JP4583514B2 - Video encoding device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a moving image encoding apparatus that encodes a moving image with motion compensation.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, there has been known a moving image coding technique that reduces the code amount (information amount) of a moving image by performing motion compensation on the moving image and predictive coding.
For example, in Japanese Patent Laid-Open No. 6-105299, when one frame of an input image composed of moving images is divided into predetermined image blocks and a plurality of candidate motion vectors are prepared for each image block, inter-frame prediction is performed. A moving picture compression apparatus that selects a motion vector that improves the coding efficiency most is disclosed.
[0003]
Specifically, the configuration is shown in FIG.
In the figure, 430 is a controller, 431 is an image memory, 432 is a subtractor, 433 is a DCT (Discrete Cosine Transform) calculation unit, 434 is a quantization unit, 435 is a variable length coding unit (VLC), 436 is a buffer, 438 is an inverse quantization unit, 439 is an inverse DCT operation unit (IDCT), 440 is an adder, 441 to 443 are switches, and 444 and 445 are predictors. In addition, the above-described inverse quantization unit 438, inverse DCT operation unit 439, adder 440, switches 441 to 443, and predictors 444 and 445 constitute a motion compensation inter-frame prediction unit (no code).
[0004]
Hereinafter, four types of operations (first to fourth operations) of the moving image compression apparatus illustrated in FIG. 6 will be described with reference to the flowchart illustrated in FIG.
In the description of each of the first to fourth operations, the steps of the flowchart shown in FIG. 7 are cited, but the steps not cited in the description of each operation are deleted from the flowchart shown in FIG. 7 as far as the operations are concerned. Shall.
[0005]
First, the first operation of the moving image compression apparatus will be described.
A series of operations described below is performed under the control of the controller 430.
Image data from the outside is stored in the image memory 431. The subtractor 432 outputs a difference between the image data read from the image memory 431 and a predicted image from a predictor 444 or 445 described later. The DCT calculation unit 433 performs orthogonal transformation on the difference data from the subtractor 432 and converts it to the frequency axis. The quantization unit 434 and the variable length coding unit 435 quantize the data from the DCT calculation unit 433, respectively, variable-length code, and output to the outside through the buffer 436 as encoded data.
[0006]
Here, the motion compensation inter-frame prediction unit (no code) performs inter-frame prediction processing for compression in the time axis direction under the control of the controller 430. That is, the data from the quantization unit 434 is decoded by the inverse quantization unit 438 and the inverse DCT calculation unit 439 and added to the predicted image from the predictor 443 or 444. Based on the predicted image, a plurality of candidate motion vectors are detected and prepared for each predetermined image block (partial image) obtained by dividing one screen (step S1).
[0007]
Then, a motion vector that gives the best coding efficiency is determined from among a plurality of candidate motion vectors (step S5), and an already coded image (predicted image) is moved by the motion vector. Thus, motion compensation is performed and inter-frame prediction is performed.
Note that the switches 441 to 443 are switched by the controller 430 in accordance with the image mode and the prediction mode.
[0008]
Next, a second operation of the moving image compression apparatus will be described.
Inter-frame prediction is performed as in the first operation described above, and a plurality of candidate motion vectors are detected and prepared for each image block (step S1). A prediction error is detected for the detected motion vectors of a plurality of candidates, and an error coefficient for the minimum prediction error is calculated for this prediction error (step S2). Then, based on the calculated error coefficient, a motion vector that gives the best coding efficiency when actually coding is determined from among a plurality of candidate motion vectors (step S5).
[0009]
Next, a third operation of the moving image compression apparatus will be described.
When a prediction error of a plurality of candidate motion vectors is detected in the same manner as in the second operation described above (steps S1 to S2), the motion vector actually to be encoded with respect to the plurality of candidate motion vectors is detected. A value is calculated (step S3). Based on the calculated value of the motion vector, the code length when encoded is calculated as a vector encoding coefficient illustrated in FIG. 8 (step S4). Based on the coding coefficient, a motion vector that gives the best coding efficiency when actually coding is determined (step S5).
[0010]
Next, a fourth operation of the moving image compression apparatus will be described.
When a prediction error of a plurality of candidate motion vectors is detected in the same manner as in the third operation described above (steps S1 to S2), the code length when encoded based on the plurality of candidate motion vectors is the code length. It is calculated as a vector coding coefficient (step S4). Then, based on the coding coefficient, a motion vector that gives the best coding efficiency when actually coding is determined (step S5).
[0011]
[Problems to be solved by the invention]
By the way, the above-described moving image compression apparatus according to the prior art selects and encodes a motion vector that gives the best encoding efficiency from a plurality of candidate motion vectors detected in advance, The code length is set regardless of the size of the motion vector. For this reason, depending on the motion vector, the code length may be redundant, and there is a problem that the code amount cannot be reduced effectively.
[0012]
Specifically, according to the above-described prior art, a motion vector is determined based on the calculated coding coefficient. This coding coefficient is uniquely determined regardless of the magnitude of the motion vector, and the motion vector is determined as follows. The rules for encoding are fixed. Therefore, even in the case of a motion vector that gives the best coding efficiency, the code length is fixed and there is a case where the motion vector becomes redundant.
[0013]
The present invention has been made in view of such a problem, and provides a moving image encoding apparatus capable of reducing the amount of code according to the size of a motion vector and improving the encoding efficiency. Let it be an issue.
[0014]
[Means for Solving the Problems]
In order to achieve the above object, the present invention has the following configuration.
That is, the present invention divides an input image into predetermined image blocks, generates a motion vector for each image block from the input image and a predicted image encoded in advance, and generates the predicted image based on the motion vector. Encoding means for encoding the input image with motion compensation by the motion compensation means, encoding the motion vector with a designated code length, and the image block; In order to encode the motion vector generated by the motion compensation unit and to determine the search range of the motion vector of the input image for the next frame by the motion compensation unit in units of a predetermined image unit consisting of Code length designating means for designating the code length of the motion vector to the encoding means, and the encoding means for the next image unit. When the input image is encoded, it is sufficient for the motion compensation means to represent a motion vector search range corresponding to the size of the motion vector based on the size of the motion vector generated in the current image unit. Code length updating means for calculating the minimum code length and updating the code length designated by the code length designation means based on the calculated minimum code length The code length update means designates the size of a predetermined percentage of motion vectors, which is the majority of motion vectors generated in the current image unit, for the current image unit. When expressed using a code length smaller than the code length, the code length specified by the code length specifying means is a minimum that is sufficient to express the size of a predetermined percentage of motion vectors that is the majority of the motion vectors. Update to the code length of .
[0017]
Furthermore, the code length update unit of the present invention encodes the input image by expressing the magnitude of the motion vector generated in the current image unit using the code length designated by the code length designation unit. The input image is encoded by expressing the motion vector generated in the current image unit using the first code amount generated sometimes and the minimum code length sufficient to express the size of the motion vector. The code length designated by the code length designation means is updated when the increment of the second code amount with respect to the first code amount is equal to or less than a predetermined threshold. It has the composition to do.
[0018]
Furthermore, the code length update unit of the present invention encodes the input image by expressing the magnitude of the motion vector generated in the current image unit using the code length designated by the code length designation unit. The input image is encoded by expressing a motion vector generated in the current image unit using a first code amount that is sometimes generated and a code length smaller than the code length specified by the code length specifying means. A code length designated by the code length designation means when the increment of the second code quantity with respect to the first code quantity is equal to or less than a predetermined threshold. The code is updated to a code length smaller than the code length specified by the length specifying means.
[0019]
Still further, the code length updating means of the present invention may be configured such that when the increment of the second code amount with respect to the first code amount exceeds a predetermined threshold, the input image is encoded by the encoding means. The code length is updated in a direction to increase the code length designated by the code length designation means within a range where the generated code amount is not more than the predetermined threshold value.
[0020]
Furthermore, the present invention further comprises code length input means for inputting a code length designated from the outside, and the code length update means comprises: Comparison between the amount of code generated when encoded based on the code length generated by the code length update means and the amount of code generated when encoded based on the code length input to the code length input means On the basis of the The code length generated by the code length update means or the code length input to the code length input means is selected, and the code length designated by the code length designation means is updated.
[0021]
Furthermore, the code length update means of the present invention generates a plurality of candidate code lengths that can be taken within a motion search range allowed for the image block, and uses the plurality of candidate code lengths to generate the motion vector. And the amount of code generated when the input image is encoded respectively, and the code length with the smallest code amount is selected from the plurality of candidate code lengths.
[0022]
Furthermore, the code length update means of the present invention includes a code amount obtained by expressing the motion vector using the code length input to the code length input means, and a code length generated by the code length update means. And a code amount obtained by expressing the motion vector with each other and comparing the weights, and selecting a code length based on the comparison result.
[0023]
Furthermore, the present invention has a configuration in which the image unit is composed of two or more frames, and the number of frames forming the image unit is variable.
[0024]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
In addition, the same code | symbol is attached | subjected to the element which is common in each figure, and the overlapping description is abbreviate | omitted.
[0025]
Embodiment 1 FIG.
FIG. 1 shows a configuration of a moving image encoding apparatus according to the first embodiment of the present invention.
In the figure, 100 divides an input image 10 consisting of a moving image into predetermined image blocks, generates a motion vector for each image block from the input image 10 and a predicted image 10A encoded in advance, and moves the motion image. It has a motion compensation prediction unit 44 (motion compensation means) that compensates for the motion of the predicted image 10A based on the vector, encodes the input image 10 with motion compensation by the motion compensation unit 44, and with a specified code length An encoding unit (encoding means) that encodes the motion vector.
[0026]
Reference numeral 50 denotes a code length designating unit (code length designating unit) for designating the code length of a motion vector to the encoding unit 100 in units of a predetermined image unit made up of the image blocks. Reference numeral 60 denotes an encoding unit 100. When encoding an input image for an image unit to be encoded next, the motion compensation prediction unit 44 uses a code length designation unit based on the magnitude of a motion vector generated in the image unit to be encoded at present. Reference numeral 50 denotes a code length update unit (code length update means) for updating the code length designated.
[0027]
Further, 31 is an image memory for storing a pre-encoded image, 32 is a difference calculator for calculating the difference between the input image 10 and the predicted image 10A from the image memory 31, and 33 is from the difference calculator 32. Is a variable length encoder (VLC) that obtains encoded data by variable length encoding the data from the encoder 33, and 36 is a variable length encoder 35. Is a buffer for temporarily accumulating encoded data from, a decoding unit for locally decoding data from the encoder 33, and a predicted image 10 A from the image memory 31 and a decoder from the decoder 38. An adder that adds data.
[0028]
Next, the operation of the moving picture coding apparatus according to the first embodiment will be described by taking the case of performing interframe predictive coding as an example.
In the first embodiment, it is assumed that the above-described “image unit” is a “frame” and that each image block obtained by dividing each frame into several predetermined image blocks is encoded.
[0029]
First, from the image memory 31, image data at the same position as the image block of the input image 10 that is the current encoding target or image data specified by the motion vector generated by the motion compensation prediction unit 44 is used as the predicted image 10A. Read for each image block. The difference calculator 32 calculates a difference between the predicted image 10A from the image memory 31 and the input image 10 to obtain a distortion evaluation value 46 and difference data.
[0030]
Here, the motion compensation predicting unit 44 receives the input image 10 from the image memory 31 so that the distortion evaluation value 46 (for example, the sum of absolute differences in units of blocks) within the motion vector search range designated in advance is minimized. A motion vector is detected by extracting the image closest to or matching the image data as the predicted image 10a.
[0031]
Difference data from the difference calculator 32 when the distortion evaluation value 46 indicates the minimum is encoded by the encoder 33 and variable-length encoded by the variable-length encoder 35. At this time, the motion vector detected by the motion compensation prediction unit 44 is encoded with the code length designated by the code length designation unit 50 described later. The data variable-length encoded by the variable-length encoder 35 is temporarily stored in the buffer 36 and output as encoded data 90 to a transmission path (not shown) according to the transmission rate.
[0032]
The data encoded by the encoder 33 is locally decoded by the decoding unit 38, decoded and added by the adder 40 and the predicted image 10 </ b> A from the image memory 31, and written to the image memory 31. As a result, the image data in the image memory 31 is updated.
As described above, inter-frame predictive encoding is performed on the input image 10.
[0033]
In the process of the series of inter-frame predictive encoding operations described above, the code length specifying unit 50 moves with respect to the variable length encoder 35 constituting the encoding unit 100 in units of one frame (predetermined image unit). Specifies the code length of the vector. This code length may be a part or all of the encoded code of the motion vector. The code length designated by the code length designation unit 50 is also given to the motion compensation prediction unit 44, and the motion vector search range in the motion compensation prediction unit 44 is determined.
[0034]
Further, the code length update unit 60 specifies the code length based on the magnitude of the motion vector generated in the current frame by the motion compensation prediction unit 44 when the encoding unit 100 encodes the input image 10 for the next frame. The code length designated by the unit 50 is updated.
[0035]
Hereinafter, the operations of the code length specifying unit 50 and the code length updating unit 60 will be specifically described by taking as an example the case of specifying (updating) the code length of a part of the encoded code of the motion vector in the horizontal direction.
[0036]
First, the code length of a part of the encoded code of the motion vector is psize, and this code length psize is expressed by an integer R that can represent the search range of the motion vector. For example, as an example, the integer R is expressed by the following formula (1). However, in Expression (1), the symbol “<<” represents a bit shift operator.
[0037]
R = 1 << psize (1)
[0038]
In this case, the integer R is represented as a binary number obtained by bit-shifting “1” to the MSB (Most Significant Bit) side by psize [bit], and is expressed as a decimal number 2 ^psize Is equivalent to
[0039]
In this way, when the code length psize is expressed by an integer R, when the unit of motion compensation is an M × N pixel block (M and N are natural numbers), the number of horizontal pixels is “M”, and thus a motion vector that can be generated. The maximum value max and the minimum value min are represented by the following expression (2), and the range range of motion vectors that can be generated is represented by the following expression (3).
[0040]
max = (M × R) -1, min = {(-M) × R} (2)
[0041]
range = (2M × R) (3)
[0042]
Here, as an example, if psize = 3 and M = 8, R = 1 << 3 = 8, max = (8 × 8) -1 = 63, min = ( (-8) × 8) =-64, range = 128 is obtained.
[0043]
Next, with the integer value mccode satisfying −M ≦ mccode ≦ M and the integer value mcres represented by the code length of psize [bit] as parameters, the motion vector magnitude value MV is set to the integer value mccode and the integer value mcrec. Expressed in combination with.
[0044]
As an example, when the condition R = 1, mccode = 0 is satisfied, the magnitude MV of the motion vector is expressed by the following equation (4), and the above condition R = 1, mccode = 0 is not satisfied The value MV of the magnitude of the motion vector is expressed by the following equation (5).
However, in equation (5), abs (mccode) represents the absolute value of the integer value mccode, and mccode When <0, MV = -MV.
[0045]
MV = mccode (4)
[0046]
MV = [{abs (mccode) -1} × R] + mcres + 1 (5)
[0047]
In this way, when the motion vector magnitude value MV is expressed, the motion vector magnitude value MV divided by the integer R {abs (mccode) -1} and the remainder (mcres + 1) are adjusted. Numeric values mccode and mcres can be set.
[0048]
As an example, when “53” is expressed as the motion vector magnitude value MV, the quotient and remainder obtained by dividing “53” by M (= 8) are “6” and “5”, respectively. = 6 + 1 = 7, mcres = 5-1 = 4. When integer values mccode and mcres are set in this way, MV = ((abs (7) -1) × 8) + 4 + 1 = 53 is obtained from the above equation (5).
[0049]
As another example, when “40” is expressed as the motion vector magnitude value MV, the quotient and remainder obtained by dividing “40” by M (= 8) are “5” and “0”, respectively. In this case, the remainder is “0” and psize [bit] giving the code length of mcres is also “0”, and the size of the motion vector cannot be expressed.
[0050]
Therefore, in this case, a part of the quotient is converted too much so that the quotient and the remainder are “4” and “8”, respectively, and mccode = 5 and mcres = 7 (“111” in binary notation). When the integer values mccode and mcres are set in this way, MV = ((abs (5) -1) × 8) + 7 + 1 = 40 is obtained from the above equation (5).
From the above example, it can be seen that the value MV of the magnitude of the motion vector is expressed using the integer values mccode and mcres as parameters.
[0051]
If the motion vector magnitude value MV is nearer to “0”, the higher the probability of occurrence, the better the coding efficiency when the integer value mccode is represented by a variable length code.
In addition, if the integer value mcres is represented by a variable-length code, the code length of the motion vector of the value before and after a multiple of the integer R is reversed. Therefore, it is more efficient to express the integer value mcres by a fixed-length code. Get better.
[0052]
By expressing the magnitude MV of the motion vector using the above formulas (4) and (5), the motion vector search range is determined in units of the integer R derived from the code length psize, and the integer value mcres is used. The gap of the search range that cannot be expressed by the integer R is filled. Therefore, the magnitude MV of the motion vector is expressed by the integer values mccode and mcres, and the code length psize can be determined based on the magnitude of the motion vector.
[0053]
Here, the description returns to FIG. 1 again.
As described above, the code length specifying unit 50 specifies the code length psize determined based on the size of the motion vector to the encoding unit 100. This code length psize affects the code length of the motion vector generated in the current frame. If the code length psize of the motion vector is large, the motion vector search range (vector distribution range) is widened. Become.
[0054]
On the other hand, the code length update unit 60 determines the code amount of the motion vector in the entire next frame based on the size of the motion vector generated in the current frame under the influence of the code length psize designated by the code length designation means 50. The code length psize designated by the code length designation unit 50 is updated so as to decrease.
As described above, the code length of the motion vector is updated based on the magnitude of the motion vector generated in the current frame, and the code amount in the next frame is reduced.
[0055]
In the first embodiment described above, the value MV is the magnitude of the motion vector. However, as the “distribution” of the magnitude of the motion vector generated in the current frame and the “difference” with the motion vector encoded in advance. It does not limit the content of the present invention.
[0056]
In addition, the magnitude of the motion vector is expressed using the integer values mccode and mcres as parameters, but the code length of a part or all of the encoded code of the motion vector is not limited to this expression method. It may be expressed so as to change according to the code length psize specified by the unit 50. Furthermore, although the difference absolute value sum is used as the distortion evaluation value 46, for example, a difference square sum may be used.
[0057]
Furthermore, in the first embodiment, inter-frame predictive encoding is performed. However, for example, it may be configured to operate as a typical moving image encoding apparatus like intra-frame encoding. In this case, the input image 10 may be configured to be directly encoded by the encoder 33 depending on conditions.
[0058]
Embodiment 2. FIG.
Next, Embodiment 2 of the present invention will be described with reference to FIG.
In the second embodiment, the code length update unit 50 (code length update means) specifies the code length for all the motion vectors generated in the current frame (current image unit) for the current frame. When the code length psize specified by the code length specifying unit 50 is expressed using a code length less than the code length psize specified by the unit 50, the code length psize specified by the code length specifying unit 50 is the minimum code sufficient to express the sizes of all the motion vectors. Configured to update to long qsize.
[0059]
For example, if psize = 3 and M = 8 in the current frame, all motion vectors in the current frame that satisfy -32 ≦ vector ≦ 32 satisfy all motions. The minimum code length required to express the vector size is “2”, and all motion vectors can be expressed even with psize = 2.
[0060]
This is because, when psize = 2, the maximum value max of the motion vector is “31” and the minimum value min of the size of the motion vector is “−32” from the above equations (1) and (2). . Therefore, the code length update unit 60 sets the code length qsize to “2” and updates the code length psize specified by the code length specifying unit 50 to the code length qsize.
[0061]
In this case, since the integer value mcres can be expressed by 2 bits, the code length per motion vector is reduced by 1 bit. Therefore, if the code length psize is set to “2” and the motion vector of the current frame is re-encoded, the amount of codes generated in the current frame can be reduced.
[0062]
However, in practice, there is no time for re-encoding in the current frame due to the limitation of the processing speed of the apparatus. Even if there is a time margin, re-encoding in the current frame is difficult in an environment where it is not possible to secure a buffer capacity sufficient to store encoded motion vectors for one frame. It becomes. Therefore, the code length update unit 60 updates the code length psize to “2” (qsize) in the next frame and encodes it.
[0063]
Here, in general, in a moving image, the motion of adjacent image frames tends to be similar when there is no sudden change in motion, and a motion vector similar to the motion vector in the current frame also exists in the next frame. Expected to be required. Therefore, even if the code length psize is updated to “2” (qsize) and encoded in the next frame, the amount of codes generated in the next frame can be effectively reduced.
[0064]
It has a processing speed sufficient for re-encoding, has a buffer capacity sufficient to store motion vectors encoded in units of frames, and encoded data output from the buffer to the transmission path is interrupted. If the specified transmission rate can be maintained without any change, the code length may be updated and re-encoded in the current frame. In this case, the amount of codes can be kept lower than when the code length is updated in the next frame.
[0065]
Embodiment 3 FIG.
Next, Embodiment 3 of the present invention will be described with reference to FIG.
In the second embodiment, the code length is updated when the “all” motion vectors generated in the current frame can be expressed using the code length qsize. However, in the third embodiment, the code length update unit is updated. 50, the size of a predetermined percentage of motion vectors, which is the “majority” of motion vectors generated in the current frame, is smaller than the code length psize specified by the code length specification unit 50 for the current image unit. When the code length is expressed using the code length, the code length psize specified by the code length specifying unit 50 is updated to the minimum code length qsize sufficient to express the size of a predetermined percentage of the motion vectors. Configured to do.
[0066]
Hereinafter, the validity of updating the code length will be described by paying attention to the above-mentioned “majority” of motion vectors of a predetermined ratio.
If the motion trends of adjacent moving images are similar, if the motion vector of “all” in the current frame can be expressed based on the code length qsize, the majority of motion vectors in the next frame will be based on the code length qsize. It is predicted that it can be expressed. Therefore, if the code length qsize is specified in the next frame, the generated code amount can be reduced with a very high probability. In the second embodiment described above, the code length is updated from this viewpoint.
[0067]
However, even if the “all” motion vector can be expressed based on the code length qsize in the current frame, the “all” motion vector can be expressed based on the code length qsize in the next frame. Is not limited. In addition, when the “most” motion vector can be expressed based on the code length qsize in the current frame, the “all” motion vector can be expressed based on the code length qsize in the next frame. Sometimes.
[0068]
That is, if it can be predicted that the “majority” motion vector can be expressed based on the code length qsize in the next frame, it is not always necessary to focus on “all” motion vectors generated in the current frame. It is sufficient to focus on a predetermined percentage of motion vectors that are “majority”. In the third embodiment, from this point of view, the code length update unit 60 updates the code length by paying attention to a predetermined percentage of motion vectors that are “majority” in the current frame.
[0069]
Embodiment 4 FIG.
Next, a fourth embodiment of the present invention will be described with reference to FIG.
In Embodiments 2 and 3 described above, when the “all” and “most” motion vectors are vectors that can be expressed based on the code length qsize, the code length psize is updated to the code length qsize. In the fourth embodiment, a condition is further added, and the code length is updated when the increment of the code amount is equal to or less than a predetermined threshold.
[0070]
That is, the moving picture encoding apparatus according to the fourth embodiment includes a code length update unit 60A instead of the code length update unit 60 in the configuration of the second or third embodiment shown in FIG.
[0071]
The code length update unit 60A generates a first motion vector when the input image 10 is encoded by expressing the size of the motion vector generated in the current frame using the code length psize designated by the code length designation unit 50. When the input image 10 is encoded by expressing the motion vector generated in the current frame using the minimum code length qsize sufficient to express the size of the current vector and the size of the motion vector in the current frame. The code length psize specified by the code length specifying unit 50 when the increment of the second code amount with respect to the first code amount is equal to or less than a predetermined threshold TH is obtained as the code length qsize. Configured to update.
[0072]
The operation (code length update method) of the code length update unit 60A according to the fourth embodiment will be specifically described below.
Comparing the amount of code of the motion vector generated when encoded based on the code length psize and when encoded based on the code length qsize, it is better to encode based on the smaller code length qsize of the motion vector itself. The code amount is smaller. However, whether or not the total code amount is reduced needs to be determined in consideration of the code amount of the difference data generated by the encoder 33.
[0073]
Hereinafter, a method for updating the code length when the code amount of the difference data generated in the encoder 33 is considered will be specifically described.
The motion vector mvp having the smallest distortion evaluation value 46 in the current frame can be encoded based on the code length psize, but if it cannot be encoded based on the code length qsize, the motion vector mvp cannot be adopted. Therefore, in this case, encoding is performed by performing motion compensation using the motion vector mvq having the smallest distortion evaluation value 46 within the motion search range based on the code length qsize.
[0074]
Here, when coding is performed by motion compensation using the motion vector mvp, the coding amount per frame is frcap (first coding amount), and the motion compensation is performed using the motion vector mvq. If the code amount per frame is frcaq (second code amount), the code amount that is increased by updating to the code length qsize in the encoding unit 33 is (frcaq-frcap). When the number of motion vectors encoded in the current frame is sufficiently large and the code amount increment (frcaq-frcap) is sufficiently small, if the code length qsize is specified in the next frame, the motion vector generated in the next frame The code amount itself is reduced.
[0075]
However, if the code amount ommv of the motion vector reduced by updating to the code length qsize is smaller than the code amount (frcaq-frcap) that increases by updating to the code length qsize, the code length in the next frame If qsize is specified, the total code amount increases and the coding efficiency deteriorates. Therefore, the code length updating unit 60A evaluates not only the code amount ommv that can be reduced but also the increasing code amount (frcaq-frcap) as follows, and determines whether or not to specify the code length qsize.
[0076]
If the number of motion vectors encoded per frame is afrmv and the number of motion vectors that can be expressed based on the code length qsize is afrmvq, one frame is obtained by updating the code length psize to the code length qsize. The code amount ommv reduced per unit is ommv = (psize−qsize) × afrmvq [bit].
[0077]
On the other hand, the code amount (frcaq-frcap) increased per frame by updating the code length psize to the code length qsize is frcaq-frcap = (bcaq-bcap) × (afrmv-afrmvq) [bit]. Here, bcaq is a code amount per one encoded block (image block) when motion compensation is performed using the motion vector mvq, and bcap is a code obtained by performing motion compensation using the motion vector mvp. This is the amount of code per one encoded block when it is converted.
[0078]
The code length update unit 50 determines the amount of code (frcaq-frcap) that increases per frame by comparing it with the threshold value TH, and when the determination condition TH ≧ (frcaq-frcap) is satisfied in the current frame, In this frame, the code length is updated to qsize. This threshold value TH is set to the code amount ommv reduced per frame. Here, in order to set a margin in consideration of changes in motion vector generation characteristics between the current frame and the next frame, a value weighted to the value of the code amount ommv (w × ommv: w = 0.7, for example) May be set as the threshold value TH.
[0079]
As an example, when there is a characteristic in which the range of the magnitude of the motion vector gradually decreases or increases on the contrary over a plurality of consecutive frames, the same characteristic is expected in the next frame. However, if the motion of the subject changes suddenly and the generation characteristics of the motion vector change, this expectation may be lost and the prediction of the total generated code amount may be greatly deviated. Therefore, when considering the possibility that the generated code amount is unpredictable due to the change in the motion vector generation characteristic, the weighting coefficient w is set to a large value (a small number close to 1).
[0080]
Embodiment 5 FIG.
Next, Embodiment 5 of the present invention will be described with reference to FIG.
In the above-described second to fourth embodiments, the code length is updated by paying attention to the size of the “all” or “majority” motion vector generated in the current frame. Then, the code length in the next frame is designated (updated) by focusing on the code amount generated in the current frame, without being limited to “all” or “majority” motion vectors.
[0081]
That is, the code length update unit 60 according to the fifth embodiment shown in FIG. 1 to be used expresses the size of the motion vector generated in the current frame using the code length psize designated by the code length designation unit 50. The motion vector generated in the current frame is expressed using the first code amount generated when the input image 10 is encoded and the code length qsize smaller than the code length psize specified by the code length specifying unit 50. The code length designation unit 50 obtains the second code amount generated when the input image 10 is encoded and the increment of the second code amount with respect to the first code amount is equal to or less than a predetermined threshold value TH. The designated code length psize is updated to a code length qsize smaller than the code length psize.
[0082]
The operation of the code length update unit 60 according to the fifth embodiment will be described below.
As described in the fourth embodiment, the code amount ommv reduced per frame by updating the code length psize to the code length qsize is ommv = (psize-qsize) × afrmvq [bit], The increasing code amount (frcaq-frcap) is frcaq-frcap = (bcaq-bcap) × (afrmv-afrmvq) [bit].
[0083]
Therefore, if `` all '' or `` most '' motion vectors can be represented by code length qsize in the current frame, the number of motion vectors afrmvq that can be represented based on code length qsize is sufficiently large, and ommv >> (frcaq-frcap)
[0084]
However, if the code amount ommv does not exceed the code amount (frcaq-frcap), the encoding efficiency is improved, so the number of motion vectors afrmvq does not necessarily have to be a sufficiently large value. That is, as long as the condition ommv ≧ (frcaq−frcap) is satisfied, the code amount in the next frame can be reduced by designating the code length qsize based on the code amounts frcap and frcaq.
[0085]
Embodiment 6 FIG.
Next, Embodiment 6 of the present invention will be described with reference to FIG.
In the fifth embodiment described above, the code length designated by the code length designation unit 50 is updated based on the code amount in the current frame. However, the code length update unit 60A according to the sixth embodiment When the increment of the second code amount with respect to the first code amount exceeds a predetermined threshold value TH, the code amount generated when the input image 10 is encoded by the encoding unit 100 is within a range where the code amount is equal to or less than the predetermined threshold value. The code length specifying unit 50 is configured to update the code length psize specified by the code length specifying unit 50.
[0086]
Here, as described above, the first code amount encodes the input image 10 by expressing the size of the motion vector generated in the current frame using the code length psize designated by the code length designation unit 50. The second code amount is input by expressing the motion vector generated in the current frame using the code length qsize smaller than the code length psize specified by the code length specifying unit 50. This is the amount of code generated when the image 10 is encoded.
[0087]
The operation of the code length update unit 60A according to the sixth embodiment will be described below.
In the above-described second to fourth embodiments, since “all” or “majority” motion vectors are focused on, the number of motion vectors afrmvq is a sufficiently large value. However, as in the above-described fifth embodiment, “ The code amount ommv reduced per frame may satisfy ommv ≧ (frcaq-frcap) without paying attention to “all” or “most” motion vectors.
[0088]
Therefore, in the above-described fifth embodiment, the threshold value TH is set to the code amount ommv, and the code length is updated to the code length psize when the determination condition TH ≧ (frcaq-frcap) is satisfied in the current frame. As a result, the generated code amount can be reduced without paying attention to “all” or “most” motion vectors.
[0089]
By the way, the increase in the total code amount exceeds the decrease in the code amount of the motion vector, and TH <(frcaq-frcap) may hold. However, the threshold value TH is set to a code amount ommv or a value (w × ommv) obtained by multiplying the code amount ommv by a weighting coefficient w. Therefore, in the sixth embodiment, when the increase in the total code amount exceeds the decrease in the code amount of the motion vector, if the motion search range is allowed in a wider range, the code length is increased in the next frame. Specify.
[0090]
Specifically, the code amount generated when the input image 10 is encoded is updated in a direction in which the code length psize specified by the code length specifying unit 50 is increased within a range where the code amount is equal to or less than a predetermined threshold value TS described later. Update to a code length rsize greater than the code length psize. As a result, the amount of generated codes can be kept low, and a code length with good coding efficiency can be specified within the motion searchable range.
[0091]
Here, as described in the first embodiment, the motion vector search range range is range = (2M × R), and the physical upper limit of the code length rsize is limited by the bit width of the integer R. However, the upper limit of the code length rsize is determined by introducing a predetermined threshold TS. That is, the upper limit of the code length rsize is selected within a range in which the amount of code generated when the input image 10 is encoded is equal to or less than the predetermined threshold value TS. This threshold value TS is appropriately set within a range in which the code amount can be effectively suppressed, and may be the above-described threshold value TH.
[0092]
Embodiment 7 FIG.
Next, a seventh embodiment of the present invention will be described with reference to FIG.
In the first to sixth embodiments described above, the code length is updated by the code update unit 60. However, the moving picture encoding apparatus according to the seventh embodiment shown in FIG. The configuration of the first embodiment further includes a code length input unit 70 for inputting a code length designated from the outside, and the code length update unit 60 generates a code length qsize generated by the code length update unit 60 according to a predetermined condition. Alternatively, the code length exsize input to the code length input unit 70 is selected, and the code length qsize designated by the code length designation unit 50 is updated.
[0093]
Hereinafter, the operation of the video encoding apparatus according to the seventh embodiment will be described.
In the code length update unit 60, the code length exsize input to the code length input unit 70 and the code length qsize generated by the code length update unit 60 are smaller than the code length psize specified by the code length specifying unit 50. If any code length exsize and qsize is adopted and the amount of code generated is smaller than when encoding is performed based on the code length psize, either one is adopted according to a predetermined condition described later.
[0094]
Conversely, although the code length exsize and the code length qsize are larger than the code length psize, any code length exsize and code length qsize is used, but it occurs when encoding is performed based on the code length psize. Similarly, when the code amount decreases, either one is adopted according to a predetermined condition.
[0095]
Here, as the predetermined condition described above, when encoding is performed based on the code amount generated when encoding is performed based on the code length qsize generated by the code length update unit 60 and the code length exsize specified from the outside. It is set to select a code length that is smaller than the generated code amount by comparing the generated code amount and encoding the input image by the encoding unit 100.
[0096]
Further, as the predetermined condition described above, it may be set that the code length exsize from the outside is set as the upper limit of the code length. If the code length qsize does not exceed the code length exsize, the code length qsize is adopted even if motion search can be performed in a range wider than the search range given by the code length exsize, according to this predetermined condition. The code length exsize is adopted when the code length qsize exceeds the code length exsize.
[0097]
Furthermore, as the predetermined condition described above, the code length exsize may be set as the lower limit of the code length. If this predetermined condition is followed, for example, when the normal encoding is performed in a situation where it is desired to encode the motion vector with a small code length due to the capacity limitation of the buffer 36 for storing the encoded data, the next frame is displayed. On the other hand, when the code length exsize or the code length q-size larger than the code length exsize is updated and encoding other than normal is performed, the code length exsize can be forcibly specified and updated.
As described above, by introducing the code length exsize from the outside, it is possible to selectively use the code length according to the encoding method.
[0098]
In the seventh embodiment, the code length update unit 60 adopts either the code length exsize or the code length qsize. However, the present invention is not limited to this, and the code length update unit 60 may be assigned to other components. Good. In the seventh embodiment, the case where the code length input unit 70 is added to the configuration of the first embodiment has been described as an example. However, the present invention may be applied to other second to sixth embodiments.
[0099]
Embodiment 8 FIG.
Next, an eighth embodiment of the present invention will be described with reference to FIG.
In the seventh embodiment described above, the code length exsize from the outside is selected and specified. However, the moving picture coding apparatus according to the eighth embodiment has the configuration of the seventh embodiment shown in FIG. The code length update unit 60B is replaced with a code length update unit 60B.
[0100]
The code length update unit 60B generates code lengths of a plurality of candidates that can be taken within the motion search range allowed for the image block, expresses a motion vector using the code lengths of the plurality of candidates, and represents the input image 10 Are compared, and the code length that minimizes the code amount is selected from among a plurality of candidate code lengths.
[0101]
Hereinafter, the operation of the moving picture coding apparatus according to the eighth embodiment will be described.
According to the above-described seventh embodiment, in practice, a code length smaller than the code length psize designated by the code length designation unit 50 may give good coding efficiency. Conversely, a large code length may give good coding efficiency. May give. Therefore, in the eighth embodiment, a plurality of code lengths including a code length larger than a code length psize designated by the code length designation unit 50 and a code length smaller than that are prepared, and the code length giving the smallest code amount is set. select.
[0102]
That is, as illustrated in FIG. 5, the code length update unit 60B generates and prepares a plurality of candidate code lengths psize1 to psize4 that can be taken within the motion search range allowed for each image block in the current frame. To do. Here, psize1 is the minimum code length and gives the minimum motion search range in the frame currently being encoded. Psize4 is the maximum code length and gives the maximum motion search range.
[0103]
The code length updating unit 60B calculates the code amount generated by the encoder 33 when encoding is performed based on each prediction image block having the minimum distortion evaluation value 46 for each code length of the code lengths psize1 to psize4. Find and accumulate. When the encoding for one frame is completed, the code amount for one frame generated by the encoding unit 33 is obtained for each code length.
[0104]
Next, a total code amount is obtained by combining the code amount generated by the encoding unit 33 for each code length and the increase / decrease in the code amount of the motion vector accompanying the change of the code length psize. Here, when the total code amount generated when encoding is performed based on the code length exsize, the code length exsize is selected.
[0105]
If the total code amount generated when encoding is performed based on the code length exsize is not minimized, the code length that minimizes the total code amount is selected from the code length psize1 to the code length psize4. The code length update unit 60B updates the code length psize designated by the code length designation unit 50 to the selected code length.
[0106]
In the eighth embodiment, the code length update unit 60B is responsible for the generation and selection of a plurality of candidate code lengths. However, the present invention is not limited to this and may be assigned to other components. It is not intended to limit the essence of the present invention. In FIG. 5, four types of code lengths are exemplified as the code lengths of a plurality of candidates. However, the code lengths of a plurality of candidates may be determined as necessary without being limited to four types.
[0107]
Embodiment 9 FIG.
Next, Embodiment 9 of the present invention will be described with reference to FIG.
In the seventh embodiment described above, the code length designated from the outside is selected according to a predetermined condition. However, the code length update unit 60 of the moving picture coding apparatus according to the ninth embodiment uses the code length. It is obtained by expressing the motion vector using the code amount obtained by expressing the motion vector using the code length exsize input from the outside to the input unit 70 and the code length qsize generated by the code length update unit 60. The code amounts are respectively weighted and compared, and the code length is selected based on the comparison result.
[0108]
Hereinafter, the operation of the moving picture encoding apparatus according to the ninth embodiment will be described.
In the above-described seventh embodiment, for example, when the code length giving the minimum total code amount is the code length exsize, the value of the code length qsize (psize) updated (designated) internally is also the code length exsize. It becomes the same value. However, in this case, the code length exsize designated externally is not preferentially selected and designated for the encoding unit 100, but the value of the code length qsize (psize) that gives the minimum total code amount is determined. Is just equal to the value of the code length exsize.
[0109]
Therefore, the code length update unit 60 of the moving picture encoding apparatus according to the ninth embodiment weights the code amount generated when encoding is performed based on the internally generated code length qsize (psize). The code amount generated when encoding is performed based on the code length exsize designated from the outside, and the code length qsize (psize) or the code length exsize giving a smaller weighted code amount is selected.
[0110]
In this way, by comparing the code amount generated when encoding based on each code length by weighting and comparing the code amount (unweighted code amount), whether or not it is minimized, the external It becomes possible to select the code length exsize that is specified more preferentially.
[0111]
In the ninth embodiment, the code length update unit 60 weights and compares the code amount and selects the code length. However, the present invention is not limited to this, and the code length update unit 60 assigns the code length to other components. However, the essence of the present invention is not limited.
[0112]
Embodiment 10 FIG.
Next, an embodiment 10 of the invention will be described.
In the first to ninth embodiments described above, the “predetermined image unit” is set to “1 frame”. However, the moving picture encoding apparatus according to the tenth embodiment is the same as that of the first embodiment shown in FIG. In the configuration, the predetermined image unit is composed of two or more frames, and the number of frames constituting the image unit is variable.
[0113]
For example, if the number of frames making up the “predetermined image unit” is variably set according to the size of the motion vector generated in the current frame, the code length is specified according to the size of the image motion. The operation related to (update) can be simplified.
[0114]
Specifically, if it is predicted from the magnitude of the motion vector in the current frame that a motion vector having the same magnitude is generated in the next few frames, the code length designation unit 50 includes the code length update unit 60. The code length update is rejected and the code length specified for the current frame is maintained for several frames. As a result, the number of code length updates is reduced, and the update operation is simplified.
[0115]
In the tenth embodiment, the number of frames is variable in the configuration of the first embodiment, but the present invention may be applied to other second to ninth embodiments.
In the first to tenth embodiments described above, an image unit is defined in units of frames. However, a part of one frame may be defined as an image unit, and if the size of the image unit is defined as necessary. Good. Further, the image block is defined by dividing the image unit into several parts. However, the size of the image block is not particularly limited as long as it does not exceed the size of the image unit.
[0116]
【The invention's effect】
As is clear from the above description, the following effects can be obtained according to the present invention.
That is, according to the present invention, an input image is divided into predetermined image blocks, a motion vector is generated for each image block from the input image and a prediction image encoded in advance, and the prediction based on the motion vector is performed. A motion compensation means for compensating for the motion of the image, the motion compensation means for motion compensation to encode the input image, and a coding means for coding the motion vector with a specified code length; and As a unit of a predetermined image unit composed of image blocks, In order to encode the motion vector generated by the motion compensation means, and to define a search range of the motion vector of the input image for the next frame by the motion compensation means, Code length designating means for designating the code length of the motion vector to the encoding means, and when the encoding means encodes the input image for the next image unit, the motion compensation means is the current image unit. Based on the magnitude of the generated motion vector Calculating a minimum code length sufficient to represent a motion vector search range according to the size of the motion vector, and based on the calculated minimum code length Since the code length updating means for updating the code length designated by the code length designation means is provided, the code amount can be reduced according to the magnitude of the motion vector, and the coding efficiency can be improved.
[0117]
The code length updating means uses a code length in which all motion vectors generated in the current image unit are smaller than the code length designated by the code length designation means for the current image unit. In this case, the code length specified by the code length specifying means is updated to the minimum code length sufficient to express the sizes of all the motion vectors. Can be kept low.
[0118]
Furthermore, the code length update means specifies the size of a predetermined percentage of motion vectors, which is the majority of the motion vectors generated in the current image unit, for the current image unit. The code length specified by the code length specifying means is sufficient to express the size of a predetermined percentage of motion vectors that is the majority of the motion vectors. Since the code length is updated to the minimum code length, the code amount in the next entire image unit can be substantially reduced.
[0119]
Furthermore, the code length update means is generated when the input image is encoded by expressing the magnitude of the motion vector generated in the current image unit using the code length designated by the code length designation means. When the input image is encoded by expressing the motion vector generated in the current image unit using the first code amount and the minimum code length sufficient to express the size of the motion vector. Since the code length designated by the code length designation means is updated when the increment of the second code amount with respect to the first code amount is equal to or less than a predetermined threshold, the code length designated by the code length designation means is updated. The amount of codes in the entire next image unit can be effectively reduced.
[0120]
Furthermore, the code length update means is generated when the input image is encoded by expressing the magnitude of the motion vector generated in the current image unit using the code length designated by the code length designation means. Occurs when the input image is encoded by expressing a motion vector generated in the current image unit using a first code amount to be performed and a code length smaller than the code length specified by the code length specifying means The code length designated by the code length designation means when the increment of the second code quantity with respect to the first code quantity is equal to or less than a predetermined threshold. Is updated to a code length shorter than the code length designated by the user, the code amount in the next image unit as a whole can be kept low.
[0121]
Furthermore, the code length update means generates a code generated when the input image is encoded by the encoding means when the increment of the second code quantity with respect to the first code quantity exceeds a predetermined threshold. Since the code length specified by the code length specifying means is updated so as to increase the code length within a range where the amount is equal to or less than the predetermined threshold, the next image unit is improved so that the coding efficiency is improved within the motion searchable range. The overall code amount can be effectively reduced.
[0122]
The code length update means further includes a code length input means for inputting a code length designated from the outside. Comparison between the amount of code generated when encoded based on the code length generated by the code length update means and the amount of code generated when encoded based on the code length input to the code length input means On the basis of the The code length generated by the code length update means or the code length input to the code length input means is selected and the code length designated by the code length designation means is updated. The code amount in the next image unit as a whole can be effectively suppressed so as to improve the conversion efficiency.
[0123]
Furthermore, the code length updating means generates a plurality of candidate code lengths that can be taken within a motion search range allowed for the image block, and expresses the motion vector using the plurality of candidate code lengths. Thus, the code amount generated when each of the input images is encoded is compared, and the code length with the smallest code amount is selected from among the plurality of candidate code lengths. In order to improve the coding efficiency within the range, it is possible to effectively reduce the code amount in the entire next image unit.
[0124]
Furthermore, the code length update means uses the code amount obtained by expressing the motion vector using the code length input to the code length input means, and the code length generated by the code length update means. Since the code amount obtained by expressing the motion vector is weighted and compared, and the code length is selected based on the comparison result, the code length input is given priority over the code length update by the code length update means. The code length designated from the outside can be designated via the means.
[0125]
Furthermore, since the image unit is composed of two or more frames, and the number of frames forming the image unit is variable, the code amount of the next image unit as a whole can be kept low according to the magnitude of image change. Can do.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a configuration of a moving picture encoding apparatus according to Embodiment 1 of the present invention.
FIG. 2 is a block diagram showing a configuration of a moving picture encoding apparatus according to Embodiment 4 of the present invention.
FIG. 3 is a block diagram showing a configuration of a moving picture encoding apparatus according to Embodiment 7 of the present invention.
FIG. 4 is a block diagram illustrating a configuration of a moving picture encoding apparatus according to an eighth embodiment of the present invention.
FIG. 5 is a diagram for explaining a relationship between a code length generated by a code length update unit of a video encoding device according to an eighth embodiment of the present invention and a motion search range.
FIG. 6 is a block diagram of a moving image compression apparatus according to the prior art.
FIG. 7 is a flowchart showing a flow of operations of the moving image compression apparatus according to the prior art.
FIG. 8 is a diagram illustrating coefficients generated internally by the moving image compression apparatus according to the related art.
[Explanation of symbols]
10 input images, 10A prediction image, 31 image memory, 32 difference calculator, 33 encoder, 35 variable encoder, 36 buffer, 38 decoder, 40 adder, 44 motion compensation prediction unit, 50 code length designation unit 60, 60A, 60B code length update unit, 70 code length input unit, 90 encoded data, 100 encoding unit.

Claims (8)

Motion compensation that divides an input image into predetermined image blocks, generates a motion vector for each image block from the input image and a previously encoded predicted image, and compensates for the motion of the predicted image based on the motion vector Encoding means for encoding the input image with motion compensation by the motion compensation means, and encoding the motion vector with a specified code length;
In order to encode the motion vector generated by the motion compensation unit in units of a predetermined image unit composed of the image block, and to define a search range of a motion vector of an input image for the next frame by the motion compensation unit Code length specifying means for specifying the code length of the motion vector to the encoding means;
When the encoding means encodes the input image for the next image unit, the motion compensation means moves the motion vector according to the magnitude of the motion vector based on the magnitude of the motion vector generated in the current image unit. A code length update unit that calculates a minimum code length sufficient to express the search range of the code and updates a code length specified by the code length specification unit based on the calculated minimum code length In the encoding device,
The code length update means
Use a code length that is smaller than the code length specified by the code length specifying means for the current image unit, and that the size of a predetermined percentage of the motion vectors generated in the current image unit is the majority. The code length designated by the code length designation means is updated to the minimum code length sufficient to represent the size of a predetermined percentage of motion vectors that is the majority of the motion vectors. A moving image encoding device. The code length update means
A first code amount generated when the input image is encoded by expressing the magnitude of a motion vector generated in the current image unit using the code length specified by the code length specifying means, and the motion A second code amount generated when the input image is encoded by expressing the motion vector generated in the current image unit using the minimum code length sufficient to express the size of the vector. 2. The moving image according to claim 1, wherein the code length designated by the code length designation unit is updated when an increment of the second code amount with respect to the first code amount is a predetermined threshold value or less. Image encoding device. Motion compensation that divides an input image into predetermined image blocks, generates a motion vector for each image block from the input image and a previously encoded predicted image, and compensates for the motion of the predicted image based on the motion vector Encoding means for encoding the input image with motion compensation by the motion compensation means, and encoding the motion vector with a specified code length;
In order to encode the motion vector generated by the motion compensation unit in units of a predetermined image unit composed of the image block, and to define a search range of a motion vector of an input image for the next frame by the motion compensation unit Code length specifying means for specifying the code length of the motion vector to the encoding means;
When the encoding means encodes the input image for the next image unit, the motion compensation means moves the motion vector according to the magnitude of the motion vector based on the magnitude of the motion vector generated in the current image unit. A code length updating unit that calculates a minimum code length sufficient to express the search range of the code, and updates a code length specified by the code length specifying unit based on the calculated minimum code length;
In a video encoding device comprising:
The code length update means
A first code amount generated when the input image is encoded by expressing the magnitude of a motion vector generated in the current image unit using the code length specified by the code length specifying means, and the code A second code amount generated when the input image is encoded by expressing a motion vector generated in the current image unit using a code length smaller than the code length specified by the length specifying means, The code length specified by the code length specifying means is smaller than the code length specified by the code length specifying means when the increment of the second code quantity with respect to the first code quantity is equal to or less than a predetermined threshold. A moving picture coding apparatus, which is updated to The code length update means
A range in which the amount of code generated when the input image is encoded by the encoding means is less than or equal to the predetermined threshold when the increment of the second code amount with respect to the first code amount exceeds a predetermined threshold 4. The moving picture coding apparatus according to claim 3, wherein the code length designation unit updates the code length so as to increase the code length. It further comprises a code length input means for inputting a code length designated from the outside,
The code length updating unit is configured to perform encoding based on a code amount generated when encoding is performed based on the code length generated by the code length updating unit and a code length input to the code length input unit. Based on the comparison with the generated code amount, the code length generated by the code length update unit or the code length input to the code length input unit is selected, and the code length designated by the code length designation unit is updated. 5. The moving picture coding apparatus according to claim 1, wherein the moving picture coding apparatus according to claim 1 is used. The code length update means
When a plurality of candidate code lengths that can be taken within the motion search range allowed for the image block are generated, and the input vector is encoded by expressing the motion vector using the code lengths of the plurality of candidates. 6. The moving picture encoding apparatus according to claim 5, wherein the code amounts generated in the plurality of candidates are compared, and the code length having the smallest code amount is selected from the code lengths of the plurality of candidates. The code length update means
Code obtained by expressing the motion vector using the code amount obtained by expressing the motion vector using the code length input to the code length input means and the code length generated by the code length updating means 6. The moving picture coding apparatus according to claim 5, wherein the amount is weighted and compared, and a code length is selected based on a result of the comparison.   8. The moving picture coding apparatus according to claim 1, wherein the image unit includes two or more frames, and the number of frames forming the image unit is variable.

Images