Adaptive entropy coding in adaptive quantization framework for video signal coding systems and processes

• US 6,111,914 A
• Filed: 12/01/1997
• Issued: 08/29/2000
• Est. Priority Date: 12/01/1997
• Status: Expired due to Term

• Current Assignee: Intel Corporation
• Original Assignee: Conexant Systems Incorporated (Synaptics Incorporated)
• Inventors: Bist, Anurag
• Primary Examiner(s): LEE, RICHARD J
• Application Number:
  US08/980,654
• Time in Patent Office: 1,002 Days
• Field of Search: 348/384, 348/390, 348/396, 348/405, 348/409-412, 348/415, 348/419, 382/232, 382/236, 382/238, 382/251, 341/67
• US Class Current: 375/240.03
• CPC Class Codes: H04N 19/126 Details of normalisation or weighting functions, e.g. normalisation matrices or variable uniform quantisers
• CPC Class Codes: H04N 19/13 Adaptive entropy coding, e.g. adaptive variable length coding [AVLC] or context adaptive binary arithmetic coding [CABAC]
• CPC Class Codes: H04N 19/147 according to rate distortion criteria rate-distortion as a criterion for motion estimation H04N19/567
• CPC Class Codes: H04N 19/154 Measured or subjectively estimated visual quality after decoding, e.g. measurement of distortion use of rate-distortion criteria H04N19/147
• CPC Class Codes: H04N 19/17 the unit being an image region, e.g. an object

Abstract

A compression system and process include adaptive quantization for selection of one quantizer, for each video frame or frame portion, from a group of quantizers, where each quantizer is a set of predefined quantizer values, and coding of the quantized values using a common entropy coding table for all quantizers, or a separate entropy coding table for each quantizer. The entropy coding tables are obtained during a training procedure. The selection of the quantizer is based on a formula which takes into account the distortion and bit rate characteristics of each quantizer. A similar formula, based on the distortion and bit rate characteristics, is used to select the particular quantizer value within the chosen quantizer for each video signal value being coded.

Claims

1. An adaptive quantization method in a coding process for coding data values corresponding to each picture element (pel) of a portion of a video frame, the method comprising the steps of:

selecting, for each portion of a video frame, a quantizer set R_x of quantizer values from a group of quantizer sets, wherein each quantizer value in each quantizer set is a multiple of a quantization coefficient QP and the quantizer sets are selected from the group consisting of;

space="preserve" listing-type="equation">R.sub.0 ={0,±

3QP-α

,±

5QP-α

,±

7QP-α

, . . . ,±

255QP-α

};

space="preserve" listing-type="equation">R.sub.1 ={0,±

3QP-α

,±

6QP-α

,±

7QP-α

, . . . ,±

255QP-α

};

space="preserve" listing-type="equation">R.sub.2 ={0,±

3QP-α

,±

4QP-α

,±

7QP-α

, . . . ,±

255QP-α

};

space="preserve" listing-type="equation">R.sub.3 ={0,±

2QP-α

,±

6QP-α

,±

7QP-α

, . . . ,±

255QP-α

};

space="preserve" listing-type="equation">R.sub.4 ={0,±

2QP-α

,±

5QP-α

,±

7QP-α

, . . . ,±

255QP-α

};

space="preserve" listing-type="equation">R.sub.5 ={0,±

2QP-α

,±

4QP-α

,±

7QP-α

, . . . ,±

255QP-α

};

space="preserve" listing-type="equation">R.sub.6 ={0,±

2QP-α

,±

3QP-α

,±

7QP-α

, . . . ,±

255QP-α

};

space="preserve" listing-type="equation">R.sub.7 ={0,±

4QP-α

,±

6QP-α

,±

7QP-α

, . . . ,±

255QP-α

};

space="preserve" listing-type="equation">R.sub.8 ={0,±

4QP-α

,±

5QP-α

,±

7QP-α

, . . . ,±

255QP-α

};

space="preserve" listing-type="equation">R.sub.9 ={0,±

1QP-α

,±

6QP-α

,±

7QP-α

, . . . ,±

255QP-α

};

space="preserve" listing-type="equation">R.sub.10 ={0,±

1QP-α

,±

5QP-α

,±

7QP-α

, . . . ,±

255QP-α

};

space="preserve" listing-type="equation">R.sub.11 ={0,±

1QP-α

,±

4QP-α

,±

7QP-α

, . . . ,±

255QP-α

};

space="preserve" listing-type="equation">R.sub.12 ={0,±

1QP-α

,±

3QP-α

,±

7QP-α

, . . . ,±

255QP-α

};

space="preserve" listing-type="equation">R.sub.13 ={0,±

1QP-α

,±

2QP-α

,±

7QP-α

, . . . ,±

255QP-α

};

space="preserve" listing-type="equation">R.sub.14 ={0,±

5QP-α

,±

6QP-α

,±

7QP-α

, . . . ,±

255QP-α

};

where the quantization set size QP is any number between 1 and 31 and α

=1 if QP is an even number and α

=0 if QP is an odd number; and

correlating each data value with a quantizer value from the selected quantizer set R_x to provide a quantized set of values corresponding to the pel data values.

2. An adaptive quantization method in a coding process for coding data values corresponding to each picture element (pel) of a portion of a video frame, the method comprising the steps of:

selecting, for each portion of a video frame, a quantizer set R_x of quantizer values from a group of a plurality of quantizer sets, wherein each quantizer value in each quantizer set is a multiple of a quantization coefficient QP and the quantizer sets are selected from the group consisting of;

space="preserve" listing-type="equation">R.sub.0 ={0,±

3QP-α

,±

5QP-α

,±

7QP-α

, . . . ,±

255QP-α

};

space="preserve" listing-type="equation">R.sub.3 ={0,±

2QP-α

,±

6QP-α

,±

7QP-α

, . . . ,±

255QP-α

};

space="preserve" listing-type="equation">R.sub.7 ={0,±

4QP-α

,±

6QP-α

,±

7QP-α

, . . . ,±

255QP-α

};

space="preserve" listing-type="equation">R.sub.14 ={0,±

5QP-α

,±

6QP-α

,±

7QP-α

, . . . ,±

255QP-α

};

where the quantization set size QP is any number between 1 and 31 and α

=1 if QP is an even number and α

=0 if QP is an odd number; and

correlating each data value with a quantizer value from the selected quantizer set R_x to provide a quantized set of values corresponding to the pel data value.

3. A method of coding sampled video signal data values corresponding to picture elements (pels) of at least a portion of a video frame, comprising the steps of:

adaptively quantizing the sampled data values by correlating each sampled data value to a value selected from a predefined set R_x of quantizer values which are multiples of a quantization coefficient QP, wherein said quantizer set is chosen from a group R₀ -R_n of quantizer sets based on a distortion and bit rate characteristics of each quantizer value in the set R_x ;

determining and quantifying the distortion and bit rate characteristics provided by each quantizer set in the group R₀ -R_n for each portion of the video frame being coded;

calculating an error value E for each set in the group R₀ -R_n according to the formula;

E=D+λ

f(QP)r, where D is a quantified distortion value for the portion of the video frame, r is a quantified bit rate value for the portion of the video frame, λ

is a weighting value selected based on the desired effect of r on the overall E and f(QP) is a function of the quantization coefficient QP;

selecting the quantizer set R_x that exhibits the lowest E value of the quantizer sets within the group R₀ -R_n ;

calculating an error value E'"'"' for each pel of said portion of the video frame and for each quantizer value in the quantizer set R_x according to the formula;

E'"'"'=D'"'"'+λ

'"'"'r'"'"', where D'"'"' is a quantified distortion value for each pel, r'"'"' is a quantified bit rate value for each pel and λ

'"'"' is a weighting value selected based on the desired effect of r'"'"' on the overall E'"'"';

selecting the quantizer value that exhibits the lowest E'"'"' value for the pel

selecting at least one VLC table having an entry for each pel event with a high probability of occurrence; and

coding the quantizer values with a variable length adaptive entropy coding method using the at least one VLC table.

4. A method of coding sampled video signal data values corresponding to picture elements (pels) of at least a portion of a video frame, comprising the steps of:

adaptively quantizing the sampled data values by correlating each sampled data value to a value selected from a predefined set R_x of quantizer values which are multiples of a quantization coefficient QP, wherein said quantizer set is chosen from a group R₀ -R_n of quantizer sets based on the a distortion and bit rate characteristics of each quantizer value in the set R_x ;

selecting at least one VLC table having an entry for each pel event with a high probability of occurrence, each of said pel event being defined by three event parameters;

a Level, a Run, and a Last;

wherein the Level is a level index to the quantizer set R_x corresponding to the selected quantizer value, the Run indicates a number of zero pels before the current event, and the Last indicates the last pel in a block which has a non-zero value;

coding the quantizer values with a variable length adaptive entropy coding method using the at least one VLC table;

wherein said coding step comprises a joint probability distribution binary coding step for simultaneous coding of all three event parameters to reduce an average binary code length for each event; and

saving the binary code for each event with the sign of the actual pel input value in the VLC table.

5. The method as recited in claim 4, wherein the step selecting the at least one VLC table further comprising a training step performed on a training signal, comprising the following steps:

keeping a count of occurrences for each event from the training signal in at least one counter table;

calculating a probability of occurrence of each said event from the total number of occurrences of the event in the training signal;

generating at least one probability table to save probabilities for each combination of the parameters Level, Run and Last, to be used in the coding step, so that the shortest binary code is assigned to the event which has the highest probability of occurrence; and

using an adaptive quantization step to find the best matching quantizer for each said event which produces the smallest error.

6. The method as recited in claim 5, wherein the training step is calculating probabilities for each said event using each quantizer set R_x with all possible values of the quantization coefficient QP and the probabilities for each said event at different QPs are averaged.

7. The method as recited in claim 5, wherein the training step generates a plurality of VLC tables, a plurality of counter tables and a plurality of probability tables, one of each for each quantizer Rx.

8. The method as recited in claim 5, wherein the training step generates one common optimized VLC table used for all quantizers.

9. A method of coding sampled video signal data values corresponding to picture elements (pels) of at least a portion of a video frame, comprising the steps of:

adaptively quantizing the sampled data values by correlating each sampled data value to a value selected from a predefined set R_x of quantizer values which are multiples of a quantization coefficient QP, wherein said quantizer set is chosen from a group of quantizer sets based on a distortion and bit rate characteristics of each quantizer value in the set R_x ;

said group of quantizer sets consisting of;

space="preserve" listing-type="equation">R.sub.0 ={0,±

3QP-α

,±

5QP-α

,±

7QP-α

, . . . ,±

255QP-α

};

space="preserve" listing-type="equation">R.sub.1 ={0,±

3QP-α

,±

6QP-α

,±

7QP-α

, . . . ,±

255QP-α

};

space="preserve" listing-type="equation">R.sub.2 ={0,±

3QP-α

,±

4QP-α

,±

7QP-α

, . . . ,±

255QP-α

};

space="preserve" listing-type="equation">R.sub.3 ={0,±

2QP-α

,±

6QP-α

,±

7QP-α

, . . . ,±

255QP-α

};

space="preserve" listing-type="equation">R.sub.4 ={0,±

2QP-α

,±

5QP-α

,±

7QP-α

, . . . ,±

255QP-α

};

space="preserve" listing-type="equation">R.sub.5 ={0,±

2QP-α

,±

4QP-α

,±

7QP-α

, . . . ,±

255QP-α

};

space="preserve" listing-type="equation">R.sub.6 ={0,±

2QP-α

,±

3QP-α

,±

7QP-α

, . . . ,±

255QP-α

};

space="preserve" listing-type="equation">R.sub.7 ={0,±

4QP-α

,±

6QP-α

,±

7QP-α

, . . . ,±

255QP-α

};

space="preserve" listing-type="equation">R.sub.8 ={0,±

4QP-α

,±

5QP-α

,±

7QP-α

, . . . ,±

255QP-α

};

space="preserve" listing-type="equation">R.sub.9 ={0,±

1QP-α

,±

6QP-α

,±

7QP-α

, . . . ,±

255QP-α

};

space="preserve" listing-type="equation">R.sub.10 ={0,±

1QP-α

,±

5QP-α

,±

7QP-α

, . . . ,±

255QP-α

};

space="preserve" listing-type="equation">R.sub.11 ={0,±

1QP-α

,±

4QP-α

,±

7QP-α

, . . . ,±

255QP-α

};

space="preserve" listing-type="equation">R.sub.12 ={0,±

1QP-α

,±

3QP-α

,±

7QP-α

, . . . ,±

255QP-α

};

space="preserve" listing-type="equation">R.sub.13 ={0,±

1QP-α

,±

2QP-α

,±

7QP-α

, . . . ,±

255QP-α

};

space="preserve" listing-type="equation">R.sub.14 ={0,±

5QP-α

,±

6QP-α

,±

7QP-α

, . . . ,±

255QP-α

};

where the quantization set size QP is any number between 1 and 31, and α

=1 if QP is an even number and α

=0 if QP is an odd number;

selecting at least one VLC table having an entry for each pel event with a high probability of occurrence; and

coding the quantizer values with a variable length adaptive entropy coding method using the at least one VLC table.

10. A method of coding sampled video signal data values corresponding to picture elements (pels) of at least a portion of a video frame, comprising the steps of:

adaptively quantizing the sampled data values by correlating each sampled data value to a value selected from a predefined set R_x of quantizer values which are multiples of a quantization coefficient QP, wherein said quantizer set is chosen from a group of quantizer sets based on a distortion and bit rate characteristics of each quantizer value in the set R_x ;

said group of quantizer sets consisting of;

space="preserve" listing-type="equation">R.sub.0 ={0,±

3QP-α

,±

5QP-α

,±

7QP-α

, . . . ,±

255QP-α

};

space="preserve" listing-type="equation">R.sub.3 ={0,±

2QP-α

,±

6QP-α

,±

7QP-α

, . . . ,±

255QP-α

};

space="preserve" listing-type="equation">R.sub.7 ={0,±

4QP-α

,±

6QP-α

,±

7QP-α

, . . . ,±

255QP-α

};

space="preserve" listing-type="equation">R.sub.14 ={0,±

5QP-α

,±

6QP-α

,±

7QP-α

, . . . ,±

255QP-α

};

where the quantization set size QP is any number between 1 and 31, and α

=1 if QP is an even number and α

=0 if QP is an odd number;

selecting at least one VLC table having an entry for each pel event with a high probability of occurrence; and

coding the quantizer values with a variable length adaptive entropy coding method using the at least one VLC table.

11. A system for coding sampled video signal data corresponding to picture elements (pels) of at least a portion of a video frame, comprising:

a storage means for storing a plurality of sets R₀ -R_n of quantizer values;

means for selecting, for each portion of the video frame being coded, a quantizer set R_x of quantizer values, which are multiples of a quantization coefficient QP, from a group of sets R₀ -R_n, dependent on a quantified distortion and bit rate of the selected set R_x ;

said selecting means comprising;

means for calculating an error E for each portion of the video frame being coded and for each quantizer set in the group R₀ -R_n, according to the formula;

E=D+λ

f(QP)r, where D is a quantified distortion value for the portion of the video frame, r is a quantified bit rate value for the portion of the video frame, λ

is a weighting value selected based on the desired effect of r on the overall E and f(QP) is a function of the quantization coefficient QP; and

means for selecting the quantizer R_x that exhibits the lowest E value of the quantizer sets within the group R₀ -R_n ;

means for correlating each video signal data value for each frame portion being coded with a quantizer value from the quantizer set R_x selected for that frame portion;

said correlating means comprising;

means for determining and quantifying the distortion and bit rate characteristics of each quantizer value within the set R_x ; and

means for selecting the quantizer value based on the distortion and bit rate characteristics provided by each quantizer value in the set R_x ;

means for selecting at least one VLC table having an entry for each pel event with a high probability of occurrence; and

means for encoding the quantizer values with a variable length adaptive entropy coding method using the at least one VLC table.

12. A system for coding sampled video signal data corresponding to picture elements (pels) of at least a portion of a video frame, comprising:

a storage means for storing a plurality of sets R₀ -R_n of quantizer values;

means for selecting, for each portion of the video frame being coded, a quantizer set R_x of quantizer values, which are multiples of a quantization coefficient QP, from a group of sets R₀ -R_n, dependent on a quantified distortion and bit rate of the selected set R_x ;

means for correlating each video signal data value for each frame portion being coded with a quantizer value from the quantizer set R_x selected for that frame portion;

means for selecting at least one VLC table having an entry for each pel event with a high probability of occurrence;

each of said pel event being defined by three event parameters;

a Level, a Run, and a Last;

wherein the Level is a level index to the quantizer set R_x corresponding to the selected quantizer value, the Run indicates a number of zero pels before the current event, and the Last indicates the last pel in a block which has a non-zero value;

means for encoding the quantizer values with a variable length adaptive entropy coding method using the at least one VLC table; and

wherein said variable length adaptive entropy coding method comprises a joint probability distribution binary coding method for simultaneous coding of all three event parameters to reduce an average binary code length for each event, and the binary code for each event is saved with the sign of the actual pel input value in the VLC table.

13. A system for coding sampled video signal data corresponding to picture elements (pels) of at least a portion of a video frame, comprising:

a storage means for storing a plurality of sets R₀ -R_n of quantizer values;

means for selecting, for each portion of the video frame being coded, a quantizer set R_x of quantizer values, which are multiples of a quantization coefficient QP, from a group of sets R₀ -R_n, dependent on a quantified distortion and bit rate of the selected set R_x ;

means for correlating each video signal data value for each frame portion being coded with a quantizer value from the quantizer set R_x selected for that frame portion;

means for selecting at least one VLC table having an entry for each pel event with a high probability of occurrence;

each of said pel event being defined by three event parameters;

a Level, a Run, and a Last;

wherein the Level is a level index to the quantizer set R_x corresponding to the selected quantizer value, the Run indicates a number of zero pels before the current event, and the Last indicates the last pel in a block which has a non-zero value;

means for encoding the quantizer values with a variable length adaptive entropy coding method using the at least one VLC table; and

means for determining the at least one VLC table in a training procedure using a training signal, comprising;

means for keeping a count of occurrences for each event from the training signal in at least one counter table;

means for calculating a probability of occurrences of each said event from a total number of occurrences of the event in the training signal; and

means for generating at least one probability table to save probabilities for each combination of the three event parameters to be used in the encoding means so that the shortest binary code is assigned to the event which has the highest probability of occurrence.

14. The system as recited in claim 13, wherein the training procedure is calculating probabilities for each said event using each quantizer set R_x with all possible values of the quantization coefficient QP and the probabilities for each said event at different QPs are averaged.

15. The system as recited in claim 13, wherein the training procedure generates a plurality of VLC tables, a plurality of counter tables and a plurality of probability tables, one of each for each quantizer Rx.

16. The system as recited in claim 13, wherein the training procedure generates one common optimized VLC table used for all quantizers wherein length of the binary codes from the VLC table are represented in tables of FIGS. 6 and 7.

17. A system for coding sampled video signal data corresponding to picture elements (pels) of at least a portion of a video frame, comprising:

a storage means for storing a plurality of sets of quantizer values;

means for selecting, for each portion of the video frame being coded, a quantizer set R_x of quantizer values, which are multiples of a quantization coefficient QP, from a group of quantizer sets, dependent on a quantified distortion and bit rate of the selected set R_x ;

said group of quantizer sets consisting of;

space="preserve" listing-type="equation">R.sub.0 ={0,±

3QP-α

,±

5QP-α

,±

7QP-α

, . . . ,±

255QP-α

};

space="preserve" listing-type="equation">R.sub.1 ={0,±

3QP-α

,±

6QP-α

,±

7QP-α

, . . . ,±

255QP-α

};

space="preserve" listing-type="equation">R.sub.2 ={0,±

3QP-α

,±

4QP-α

,±

7QP-α

, . . . ,±

255QP-α

};

space="preserve" listing-type="equation">R.sub.3 ={0,±

2QP-α

,±

6QP-α

,±

7QP-α

, . . . ,±

255QP-α

};

space="preserve" listing-type="equation">R.sub.4 ={0,±

2QP-α

,±

5QP-α

,±

7QP-α

, . . . ,±

255QP-α

};

space="preserve" listing-type="equation">R.sub.5 ={0,±

2QP-α

,±

4QP-α

,±

7QP-α

, . . . ,±

255QP-α

};

space="preserve" listing-type="equation">R.sub.6 ={0,±

2QP-α

,±

3QP-α

,±

7QP-α

, . . . ,±

255QP-α

};

space="preserve" listing-type="equation">R.sub.7 ={0,±

4QP-α

,±

6QP-α

,±

7QP-α

, . . . ,±

255QP-α

};

space="preserve" listing-type="equation">R.sub.8 ={0,±

4QP-α

,±

5QP-α

,±

7QP-α

, . . . ,±

255QP-α

};

space="preserve" listing-type="equation">R.sub.9 ={0,±

1QP-α

,±

6QP-α

,±

7QP-α

, . . . ,±

255QP-α

};

space="preserve" listing-type="equation">R.sub.10 ={0,±

1QP-α

,±

5QP-α

,±

7QP-α

, . . . ,±

255QP-α

};

space="preserve" listing-type="equation">R.sub.11 ={0,±

1QP-α

,±

4QP-α

,±

7QP-α

, . . . ,±

255QP-α

};

space="preserve" listing-type="equation">R.sub.12 ={0,±

1QP-α

,±

3QP-α

,±

7QP-α

, . . . ,±

255QP-α

};

space="preserve" listing-type="equation">R.sub.13 ={0,±

1QP-α

,±

2QP-α

,±

7QP-α

, . . . ,±

255QP-α

};

space="preserve" listing-type="equation">R.sub.14 ={0,±

5QP-α

,±

6QP-α

,±

7QP-α

, . . . ,±

255QP-α

};

where the quantization set size QP is any number between 1 and 31, and α

=1 if QP is an even number and α

=0 if QP is an odd number;

means for correlating each video signal data value for each frame portion being coded with a quantizer value from the quantizer set R_x selected for that frame portion;

means for selecting at least one VLC table having an entry for each pel event with a high probability of occurrence; and

means for encoding the quantizer values with a variable length adaptive entropy coding method using the at least one VLC table.

18. A system for coding sampled video signal data values corresponding to picture elements (pels) of at least a portion of a video frame, comprising the steps of:

a storage means for storing a plurality of sets of quantizer values;

means for selecting, for each portion of the video frame being coded, a quantizer set R_x of quantizer values, which are multiples of a quantization coefficient QP, from a group of quantizer sets, dependent on a quantified distortion and bit rate of the selected set R_x ;

said group of quantizer sets consisting of;

space="preserve" listing-type="equation">R.sub.0 ={0,±

3QP-α

,±

5QP-α

,±

7QP-α

, . . . ,±

255QP-α

};

space="preserve" listing-type="equation">R.sub.3 ={0,±

2QP-α

,±

6QP-α

,±

7QP-α

, . . . ,±

255QP-α

};

space="preserve" listing-type="equation">R.sub.7 ={0,±

4QP-α

,±

6QP-α

,±

7QP-α

, . . . ,±

255QP-α

};

space="preserve" listing-type="equation">R.sub.14 ={0,±

5QP-α

,±

6QP-α

,±

7QP-α

, . . . ,±

255QP-α

};

where the quantization set size QP is any number between 1 and 31, and α

=1 if QP is an even number and α

=0 if QP is an odd number;

means for correlating each video signal data value for each frame portion being coded with a quantizer value from the quantizer set R_x selected for that frame portion;

means for selecting at least one VLC table having an entry for each pel event with a high probability of occurrence; and

means for coding the quantizer values with a variable length adaptive entropy coding method using the at least one VLC table.