Image analysis – Image compression or coding – Including details of decompression
Reexamination Certificate
1997-12-30
2001-03-20
Mehta, Bhavesh (Department: 2721)
Image analysis
Image compression or coding
Including details of decompression
C382S246000, C382S298000
Reexamination Certificate
active
06205251
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATION
This application claims the priority benefit of Taiwan application Ser. No. 86116555, filed Nov. 6, 1997, the full disclosure of which is incorporated herein by reference.
BACKGROUND OF THE INVENTION
1. Field of Invention
The present invention relates to a device and method for processing video image. More particularly, the present invention relates to the device and method for decompressing the compressed video data of a video image in a system that uses a variable-length encoding method with a line-end-code.
2. Description of Related Art
Following the recent advance in computer technologies, computer systems have become part of our life. Through linking to the Internet, the newest information from the world can be obtained in your personal computer. In recent years, the quantity of information flowing through a computer network has increased tremendously. Beside the general alphanumeric data, other types of data such as voice and video image are transmitted in vast quantities. The favored gem of today's PC hobbyist and general users is the multimedia system. A multimedia system need to shuttle vast amount of voice and video data around, hence, whether to store or to transmit, these data must be compressed in order to save memory space and increase processing time. For a multimedia system, the system must also include some other functions such as the enlargement and contraction of images besides having the basic function of decompressing the compressed video data.
There are a number of methods for decompressing the compressed video data. For example, one conventional method is to target the decompression of one horizontal line at a time. In practice, the first line of compressed video data is decompressed first, before the decompression of the second line is executed, and so on processing sequentially from the top line down to the bottom line. The conventional formats for storing row compressed video data are shown in
FIGS. 1 through 4
. They are composed of two parts, namely, a first part for storing the number of pixels and a second part for storing the color of the pixels. The length for storing the number of pixels is variable, for example, ranging from occupying 2-bits up to 14-bits as shown in
FIGS. 1 through 4
. On the other hand, the length for storing the color of the pixels is fixed, normally occupies just two bits. Therefore, when information from these two parts is obtained the number of pixels and its color in the horizontal direction is completely specified. By receiving and then decompressing the row compressed video data piece by piece in a left to right manner before reaching the line-end-code, the complete pixel image in a horizontal line is thus obtained. The line-end-code is very similar in format to the row compressed video data as shown in
FIG. 5
, except that the first part is of fixed length and all consists of zeros; while the second part stores the color of the pixels. When the receiver picks up the line-end-code, it will interpret to mean that the horizontal pixels from that point on are of the same color as specified in the color part of the line-end-code. The receiving of a line-end-code implies the end of a line, and therefore, anything received thereafter represent the code for the next line down. Again, decompression starts from the left side in a sequential order until the line-end-code is again received. The whole process is repeated many times from top to bottom line by line to form a decompressed data into a video image.
To enlarge or contract video images, the conventional method is to receive the whole packet of compressed video data, decompress it before applying the enlargement or contraction to create the actual image. As mentioned before, a large storage area is required to store up the decompressed video data; hence, a large capacity storage buffer is needed. This represents a waste in the memory storage space. At present, although the memory capacity of a dynamic random access memory (DRAM) chip is large and unit cost of it is rather cheap, DRAM chips are by no means cheap. Moreover, time is also wasted in writing a large quantity of data to a DRAM chip and then reading it from the DRAM chip for processing. In other words, the conventional method of processing image data is uneconomical.
In light of the foregoing, there is a need to provide devices and improved method for decompressing video image data.
SUMMARY OF THE INVENTION
Accordingly, the present invention is to provide a device and method for decompressing video image data. Through going through a pre-processing operation of the compressed data before entering the decompression stage, memory space are saved and processing time is decreased.
To achieve these and other advantages and in accordance with the purpose of the invention, as embodied and broadly described herein, the invention provides a device and method for decompression video image data such that the compressed data related to the vertical direction is processed first. In other words, before the compressed video data is decompressed, the compressed data of the image is processed for the enlargement or contraction in the vertical direction first. In an image contraction process, that portion of the row compressed data where no processing is required is discarded before data decompression. Hence, there is no need to perform decompression again, and so processing time can be saved. Furthermore, the decompressing method used in this invention is processing only a row of video image at a time. Therefore, only a buffer large enough to hold a line of data is required, and much memory space is saved.
In this invention, decompression and the enlargement or contraction of video image data is performed together. First, an enlargement/contraction pre-processor receives the compressed image data. Next, the compressed image data is searched to find the line-end-code, and then a row compressed image data is sent to a compressed data buffer. According to the line-end-code, the row number of a line can be found. Then, according to an enlargement/contraction ratio, whether the line received in the compressed data buffer need to be further processed and in what ways is determined. If the image needs to be enlarged, then the row compressed data in the compressed data buffer can be duplicated and then sent out. Alternatively, if the image needs to be contracted, then the row compressed data in the compressed data buffer can be discarded or be sent out directly. If an enlargement/contraction ratio same as the original is wanted, then the row compressed data in the compressed data buffer can be directly sent out without any enlargement/contraction processing. Thereafter, the row compressed data in the compressed data buffer is transferred to a variable length decoder to decompress the row compressed data and obtain row image data. Subsequently, the row image data is sent to a decompressed data buffer. When the decompressed data buffer has received a whole line of row image data, the whole line of row image data will be sent to an enlargement/contraction post-processor. The enlargement/contraction post-processor performs the necessary horizontal enlargement or contraction according to the enlargement/contraction ratio. Its principle of operation is very similar to the operation of the aforementioned enlargement/contraction pre-processor. If an image needs to be enlarged, the post-processor will display some pixels repeatedly according to the enlargement ratio. On the other hand, if an image needs to be contracted, then a few pixels will be discarded according to the contraction ratio. Hence, the required horizontal enlargement or contraction of an image is achieved. Since vertical enlargement or contraction processing is already achieved on reaching the compressed data buffer, compressed data of the whole image can be decompressed accompanied by the necessary enlargement/contraction by repeating the above operation.
It is to be understood that both the foregoing general description and the f
Hsieh Tsung-Hsien
Hsu Rong-Fu
Cislo & Thomas LLP
Cislo, Esq. Daniel M.
Mehta Bhavesh
Winbond Electronics Corp.
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