Image coding device and method of image coding

• US 7,215,710 B2
• Filed: 01/19/2001
• Issued: 05/08/2007
• Est. Priority Date: 06/28/2000
• Status: Expired due to Fees

• Current Assignee: Mitsubishi Denki Kabushiki Kaisha (Mitsubishi Electric Corporation)
• Original Assignee: Mitsubishi Denki Kabushiki Kaisha (Mitsubishi Electric Corporation)
• Inventors: Yamada, Yoshihisa, Asai, Kohtaro, Murakami, Tokumichi, Tanno, Okikazu
• Primary Examiner(s): RAO, ANAND SHASHIKANT
• Application Number:
  US09/764,312
• Publication Number:
  US 20020001345A1
• Time in Patent Office: 2,300 Days
• Field of Search: 37524001-24029
• US Class Current: 375/240.24
• CPC Class Codes: G06T 9/007 Transform coding, e.g. discrete cosine transform
• CPC Class Codes: H04N 19/132 Sampling, masking or truncation of coding units, e.g. adaptive resampling, frame skipping, frame interpolation or high-frequency transform coefficient masking
• CPC Class Codes: H04N 19/16 for a given display mode, e.g. for interlaced or progressive display mode
• CPC Class Codes: H04N 19/172 the region being a picture, frame or field
• CPC Class Codes: H04N 19/587 involving temporal sub-sampling or interpolation, e.g. decimation or subsequent interpolation of pictures in a video sequence
• CPC Class Codes: H04N 19/85 using pre-processing or post-processing specially adapted for video compression

Abstract

The input image controller reduces the frame rate of a motion image signal as a preprocessing, provides process information indicating the skipped frames and/or skipped fields to the image coder, wherein the image coder codes, by use of the MPEG 2 method, the motion image signal whose frame rate has been reduced, and outputs the data which is in conformity with the MPEG 2 method and includes overhead information on the basis of the process information.

Claims

1. An image coding device for coding a motion image signal, and outputting the coded data as a bit stream, said image coding device comprising:

an input image controller that executes a predetermined processing to an input motion image signal for reducing the amount of coded data when coding the motion image signal by a coding method in which it is prescribed that the frame rate of a motion image signal is set to a constant level to be output at its decoding time, and outputs the processed motion image signal, together with the process information indicating the detail of said processing; and

an image coder for coding the motion image signal processed at said input image controller into a data in conformity with said coding method on the basis of said process information;

wherein said input image controller excludes either one field of each of the frames at a predetermined rate when the input motion image signal is of the interlace method, and outputs the processed motion image signal, together with the process information showing the thus excluded fields, and

said image coder detects the exclusion of fields on the basis of said process information, performs a predictive coding with respect to the thus excluded fields on the basis of the other fields, and generates a coded data corresponding to said excluded fields.

7. The image coding device according to claim 1, wherein the input image controller executes the predetermined processing to the motion image signal when the frame rate of the motion image signal is greater than a predetermined frame rate.

8. The image coding device according to claim 1, wherein the predetermined processing that is executed by the input image controller includes excluding a field or frame of the motion image signal such that the frame rate of the motion image signal is reduced to a predetermined frame rate.

9. The image coding device according to claim 8, wherein the process information indicates which fields or frames have been excluded.

16. The image coding device according to claim 1, wherein said coding method is the MPEG 2.

17. The image coding device according to claim 1, wherein said input image controller excludes either one field of each of the frames at a predetermined rate when the input motion image signal is of the interlace mode, and outputs the processed motion image signal together with the process information showing the thus excluded fields, and

said image coder detects the exclusion of fields on the basis of said process information, and adds an instruction to output another field instead of the excluded field at the time of decoding as overhead information before coding said processed motion image signal.

18. The image coding device according to claim 1, wherein said input image controller excludes frames at a predetermined rate when the input motion image signal is of the progressive mode, and outputs the processed motion image signal together with the process information showing the thus excluded frames, and

said image coder detects the exclusion of frames on the basis of said process information, and adds an instruction to output another frame field instead of the excluded frame at the time of decoding as overhead information before coding said processed motion image signal.

19. The image coding device according to claim 1, wherein said image coder changes the size of a motion image signal, outputs the motion image signal after processing, and also outputs process information indicating that the image size has been changed, and

said image coder detects frames whose image sizes have been changed within the whole processed motion image signal on the basis of the process information, and performs an intra-coding operation with respect to the first coded frame.

20. The image coding device according to claim 19, wherein said image coder changes the size of a motion image signal at the top of every predetermined image units, and

said image coder performs an intra-coding operation with respect to the frame whose image size has been changed.

21. The image coding device according to claim 20, wherein said input image controller changes the size of a frame immediately after a GOP header.

22. The image coding device according to claim 1, wherein said input image controller suppresses high-frequency components of a motion image signal.

23. The image coding device according to claim 1, wherein said input image controller executes a predetermined processing in accordance with the picture mode of each frame.

24. The image coding device according to claim 1, wherein said input image controller determines the amount of coding at the image coder on the basis of at least either one of the discrete state of pixel values in each frame, the difference of pixels between frames and a motion vector, and executes a predetermined processing in accordance with the thus determined amount of coding.

25. The image coding device according to claim 1, wherein said input image controller determines the amount of coding at the image coder on the basis of the mode of pictured scene, and executes a predetermined processing in accordance with the thus determined mode of pictured scene.

2. An image coding device for coding a motion image signal, and outputting the coded data as a bit stream, said image coding device comprising:

an input image controller that executes a predetermined processing to an input motion image signal for reducing the amount of coded data when coding the motion image signal by a coding method in which it is prescribed that the frame rate of a motion image signal is set to a constant level to be output at its decoding time, and outputs the processed motion image signal, together with the process information indicating the detail of said processing; and

an image coder for coding the motion image signal processed at said input image controller into a data in conformity with said coding method on the basis of said process information;

wherein said input image controller excludes either one field of each of the frames at a predetermined rate when the input motion image signal is of the interlace method, and outputs the processed motion image signal, together with the process information showing the thus excluded fields;

said image coder detects the exclusion of fields on the basis of said process information, performs a predictive coding with respect to the thus excluded fields on the basis of the other fields, and generates a coded data corresponding to said excluded fields; and

said image coder executes a predictive coding, considering all the motion vectors in the horizontal and vertical directions to be “

0”

.

3. An image coding device for coding a motion image signal, and outputting the coded data as a bit stream, said image coding device comprising:

an input image controller that executes a predetermined processing to an input motion image signal for reducing the amount of coded data when coding the motion image signal by a coding method in which it is prescribed that the frame rate of a motion image signal is set to a constant level to be output at its decoding time, and outputs the processed motion image signal, together with the process information indicating the detail of said processing; and

an image coder for coding the motion image signal processed at said input image controller into a data in conformity with said coding method on the basis of said process information;

wherein said input image controller excludes either one field of each of the frames at a predetermined rate when the input motion image signal is of the interlace method, and outputs the processed motion image signal, together with the process information showing the thus excluded fields;

said image coder detects the exclusion of fields on the basis of said process information, performs a predictive coding with respect to the thus excluded fields on the basis of the other fields, and generates a coded data corresponding to said excluded fields; and

said image coder executes a predictive coding, considering all the motion vectors in the horizontal direction to be “

0”

, and all the motion vectors in the vertical direction to be either “

+0.5”

or “

−

0.5”

.

4. An image coding device for coding a motion image signal, and outputting the coded data as a bit stream, said image coding device comprising:

an input image controller that executes a predetermined processing to an input motion image signal for reducing the amount of coded data when coding the motion image signal by a coding method in which it is prescribed that the frame rate of a motion image signal is set to a constant level to be output at its decoding time, and outputs the processed motion image signal, together with the process information indicating the detail of said processing; and

an image coder for coding the motion image signal processed at said input image controller into a data in conformity with said coding method on the basis of said process information;

wherein said input image controller excludes either one field of each of the frames at a predetermined rate when the input motion image signal is of the interlace method, and outputs the processed motion image signal, together with the process information showing the thus excluded fields,

said image coder detects the exclusion of fields on the basis of said process information, performs a predictive coding with respect to the thus excluded fields on the basis of the other fields, and generates a coded data corresponding to said excluded fields;

either said image coder or said input image controller observes a motion vector from two fields;

namely preceding and following fields of each of said excluded fields, and

said image coder interpolates said determined motion vector in accordance with each of the intervals between each of said excluded fields and said two fields, and executes a predictive coding about said excluded fields.

5. A method of image coding for coding a motion image signal and outputting the thus coded data as a bit stream, said method comprising the steps of:

executing a predetermined processing to an input motion image signal for reducing the amount of coded data when coding the motion image signal by a coding method in which it is prescribed that the frame rate of a motion image signal is set to a constant level to be output at its decoding time, and outputting the processed motion image signal, together with the process information indicating the detail of said processing, and

coding the motion image signal processed at said input image controller into a data in conformity with said coding method on the basis of said process information.

10. The image coding method according to claim 5, wherein the predetermined processing to the input motion image signal is executed when the frame rate of the motion image signal is greater than a predetermined frame rate.

11. The image coding method according to claim 5, wherein the predetermined processing includes excluding a field or frame of the motion image signal such that the frame rate of the motion image signal is reduced to a predetermined frame rate.

12. The image coding device according to 11, wherein the process information indicates which fields or frames have been excluded.

6. An image coding device for coding a motion image signal and outputting the thus coded data as a bit stream, said device comprising:

an input image controller which, in the case where the motion image signal is of the interlace mode, equalizes two fields of each frame at a predetermined rate, and outputs the thus processed motion image signal, and

an image coder that codes the motion image signal processed at said input image controller by a decoding method which is in conformity with a method that is designed for outputting a motion image signal at a constant frame rate.

13. The image coding device according to claim 6, wherein the input image controller executes the predetermined processing to the motion image signal when the frame rate of the motion image signal is greater than a predetermined frame rate.

14. The image coding device according to claim 6, wherein the predetermined processing that is executed by the input image controller includes excluding a field or frame of the motion image signal such that the frame rate of the motion image signal is reduced to a predetermined frame rate.

15. The image coding device according to 14, wherein the process information indicates which fields or frames have been excluded.