(1) Field of the Invention
The present invention relates to an image processing apparatus, an image processing method, and an image processing system, and more particularly to an image processing apparatus, an image processing method, and an image processing system for capturing and processing still images.
(2) Description of the Related Art
As the displaying capability of personal computers and the processing capability of CPUs (Central Processing Units) have grown and the storage capacity of hard disks have increased in recent years, expansion cards (so-called video capture apparatus) for reading video data from video units such as video decks as digital data into personal computers are becoming popular in the art.
One problem with a video capture apparatus in reading a high-definition digital video signal into a personal computer is concerned with a data transfer ability required to transfer image data from the video capture apparatus to a memory.
For example, high-definition television signals which have a data rate of about 75 Mpixels per second require a data transfer ability of about 150 Mbytes per second if the amount of data of one pixel is 2 bytes. On the other hand, PCI (Peripheral Components Interconnect) buses which are typically used for systems such as personal computers have a peak data transfer ability of about 132 Mbytes per second for 32-bit signals having an operating frequency of 33 MHz, and a normal data transfer ability which is half the peak data transfer ability or less than half the peak data transfer ability. Therefore, many video capture apparatus temporarily store captured image data in a buffer which has a storage capacity for one frame of image data, and then transfer the captured image data to a memory.
High-definition television signals represent images having a size of 1920×1080 pixels.
Therefore, if the amount of data of one pixel is 2 bytes, then a video capture apparatus needs a buffer having a storage capacity of 4 Mbytes for storing high-definition television signals. When a video capture apparatus is constructed as an LSI (large Scale Integration) circuit, it is the general practice to add a buffer RAM (Random Access Memory) as an external circuit to the LSI circuit. The LSI circuit, therefore, has an increased number of terminals and, as a result, suffers an increased cost.
Since the data of one image is necessarily stored altogether in a buffer at one time, the size of an image that can be captured by a video capture apparatus is limited by the storage capacity of the buffer. Consequently, it is impossible for the video capture apparatus to capture an image whose size is in excess of the storage capacity of the buffer even if the bus from the video capture apparatus to the buffer has an excess data transfer capability.