Bit-rate control method and apparatus for normalizing visual quality

• US 20050084015A1
• Filed: 10/20/2004
• Published: 04/21/2005
• Est. Priority Date: 10/20/2003
• Status: Abandoned Application

• Current Assignee: Samsung Electronics Co. Ltd.
• Original Assignee: Samsung Electronics Co. Ltd.
• Inventors: Ha, Ho-jin, Han, Woo-jin, Lee, Bae-keun
• Application Number:
  US10/968,491
• Publication Number:
  US 20050084015A1
• Time in Patent Office: Days
• US Class Current: 375/240.190
• CPC Class Codes: H04N 19/115 Selection of the code volume for a coding unit prior to coding
• CPC Class Codes: H04N 19/149 by estimating the code amount by means of a model, e.g. mathematical model or statistical model
• CPC Class Codes: H04N 21/234327 by decomposing into layers, e.g. base layer and one or more enhancement layers
• CPC Class Codes: H04N 21/6377 directed to server one-way streaming services wherein the source is controlled by the destination H04L65/613
• CPC Class Codes: H04N 21/658 Transmission by the client directed to the server
• CPC Class Codes: H04N 7/17318 Direct or substantially direct transmission and handling of requests

Abstract

A scalable video codec includes an encoder that encodes an original moving picture; a rate control unit that allocates an optimal amount of bits for each coding unit based on a bit-rate desired by a user; a pre-decoder that receives a bit-stream and extracts a bit-stream having an appropriate amount of bits; and a decoder that decodes image sequences of the moving picture from the extracted bit-stream, so as to reconstruct the original moving picture. In particular, the present invention focuses on the operation performed in the rate control unit 340. The rate control unit operates a definition step of a bit-rate function available for use in the predecoder, a pre-summation step to thereby obtain the uniform visual quality, an approximation to determine the distortion function, and a normalization step to allow the total allocated bit-rates to be equal to a target bit-rate.

Claims

1. A bit-rate control method, comprising:

determining an amount of bits for each of a plurality of coding units from a bit-stream generated by encoding an original moving picture, so as to allow a visual quality of the moving picture to be uniform relative to the coding units thereof; and

extracting a bit-stream having the amount of bits by truncating a part of the bit-stream based on the determined bit amount.

2. The method as claimed in claim 1, wherein a peak signal-to-noise ratio (PSNR) is employed as a reference for measuring the visual quality.

3. The method as claimed in claim 1, wherein the bitstream generated by an encoder follows a wavelet-based video coding scheme and is modified adaptively to a scalability condition by the pre-decoder.

4. The method as claimed in claim 1, wherein a flattening of a quality measuring reference is performed by increasing the bits allocated for a first coding unit and decreasing the bits allocated for a second coding unit, and

wherein the first coding unit has a lower quality image than the second coding unit.

5. The method as claimed in claim 1, wherein the determination of the bit amount includes:

defining a bit-rate function available in the pre-decoder by using a bit distribution and a distortion function with a constant number of bitplanes; and

presuming the bit-rate by modifying the bit-rate function, so as to obtain uniform visual quality.

6. The method as claimed in claim 5, wherein the determination of the bit amount further includes initially approximating the distortion function, with the use of the bit distribution, to determine the distortion function with information useable in the pre-decoder.

7. The method as claimed in claim 6, wherein the determination of the bit amount further includes normalizing the bit-rate function by modifying the bit-rate function so that a total allocated bit-rate is equal to a target bit-rate.

8. A bit-rate control apparatus, comprising:

a first means for determining a bit amount for each of a plurality of coding units from a bit-stream generated by encoding an original moving picture, so as to make the visual quality of the moving picture uniform relative to the coding units thereof; and

a second means for extracting a bit-stream having the amount of bits by truncating a part of the bit-stream based on the determined bit amount.

9. The apparatus as claimed in claim 8, wherein the bitstream created by an encoder, which follows a wavelet-based video coding scheme, is modified adaptively to a scalability condition by the pre-decoder.

10. The apparatus as claimed in claim 8, wherein the first means includes a means for defining a bit-rate function available in the pre-decoder by using a bit distribution and a distortion function with a constant number of bitplanes, and presuming the bit-rate by modifying the bit-rate function, so as to obtain uniform visual quality.

11. The apparatus as claimed in claim 10, wherein the first means further includes a means for initially approximating the distortion function, with the use of the bit distribution, to determine the distortion function with information useable in the pre-decoder.

12. The apparatus as claimed in claim 10, wherein the first means further includes a means for normalizing the bit-rate function by modifying the bit-rate function so that a total allocated bit-rate equals a target bit-rate.

13. A computer-readable recording medium for recording a computer program code for enabling a computer to provide a service of a bit-rate control method, comprising;

determining an amount of bits for each of a plurality of coding units from a bit-stream generated by encoding an original moving picture, so as to allow a visual quality of the moving picture to be uniform relative to the coding units thereof; and

extracting a bit-stream having the amount of bits by truncating a part of the bit-stream based on the determined bit amount.

14. A bit-rate control apparatus, comprising:

a determining unit determining a bit amount for each of a plurality of coding units from a bit-stream generated by encoding an original moving picture, so as to make the visual quality of the moving picture uniform relative to the coding units thereof; and

an extracting unit extracting a bit-stream having the amount of bits by truncating a part of the bit-stream based on the determined bit amount.

15. The apparatus as claimed in claim 14, wherein the bitstream created by an encoder follows a wavelet-based video coding scheme and is modified adaptively to a scalability condition by the pre-decoder.

16. The apparatus as claimed in claim 14, wherein the determining unit includes a defining unit defining a bit-rate function available in the pre-decoder by using a bit distribution and a distortion function with a constant number of bitplanes, and a pre-summation unit modifying the bit-rate function so as to obtain uniform visual quality.

17. The apparatus as claimed in claim 16, wherein the determining unit further includes an approximating unit that initially approximates the distortion function, with the use of the bit distribution, in order to determine the distortion function with information useable in the pre-decoder.

18. The apparatus as claimed in claim 16, wherein the determining unit further includes a normalizing unit normalizing the bit-rate function by modifying the bit-rate function so that a total allocated bit-rate equals a target bit-rate.