have higher priority, as, for example, a text announcement superimposed over a normal entertainment program image.
