Frame memory device and method

A method of outputting raster-scanned digital color image signals at lower resolution than that of sequentially received raster-scanned digital color image signals, comprising:

• rearranging the order of received signals;
• sequentially storing the rearranged signals in a memory having a two-dimensional address structure, such that vertical addresses represent the order of entry of respective scan lines that constitute the received image signals and horizontal addresses represent the order of entry of respective signals that belong to each of the scan lines;
• and
• subsampling and reading out stored signals while skipping horizontal and vertical addresses of said memory at regular intervals;
• wherein the rearranging and subsampling are correlated so as to output raster-scanned image signals at lower resolution than that of the received image signals.

A method of writing and reading image signals, comprising the steps of:

• dividing horizontal and vertical addresses of an address region of a memory storing the image signals into a plurality of blocks each having a predetermined number of addresses as a unit;
• reading the image signals from each of said plurality of blocks, while skipping read-out addresses at predetermined intervals and subsampling the image signals;
• and
• when the image signals are written into the memory, rearranging the image signals in an order that is determined based on the predetermined intervals at which the read-out addresses are skipped.

A method of writing and reading image signals, comprising the steps of:

• dividing horizontal and vertical addresses of a memory that stores raster-scanned color image signals having YCBCR signals at a ratio of 4:2:2, into a plurality of blocks each having 2m successive addresses as a unit, where m is a first integer;
• reading the color image signals stored at 2n addresses from each of said plurality of blocks, while skipping the addresses at predetermined intervals, n being a second integer, said first integer and said second integer being prime to each other, said first integer being larger than said second integer;
• and
• when the color image signals are stored in said memory, storing Y signals into the memory in an order of entry without performing rearrangement, while rearranging CBCR signals in an order which is different from an order of entry and is determined based on the predetermined intervals at which the addresses are skipped, and storing the rearranged CBCR signals into the memory.

A memory device comprising:

• a memory having a two-dimensional address structure;
• writing means for sequentially receiving raster-scanned color image signals, and writing the color image signals into said memory such that vertical addresses of the memory represent an order of entry of scan lines that constitute the color image signals, and horizontal addresses of the memory represent an order of entry of the color image signals that belongs to each of the scan lines;
• reading means for sequentially reading out the stored color image signals from said memory, to output the signals as said raster-scanned color image signals;
• and
• signal rearranging means connected to an input terminal of said writing means, for changing an order of the color image signals to be entered into the writing means;
• wherein said reading means reads out the color image signals stored in said memory while subsampling the signals by skipping the horizontal addresses and vertical addresses of the memory at predetermined intervals.

A memory device comprising:

• a memory that stores raster-scanned color image signals having YCBCR signal components at a ratio of 4:2:2, said memory comprising a Y memory that stores Y signals of the color image signals, and a C memory that stores CB and CR signals of the color image signals;
• a C bus through which the CB and CR signals of the color image signals are transmitted while being alternately multiplexed;
• a Y bus through which the Y signals of the color image signals are transmitted in synchronization with CB and CR signals transmitted through said C bus;
• signal rearranging means connected to said C bus, for rearranging the multiplexed CB and CR signals to alternate the signals at every other pixel;
• writing means for writing the Y signals from said Y bus, and the CB and CR signals rearranged by said signal rearranging means, into said Y memory and said C memory, respectively, in an order of raster-scanning;
• and
• reading means for reading out the Y signals and CB and CR signals respectively stored at every other pixel in the Y memory and the C memory in the order of raster-scanning.