Deblocking filter for encoder/decoder arrangement and method with divergence reduction

• US 6,160,503 A
• Filed: 07/09/1998
• Issued: 12/12/2000
• Est. Priority Date: 02/19/1992
• Status: Expired due to Term

• Current Assignee: 8X8, Inc.
• Original Assignee: 8X8, Inc.
• Inventors: Andrews, Barry D., Voois, Paul A., Martin, Bryan R., Ning, Paul, Kwan, Katherine, Chiang, May Shu-Pei, Hu, Ruili, Bryant, Stephane
• Primary Examiner(s): YOUNG, BRIAN K
• Application Number:
  US09/112,612
• Time in Patent Office: 887 Days
• Field of Search: 341/94, 348/405, 348/409, 348/404, 348/415
• US Class Current: 341/94
• CPC Class Codes: G06T 9/007 Transform coding, e.g. discrete cosine transform
• CPC Class Codes: H04N 19/82 involving filtering within a prediction loop
• CPC Class Codes: H04N 19/86 involving reduction of coding artifacts, e.g. of blockiness
• CPC Class Codes: H04N 7/141 between two video terminals, e.g. videophone telephonic communication systems combined with television receiver for reception of entertainment or information matter H04M11/085
• CPC Class Codes: H04N 7/15 Conference systems

Abstract

According to one aspect of the disclosure, the present invention provides methods and arrangements for the removal or reduction of divergence artifacts between a transmitting codec and a receiving codec. One of a number of implementations includes using a deblocking filter in an inverse transformer loop and selectively disabling the filter upon certain conditions.

Claims

1. A method for transmitting a representation of an image from a first terminal to a second terminal using a communications channel, comprising:

operating each of the first and second terminals using an inverse transformer loop having a decoding algorithm that accumulates at least one error; and

selectively using a loop filter in the inverse transformer loop based on at least one predetermined condition.

2. A method, according to claim 1, wherein said at least one predetermined condition includes at least one of:

surpassing a quantization parameter threshold; and

processing chroma channel data.

3. A method, according to claim 1, wherein said at least one predetermined condition includes a quantization parameter threshold approximately equal to 5.

4. A method, according to claim 3, wherein said quantization parameter threshold being equal to 5 corresponds to an average of several quantization parameters.

5. A method, according to claim 1, further including refreshing.

9. An image communication terminal having a circuit constructed and arranged to operate according to claim 1.

10. An image communication terminal having a circuit constructed and arranged to operate according to claim 2.

11. An image communication terminal having a circuit constructed and arranged to operate according to claim 3.

6. A method for encoding and decoding a representation of an image for communication between a first terminal and a second terminal, comprising:

operating each of the first and second terminals using an inverse transformer loop; and

preventing unacceptable accumulation of an error within the inverse transformer loop by at least one of;

pre-processing input data before using the inverse transformer loop to process the input data;

using the inverse transformer in the loop according to a bit-exact specification between the encoder and decoder in the respective first and second terminals;

using the inverse transformer in the loop according to one of a plurality of bit-exact specifications between the encoder and decoder in the respective first and second terminals and negotiating a common decision on the particular specification through encoder/decoder negotiation;

providing a quantization value in the inverse transformer loop that is less prone to divergence;

adjusting or providing transform coefficients to limit divergence;

choosing an encoding mode for macro-blocks of input data;

modifying the encoder to refresh portions of the image that are diverging;

modifying the loop filter characteristics so that inverse transform mismatches are not amplified;

applying the loop filter to input data corresponding to a frame buffer image just before sending to a display circuit without writing back the results to a frame buffer in the loop;

selectively using a loop filter in each inverse transformer loop based on at least one predetermined condition.

7. A method, according to claim 6, wherein said at least one predetermined condition includes at least one of:

surpassing a quantization parameter threshold, and processing chroma channel data.

8. An image communication terminal having a circuit constructed and arranged to operate according to claim 6.

12. For communicating a representation of an image between a first terminal and a second terminal using a communications channel, an arrangement in at least one of the terminals, comprising:

means for operating the terminal using an inverse transformer loop having a decoding algorithm that accumulates at least one error; and

means for selectively using a loop filter in each inverse transformer loop based on at least one predetermined condition.

13. For communicating a representation of an image between a first terminal and a second terminal using a communications channel, an arrangement in at least one of the terminals, comprising:

means for operating the terminal using an inverse transformer loop; and

means for preventing unacceptable accumulation of an error within the inverse transformer loop by at least one of;

pre-processing input data before using the inverse transformer loop to process the input data;

using the inverse transformer in the loop according to a bit-exact specification between the encoder and decoder in the respective first and second terminals;

using the inverse transformer in the loop according to one of a plurality of bit-exact specifications between the encoder and decoder in the respective first and second terminals and negotiating a common decision on the particular specification through encoder/decoder negotiation;

providing a quantization valuer in the inverse transformer loop that is less prone to divergence;

adjusting or providing transform coefficients to limit divergence;

choosing an encoding mode for macro-blocks of input data;

modifying the encoder to refresh portions of the image that are diverging;

modifying the loop filter characteristics so that inverse transform mismatches are not amplified;

applying the loop filter to input data corresponding to a frame buffer image just before sending to a display circuit without writing back the results to a frame buffer in the loop;

selectively using a loop filter in each inverse transformer loop based on at least one predetermined condition.