JP2008517495A - LASeR binary representation point sequence encoding / decoding method and apparatus - Google Patents

Abstract

  The present invention proposes a selective encoding / decoding method and apparatus for point sequences in order to maximize the bit efficiency of LASeR binary representation. In the point sequence encoding method according to the present invention, for each point sequence of LASeR (Lightweight Application Scene Representation), (a) Exponential Golomb (EG) encoding or Fixed Length (FL) ) Selecting one of the encoding schemes; and (b) encoding the point sequence based on the FL encoding scheme and generating a binary stream when the FL encoding scheme is selected, And (c) when the EG encoding method is selected, encoding the point sequence based on the EG encoding method and generating a binary stream, and showing a selection result of the encoding method Flag and parameter k value that can most effectively perform EG coding when the selected coding method is an EG coding method Characterized in that it is included in the binary stream. The encoding method has an advantage in that it provides more efficient LASeR point sequence encoding and does not add a large overhead to a decoder (terminal) during decoding.

Description

  The present invention relates to a method and apparatus for efficiently encoding / decoding a point sequence, and more specifically, efficiently encoding / decoding a point sequence of a LASeR (Lightweight Application Scene Representation) binary representation. The present invention relates to a method and an apparatus.

  LASeR is a multimedia content format defined for providing a simple multimedia service in a terminal having a shortage of resources such as a mobile phone. Applications of LASeR can be considered for applications such as mobile terminal maps, animations and 2D vector graphics. Many parts of such application data consist of point data. Therefore, a method for efficiently encoding point data needs to be devised. The two main elements of LASeR to consider for this are an efficient binary representation and a small memory on the decoder.

  The LASeR Text of ISO / IEC 14496-20 CD published in July 2004 proposes a fixed length (FL) encoding method for point data encoding of LASeR binary representation. In the FL encoding method, when the number of points (nbPoint) is smaller than 3, the actual point data is encoded, and when the number of points is 3 or more, the entire points are determined to determine the dynamic range of the point sequence. In this method, a sequence is inspected and encoded using a fixed length obtained as a result. Such a method can be implemented very simply, but there is not only a 10-bit overhead for specifying the length field for each point sequence, but also unnecessary for the subsequent data fields. There are a number of allocated bits.

  Entropy encoding / decoding can be considered for efficient compression and decompression of image data. In general, entropy coding is a method of coding a value having a high frequency using a small number of bits in consideration of various values from which data can be taken.

  Although there are various entropy encoding methods, they can be broadly classified into two groups: an encoding method using an encoding table and an encoding method not using an encoding table. The Huffman coding method represents a group using a coding table. Although this method can calculate a compression ratio that is almost optimal, the encoding table must be transferred, and the overhead of having to access the memory location every time the point data is decoded is increased. There is a problem that the weight is applied to the decoder (terminal) side. Since LASeR requires a light-weight memory and a minimum complexity, the Huffman encoding method using the encoding table in this way is not suitable for encoding point data.

  Other groups of entropy coding schemes (ie, coding schemes that do not use a coding table) include arithmetic coding and EG coding. Although arithmetic coding is an efficient coding method, it has a disadvantage in that it is difficult to be used for LASeR due to lack of error recovery.

  On the other hand, EG (Exponential Golomb) coding has some characteristics suitable for the LASeR environment. This method can select a parameter k suitable for a specific distribution while giving less overhead to the encoder side. Also, it can be easily converted to reversible variable length coding (VLC) to add error recovery function (ISO / IEC JTC 1 / SC 29 / WG 1 (ITU-T SG8), See “Reversible VLC for added error resilience”). Another advantage is low overhead on the decoder side. This method can be implemented without adding a large overhead to a small device such as a mobile phone, since the decoding process can be performed using only addition and bit shift hiding.

  An object of the present invention is to select a point sequence encoding method in order to improve the compression efficiency of LASeR binary representation, a flag indicating the selected encoding method, and the selected encoding method is EG encoding It is another object of the present invention to provide a point sequence encoding method and apparatus for further encoding a parameter k value used for EG encoding in the case of a scheme and transferring it together with a LASeR binary stream.

  Another object of the present invention is to extract a flag indicating an encoding method from an encoded LASeR stream, determine a decoding method according to the value, and determine the parameter k when determined as an EG decoding method. It is another object of the present invention to provide a method and apparatus for extracting and decoding the encoded LASeR stream.

  The present invention proposes a selective encoding / decoding method and apparatus for point sequences in order to maximize the bit efficiency of LASeR binary representation.

  According to an aspect of the present invention, a LASeR point sequence encoding method is provided, the encoding method comprising: (a) Exponential Golomb (EG) encoding or fixed for each point sequence. Selecting either one of a length (Fixed Length: FL) encoding scheme; and (b) when the FL encoding scheme is selected, encoding the point sequence based on the FL encoding scheme; Generating a binary stream; and (c) encoding the point sequence based on an EG encoding scheme and generating a binary stream when an EG encoding scheme is selected, A flag indicating the selection result of the encoding method, and a parameter capable of performing the EG encoding most effectively when the selected encoding method is the EG encoding method. k value is equal to or included in the binary stream.

  According to another aspect of the present invention, there is provided a method for decoding a LASeR binary stream, wherein the decoding method extracts information indicating an encoding scheme from the LASeR binary stream, and the extracted information Determining one of an EG decoding method and an FL decoding method based on the method, and decoding the LASeR binary stream based on the determined decoding method. .

  According to still another aspect of the present invention, an encoded LASeR scene description elementary stream is generated by encoding a LASeR point sequence indicating scene description information (Scene Description) by the decoding method described above. Multiplexes for multiplexing the LASeR scene encoding means, the encoded LASeR scene description elementary stream, and other elementary streams constituting the LASeR scene to generate a multiplexed LASeR binary stream There is provided a server comprising: a converting means; and a transmitting means for transferring the multiplexed LASeR binary stream to a user terminal.

  According to yet another aspect of the present invention, receiving means for receiving a LASeR binary stream, and demultiplexing for outputting a LASeR scene description stream and other elementary streams from the received LASeR binary stream. And a plurality of decoded LASeR access units that can be individually accessed by decoding the LASeR scene description elementary stream output from the demultiplexing means by the decoding method described above. A scene tree is generated from the LASeR scene decoding means, the other elementary decoding means for decoding the other elementary stream output from the demultiplexing means, and the decoded access unit Scene tree manager for the generated scene The user terminal device comprising a, a renderer (renderer) LASeR for providing a LASeR service to a user using other elementary stream the decrypted tree is provided.

  According to still another aspect of the present invention, a flag for indicating either the FL encoding method or the EG encoding method in the encoding method, and EG when the flag has a value indicating the EG encoding method. A data structure of a LASeR point sequence encoded data stream is provided that includes a parameter k value that can be most effectively encoded.

  As described above, when the point sequence is encoded / decoded by the encoding method of the present invention, a data compression gain of 6 to 17% can be obtained. Therefore, when the coding method according to the present invention is used for applications such as maps, cartoons and vector graphics containing a large amount of point sequences, good compression efficiency can be achieved with low decoder complexity. Can do.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, the following detailed description is provided for illustrative purposes only and should not be construed to limit the concepts of the present invention to any particular physical configuration.

  FIG. 1 is a block diagram illustrating a system to which selective encoding / decoding of a LASeR point sequence according to the present invention is applied. As illustrated, the server system 10 includes a LASeR scene encoding unit 11, a SAF multiplexing unit 12, and a transmission unit 13. The LASeR scene encoding unit 11 is inputted with a descriptor (Scene Description) for a scene, for example, SVG (Scalable Vector Graphics) data or LASeR XML data, and is compressed (encoded) LASeR scene description elementary. Create a stream. The LASeR point sequence selective encoding method according to the present invention can be applied to the LASeR scene encoding unit 11.

  The SAF multiplexing unit 12 performs a LASeR scene description elementary stream and other elementary streams constituting the LASeR scene (for example, video, audio, image, font, or metadata elementary stream depending on the scene). Include) to generate one multiplexed LASeR binary stream. The transmission unit 13 transfers the LASeR binary stream to the user terminal 20 via various communication networks such as IP, wireless Internet, or CDMA network. The user terminal 20 includes a receiving unit 21, a SAF demultiplexing unit 22, a LASeR scene decoding unit 23, other elementary decoding units 24 and a LASeR renderer 26. The SAF demultiplexer 23 receives the data stream transferred by the receiver 21 and generates a LASeR scene description stream and other elementary streams. The LASeR scene decoding unit 23 receives the LASeR scene description elementary stream from the output of the SAF demultiplexing unit 22 and generates a decoded access unit. An access unit is a portion of data that can be individually accessed from a media stream. The LASeR point sequence decoding method according to the present invention can be applied to the LASeR scene decoding unit 23.

  The other elementary decoder 24 outputs other elementary streams from the output of the SAF demultiplexer 23 excluding the LASeR scene description elementary stream, that is, a video, audio, image, font, or metadata elementary stream. Decrypt etc. A scene tree manager 25 receives a decoded access unit and generates a scene tree. The scene tree means a hierarchical structure of a scene description for indicating a temporal / spatial position of objects constituting the LASeR scene. The LASeR renderer 26 receives the scene tree and receives other types of other elementary streams output from the other elementary decoding unit 24 and provides the user with the LASeR service.

  FIG. 2 is a flow diagram illustrating a process for encoding a point sequence according to the present invention. For each point sequence, step 210 determines either the FL or EG encoding scheme. As an example, after all EG encoding and FL encoding are performed, an encoding scheme that generates the smallest number of bits is selected. If it is selected as the FL encoding method, the encoding selection flag is encoded to “0” in step 220 (flag = 0), and the point sequence is encoded using the FL encoding method in step 230.

  The FL encoding scheme can be performed by the following procedure.

Assuming that the point sequence consists of n + 1 points of (x ₀ , y ₀ ) (x ₁ , y ₁ ) ... (x _n , y _n )
1) If the number of points is 2 or less,
i) Calculate and encode the minimum number of bits (bits) that can encode all of x ₀ , y ₀ , x ₁ and y ₁ .
ii) The points (x ₀ , y ₀ ) and (x ₁ , y ₁ ) are encoded using the number of bits (bits) obtained in i).
2) Or, if the number of points is 3 or more,
i) Calculate and encode the minimum number of bits (bits) that can encode all the points (x ₀ , y ₀ ).
ii) The point (x ₀ , y ₀ ) is encoded using the minimum number of bits (bits) obtained in i).
iii) dx ₁₀ ,..., dx _nn−1 (where dx _nn−1 = x _n −x _n−1 ) is obtained, and then the number of bits (bitsx) necessary for these encodings is obtained.
iv) After obtaining dy ₁₀ ,... dy _nn−1 (where dy _nn−1 = y _n −y _n−1 ), the number of bits (bitsy) necessary for these encodings is obtained.
v) Encode the number of bits (bitsx and bitsy).
vi) Encode dx ₁₀ , dy ₁₀ ..., dx _nn−1 , dy _nn−1 .

  On the other hand, when the EG encoding method is selected, the encoding selection flag is encoded to “1” in step 240 (flag = 1), and EG encoding can be most effectively performed in step 250. Determine the parameter k and encode it. In step 260, the point sequence is encoded based on the EG encoding scheme.

  EG coding is one of the entropy coding methods, and has a regular configuration method that is advantageous for compression of point sequences in which small numbers are frequently generated by assigning shorter codes to small numbers. In the Huffman coding method, which is another entropy coding method, a code table for specifying the relationship between symbols and code numbers is required, and such a code table must be stored in the user terminal. In contrast to this, EG encoding uses a regular configuration method, and therefore can be said to be an encoding method more suitable for LASeR since it does not require a code table. EG coding does not assign codewords with accurate symbol statistics. Instead, the EG encoding can be matched to various variances of the geometric distribution by adjusting the parameter k. In the EG encoding, each code is configured as follows.

[M zeros] [1] [INFO]
Here, M is the number of leading zeros, and INFO is a (M + k) bit suffix offset value that carries information. The leading zero and the next “1” serve as a prefix code that separates each code. The code number (CodeNum) is determined as follows.
Formula 1
CodeNum = 2 ^{M + k} + INFO-2 ^k

Since the INFO value does not affect the length of the reading zero, the number M of reading zero can be obtained by the following formula 2 by ignoring the INFO term in the above formula.
Formula 2
M = [log ₂ (CodeNum + 2 ^k )] − k

Next, INFO can be obtained by the following Equation 3 derived from Equation 2 above.
Formula 3
INFO = CodeNum + 2 ^k −2 ^{M + k}

Table 1 below exemplarily shows 11 EG encoded codes each configured when parameters k = 0, k = 1, k = 2, and k = 3.

  From the above table, it can be seen that the codes increase in a logical order.

* Since an EG code has only an unsigned code number, a signed EG code must be mapped to an unsigned EG code. Signed EG codes are parsed by retrieving an unsigned EG code number (CodeNum) from the bitstream and mapping it to a signed one using the following rules.
If (CodeNum is 0) signed code = 0;
else if (CodeNum is even) signed code = -CodeNum / 2;
else if (CodeNum is odd) signed code = (CodeNum + 1) / 2;

Table 2 below provides an example for unsigned-signed mapping.

  As an example, the EG encoding scheme may be performed by the following procedure.

Assuming that the point sequence consists of n + 1 points of (x ₀ , y ₀ ) (x ₁ , y ₁ ) ... (x _n , y _n )
(1) Calculate and encode the minimum number of bits that can encode the point (x ₀ , y ₀ ).
(2) The point (x ₀ , y ₀ ) is encoded using the minimum number of bits.
(3) For each of the remaining points of the point sequence, the difference data of the x and y coordinates between the previous point and the current point are respectively mapped to an EG code number (CodeNum) based on a predetermined rule, and the EG code EG encoding is performed by generating an EG code word corresponding to each of the difference data of the x and y coordinates using the number and the parameter k value.

Specifically, the following process is performed for encoding one point (x _i , y _i ).
(I) A difference (diffx) between x _i and x _i−1 is mapped to an unsigned EG code number (CodeNum) according to the following rule.
if (diffx> = 0) CodeNum = diffx * 2-1;
else CodeNum = | diffx | * 2;
(Ii) M indicating the number of reading zeros can be obtained by Equation 2 described above.
(Iii) Only 0 is recorded for M bits.
(Iv) 1 is recorded for only 1 bit.
(V) INFO, which is a suffix offset for carrying information, can be obtained by Equation 3 described above.
(Vi) INFO is recorded in M + k bits.
(Vii) The difference (diffy) between y _i and y _i−1 is mapped to an unsigned EG code number (CodeNum) according to the following rule.
if (diffy> = 0) CodeNum = diffy * 2-1;
else CodeNum = | diffy | * 2;
(Viii) M indicating the number of reading zeros is obtained using Equation 2 above.
(Ix) Only 0 is recorded for M bits.
(X) Record 1 for only 1 bit.
(Xi) INFO, which is a suffix offset for carrying information, is obtained using Equation 3.
(Xii) INFO is recorded in M + k bits.

  FIG. 3 is a flow diagram illustrating a process for decoding a point sequence according to the present invention. As shown, at step 310, either the FL or EG decoding scheme is determined for the LASeR binary stream. Such a determination can be made by reading an encoding selection flag included in the LASeR binary stream. As described above, the encoding selection flag included in the binary stream is a flag indicating whether the point sequence is encoded by any one of the FL and EG encoding methods. Will come to decide.

  If the FL decoding method is determined, the point sequence is decoded based on the FL decoding method (step 320). The FL decoding scheme can be performed by the following procedure.

Assuming that the LASeR binary stream is decoded into a point sequence (x ₀ , y ₀ ) (x ₁ , y ₁ ) ... (x _n , y _n )
(1) The number of points in the point sequence is extracted from the LASeR binary stream.
(2) Extract the number of bits (bits) required for x and y of points from the LASeR binary stream.
(3) If there are two or less points, only bits are read and the values of x ₀ , y ₀ , x ₁ , y ₁ are extracted.
(4) Or,
(I) bits only read the extracts respectively _{x 0} and _{y 0.}
(Ii) Bitsx and bitsy that are the number of bits necessary for the difference between x and y (each dx and dy) are extracted.
(Iii) Place i = 1.
(Iv) Read only bitsx and bitsy, extract the values of dx and dy, respectively, and calculate _xi = xi _-1 + dx and _yi = _yi-1 + dy.
(V) i = i + 1, and the item (iv) is performed n-1 times.

  On the other hand, if it is determined as the EG decoding method, a parameter k for EG decoding is further extracted from the LASeR binary stream in step 330, and EG decoding is performed using the extracted parameter k in step 340. I do.

  As an example, the EG decoding scheme may be performed by the following procedure.

Assuming that the LASeR binary stream is decoded into a point sequence (x ₀ , y ₀ ) (x ₁ , y ₁ ) ... (x _n , y _n )
(1) Read the point number information of the point sequence, the number of bits used to encode the point, and the parameter k information from the LASeR binary stream.
(2) The bits are read in units of the extracted bits (bits), and the first point coordinates (x ₀ , y ₀ ) are decoded.
(3) Read an EG code word corresponding to each of the difference data of the x and y coordinates of the previous point and the current point from the LASeR binary stream, decode it using the parameter k, and decode the decoded x and y coordinates Are added to the coordinates of the previous point to calculate the coordinates of the current point.
(4) Steps (3) are repeated for the number of remaining points excluding the first point.

Specifically, the following process is performed for decoding one point (x _i , y _i ).
(I) Read one bit at a time until 1 is found, and the total number of bits is called M.
(Ii) Read 1 and discard.
(Iii) Read M + k bits and call it INFO.
(Iv) CodeNum = 2 ^{M + k} + INFO-2 ^k is obtained.
(V) Obtain dx from CodeNum.
(Vi) Calculate x _i = x _i-1 + dx.
(Vii) One bit is read out until 1 is found, and the total number of bits is referred to as M.
(Viii) 1 is read and discarded.
(Ix) Read M + k bits and call it INFO.
(X) CodeNum = 2 ^{M + k} + INFO-2 ^k is obtained.
(Xi) Obtain dy from CodeNum.
(Xii) Calculate y _i = y _i−1 + dy.

The decoding process of the LASeR binary stream according to the present invention can be expressed by the syntax and semantics expressed by the following pseudo code.
Syntax:
decodingPointSequence {
nbPoints = Read (lenBits);
flag = Read (1);
if (flag == 0) {
if (nbPoints <3) {
bits = Read (5);
for (int i = 0; i <nbPoints; i ++) {
x [i] = Read (bits);
y [i] = Read (bits);
}
}
else {
bits = Read (5);
x [0] = Read (bits);
y [0] = Read (bits);
bitsx = Read (5);
bitsy = Read (5);
for (int i = 1; i <nbPoints; i ++) {
dx = Read (bitsx);
dy = Read (bitsy);
x [i] = dx + x [i-1];
y [i] = dy + y [i-1];
}
}
}
else {
bits = Read (5);
x [0] = Read (bits);
y [0] = Read (bits);
kvalue = Read (4);
for (i = 1; i <nbPoints; i ++) {
l_zero = 0;
while (Read (1) == 0) l_zero ++;
Mvalue = l_zero;
Read (1);
INFO = Read (Mvalue + kvalue);
CodeNum = 2 ^{M + kvalue} + INFO-2 ^kvalue ;
if (CodeNum == 0) dx = 0;
else if (CodeNum == even) dx = -CodeNum / 2;
else if (CodeNum == odd) dx = (CodeNum + 1) / 2;
x [i] = dx + x [i-1];
l_zero = 0;
while (Read (1) == 0) l_zero ++;
Mvalue = l_zero;
Read (1);
INFO = Read (Mvalue + kvalue);
CodeNum = 2 ^{M + kvalue} + INFO-2 ^kvalue ;
if (CodeNum == 0) dy = 0;
else if (CodeNum == even) dy = -CodeNum / 2;
else if (CodeNum == odd) dy = (CodeNum + 1) / 2;
y [i] = dy + y [i-1];
}
}
}

Semantics:
flag-Flag indicating FL encoding (flag = 0) or EG encoding (flag = 1) kvalue-A parameter for EG encoding, and a different value is used depending on the type of geometric distribution. For example, as the kvalue value increases, the geometric distribution becomes gradually gentler.
Mvalue-number of reading zeros CodeNum-code number dx-difference between the x coordinate value of the current point and the x coordinate value of the previous point.
dx = x [i] −x [i−1]
dy—the difference between the y coordinate value of the current point and the y coordinate value of the previous point.
dy = y [i] -y [i-1]
INFO-a value with information about dx or dy

The LASeR binary stream decoding process according to the present invention can be expressed by a syntax expressed by the following pseudo code as an example.
Syntax:
decodingPointSequence {
nbPoints = Read (lenBits);
flag = Read (1);
if (flag == 0) {
if (nbPoints <3) {
bits = Read (5);
for (int i = 0; i <nbPoints; i ++) {
x [i] = Read (bits);
y [i] = Read (bits);
}
}
else {
bits = Read (5);
x [0] = Read (bits);
y [0] = Read (bits);
bitsx = Read (5);
bitsy = Read (5);
for (int i = 1; i <nbPoints; i ++) {
dx = Read (bitsx);
dy = Read (bitsy);
x [i] = dx + x [i-1];
y [i] = dy + y [i-1];
}
}
}

else {
kvalue = Read (4);
bits Read (5);
x [0] = Read (bits);
y [0] = Read (bits);
for (i = 1; i <nbPoints; i ++) {
l_zero = 0;
while (Read (1) == 0) l_zero ++;
Mvalue = l_zero;
Read (1);
INFO = Read (Mvalue + kvalue);
CodeNum = 2 ^{M + kvalue} + INFO-2 ^kvalue ;
if (CodeNum == 0) dx = 0;
else if (CodeNum == even) dx = -CodeNum / 2;
else if (CodeNum == odd) dx = (CodeNum + 1) / 2;
x [i] = dx + x [i-1];
l_zero = 0;
while (Read (1) == 0) l_zero ++;
Mvalue = l_zero;
Read (1);
INFO = Read (Mvalue + kvalue);
CodeNum = 2 ^{M + kvalue} + INFO-2 ^kvalue ;
if (CodeNum == 0) dy = 0;
else if (CodeNum == even) dy = -CodeNum / 2;
else if (CodeNum == odd) dy = (CodeNum + 1) / 2;
y [i] = dy + y [i-1];
}
}
}

The LASeR binary stream decoding process according to the present invention may be expressed in a syntax expressed in SDL (Syntactic Description Language) code as one modified embodiment.
Syntax:
decodingPointSequence {
uivlc5 nbPoints;
uint (1) flag;
if (flag == 0) {
if (nbPoints <3) {
uint (5) bits;
for (int i = 0; i <nbPoints; i ++) {
uint (bits) x [i];
uint (bits) y [i];

*}
} else {
uint (5) bits;
uint (bits) x [0];
uint (bits) y [0];
uint (5) bitsx;
uint (5) bitsy;
for (int i = 1; i <nbPoints; i ++) {
uint (bitsx) dx;
uint (bitsy) dy;
x [i] = dx + x [i-1];
y [i] = dy + y [i-1];
}
}
}
else {
uint (4) kvalue;
uint (5) bits;
uint (bits) x [0];
uint (bits) y [0];
int XMvalue, YMvalue = 0;
int CodeNum = 0;
int Diff = 0;
for (i = 1; i <nbPoints; i ++) {
// to calculate X point
do {
bit (1) bitX;
XMvalue ++;
} while (bitX == 0);
const bit (1) endX = 1;
uint (XMvalue + kvalue) INFO_dx;
CodeNum = GetCodeNum (kvalue, XMvalue, INFO_dx);
Diff = GetDiff (CodeNum);
x [i] = x [i-1] + Diff
// to calculate Y point
do {
unit (1) bitY;
YMvalue ++;
} while (bitY == 0);
const bit (1) endY = 1;
uint (YMvalue + kvalue) INFO_dy;
CodeNum = GetCodeNum (kvalue, YMvalue, INFO_dy);
Diff = GetDiff (CodeNum);
y [i] = y [i-1] + Diff
}
}
}

uint GetCodeNum (int k, int Mvalue, int INFO) {
return 2 ^{(k + Mvalue)} + INFO-2 ^k ;
}
int GetDiff (int CM) {
if ((CM% 2) == 0) return -1 * CM / 2;
else return CM // 2;
}

  In the syntax expression, the operator% indicates a modulus operator, the operator // is an integer division, and the remainder is rounded to the nearest integer. In some examples, 1/2 is 1 and 3/2 is 2 and 5/2 is 3.

  The present invention described above can be provided as one or more computer readable media embodied on one or more products. The product may include a floppy disk, hard disk, CD ROM, flash memory card, PROM, RAM, ROM, or magnetic tape. In general, a computer-readable program can be implemented in any programming language. Examples of usable languages include C, C ++, or JAVA.

  The present invention has been described above with reference to specific embodiments. However, the present invention is not limited to the above-described embodiments and the accompanying drawings, and a person having ordinary knowledge in the technical field to which the present invention belongs. It will be apparent that various substitutions, modifications and changes can be made without departing from the technical idea of the present invention.

1 is a configuration diagram illustrating a system to which selective encoding / decoding of a LASeR point sequence according to the present invention is applied. FIG. 4 is a flow diagram illustrating a process for encoding a point sequence according to the present invention. 4 is a flow diagram illustrating a process for decoding a point sequence according to the present invention.

Claims (17)

In a method of encoding a point sequence of LASeR (Lightweight Application Scene Representation), for each point sequence,
(A) selecting one of Exponential Golomb (EG) encoding or Fixed Length (FL) encoding;
(B) when the FL encoding scheme is selected, encoding the point sequence based on the FL encoding scheme to generate a binary stream;
(C) when an EG encoding scheme is selected, encoding the point sequence based on the EG encoding scheme to generate a binary stream, and
The binary stream includes a flag indicating a selection result of the encoding scheme and a parameter k value that can most effectively perform EG encoding when the selected encoding scheme is an EG encoding scheme. LASeR point sequence coding method characterized by the above-mentioned.   The LASeR point sequence encoding method according to claim 1, wherein the step (c) further comprises a step of obtaining a parameter k that can perform EG encoding most effectively.   The method according to claim 1, wherein, in the step (a), after performing EG coding and FL coding on the point sequence, a coding method that generates the smallest number of bits is selected. LASeR point sequence encoding method. FL encoding scheme of step (b), point sequence _{(x 0, y 0) (} x 1, y 1) ... (x n, y n) relative to,
(B1) When the number of points in the point sequence is 2 or less,
(B1-i) calculating and encoding the minimum number of bits (bits) that can encode the coordinates (x ₀ , y ₀ ) (x ₁ , y ₁ ) of the point;
(B1-ii) encoding the coordinates (x ₀ , y ₀ ) (x ₁ , y ₁ ) of the point using the minimum number of bits (bits);
(B2) When the number of points in the point sequence exceeds 2,
(B2-i) calculating and encoding the minimum number of bits (bits) that can encode the coordinates (x ₀ , y ₀ ) of the first point;
(B2-ii) encoding the coordinates (x ₀ , y ₀ ) of the first point using the minimum number of bits (bits);
(B2-iii) x coordinate difference data (dx ₁₀ ,..., Dx _nn−1 , where dx _nn−1 = x _n −x _n−1 ) between adjacent points is obtained, and the difference between the x coordinates Calculating the number of bits (bitsx) required to encode the data;
(B2-iv) Find y coordinate difference data (dy ₁₀ ,..., Dy _nn−1 , where dy _nn−1 = y _n −y _n−1 ) between adjacent points, and calculate the y coordinate difference Calculating the number of bits needed to encode the data (bitsy);
(B2-v) encoding the number of bits necessary for encoding the difference data of the x coordinate and the number of bits necessary for encoding the difference data of the y coordinate;
(B2-vi) The LASeR point sequence encoding method according to claim 1, further comprising: encoding the difference data of the x coordinate and the difference data of the y coordinate. EG encoding scheme of step (c), point sequence _{(x 0, y 0) (} x 1, y 1) ... (x n, y n) relative to,
(C1) calculating and encoding a minimum number of bits that can encode the coordinates (x ₀ , y ₀ ) of the first point;
(C2) encoding the coordinates (x ₀ , y ₀ ) of the first point using the minimum number of bits;
(C3) For each of the remaining points, the difference data of the x and y coordinates between the previous point and the current point is mapped to an EG code number (CodeNum) based on a predetermined rule, and the EG code number and the parameter The LASeR FOR of claim 1, further comprising: performing EG encoding by generating an EG code word corresponding to each of the difference data of the x and y coordinates using a k value. In-TE sequence encoding method. In step (c3), for each of the remaining points,
(C3-i) mapping x-coordinate difference data between the previous point and the current point to an EG code number (CodeNum) based on a predetermined rule;
(C3-ii) A step of obtaining the number of reading zeros (M) and a suffix offset (INFO) carrying information using the EG code number (CodeNum) obtained in the step (c3-i) and the parameter k value. When,
(C3-iii) By concatenating the M-bit “0”, the 1-bit “1”, and the M + k-bit suffix offset (INFO) obtained in the step (c3-ii), Generating an EG codeword corresponding to the difference data;
(C3-iv) mapping the difference data of the y coordinate between the previous point and the current point to an EG code number (CodeNum) based on a predetermined rule;
(C3-v) using the EG code number (CodeNum) obtained in the step (c3-iv) and the parameter k value to obtain the number of reading zeros (M) and the suffix offset (INFO) for carrying information; ,
(C3-vi) The y coordinate is obtained by concatenating the M-bit “0”, the 1-bit “1”, and the M + k-bit suffix offset (INFO) obtained in the step (c3-v). 6. The LASeR point sequence encoding method according to claim 5, further comprising: generating an EG code word corresponding to the difference data. In a method for decoding a LASeR binary stream,
Extracting information indicating an encoding scheme from the LASeR binary stream, and determining one of an EG decoding scheme and an FL decoding scheme based on the extracted information;
Decoding the LASeR binary stream based on the determined decoding method, comprising: a LASeR binary stream decoding method. When the FL decoding scheme is determined, it is assumed that the LASeR binary stream is decoded into a point sequence (x ₀ , y ₀ ) (x ₁ , y ₁ )... (X _n , y _n ). ,
(A) reading from the LASeR binary stream point number information of a point sequence and bits number information used to encode the points;
(B) when the number of read points is 2 or less, sequentially reading bits in units of the read bits and decoding the 2 or less point coordinates;
(C) When the number of points exceeds 2,
(C1) sequentially reading bits in units of the read bits and decoding first point coordinates (x ₀ , y ₀ );
(C2) sequentially reading the number of bits (bitsx, bitsy) information used for encoding the difference data of the x and y coordinates between adjacent points from the LASeR binary stream;
(C3) The bits corresponding to each of the read bit numbers (bitsx, bitsy) are sequentially read, each of the difference data of the x and y coordinates between the previous point and the current point is decoded, and the decoded calculating the coordinates of the current point by adding the difference data of the x and y coordinates to the coordinates of the previous point;
The LASeR binary stream decoding method according to claim 7, further comprising: (c4) repeating the step (c3) by the number of remaining points excluding the first point.   If the EG decoding method is determined, the parameter k necessary for the EG decoding is extracted from the LASeR binary stream, and the LASeR binary stream is decoded based on the EG decoding method using the parameter k. The LASeR binary stream decoding method according to claim 7, further comprising the step of: The step of decoding the LASeR binary stream based on the EG decoding scheme is performed when the LASeR binary stream is a point sequence (x ₀ , y ₀ ) (x ₁ , y ₁ ) (x _n , y _n ). Assuming that
(A) reading point number information of a point sequence from the LASeR binary stream, bit number information used for encoding the point, and the parameter k information;
(B) sequentially reading bits in units of the extracted bits and decoding first point coordinates (x ₀ , y ₀ );
(C) Read an EG code word corresponding to each of the difference data of the x and y coordinates of the previous point and the current point from the LASeR binary stream, decode it using the parameter k, and decode the decoded x and y Calculating the coordinates of the current point by adding coordinate difference data to the coordinates of the previous point;
10. The LASeR binary stream decoding method according to claim 9, further comprising: (d) repeating the step (c) by the number of remaining points excluding the first point. A LASeR scene code for generating an encoded LASeR scene description elementary stream by encoding a LASeR point sequence indicating scene description information (Scene Description) by the method according to any one of claims 1 to 6. And
Multiplexing means for multiplexing the encoded LASeR scene description elementary stream and other elementary streams constituting the LASeR scene to generate a multiplexed LASeR binary stream;
And a transmission means for transferring the multiplexed LASeR binary stream to a user terminal. Receiving means for receiving the LASeR binary stream;
Demultiplexing means for outputting a LASeR scene description stream and other elementary streams from the received LASeR binary stream;
A plurality of decoded LASeR access units that can be individually accessed by decoding the LASeR scene description elementary stream output from the demultiplexing means by the method according to any one of claims 7 to 10. LASeR scene decoding means for generating;
Other elementary decoding means for decoding the other elementary stream output from the demultiplexing means;
A scene tree manager for generating a scene tree from the decoded access unit;
A user terminal device comprising: a LASeR renderer for providing a LASeR service to a user using the generated scene tree and the decoded other elementary stream.   A computer-readable recording medium on which a computer program for performing the LASeR point sequence encoding method according to claim 1 is recorded.   A computer-readable recording medium on which a computer program for performing the LASeR binary stream decoding method according to claim 7 is recorded.   The flag for indicating either the FL encoding method or the EG encoding method in the encoding method, and the EG encoding can be most effectively performed when the flag has a value indicating the EG encoding method. A data structure of a LASeR point sequence encoded data stream characterized in that it includes a parameter k value. A LASeR scene code for generating an encoded LASeR scene description elementary stream by encoding a LASeR point sequence indicating scene description information (Scene Description) by the method according to any one of claims 1 to 6. And
A multiplexing unit for multiplexing the encoded LASeR scene description elementary stream and other elementary streams constituting the LASeR scene to generate a multiplexed LASeR binary stream;
And an output unit for outputting the multiplexed LASeR binary stream. An input unit for inputting the LASeR binary stream;
A demultiplexing unit for outputting a LASeR scene description stream and other elementary streams from the input LASeR binary stream;
A plurality of decoded LASeR access units that can be individually accessed by decoding the LASeR scene description elementary stream output from the demultiplexer by the method according to any one of claims 7 to 10. A LASeR scene decoding unit for generating;
Another elementary decoding unit for decoding the other elementary stream output from the demultiplexing unit;
A scene tree manager for generating a scene tree from the decoded access unit;
A decoding apparatus comprising: a LASeR renderer for providing a LASeR service to a user using the generated scene tree and the other decoded elementary streams.

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