Video image compression/decompression device
An image compression/decompression device achieving increased utilization efficiency of the memory bandwidth in the access to the memory used for the compression/decompression operation while maintaining ill effect on the images at a low level is realized. The image compression/decompression device comprises a data conversion unit which reduces the data access rate when original images (as input images at the time of performing the compression) and reference images (used for performing the interframe prediction) are stored in the memory by accessing the memory. The access to the memory is performed in an address sequence (order) that differs between data write and data read. This makes it possible to increase the utilization efficiency of the memory bandwidth, and further to reduce the capacity of the buffer memory used for the data read.
1. A video image compression/decompression device for performing compression and decompression of video image data, comprising:
a video image data compression/decompression processing unit which outputs first video image compression data obtained by performing data compression on a video image signal inputted to the video image compression/decompression device by performing interframe prediction on images of the video image signal, and outputs a video image signal obtained by performing data decompression on video image compression data inputted to the video image compression/decompression device; and
a data conversion unit which obtains second video image compression data by performing data compression on the video image signal to undergo the data compression by the video image data compression/decompression processing unit and on a reference image signal to be referred to at the time of performing the interframe prediction by use of a method different from the data compression by the video image data compression/decompression processing unit, writes the second video image compression data to a memory provided as an external or built-in memory of the video image compression/decompression device, and performs data decompression on the second video image compression data read out from the memory, wherein
the data conversion unit changes a memory address sequence, which is used at the time of writing/reading the second video image compression data to/from the memory, between the data writing and the data reading in the same image frame, wherein the memory address sequence is changed based off of a selection between either a lossless compression mode or a lossy compression mode, wherein the data conversion unit generating the second video image compression data compresses data of scan lines of the video image signal by segmenting the data into a plurality of bursts in units of bursts having a first data quantity and then successively writes the bursts each of which has been compressed into a second data quantity to the memory as data in the scanning direction of the scan lines, and the data conversion unit reading out the data written to the memory reads out the data corresponding to the first data quantity from the data of the scan lines successively in a direction orthogonal to the scan lines.
2. A video image compression/decompression device for performing compression and decompression of video image data, comprising:
a video image data compression/decompression processing unit which outputs first video image compression data obtained by performing data compression on a video image signal inputted to the video image compression/decompression device by performing interframe prediction on images of the video image signal, and outputs a video image signal obtained by performing data decompression on video image compression data inputted to the video image compression/decompression device; and
a data conversion unit which obtains second video image compression data by performing data compression on the video image signal to undergo the data compression by the video image data compression/decompression processing unit and on a reference image signal to be referred to at the time of performing the interframe prediction by use of a method different from the data compression by the video image data compression/decompression processing unit, writes the second video image compression data to a memory provided as an external or built-in memory of the video image compression/decompression device, and performs data decompression on the second video image compression data read out from the memory, wherein
the data conversion unit changes a memory address sequence, which is used at the time of writing/reading the second video image compression data to/from the memory, between the data writing and the data reading in the same image frame, wherein the memory address sequence is changed based off of a selection between either a lossless compression mode or a lossy compression mode, wherein the data conversion unit generating the second video image compression data compresses data of scan lines of the video image signal by segmenting the data into a plurality of bursts in units of bursts having a first data quantity and then successively writes the bursts each of which has been compressed into a second data quantity to the memory as data in a direction orthogonal to the scanning direction of the scan lines, and the data conversion unit reading out the data written to the memory reads out the data corresponding to the first data quantity from the data of the scan lines successively in order of the writing.