United States Patent 19)
`Auyeung
`
`||||||||||
`US005473376A
`5,473,376
`11
`Patent Number:
`Dec. 5, 1995
`45) Date of Patent:
`
`54 METHOD AND APPARATUS FOR ADAPTIVE
`ENTROPY ENCODING/DECODING OF
`QUANTIZED TRANSFORM COEFFICIENTS
`IN A WIDEO COMPRESSION SYSTEM
`
`"Video Codec Test Model, TMN4', ITU Telecommunicaton
`Standardization Sector, Study Group 15, Working Party
`15/1, LBC-94.
`
`75 Inventor: Cheung Auyeung, Hoffman Estates, Ill.
`73) Assignee: Motorola, Inc., Schaumburg, Ill.
`
`Primary Examiner-Tommy P. Chin
`Assistant Examiner-Anand S. Rao
`Attorney, Agent, or Firm-Darleen J. Stockley
`
`(21) Appl. No.: 347,639
`22 Filed:
`Dec. 1, 1994
`(51) Int. Cl. ................................ H04N 7/26; H04N 7/30
`52 U.S. Cl. .......................... 348/403; 348/405; 348/404;
`348/419; 348/420
`58) Field of Search ..................................... 348/384,395,
`348/403, 405, 395,404, 419, 420
`
`56)
`
`References Cited
`U.S. PATENT DOCUMENTS
`4,633,296 12/1986 Chan et al. ............................ 348,403
`5,038,209 8/1991
`... 348/420
`5,162,908 11/1992
`... 348/403
`5,253,055 10/1993
`. 348/49
`5,272,528 12/1993
`348/403
`5,282,031
`1/1994
`5,371,549 12/1994
`a
`a
`5,396,291
`3/1995 Sanpei..................................... 348/403
`OTHER PUBLICATIONS
`"Coding of Moving Pictures and Associated Audio-For
`Digital Storage Media at up to about 1.5 Mbit/s-”, CD
`11172-2, Part 2 Video, Apr. 3, 1992.
`
`ABSTRACT
`(57)
`The present invention is a method (100) and apparatus (300)
`for adaptive entropy encoding/decoding of a plurality of
`quantised transform coefficients in a videolimage compres
`sion system. For encoding, first, a predetermined number of
`quantized transform coefficients are received in a predeter
`mined order, giving a generally decreasing average power,
`Then the quantized transform coefficients are parsed into a
`plurality of coefficient groups. When the last coefficient
`group comprises all zero quantized coefficients, it is dis
`carded. The coefficient groups are then converted into a
`plurality of parameter sets in the predetermined order. A
`current parameter set is obtained from the parameter sets in
`the reverse order of the predetermined order. A current
`entropy encoder is selected adaptively based on the previ
`ously selected entropy encoder and the previous parameter
`set. The current parameter set is encoded by the current
`entropy encoder to provide entropy encoded information
`bits.
`
`- 18 Claims, 3 Drawing Sheets
`
`300
`
`
`
`
`
`PARAMEER
`SETDETERMINER
`
`
`
`QUANIZED
`FIRS
`TRANSFORM
`CEFFICIENTS 350 MEMORY UNI
`
`DECODED OUANTIZED
`TRANSFORM
`COEFFICIENTS 3
`
`328
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`U.S. Patent
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`Dec. 5, 1995
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`Sheet 1 of 3
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`5,473,376
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`f02
`100
`PARSINGAPREDETERMINEDNUMBER OF QUANTIZEDTRANSFORMCOEFFICIENTS INTO
`APLURALITY OF COEFFICIENT GROUPS AND CONVERTING THE COEFFICIENT GROUPS
`INTO APLURALITY OF PARAMETER SESACCORDING TO APREDETERMINED SCHEME
`AND STORING THE PARAMETER SETSINTHE MEMORY UNIT, WHEREINEACH PARAM
`ETERSETINCLUDESALEVEL PARAMETER WHICH IS AWALUE OF ANONZEROQUAN
`TIZEDTRANSFORMCOEFFICIENT, WHEREIN, WHERE ALAST COEFFICIENT GROUP
`COMPRISES ALLZEROQUANTIZEDTRANSFORMCOEFFICIENTS, THELAST COEFFIC
`ENT GROUPSDISCARDED
`
`55:55,
`
`ACESSING, FROM THE MEMORY UNIT, EACH PARAMETER SET OF THE PLURALITY OF
`PARAMETER SETSINAREVERSE ORDER OF THE PREDETERMINEDSCANNING ORDER
`106
`ADAPTIVELYSELECTING ACURRENTENTROPYENCODER OF APLURALITY OF ENTROPY
`ENCODERS BASED ONAPREVIOUSLEVEL PARAMETER OF APREVIOUSPARAMETER SET
`ANDAPREVIOUSLYSELECTED ENTROPYENCODER
`
`ENCODING, BYTHECURRENTENTROPYENCODER, ACURRENTPARAMETER SETTO
`PROVIDEENTROPYENCODED INFORMATION BITS
`Fig.1
`
`2O2
`200
`DECODING, BY ACURRENTENTROPYDECODER THEENTROPYENCODED INFORMATION
`BITSTOPROVIDEADECODEDCURRENPARAMETER SET
`
`BIOGETEEAAE-fiello
`"EGS".
`
`ADAPTIVELYSELECTING ANEXTENTROPYDECODER OF A PLURALITY OF ENTROPY
`DECODERS BASED ONADECODEDCURRENTLEVEL PARAMETER OF THEDECODEDCUR
`RENPARAMETER SETANDAPREVIOUSLYSELECTED ENTROPYDECODER
`
`206
`STORING INTO THE MEMORY UNIT, EACH PARAMETERSET OF APLURALITY OF DE
`CODEDPARAMETERSETSINTHEREVERSE ORDER OF
`THE PREDETERMINED SCANNING ORDER
`
`
`
`CONVERTING THEDECODEDPARAMETERSETSINTO ANUMBER OF DECODED QUANTIZED
`TRANSFORMCOEFFICIENTSACCORDINGTOTHE PREDETERMINED SCHEMENTHEPRE
`DETERMINED SCANNING ORDER AND STORING THE DECODED OUANTIZEDTRANSFORM
`COEFFICIENTS INTHE MEMORY UNIT, WHEREIN, WHERE THENUMBER OF DECODED
`QUANIZEDTRANSFORMCOEFFICIENTSISLESS THENTHE PREDETERMINEDNUMBER OF
`QUANTIZEDTRANSFORMCOEFFICIENTS, ZEROVALUEDDECODED QUANTIZEDTRANS
`FORMCOEFFICIENTS WILL BEAPPENDED
`
`Fig.2
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`Dec. 5, 1995
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`Sheet 2 of 3
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`5,473,376
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`U.S. Patent
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`Dec. 5, 1995
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`Sheet 3 of 3
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`5,473,376
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`Z2721
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`(W1.
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`1.
`METHOD AND APPARATUS FOR ADAPTIVE
`ENTROPY ENCODING/DECODING OF
`QUANTIZED TRANSFORM COEFFICIENTS
`NAVIDEO COMPRESSION SYSTEM
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`BACKGROUND OF THE INVENTION
`1. Field of the Invention
`The invention relates generally to the field of video
`compression, and in particular, to entropy coding.
`2. Description of the Prior Art
`Video systems are known to include a plurality of com
`munication devices and communication channels, which
`provide the communication medium for the communication
`devices. For example, the communication channel may be
`wireline connections or radio frequency, RF, carriers. To
`increase the efficiency of the video system, video that needs
`to be communicated over the communication medium is
`digitally compressed. Digital compression reduces the num
`20
`ber of bits needed to represent the video while maintaining
`perceptual quality of the video. The reduction in bits allows
`more efficient use of channel bandwidth and reduces storage
`requirements. To achieve digital video compression, each
`communication device may include an encoder and a
`decoder. The encoder allows a communication device to
`compress video before transmission over a communication
`channel. The decoder enables the communication device to
`receive compressed video from a communication channel
`and render it visible. Communication devices that may use
`digital video compression include high definition television
`transmitters and receivers, cable television transmitters and
`receivers, video telephones, computers and portable radios.
`Several emerging standards for digital video compression
`are being developed, including International Telecommuni
`cations Union (ITU), ITU-T Recommendation H.26P, the
`International Standards Organization/International Electro
`technical Committee (ISO/IEC), and International Standard
`MPEG-4. These standards are likely to use transform coding
`as part of the building blocks for good coding efficiency.
`Currently, the Expert's Group on Very Low Bitrate Visual
`Telephony, LBC, is considering using the discrete cosine
`transform for coding efficiency. The Moving Pictures
`Expert's Group, MPEG, is also likely to use the discrete
`cosine transform or other type of transform. To achieve
`compression, the transform coefficients are quantized and
`entropy coded.
`Therefore, to maximize the compression capability, a
`need exists for a method and apparatus for entropy coding
`the quantized transform coefficients more efficiently than the
`emerged standard H.261, MPEG-1, and MPEG-2, especially
`for low bit rate applications.
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`
`SUMMARY OF THE INVENTION
`The present invention is a method and apparatus for
`adaptive entropy encoding/decoding of a plurality of
`quantized transform coefficients in a video/image com
`pression system. For encoding, first, a predetermined
`number of quantized transform coefficients are
`received in a predetermined order, giving a generally
`decreasing average power. Then the quantized trans
`form coefficients are parsed into a plurality of coeffi
`cient groups. When the last coefficient group comprises
`all zero quantized coefficients, it is discarded. The
`coefficient groups are then converted into a plurality of
`parameter sets in the predetermined order. A current
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`parameter set is obtained from the parameter sets in the
`reverse order of the predetermined order. A current
`entropy encoder is selected adaptively based on the
`previously selected entropy encoder and the previous
`parameter set. The current parameter set is encoded by
`the current entropy encoder to provide entropy encoded
`information bits.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`FIG. 1 is a flow diagram of steps for one embodiment of
`a method for adaptive entropy encoding in accordance with
`the present invention.
`FIG. 2 is a flow diagram of steps for one embodiment of
`a method for adaptive entropy decoding in accordance with
`the present invention.
`FIG. 3 is a block diagram of one embodiment of an
`apparatus for adaptive entropy encoding/decoding in accor
`dance with the present invention.
`FIG. 4 is an exemplary prior art illustration of a method
`of scanning and transforming a two dimensional block to
`provide a one dimensional array of scanned coefficients.
`FIG. 5 is a graphical depiction of the average power, in
`general, of the scanned coefficients with respect to the index;
`a distinction between lower and higher power coefficient is
`made in accordance with the present invention.
`
`DESCRIPTION OF A PREFERRED
`EMBODEMENT
`The present invention is a method and an apparatus for
`adaptive entropy encoding/decoding of a plurality of quan
`tized transform coefficients in a video/image compression
`system. For encoding, first, a predetermined number of
`quantized transform coefficients are received in a predeter
`mined order giving a generally decreasing average power.
`Then the quantized transform coefficients are parsed into a
`plurality of coefficient groups. When a last coefficient group
`comprises all zero quantized coefficients, the last coefficient
`group is discarded. The coefficient groups are then converted
`into a plurality of parameter sets in the predetermined order.
`A current parameter set is obtained from the parameter sets
`in the reverse order of the predetermined order. A current
`entropy encoder is selected adaptively based on the previ
`ously selected entropy encoder and the previous parameter
`set. The current parameter set is encoded by the current
`entropy encoder to provide entropy encoded information
`bits.
`This invention may be used with a compression algorithm
`that processes a picture into two-dimensional blocks of
`quantized transform coefficients with predetermined trans
`form sizes. Each block is then scanned into a one-dimen
`sional array in a predetermined order giving generally
`decreasing average power.
`The one-dimensional array of quantized transform coef
`ficients are parsed into a sequence of coefficient groups as
`shown by the following example. For example, consider an
`array having 64 coefficients, only five of which are non-zero:
`
`{0,0,1,0-2,3,0,1,0,0,1,0,0,...}
`After parsing, the coefficient groups are
`
`(1)
`
`{0,0,1},{0,-2}{3}, {0,1},{0,0,1}.
`(2)
`In general, the number of coefficient groups is the same as
`the number of non-zero coefficients since the last group {0,
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`0, ... }, which consists of all zero coefficients, is discarded.
`Each coefficient group has the form
`{0, ...,0,1}
`(3)
`which consists of a sequence of zero coefficients followed by
`a non-zero coefficient. The coefficient groups are also
`ordered in the same manner as the coefficients.
`Each coefficient group {0, ..., 0,l} is then converted into
`a parameter set
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`The fourth and final step in the decoding method is con
`verting the decoded parametersets into a number of decoded
`quantized transform coefficients according to the predeter
`mined scheme in the predetermined scanning order and
`storing the decoded quantized transform coefficients in the
`memory unit (208). Where the number of decoded quantized
`transform coefficients is less than the predetermined number
`of quantized transform coefficients, zero-valued decoded
`quantized transform coefficients will be appended. The
`decoding process is repeated until the end-of-block param
`eter of the current parameter set indicates that the current
`parameter set is the last parameter set to be decoded.
`The current entropy encoder for encoding the current
`parameter set is adaptively chosen from a sequence of
`entropy encoders, and the current entropy decoder for
`decoding the entropy encoded information bits is adaptively
`chosen from a sequence of entropy decoders corresponding
`to the sequence of entropy encoders. The entropy encoders/
`decoders can be based on variable length codes or arithmetic
`codes. Let n22, and E, E, ... Ebe a sequence of entropy
`encoders/decoders, and T, T, ..., T be the correspond
`ing sequence of positive thresholds of increasing magnitude.
`The sequence of entropy encoders/decoders is arranged in
`the order of ability to code increasing levels. A more efficient
`coding scheme for a particular encoder/decoder is selected
`based on the information that the levels to be coded by the
`particular encoderddecoder do not exceed a corresponding
`threshold. When n=2, a preferred T is one for the emerging
`H.26P standard. The adaptation is performed as follows.
`Initially, E is used to encode/decode the first parameter
`set. Let E be the entropy encoder/decoder used to encode/
`decode the previous parameter set, (r, l, e). If Ill2T, then
`E is used to encode/decode the current parameter set,
`otherwise E is used to encode/decode the current param
`eter Set.
`FIG. 3, numeral 300, is a block diagram of an apparatus
`for adaptive entropy encoding/decoding in accordance with
`the present invention. The apparatus comprises a first
`memory unit (302), a parameter set determiner (304), an
`order reverser (306), an encoder controller (308), and a
`plurality of entropy encoders (310). When decoding is
`performed, the apparatus further comprises a plurality of
`entropy decoders (312), a decoder controller (314), a second
`memory unit (316), and a parameter set converter (318).
`For encoding, the quantized transform coefficients (320)
`are received and stored in the first memory unit (302). The
`parameter set determiner (304) accesses the quantized coef
`ficients in the memory unit (302). The parameter set deter
`miner (304) parses and converts the quantized transform
`coefficients (320) into a plurality of parameter sets (322) in
`a predetermined order of generally increasing average power
`and stores the parameter sets in the memory unit (302). The
`order reverser (306) accesses the parameter sets (322) in the
`memory unit (302) in the reverse order of the predetermined
`order. The order reverser (306) sends the level of the current
`parameter set (324) to the encoder controller (308). The
`encoder controller (308) adaptively selects a current entropy
`encoder from the plurality of entropy encoder (310) based
`on the previous entropy encoder and the previous level. The
`encoder controller (308) then switches the current parameter
`set (326) to the current entropy encoder and switches the
`output of the current entropy encoder to form the entropy
`encoded information bits (328).
`For decoding, the decoder controller (314) switches the
`entropy encoded information bits (328) to the current
`entropy decoder in the plurality of entropy decoders (312).
`The current entropy decoder decodes the entropy encoded
`
`where r is the run, which may be equal to zero, defined as
`the number of zero coefficients in the coefficient group, l is
`the level, and e is the end-of-block indicator which indicates
`whether the parameter set is the first set of the coefficient
`groups. Thus, where the parameter set is the first set of the
`coefficient groups, e is set to one, and where the parameter
`set is other than the first set of coefficient groups, e is set to
`zero. For example, the coefficient group {0, 0, 1}becomes
`the parameter set {2, 1, 1}, and the coefficient group {3}
`becomes the parameter set {0, 3, 0}.
`The present invention can be more fully described with
`reference to FIGS. 1-4. FIG. 1, numeral 100, is a flow
`diagram of steps for one embodiment of a method for
`adaptive entropy encoding in accordance with the present
`invention. A plurality of quantized transform coefficients are
`scanned in a predetermined scanning order giving a gener
`ally decreasing average power and the plurality of quantized
`transform coefficients are stored in a memory unit. The first
`step in the encoding method is parsing a predetermined
`number of quantized transform coefficients into a plurality
`of coefficient groups and converting the coefficient groups
`into a plurality of parameter sets according to a predeter
`mined scheme and storing the parameter sets in the memory
`unit (102). Each parameter set includes a level parameter
`which is a value of a non zero quantized transform coeffi
`cient. When a last coefficient group comprises all Zero
`quantized transform coefficients, the last coefficient group is
`discarded. The second step in the encoding method is
`accessing, from the memory unit, each parameter set of the
`plurality of parameter sets in a reverse order of the prede
`termined scanning order (104). The third step in the encod
`ing method is adaptively selecting a current entropy encoder
`of a plurality of entropy encoders based on a previous level
`parameter of a previous parameter set and a previously
`selected entropy encoder (106). The fourth and final step in
`the encoding method is encoding, by the current entropy
`encoder, a current parameter set to provide entropy encoded
`information bits (108). The parameter sets and stored in the
`memory unit in the form {rl,e}. The encoding process is
`repeated until the end-of-block parameter of the final param
`eter set indicates that the current parameter set is the last
`parameter set to be encoded.
`FIG. 2, numeral 200, is a flow diagram of steps for one
`embodiment of a method for adaptive entropy decoding in
`accordance with the present invention. The first step in the
`decoding method is decoding, by a current entropy decoder,
`the entropy encoded information bits to provide a decoded
`current parameter set (202). The second step in the decoding
`method is adaptively selecting a next entropy decoder of a
`plurality of entropy decoders based on a decoded current
`level parameter of the decoded current parameter set and a
`previously selected entropy decoder (204). The third step in
`the decoding method is storing, into the memory unit, each
`parameter set of a plurality of decoded parameter sets in the
`reverse order of the predetermined scanning order (206).
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`information bits (328) and generates the current decoded
`parameter set (330). The decoder controller (314) then
`adaptively selects the next entropy decoder from the plural
`ity of entropy decoders (312), corresponding to the set of
`entropy encoders (310), based on the current entropy
`decoder and the current level of the current decoded param
`eter set (330). The current parameter set (330) is stored in a
`second memory unit (316). The parameter set converter
`(378) accesses the second memory unit (316) to convert the
`parameter sets back into quantized transform coefficients
`and store the quantized transform coefficients in the second
`memory unit (316). The decoded quantized transform coef
`ficients (332) are then output from the second memory unit
`(316).
`The present invention is based on the observation that the
`quantized transform coefficients scanned in the order of
`decreasing average power have different amount of average
`power in different locations of the scan. Therefore different
`entropy encoders should be used adaptively to code the
`quantized transform coefficients in different location of the
`SCall.
`FIG.4, numeral 400, is an exemplary prior artillustration
`of a method of scanning and transforming a two dimensional
`block to provide a one dimensional array of scanned coef
`ficients. A two-dimensional block of 64 quantized discrete
`cosine transform coefficients is illustrated by the two-di
`mensional grid (402) in increasing horizontal frequency
`(406) from left to right and in increasing vertical frequency
`(408) from top to bottom. The quantized transform coeffi
`cients are scanned in a zig-zag order (404) as described in
`the MPEG-1 and H.261 standard to form a one-dimensional
`array of 64 quantized coefficients.
`FIG. 5, numeral 500, is a graphical depiction of the
`average power, in general, of the scanned coefficients, where
`the graph of the average power of the scanned coefficients is
`separated into higher (506) and lower (508) power coeffi
`cient groupings. A distinction between lower and higher
`power coefficient is made in accordance with the present
`invention. In general the average power (502) of the zig-zag
`scanned coefficients in 400 decreases as a function of its
`index (504). The index is defined as the order in which a
`coefficient was scanned. In this example, the zig-zag
`scanned coefficient are divided into the higher power coef
`ficients (506), and the lower power coefficients (508) by a
`threshold (510). Because of different statistical properties of
`45
`the higher power coefficients (506) and the lower power
`coefficients (508), one entropy encoder is used to code the
`higher power coefficients (506), and another entropy
`encoder is used to code the lower power coefficients (508).
`The present invention codes the quantized transform
`coefficients with less number of bits than the coding method
`used in MPEG-1, MPEG-2, and H.261. The present inven
`tion adapts to each block of quantized transform coefficients
`while the coding method in MPEG-1, MPEG-2, and H.261
`does not.
`I claim:
`1. A method for adaptive entropy encoding/decoding of a
`plurality of quantized transform coefficients in a video
`compression system, wherein the plurality of quantized
`transform coefficients are scanned in a predetermined scan
`ning order giving a generally decreasing average power and
`the plurality of quantized transform coefficients are stored in
`a memory unit, the method comprising at least one of:
`A) encoding by:
`Al) parsing a predetermined number of quantized
`transform coefficients into a plurality of coefficient
`groups and converting the coefficient groups into a
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`plurality of parameter sets according to a predeter
`mined scheme and storing the parameter sets in the
`memory unit, wherein each parameter set includes a
`level parameter which is a value of a non zero
`quantized transform coefficient, wherein, where a
`last coefficient group comprises all zero quantized
`transform coefficients, the last coefficient group is
`discarded;
`A2) accessing, from the memory unit, each parameter
`set of the plurality of parameter sets in a reverse
`order of the predetermined scanning order;
`A3) adaptively selecting a current entropy encoder of a
`plurality of entropy encoders based on a previous
`level parameter of a previous parameter set and a
`previously selected entropy encoder; and
`A4) encoding, by the current entropy encoder, a current
`parameter set to provide entropy encoded informa
`tion bits; and
`B) decoding by:
`B1) decoding, by a current entropy decoder, the entropy
`encoded information bits to provide a decoded cur
`rent parameter set;
`B2) adaptively selecting a next entropy decoder of a
`plurality of entropy decoders based on a decoded
`current level parameter of the decoded current
`parameter set and a previously selected entropy
`decoder;
`B3) storing, into the memory unit, each parameter set
`of a plurality of decoded parameter sets in the
`reverse order of the predetermined scanning order;
`and
`B4) converting the decoded parameter sets into a
`number of decoded quantized transform coefficients
`according to the predetermined scheme in the pre
`determined scanning order and storing the decoded
`quantized transform coefficients in the memory unit,
`wherein, where the number of decoded quantized
`transform coefficients is less than the predetermined
`number of quantized transform coefficients, zero
`valued decoded quantized transform coefficients will
`be appended.
`2. The method of claim 1 wherein the predetermined
`scheme forms coefficient groups by grouping consecutive
`zero-valued quantized transform coefficients up to and
`including a non-zero quantized transform coefficient.
`3. The method of claim 1, wherein each parameter set
`further comprises an end-of-block parameter which signifies
`a final parameter set to be encoded in the plurality of
`parameter sets.
`4. The method of claim 1, wherein each entropy encoder
`is a variable length encoder.
`5. The method of claim 1, wherein each entropy encoder
`is an arithmetic encoder.
`6. The method of claim 1, wherein the plurality of entropy
`encoders are in a predetermined order.
`7. The method of claim 1, wherein the plurality of entropy
`encoders is two entropy encoders.
`8. The method of claim 2, wherein each parameter set
`further comprises a run parameter which is a number of
`consecutive zero-valued quantized transform coefficients
`prior to the non zero quantized transform coefficient.
`9. The method of claim 6, wherein a next entropy encoder
`is selected when a current level exceeds a predetermined
`threshold.
`10. A apparatus for adaptive entropy encoding/decoding
`of a plurality of quantized transform coefficients in a video
`compression system, wherein the plurality of quantized
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`transform coefficients are scanned in a predetermined scan
`ning order giving a generally decreasing average power and
`the plurality of quantized transform coefficients are stored in
`a memory unit, the apparatus comprising at least one of:
`A) an encoding apparatus comprising:
`A1) a first memory unit, operably coupled to receive
`the plurality of quantized transform coefficients and
`to a parameter set determiner, for storing the quan
`tized transform coefficients;
`A2) the parameter set determiner, operably coupled to
`the first memory unit, for parsing a predetermined
`number of quantized transform coefficients into a
`plurality of coefficient groups and converting the
`coefficient groups into a plurality of parameter sets
`according to a predetermined scheme and storing the
`parameter sets in the first memory unit, wherein each
`parameter set includes a level parameter which is a
`value of a non Zero quantized transform coefficient,
`wherein, where a last coefficient group comprises all
`zero quantized transform coefficients, the last coef
`ficient group is discarded;
`A3) an order reverser, operably coupled to the first
`memory unit, for accessing each parameter set of the
`plurality of parameter sets in reverse order of the
`predetermined scanning order and providing the
`parameter sets to an encoder controller and a plural
`ity of entropy encoders;
`A4) the encoder controller, operably coupled to the
`order reverser, for choosing a current entropy
`encoder of the plurality of entropy encoders based on
`a previous level parameter of a previous parameter
`set, and
`A5) the plurality of entropy encoders, operably coupled
`to the encoder controller and the order reverser, for
`encoding a current parameter set to provide entropy
`encoded information bits; and
`B) a decoding apparatus comprising:
`B1) a plurality of entropy decoders, operably coupled
`to receive the entropy encoded information bits from
`the plurality of entropy encoders, for decoding the
`entropy encoded information bits to provide a
`decoded current parameter set;
`B2) a decoder controller, operably coupled to the
`plurality of entropy decoders, for adaptively select
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`ing a next entropy decoder of the plurality of entropy
`decoders based on a decoded current level parameter
`of the decoded current parameter set and a previ
`ously selected entropy decoder;
`B3) a second memory unit, operably coupled to the
`plurality of entropy decoders, for storing each
`parameter set of a plurality of decoded parameter
`sets in the reverse of the predetermined scanning
`order, and
`B4) a parameter set converter, operably coupled to the
`second memory unit, for converting the decoded
`parameter sets into a number of decoded quantized
`transform coefficients according to the predeter
`mined scheme in the predetermined scanning order
`and storing the decoded quantized transform coeffi
`cients in the second memory unit, wherein, where the
`number of decoded quantized transform coefficients
`is less than the predetermined number of quantized
`transform coefficients, zero-valued decoded quan
`tized transform coefficients will be appended.
`11. The apparatus of claim 10 wherein the predetermined
`scheme forms coefficient groups by grouping consecutive
`Zero-valued quantized transform coefficients up to and
`including a non-zero quantized transform coefficient.
`12. The apparatus of claim 10, wherein each parameterset
`further comprises a run parameter which is a number of
`Zero-valued quantized transform coefficients prior to the non
`Zero quantized transform coefficient.
`13. The apparatus of claim 10, wherein each parameterset
`further comprises an end-of-block parameter which signifies
`a final parameter jet in the plurality of parameter sets to be
`encoded.
`14. The apparatus of claim 10, wherein each entropy
`encoder is a variable length encoder.
`15. The apparatus of claim 10, wherein each entropy
`encoder is an arithmetic encoder.
`16. The apparatus of claim 10, wherein the plurality of
`entropy encoders are in a predetermined order.
`17. The apparatus of claim 10, wherein the plurality of
`entropy encoders is two entropy encoders.
`18. The apparatus of claim 16, wherein a next entropy
`encoder is chosen when a current level exceeds a predeter
`mined threshold.
`
`IPR2018-01413
`Sony EX1020 Page 8
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