TWI589151B - Image data compression device and its compression method - Google Patents

Description

Image data compression device and compression method thereof 【0001】

The present invention relates to an image material, and more particularly to a compression device and a compression method for compressing image data.

【0002】

Today's technology is booming, and in order to be closer to human needs, many electronic products are equipped with displays to allow users to conveniently operate electronic products. Small electronic products such as mobile phones, tablets or watches, etc., such mobile devices cannot be directly connected to external power sources, so the control of power consumption is very important.

[0003]

The internal memory system of a driver IC of a general display acts as a frame buffer for storing pixel data transmitted by a host. In order to save power consumption and reduce the space occupied by the memory, in the prior art, the pixel data is compressed by compression coding, thereby reducing the amount of data, the storage space of the memory and the power consumption. Will be reduced together. The data compression method is divided into fixed length coding and variable length coding, for example, Pulse-Code Modulation (hereinafter referred to as PCM), and the number of bits of the encoded data generated by the PCM coding is the same, so the system is fixed. One type of length coding; Differential Pulse-Code Modulation (DPCM) is a type of variable length coding. DPCM mainly includes a predictor, and its compression performance depends on the design of the predictor. However, if the value predicted by the predictor is too large, the number of bits of the encoded data generated after encoding will be too long. Overall, the performance of variable length coding is better than the performance of fixed length coding.

[0004]

In general, since the number of bits of the coded data of the fixed length code is the same, the number of bits of each coded data can be controlled, but the compression performance is not as good as the compression performance of the variable length code. However, the variable length coding cannot accurately control the number of bits of the encoded data, so the length of the encoded data may be too long, and it is not suitable for storage in the frame buffer.

[0005]

In summary, in order to encode the data and store it in the frame buffer, the compression ratio must be considered to ensure that the encoded data generated after the compression process can be stored in the frame buffer, and the compression efficiency should be balanced. It is even more difficult, and the conventional processing of image data still cannot achieve the best of both worlds.

[0006]

The main object of the present invention is to provide a compression device for image data and a compression method thereof, which encodes image input data by using fixed length coding and variable length coding to ensure that the compression ratio can reach a predetermined compression ratio, and the image input data is ensured. After compression processing, it can be stored in the storage unit.

【0007】

Another object of the present invention is to provide a compression device for image data and a compression method thereof, which divide each horizontal pixel data of the image display device into a plurality of block pixel data and use it as a plurality of image input data for compression. Processing, so easy to compress processing to improve the efficiency of the compression process.

[0008]

Another object of the present invention is to provide a compression device for image data and a compression method thereof, which encodes image input data by using fixed length coding and variable length coding, and examines the quality of two encoded data generated by the two, In addition to ensuring the compression ratio, higher compression performance can be achieved.

【0009】

The invention discloses a compression device for image data, which comprises a fixed length coding unit, a variable length coding unit, a selection unit and a control unit. The fixed length coding unit receives an image input data, and performs a fixed length coding on the image input data to generate a first encoded data. The variable length coding unit receives the image input data, and performs a variable length coding on the image input data to generate a second encoded data. The selecting unit receives the first encoded data and the second encoded data, and outputs the first encoded data or the second encoded data to a storage unit. The control unit compares the length of the second encoded data with a threshold. When the length of the second encoded data is less than the threshold, the control unit controls the selecting unit to output the second encoded data to the storage unit; when the length of the second encoded data is greater than the threshold, The control unit controls the selection unit to output the first encoded data to the storage unit.

[0010]

The present invention discloses a method for processing image data, which receives an image input data, performs a fixed length encoding and a variable length encoding on the image input data, and generates a first encoded data and a second encoded data; The length of the second encoded data and a threshold, when the length of the second encoded data is less than the threshold, the second encoded data is stored in a storage unit; when the length of the second encoded data is greater than the threshold, the first encoded data is stored In the storage unit.

[0011]

The invention further discloses a compression device for image data, comprising a fixed length coding unit, a variable length coding unit, a selection unit, a comparison unit and a control unit. The fixed length coding unit receives an image input data, and performs a fixed length coding on the image input data to generate a first encoded data. The variable length coding unit receives the image input data, and performs a variable length coding on the image input data to generate a second encoded data. The selecting unit receives the first encoded data and the second encoded data, and outputs the first encoded data or the second encoded data to a storage unit. The comparing unit compares the quality of the first encoded data with the quality of the second encoded data to generate a comparison signal. The control unit compares the length of the second encoded data with a threshold. When the length of the second encoded data is less than the threshold, the control unit determines whether the quality of the second encoded data is higher than the quality of the first encoded data according to the comparison signal, if the second The quality of the encoded data is higher than the quality of the first encoded data, and the control unit controls the selecting unit to output the second encoded data to the storage unit. If the quality of the second encoded data is lower than the quality of the first encoded data, the control unit controls the selecting unit. And outputting the first encoded data to the storage unit; when the length of the second encoded data is greater than the threshold, the control unit controls the selecting unit to output the first encoded data to the storage unit.

1‧‧‧Host
3‧‧‧Drive chip
5‧‧‧ storage unit
9‧‧‧Image display device
10‧‧‧Compression device
11‧‧‧Fixed length coding unit
13‧‧‧Variable length coding unit
15‧‧‧Control unit
17‧‧‧Selection unit
19‧‧‧ Division
21‧‧‧Comparative unit
30‧‧‧Decompression device
31‧‧‧Header Decoding Unit
33‧‧‧Switch unit
35‧‧‧Fixed length decoding unit
37‧‧‧Variable length decoding unit
39‧‧‧Selection unit

[0012]

First: a block diagram of a driving chip applied to an image display device of the compression device of the present invention;
Second drawing: a block diagram of an embodiment of a compression device of the present invention;
Third drawing: a block diagram of another embodiment of a compression device of the present invention;
Figure 4 is a block diagram of yet another embodiment of a compression device of the present invention; and a fifth diagram: a block diagram of one embodiment of a decompression device of the present invention.

[0013]

Certain terms are used throughout the description and following claims to refer to particular elements. Those of ordinary skill in the art should understand that a hardware manufacturer may refer to the same component by a different noun. The scope of this specification and the subsequent patent application do not use the difference of the names as the means for distinguishing the elements, but the difference in function of the elements as the criterion for distinguishing. The term "including" as used throughout the specification and subsequent claims is an open term and should be interpreted as "including but not limited to". In addition, the term "coupled" is used herein to include any direct and indirect electrical connection. Therefore, if a first device is coupled to a second device, it means that the first device can be directly electrically connected to the second device or indirectly electrically connected to the second device through other devices or connection means.

[0014]

In order to provide a better understanding and understanding of the features and the efficacies of the present invention, the preferred embodiment and the detailed description are as follows:

[0015]

Referring to the first figure, it is a block diagram of a driving device of the present invention applied to a driving chip of an image display device. As shown in the figure, the compression device 10 of the present invention is disposed in the driving chip 3. The driving chip 3 is further provided with a storage unit 5 and a decompression device 30. The driving chip 3 is coupled between the host 1 and the image display device 9. The drive wafer 3 is a display drive wafer. The host 1 transmits a plurality of pixel data to the driving chip 3. The compression device 10 that drives the chip 3 receives the pixel data as a plurality of image input data, compresses the image input data, and inputs the compressed image into the data. It is stored in the storage unit 5. The decompressing device 30 reads the compressed image input data stored in the storage unit 5, performs decompression processing, and transmits the decompressed image input data to the image display device 9 to display the image. The host 1 described above may be a computer, a digital camera, or other device that can transmit pixel data to the drive chip 3. Further, the host 1 may be a baseband IC, such as a baseband chip of a mobile phone, and the drive die 3 is a display driver chip of a mobile phone. In an embodiment of the invention, the storage unit 5 is a random access memory RAM for use as a frame buffer.

[0016]

The compression device 10 of the present invention can ensure that the compression ratio of the compression process can reach a predetermined compression rate, and the image input data can be stored in the storage unit 5 after being compressed. The compression device 10 will be described in detail below.

[0017]

Please refer to the second figure, which is a block diagram of an embodiment of a compression device of the present invention. As shown, the compression device 10 includes a fixed length coding unit 11, a variable length coding unit 13, a control unit 15, and a selection unit 17. Both the fixed length coding unit 11 and the variable length coding unit 13 are coupled to the host 1 (as shown in the first figure) to receive image input data. The fixed length encoding unit 11 performs fixed length encoding on the image input data to generate a first encoded data, and the length (number of bits) of the first encoded data is a fixed value. The variable length encoding unit 13 performs variable length encoding on the image input data to generate a second encoded data, and the length (number of bits) of the second encoded data is a variable value. The first encoded data and the second encoded data each include a header bit, which indicates which encoding mode is used by the first encoded data and the second encoded data.

[0018]

There are many types of fixed length coding units 11, such as Pulse-Code Modulation (PCM), Block Truncation Coding (BTC), and Vector Quantization Block Truncation Coding. , VQ-BTC) and so on. There are many types of variable length coding units 13, such as Differential Pulse-Code Modulation (DPCM). The above-described examples are merely embodiments of the present invention, and are not intended to limit the present invention to only the above-described examples as the fixed length coding unit 11 or the variable length coding unit 13.

[0019]

Referring to the second figure, the selecting unit 17 is coupled to the fixed length encoding unit 11 and the variable length encoding unit 13, and receives the first encoded data and the second encoded data, and outputs the first encoded data or the second encoded data to the storage unit 5. To be stored in the storage unit 5. The control unit 15 is also coupled to the fixed length encoding unit 11 and the variable length encoding unit 13. The fixed length encoding unit 11 and the variable length encoding unit 13 encode a video encoded data to transmit a first encoded data length and a second encoded data length. To the control unit 15. The length of the first encoded data and the length of the second encoded data represent the length (number of bits) of the first encoded data and the length (number of bits) of the second encoded data, respectively.

[0020]

The control unit 15 compares the length of the second encoded data with a threshold. When the length of the second encoded data is less than the threshold, the control unit 15 controls the selecting unit 17 to output the second encoded data to the storage unit 5. If the length of the second encoded data is greater than the threshold, it indicates that the number of bits of the second encoded data is too large to be stored in the storage unit 5, so the control unit 15 controls the selecting unit 17 to output the first encoded data to the storage unit 5. In an embodiment of the invention, the selection unit is a multiplexer. The control unit 15 compares the length and threshold of the second encoded data to know whether the number of bits of the second encoded data generated by the variable length encoding unit 13 is too large, and is not suitable for storage in the storage unit 5. If the number of bits of the second encoded data is too large, the first encoded data generated by the fixed length encoding unit 11 is stored in the storage unit 5. The length of the first encoded data is less than or equal to the threshold, so that the compression ratio of the compression device 10 can be ensured to meet the predetermined compression ratio, and the image input data can be stored in the storage unit 5 after being compressed by the compression device 10.

[0021]

In general, the compression performance of the variable length coding is not necessarily better than the compression performance of the fixed length coding, but is generally better than the compression performance of the fixed length coding, so that the second encoded data generated by the variable length coding unit 13 can be stored. When the unit 5 is stored, the compression performance should be improved. It can be seen from the above that the compression device 10 of the present invention encodes the image input data by using the fixed length coding and the variable length coding. In addition to ensuring that the image input data can be stored in the storage unit 5 after being compressed, the compression performance should be improved.

[0022]

In general, the way in which the host 1 (as shown in the first figure) transmits pixel data is generally to sequentially transmit horizontal line pixel data to be displayed on the image display device 9 (as shown in the first figure). Each pixel data (each horizontal line pixel data) transmitted by the host computer 1 represents each horizontal line image displayed on the image display device 9. For example, if the display resolution of the image display device 9 is 1280*720, each horizontal line pixel data transmitted by the host 1 includes data of 720 pixel points, and each pixel point is a color picture. The prime point contains red, green and blue sub-pixels, each sub-pixel is represented by 8 bits, so that each horizontal line of pixel data has a total of 17280 (720 * 24) bits. The storage unit 5 is configured to store the compressed horizontal line pixel data. In order to improve the processing efficiency of the compression device 10, the compression device 10 of the present invention first divides the horizontal line pixel data transmitted by the host 1 to generate a plurality of block pixel data, and supplies the data to the fixed length coding unit 11 and the variable length coding. Unit 13.

[0023]

Please refer to the third figure, which is a block diagram of another embodiment of the compression device of the present invention. As shown in the figure, the compression device 10 of this embodiment further includes a dividing unit 19 coupled to the host 1 (as shown in the first figure) to receive the transmitted horizontal line pixel data and divide the horizontal line pixels. The data is used as a plurality of image input data to generate a plurality of block pixel data. The dividing unit 19 is further coupled to the fixed length encoding unit 11 and the variable length encoding unit 13 to sequentially transmit the block pixel data to the fixed length encoding unit 11 and the variable length encoding unit 13. In this embodiment, the dividing unit 19 divides each horizontal line pixel data into 90 block pixel data, for example, divides horizontal line pixel data including 720 pixels into 90 block pixel data. Therefore, each block of pixel data contains 8 pixels of data.

[0024]

In this embodiment, the fixed length encoding unit 11 and the variable length encoding unit 13 receive the block pixel data (image input data) and perform encoding processing to generate the first encoded data and the second encoded data, and transmit the first The length of the encoded data and the length of the second encoded data are sent to the control unit 15, and the control unit 15 compares the length and threshold of the second encoded data to determine whether the second encoded data is too long, and determines to store the second encoded data or the first encoded data. In the storage unit 5.

[0025]

In an embodiment, the threshold may be a fixed threshold. The fixed threshold is the total number of pixel points for each image input data, the total number of bits per pixel point, and the predetermined compression ratio. In this embodiment, each image input data (block pixel data) includes 8 pixel points, each pixel point is represented by 24 bits, and the predetermined compression ratio is 0.5, so the fixed threshold is 96 (8*). 24*0.5), which means that the number of bits of the second encoded material must be equal to or less than 96 to be stored in the storage unit 5. In addition, since the fixed length encoding unit 11 can be set such that the number of bits of the first encoded material generated is less than or equal to the threshold, the first encoded data can be stored in the storage unit 5. In this way, the compression ratio of the compression device 10 can be ensured to meet the predetermined compression ratio, so as to ensure that the image input data can be stored in the storage unit 5 after being compressed, and the compression performance can be improved.

[0026]

In another embodiment of the invention, the threshold may be a varying threshold. The control unit 15 determines the change threshold according to a quota bit and a redundant bit, and the change threshold is the sum of the quota bit and the extra bit. The quota bit is the number of storage bits corresponding to each image input data quota, that is, the space size that can be stored for each coded data corresponding to each image input data. In an embodiment, the quota bit is the same as the fixed threshold described above, which is the total number of pixel points of a piece of image input data, the total number of bits per pixel point and a predetermined compression ratio, and the quota bit is one. Fixed value. For example, if the quota bit is 96 bits, it means that the encoded data generated by the compression processing of each image input data is allocated 96 bits of storage space. The extra bit is the number of redundant storage bits of the storage unit 5, that is, the storage space currently stored by the storage unit 5.

[0027]

According to the above description, the quota bit indicates the size of the space allocated to the storage unit 5 for each piece of coded data corresponding to each image input data. The storage unit 5 has a predetermined storage space for storing data of a horizontal line image, that is, a coded data for storing a horizontal line of pixel data after compression processing, so that all block pixels of a horizontal line of pixel data The sum of the quota bits of the data must be less than or equal to the predetermined storage space of the storage unit 5. In the embodiment of the present invention, the quota bits of each image input data (block pixel data) are the same value, but may also be different, as long as all the block pixel data of one horizontal line pixel data are met. The sum of the quota bits may be less than or equal to the condition of the predetermined storage space of the storage unit 5.

[0028]

In the above description, the quota bits of each image input data (block pixel data) may be different values, which are preset in the control unit 15, and the coding parameters of the fixed length code are preset to be fixed corresponding to the quota bits. The length encoding unit 11 so that the fixed length encoding unit 11 sequentially receives the pen image input data, and performs fixed length encoding according to the preset encoding parameters to match the preset quota bit, for example, the first pen and The quota bit of the third image input data is 96, and the quota bit of the second image input data is 48, so the compression ratio corresponding to the first and third image input data is 0.5, the first pen and The length of the first encoded data of the third stroke is 96 bits (8*24*0.5), and the compression ratio corresponding to the second image input data is 0.25, and the length of the first encoded data of the second stroke is 48. Bit (8*24*0.25).

[0029]

Although the quota bit of the above embodiment is not fixed, the quota bit of each image input data is predetermined, and the coding parameter of the fixed length coding unit 11 is also set in advance, which indicates that the fixed length coding unit 11 generates The length of each first encoded data has been determined in advance, so regardless of the content of the image input data, the length of the first encoded data generated by the fixed length encoding unit 11 after encoding the image input data is a preset encoding length. For a fixed code length, for example, the length of the first coded data of the first pen and the third pen is fixed to 96 bits, and the length of the first coded data of the second pen is fixed to 48 bits.

[0030]

The following is a detailed description of the operation and compression mode of the compression device 10 of this embodiment. At first, the compression device 10 has not received the image input data, and the storage unit 5 has not stored the data, and the redundant bit is set to 0, and the quota bit is 96. Bit, so the initial change threshold (the sum of the extra bits and the quota bits) is 96. The fixed length encoding unit 11 and the variable length encoding unit 13 encode the first image input data to generate the first encoded data and the second encoded data. The length of the first encoded data is less than or equal to the quota bit. In this embodiment, the length of the first encoded data is 96 bits, and the length of the second encoded data is 40 bits.

[0031]

The control unit 15 compares the second encoded data length with the variation threshold, and the second encoded data length is smaller than the variation threshold, so the control unit 15 controls the selection unit 17 to output the second encoded data to the storage unit 5, and stores the second encoded data. Since the length of the second encoded data corresponding to the first image input data is 40 bits, and the quota bit and the variation threshold are 96 bits, the storage unit 5 has 56 more bits (change threshold and The difference between the lengths of the second encoded data stored in the storage unit 5, so that the redundant bits are updated to 56 bits, and the change threshold is also changed to 152 (the total of the quota bits and the redundant bits) In addition, the new change threshold (152) corresponds to the next image input data (next block pixel data), which indicates that the maximum length of a piece of coded data stored in the storage unit 5 can be 152 bits. .

[0032]

If the length of the second encoded data corresponding to the first image input data is 130 bits, and is greater than the initial variation threshold (96), the control unit 15 controls the selection unit 17 to output the first encoded data to the storage unit. 5. Since the length of the first encoded data is 96 bits and is equal to the quota bit (96), the storage unit 5 does not have more bits, so the redundant bits are also maintained at 0, and the change threshold does not change accordingly. And the same is 96 (the sum of quota bits and extra bits). It can be seen from the above that the storage threshold of the storage unit 5 can be effectively utilized by using the variation threshold, and a plurality of second encoded data having a long data length can be stored, so that the compression performance can be improved. In addition, the initial redundant bit is not necessarily 0. For example, the predetermined storage space of the storage unit 5 is large, and the sum of the quota bits of all the block pixel data of one horizontal line of pixel data is smaller than the predetermined storage space. Next, the initial extra bits will not be 0, and the initial extra bits are represented as follows:
Initial extra bit = predetermined storage space - the sum of the quota bits of all block pixel data

[0033]

It can be seen from the above description that after the storage unit 5 stores the first coded data or the second coded data, the control unit 15 updates the excess bit to the length of the first coded data or the second coded data stored in the current change threshold and the storage unit 5. For the difference, the control unit 15 adjusts the change threshold according to the quota bit and the updated extra bit to apply to the compression process of the next image input data. In addition, the control unit 15 further has a counting function. After completing each comparison, the control unit 15 counts once to know the total number of image input materials processed by the compression device 10, and determines whether a horizontal line has been processed. Pixel information. In this embodiment, one horizontal line pixel data (720 pixel points) is divided into 90 pieces of image input data, so when the control unit 15 counts to 90, it means that the compression device 10 has completed compressing one horizontal line of pixel data. The encoded data generated by compressing the horizontal line pixel data is stored in the storage unit 5. If the count value is not 90, it means that the compression device 10 has not finished compressing one horizontal line of pixel data, and the compression device 10 successively processes the next image input data according to the above processing manner until the processing of 90 pieces of image input data is completed.

[0034]

Please refer to the fourth figure, which is a block diagram of still another embodiment of the compression device of the present invention. As shown in the figure, this embodiment further includes a comparison unit 21, which is coupled to the fixed length coding unit 11, the variable length coding unit 13, and the control unit 15. After the fixed length encoding unit 11 and the variable length encoding unit 13 of the embodiment complete encoding the image input data, the two perform an image quality assessment (IQA), and respectively the first encoded data and the second encoding. The data is subjected to quality evaluation, and a first quality assessment and a second quality assessment are respectively obtained, and the first quality assessment and the second quality assessment are output to the comparison unit 21. The value of the first quality assessment indicates the quality of the first encoded material, and the value of the second quality assessment indicates the quality of the second encoded material. There are many ways to evaluate image quality, such as Mean Square Error (MSE), Sum of Absolute Difference (SAD) and Structural Similarity (SSIM).

[0035]

The comparing unit 21 receives the first quality assessment and the second quality assessment, and compares the first quality assessment with the second quality assessment to compare the quality of the second encoded data with the quality of the first encoded data, and outputs a comparison signal to the control unit. 15. In this way, the control unit 15 can know whether the quality of the second encoded data generated by the variable length encoding unit 13 is better than the quality of the first encoded data generated by the fixed length encoding unit 11 according to the comparison signal, and the quality of the encoded data is Indicates the compression performance of the coding unit. When the length of the second encoded data is less than the threshold, the control unit 15 further determines whether to store the second encoded data in the storage unit 5 according to the comparison signal. If the quality of the second encoded data is higher than the quality of the first encoded data, the control unit 15 controls the selecting unit 17 to output the second encoded data to the storage unit 5. If the quality of the second encoded data is lower than the quality of the first encoded data, the control unit 15 controls the selecting unit 17 to output the first encoded data to the storage unit 5. In this way, it is ensured that the encoded data of better quality is stored in the storage unit 5, so that the compression device 10 can achieve higher compression performance in addition to ensuring the compression ratio.

[0036]

In addition, the comparing unit 21 further receives the consistent energy signal, and the enabling signal is used to enable the comparing unit 21 to drive the comparing unit 21 to operate normally. If the enabling signal does not enable the comparing unit 21, the comparing unit 21 does not compare the first quality assessment with the second quality assessment. In general, the compression performance of the variable length coding is much better than the compression performance of the fixed length coding. Therefore, when the comparison unit 21 is not enabled, the comparison signal generated by the comparison unit 21 indicates that the selection variable length coding unit 13 generates the first generation. The second coded data is such that when the length of the second coded data is less than the change threshold, the control unit 15 outputs the second coded data to the storage unit 5 according to the comparison signal control selection unit 17.

[0037]

In another embodiment of the present invention, the enable signal is further sent to the control unit 15 (not shown). When the signal enable comparison unit 21 is enabled, the control unit 15 uses the comparison signal according to the enable signal. If the enabling unit 21 does not enable the comparing unit 21, the control unit 15 knows that the comparing unit 21 is not enabled according to the enabling signal, so that the control unit 15 does not use the comparison signal, so when the second encoded data length is less than the threshold The control unit 15 then controls the selection unit 17 to output the second encoded material to the storage unit 5.

[0038]

Please refer to the fifth figure, which is a block diagram of an embodiment of the decompression device of the present invention. As shown, the decompression device 30 includes a header decoding unit 31, a switching unit 33, a fixed length decoding unit 35, a variable length decoding unit 37, and a selection unit 39. The header decoding unit 31 and the switching unit 33 are coupled to the storage unit 5. The switching unit 33 reads the encoded data stored in the storage unit 5, which is the first encoded data or the second encoded data, and the header decoding unit 31 reads the encoded code. The header bit of the data, and decoding the header bit to know that the encoded data read by the switching unit 33 is the first encoded data or the second encoded data, and outputs a decoded signal to the switching unit 33, and the switching unit 33 transmits the read encoded data to the fixed length decoding unit 35 or the variable length decoding unit 37 in accordance with the decoded signal.

[0039]

As described above, when the decoded signal indicates that the encoded data is the first encoded data, the switching unit 33 transmits the first encoded data to the fixed length decoding unit 35 according to the decoded signal, and the fixed length decoding unit 35 will be the first encoded data. Decoding is performed, and a first decoded data is output to the selection unit 39. When the decoded signal indicates that the encoded data is the second encoded data, the switching unit 33 transmits the second encoded data to the variable length decoding unit 37 according to the decoded signal, and the variable length decoding unit 37 decodes the second encoded data, and outputs A second decoded data is sent to the selection unit 39. The selecting unit 39 is coupled to the header decoding unit 31, and receives the decoded signal and outputs the first decoded data or the second decoded data according to the decoded signal to provide the first decoded data or the second decoded data to the image display device 9 (eg, the first The figure shows) and the image is displayed. In an embodiment of the invention, the selection unit 39 is a multiplexer.

[0040]

In summary, the compression device and the compression method of the image data disclosed by the present invention encode the image input data by using fixed length coding and variable length coding, and if the variable length coding encodes the image input data, the encoded data is generated. If the length is less than the threshold, the coded data is stored in the storage unit. If the length of the coded data is greater than the threshold, the coded data generated by encoding the image input data by the fixed length code is stored. In this way, the compression ratio can be ensured to meet the predetermined compression ratio, and the image input data can be stored in the storage unit after being compressed.

[0041]

In addition, before storing the encoded data generated by the variable length coding, it may be determined whether the quality of the encoded data generated by the variable length coding is higher than the quality of the encoded data generated by the fixed length coding. If the quality of the encoded data generated by the variable length coding is lower than the quality of the encoded data generated by the fixed length coding, the encoded data generated by the fixed length coding is stored. In this way, in addition to ensuring the compression ratio, higher compression performance can be achieved.

[0042]

Therefore, the present invention is a novelty, progressive and available for industrial use. It should be in accordance with the requirements of patent applications for patent law in China. It is undoubtedly to file an invention patent application according to law, and the Prayer Council will grant patents as soon as possible.

[0043]

The above is only an embodiment of the present invention, and is not intended to limit the scope of the present invention, so that the shapes, structures, features, and spirits described in the claims of the present invention are equally changed and modified. All should be included in the scope of the patent application of the present invention.

5‧‧‧ storage unit

10‧‧‧Compression device

11‧‧‧Fixed length coding unit

13‧‧‧Variable length coding unit

15‧‧‧Control unit

17‧‧‧Selection unit

Claims (13)

A compression device for image data, comprising: a fixed length coding unit, receiving an image input data, and performing a fixed length coding on the image input data to generate a first encoded data; and a variable length coding unit receiving the image Inputting data, and performing a variable length coding on the image input data to generate a second encoded data; a selecting unit coupled to the fixed length encoding unit and the variable length encoding unit, respectively receiving the first encoded data and the The second encoded data is coupled to a storage unit and outputs the first encoded data or the second encoded data to the storage unit; and a control unit coupled to the variable length encoding unit and receiving the second encoded data Length, coupled to the selection unit, comparing the length of the second encoded data with a threshold, when the length of the second encoded data is less than the threshold, the control unit controls the selecting unit to output the second encoded data to the storage a unit; when the length of the second encoded data is greater than the threshold, the control unit controls the selection unit to lose The first encoded data is sent to the storage unit; wherein the threshold is a change threshold, a quota bit and a redundant bit determine the change threshold, and the quota bit is a storage bit corresponding to the quota of the image input data. Number The excess bit is the number of redundant storage bits of the storage unit. The compression device of claim 1, wherein the storage unit stores the first coded data or the second coded data, and the redundant bit is updated to the change threshold and the first stored by the storage unit. A difference between the length of the coded data or the second coded data, and then the change threshold is changed according to the quota bit and the updated redundant bit. The compression device of claim 1, wherein the length of the first encoded data is less than or equal to the quota bit, and the quota bit is a fixed value. The compression device of claim 1, wherein the quota bit is a product of a total number of complex pixel points of the image input data, a total number of bits per pixel point, and a predetermined compression ratio. The compression device of claim 1, wherein the image input data is a block of pixel data, and one horizontal pixel of the image display device comprises a plurality of block pixel data, and the storage unit is temporarily stored. The horizontal line of pixel data processed by compression. The compression device of claim 5, further comprising a dividing unit coupled to the fixed length coding unit and the variable length coding unit, and receiving the horizontal line pixel data to divide the horizontal line pixel data Produce the blocks And the block data is sequentially transmitted to the fixed length coding unit and the variable length coding unit. A method for compressing image data, comprising: receiving an image input data; performing a fixed length encoding and a variable length encoding on the image input data to generate a first encoded data and a second encoded data; and comparing the second The length of the encoded data and a threshold, when the length of the second encoded data is less than the threshold, storing the second encoded data in a storage unit; when the length of the second encoded data is greater than the threshold, The first coded data is stored in the storage unit; wherein the threshold is a change threshold, a quota bit and a redundant bit determine the change threshold, and the quota bit is a storage bit corresponding to the quota of the image input data. The number of excess bits is the number of redundant storage bits of the storage unit. The compression method of claim 7, wherein the storage unit stores the first coded data or the second coded data, and the redundant bit is updated to the change threshold and the first stored by the storage unit. A difference between the length of the coded data or the second coded data, and then the change threshold is changed according to the quota bit and the updated extra bit for use in compression processing of the next image input data. The compression method of claim 7, wherein the length of the first encoded data is less than or equal to the quota bit, and the quota bit is a fixed value. The compression method of claim 7, wherein the quota bit is a product of a total number of complex pixel points of the image input data, a total number of bits per pixel point, and a predetermined compression ratio. The compression method of claim 7, wherein the image input data is a block of pixel data, and one horizontal image of the image display device comprises a plurality of block pixel data, and the storage unit is temporarily stored. The horizontal line of pixel data processed by compression. The compression method of claim 11, further comprising: receiving the horizontal line pixel data, and dividing the horizontal line pixel data to generate the block pixel data. A compression device for image data, comprising: a fixed length coding unit, receiving an image input data, and performing a fixed length coding on the image input data to generate a first encoded data, and performing quality on the first encoded data Evaluating, obtaining a first quality assessment; a variable length coding unit, receiving the image input data, and performing a variable length coding on the image input data to generate a second encoded data, and the second encoding resource The quality evaluation is performed to obtain a second quality evaluation; a selection unit is coupled to the fixed length coding unit and the variable length coding unit, and respectively receives the first coded data and the second coded data, and is coupled to the first coded data. And storing, by the storage unit, the first coded data or the second coded data to the storage unit; a comparison unit coupled to the fixed length coding unit and the variable length coding unit, respectively receiving the first quality assessment and the second Quality evaluation, and comparing the first quality assessment with the second quality assessment to generate a comparison signal; and a control unit coupled to the variable length coding unit to receive the length of the second encoded data and coupled to the The comparing unit and the selecting unit compare the length of the second encoded data with a threshold. When the length of the second encoded data is less than the threshold, the control unit determines, according to the comparison signal, whether the second quality assessment is higher than the threshold a first quality assessment, if the second quality assessment is higher than the first quality assessment, the control unit controls the selection unit to output the second encoding resource Up to the storage unit, if the second quality assessment is lower than the first quality assessment, the control unit controls the selection unit to output the first encoded data to the storage unit; when the length of the second encoded data is greater than the threshold, The control unit controls the selection unit to output the first Encoding data to the storage unit; wherein the threshold is a change threshold, a quota bit and a redundant bit determine the change threshold, the quota bit is a quantity of storage bits corresponding to the quota of the image input data, The extra bit is the number of excess storage bits of the storage unit.