JPH11146367A - Mobile videophone - Google Patents

Abstract

(57) [Summary] [PROBLEMS] In a conventional videophone, image quality and data amount are almost controlled by a quantization coefficient Q value. However, by itself, the data amount is reduced while maintaining subjective image quality. It was not enough. Therefore, it is an object of the present invention to provide a mobile videophone that reduces the amount of data and improves the frame rate without lowering the subjective image quality. SOLUTION: In the block division in the encoding process, it is possible to divide the image into macroblocks of a plurality of sizes, to reduce the size in a portion of the image where the importance of the image quality is high, and to reduce the size in a portion where the importance is low. By reducing the amount of data, the amount of data in a portion with low importance is reduced, the amount of data is reduced while maintaining the subjective image quality, the frame rate is improved, and the overall image quality is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mobile videophone using a wireless network.

[0002]

2. Description of the Related Art With the spread of wireless digital communication networks, the market for mobile videophones using wireless networks is expected to expand in the future. Hereinafter, a conventional videophone will be described.

FIG. 3 is a diagram showing an encoding process of a conventional mobile videophone, and FIG. 4 is a diagram showing the same block processing. In FIG. 3, 1 is an original image of a moving image, 2 is a block unit, and 3 is a DCT.
, 4 is a quantization coefficient Q used for quantization, 5 is a quantization unit, 6 is a variable length coding unit, 7 is coded data, 8 is coded data received, 9 is a variable length decompression unit, 10 is an inverse quantization unit, 11 is an inverse DCT unit, 12 is an inverse block unit, 13
Is an expanded image.

[0004] A conventional video coding for a videophone will be described below with reference to FIG. First, the original image 1 of the moving image is divided by the blocking unit 2 into a plurality of macroblocks of 8 × 8 pixels. The DCT unit 3 performs a DCT process for each macroblock divided in the previous stage, and quantizes the result using the quantization coefficient Q4 in the quantization unit 5. Thereafter, the variable length coding unit 6 performs a variable length coding process to reduce the amount of information and generate final coded data 7. The generated encoded data is multiplexed with audio data and the like in post-processing and transmitted. Conversely, the coded data 8 received and separated is subjected to decompression processing by the variable-length decompression unit 9, and is subjected to dequantization processing by the dequantization unit 10 using the quantization coefficient Q4 used for quantization. Inverse DCT processing is performed in the DCT unit 11 and a plurality of macroblocks are
The two images are combined to obtain a moving image, which is a 13 expanded image.

The above contents will be described in more detail with reference to FIG. In FIG. 4, reference numeral 14 denotes an original picture of a moving image, and 15 denotes 8 ×
The macroblock of 8 pixels, 16 is the result after performing DCT processing, and 17 is the result after performing quantization processing. First, 14 original images are divided into a plurality of blocks of 8 × 8 pixels such as 15 by performing block processing, and DCT processing is performed for each of the divided macro blocks. The result 15
After the DCT processing, the lower left component becomes the lower frequency component and the lower right component becomes the higher frequency component. Generally, the lower the frequency component, the larger the value, and the higher the frequency component, the smaller the value. 16
Is performed on the result by the quantization coefficient Q, that is, each value of 16 is divided by Q, and the value is large in the low-frequency component where the original value is large, but is large in the high-frequency component. Since the value is small, the value becomes small and becomes almost 0. These continuous 0 values are coded by variable length coding to generate coded data. Conversely, in the case of extension, the reverse procedure is performed.

[0006]

In the case of using an unstable wireless data network with a small data transmission amount, it is necessary to further reduce the data amount without lowering the apparent image quality in order to improve the quality of moving picture reproduction. There is. However, in the above-described conventional configuration, the image quality and the data amount are almost controlled by the Q value which is a quantization coefficient, and this alone is insufficient.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a mobile videophone that solves the above-mentioned problems and reduces the amount of data and improves the frame rate without lowering the subjective image quality.

[0008]

According to the mobile videophone of the present invention, the size of a macro block is reduced in a portion where the image quality is important at the center of the screen, and the macro block is used in a portion where the image quality is low in a peripheral portion. The size of the block is increased, and the amount of encoded data in the peripheral portion is reduced.

With this configuration, the size is reduced and the image quality is maintained in a portion where the importance of image quality is high, and the size is increased and the data amount is reduced in a portion where the importance is low, thereby reducing the overall data amount. Improve rate.

[0010]

According to the first aspect of the present invention, the size of a macroblock is reduced in a central portion of a screen where the importance of image quality is high, and in a portion where the importance of image quality is low in a peripheral portion. Has been increased, and the amount of encoded data in the peripheral portion has been reduced.

With this configuration, the data amount can be reduced and the frame rate can be improved without lowering the subjective image quality.

According to a second aspect of the present invention, a portion where the importance of the image quality of the screen is high and a portion where the importance is low are set in advance, and the setting of the high importance portion and the low importance portion are changed in accordance with the motion vector. The macroblock size is reduced in parts where the image quality is important, the macroblock size is increased in parts where the image quality is low, and the amount of encoded data is reduced in the parts where the image quality is low. I did it.

With this configuration, the data amount can be reduced and the frame rate can be further improved without lowering the subjective image quality.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a block size variable encoding process diagram of a mobile videophone according to an embodiment of the present invention;
FIG. 2 is a diagram showing the same size variable block processing.

In FIG. 1, reference numeral 18 denotes an original picture of a moving image, 19 denotes a variable-size block forming unit, 20 denotes a variable-size DCT unit,
21 is a quantization coefficient Q used for variable size quantization, 22
Is a variable size quantization unit, 23 is a variable size variable length coding unit, 24 is encoded data, 25 is received encoded data, 26 is a variable size variable length decompression unit, 27 is a variable size inverse quantization unit, Reference numeral 28 denotes a variable size inverse DCT unit, 29 denotes a variable size inverse blocking unit, and 30 denotes an expanded image, that is, an expanded moving image.

The operation will be described below with reference to FIG. First, the original image 18 of the moving image is converted to 8 × 8 pixels or another size (for example, 16 ×
(16 pixels). In the variable-size DCT unit 20, DCT processing is performed in accordance with each macroblock size in units of macroblocks divided in the previous stage, and the result is quantized in the variable-size quantization unit 22 using the quantization coefficient Q21. . Thereafter, the variable-length encoding process is performed by the variable-size variable-length encoding unit 23 to reduce the amount of information and generate final encoded data 24.

The generated encoded data 24 is multiplexed with audio data and the like in post-processing and transmitted. Conversely, the coded data 25 received and separated is the size-variable-variable-length decompression unit 2.
6 and the quantization coefficient Q21 used for quantization.
, The inverse quantization process is performed by the variable-size inverse quantization unit 27, the inverse DCT process is performed by the variable-size inverse DCT unit 28, and a plurality of macroblocks of a plurality of sizes are converted by the variable-size inverse deblocking unit 29. Combine to obtain 30 stretches.

The size variable blocking section 19 will be described in more detail with reference to FIG. In FIG. 2, reference numeral 31 denotes an original picture of a moving image, 32 denotes a macro block of 8 × 8 pixels, 33
Is a macroblock of 16 × 16 pixels. In the 31 original images, a portion having high image quality and a portion having low importance are set in advance, and a portion having high importance based on the setting is set to a small size such as 32 × 8 pixels. For a portion where the importance of image quality is low, on the other hand, for example, 16 × 16 like 33
Divide into macroblocks of large size such as pixels. Thereafter, DCT processing corresponding to each size is performed. Conversely, in the case of extension, the reverse procedure is performed.

Next, the second processing method will be described with reference to FIG. First, based on the detection information obtained by detecting the motions of the high and low image quality parts by the motion information detection unit 34, the size of the original image 18 of the moving image is changed to 8 × 8 Pixels or other size (for example, 16 × 16 pixels)
Divide into multiple macroblocks of multiple sizes. The variable-size DCT unit 20 performs DCT processing in accordance with the size of each macroblock for each macroblock divided in the previous stage, and applies a quantization coefficient Q2
1 is used to perform quantization in the variable-size quantization unit 22, and then variable-length coding is performed by the variable-size variable-length coding unit 23 to reduce the amount of information and generate final coded data 24.

The generated coded data 24 is multiplexed with audio data and the like in post-processing and transmitted. Conversely, the coded data 25 received and separated is the size-variable-variable-length decompression unit 2.
6 and the quantization coefficient Q21 used for quantization.
, The inverse quantization process is performed by the variable-size inverse quantization unit 27, the inverse DCT process is performed by the variable-size inverse DCT unit 28, and a plurality of macroblocks of a plurality of sizes are converted by the variable-size inverse deblocking unit 29. Combine to obtain 30 stretches. Conversely, in the case of extension, the reverse procedure is performed.

[0021]

As described above, according to the present invention, the encoded data amount of a moving image can be reduced without lowering the subjective image quality, and the frame rate can be improved and the total moving image Image quality can be improved.

[Brief description of the drawings]

FIG. 1 is a block size variable encoding process diagram of a mobile videophone according to an embodiment of the present invention;

FIG. 2 is a diagram illustrating a size-variable blocking process of a mobile videophone according to an embodiment of the present invention.

FIG. 3 is an encoding processing diagram of a conventional mobile videophone.

FIG. 4 is a block diagram of a conventional mobile videophone.

[Explanation of symbols]

 18 Original Picture 19 Size Variable Blocking Unit 20 Size Variable DCT Unit 21 Quantization Coefficient Q 22 Size Variable Quantizing Unit 23 Size Variable Variable Length Encoding Unit 24 Encoded Data 25 Encoded Data 26 Size Variable Variable Length Decompression Unit 27 Size Variable inverse quantization unit 28 Size variable inverse DCT unit 29 Size variable inverse block unit 30 Decompressed image 31 Original image 32 8 × 8 pixel macroblock 33 16 × 16 pixel macroblock 34 Motion information detection unit

Claims (2)

[Claims] 1. A macroblock size is reduced in a central portion of a screen where image quality is important, and a macroblock size is increased in a peripheral portion where image quality is low in importance. A mobile videophone characterized in that the amount of encrypted data is reduced. 2. The method according to claim 1, further comprising: setting in advance a portion having a high importance of the image quality of the screen and a portion having a low importance of the image quality, changing a setting of a portion having a high importance and a portion having a low importance according to the motion vector, and The size of the macroblock is reduced in the part, the size of the macroblock is increased in the part where the image quality is less important, and the amount of encoded data is reduced in the part where the image quality is less important. Mobile videophone.