JP4936557B2 - Encoder - Google Patents

Description

  The present invention relates to an encoding device that compresses and encodes a moving image.

  Along with the development of multimedia in recent years, various video compression encoding methods have been proposed. Representative examples include MPEG-1, 2, 4 and H.264. There are 26L. These encoding methods achieve a high compression rate by using both intraframe encoding and interframe predictive encoding. In inter-frame predictive coding, by adding motion compensation and motion prediction, it is possible to realize a higher compression rate than mere inter-frame coding that encodes a difference value between frames. In order to avoid error propagation, frames at predetermined intervals are compression-coded with a picture type of intra-frame coding, and a plurality of frames therebetween are compression-coded with a picture type of inter-frame predictive coding. A frame that is intra-coded is called an I picture. Of the frames to be subjected to inter-frame prediction coding, a frame using unidirectional prediction is called a P picture, and a frame using bidirectional prediction is called a B picture. Of course, there is also encoding in field units, but here, description will be made with encoding in frame units.

  When a moving image is compressed and encoded, the amount of generated code varies greatly depending on the spatial frequency characteristics of each picture, the quantization scale value, and the degree of change between scenes. Usually, a code amount control technique that maintains a certain level of image quality while suppressing the generated code amount is employed. For example, TM5 (Test Model 5) is known as one of the code amount control algorithms (Patent Document 1).

  The code amount control algorithm based on TM5 controls the code amount in the following three steps so that the bit rate is constant for each GOP (Group Of Picture). The GOP is composed of, for example, 16 pictures.

(Step 1)
The target code amount of the picture to be encoded from now is determined. Rgop, which is a code amount that can be used in the current GOP, is calculated by the following equation (1). That is,
Rgop = (ni + np + nb) * (bits_rate / picture_rate) (1)
Here, ni, np, and nb are the number of remaining pictures of the I picture, P picture, and B picture, respectively, in the current GOP. bits_rate indicates the target bit rate. picture_rate indicates the picture rate.

Furthermore, picture complexity Xi, Xp, Xb is calculated from the encoding result for each of the I picture, P picture, and B picture according to the following equation (2). That is,
Xi = Ri * Qi
Xp = Rp * Qp (2)
Xb = Rb * Qb
Here, the complexity levels Xi, Xp, and Xb are also referred to as complexity. Ri, Rp, and Rb are code amounts obtained as a result of encoding the I picture, P picture, and B picture, respectively. Qi, Qp, and Qb are average values of the Q scale (quantization scale) in all macroblocks in the I picture, P picture, and B picture, respectively.

From equations (1) and (2), the target code amounts Ti, Tp, and Tb for each of the I picture, P picture, and B picture can be obtained by equation (3). That is,
Ti = max {(Rgop / (1 + ((Np * Xp) / (Xi * Kp)) + ((Nb * Xb) / (Xi * Kb)))), (bit_rate / (8 * picture_rate))}
Tp = max {(Rgop / (Np + (Nb * Kp * Xb) / (Kb * Xp))), (bit_rate / (8 * picture_rate))} (3)
Tb = max {(Rgop / (Nb + (Np * Kb * Xp) / (Kp * Xb))), (bit_rate / (8 * picture_rate))}
Np and Nb indicate the remaining number of P pictures and B pictures in the current GOP, respectively. Constants Kp = 1.0 and Kb = 1.4.

(Step 2)
A virtual buffer is used for each of the I picture, the P picture, and the B picture, and the difference between the target code amount obtained by Expression (3) and the generated code amount is managed. Based on the data accumulation amount of each virtual buffer, a Q scale reference value is set for the macroblock to be encoded next so that the actual generated code amount approaches the target code amount. For example, when the current picture type is a P picture, the difference between the target code amount and the generated code amount can be obtained by arithmetic processing according to the following equation (4). That is,
dp, j = dp, 0 + Bp, j-1-((Tp * (j-1)) / MB_cnt) (4)
Here, the subscript j indicates the number of the macroblock in the picture. dp, 0 indicates the initial fullness of the virtual buffer. Bp, j represents the total code amount up to the j-th macroblock. MB_cnt indicates the number of macroblocks in the picture.

Next, using dp, j (hereinafter referred to as “dj”), a reference value of the Q scale in the j-th macroblock is obtained. The result is as shown in the following formula (5):
Qj = (dj * 31) / r (5)
Where
r = 2 * bits_rate / picture_rate (6)
It is.

(Step 3)
The quantization scale is finally determined based on the spatial activity of the macroblock to be encoded so that the quality of the decoded image is visually good. In particular,
ACTj = 1 + min (vblk1, vblk2, ..., vblk8) (7)
vblk1 to vblk4 indicate spatial activities in 8 × 8 sub-blocks in a macroblock having a frame structure. vblk5 to vblk8 indicate spatial activities of 8 × 8 sub-blocks in the field-structure macroblock. The space activity itself can be obtained by the following equations (8) and (9). That is,
vblk = Σ (PI-Pbar) 2 (8)
Pbar = (1/64) * ΣPi (9)
Here, Pi is a pixel value in the i-th macroblock. In the equations (8) and (9), Σ represents cumulative addition of i = 1 to 64.

The ACTj obtained by the equation (7) is normalized by the following equation (10). That is,
N_ACTj = (2 * ACTj + AVG_ACT) / (ACTj + 2 * AVG_ACT) (10)
Here, AVG_ACT is a reference value of ACTj in a previously encoded picture. The quantization scale (Q scale value) MQUANTj is finally obtained by the following equation (11). That is,
MQUANTj = Qj * N_ACTj (11)
And

  According to the above TM5 algorithm, a large amount of code is allocated to the I picture by the processing of step 1. Further, in the picture, a large amount of code is distributed to a flat portion (a portion having a low spatial activity) that is easily visually deteriorated. By such code amount control and quantization control, it is possible to suppress degradation of image quality within a predetermined bit rate.

  This code amount control algorithm achieves high image quality by balancing the code amount for the intra-frame coded picture and the inter-frame coded picture. However, it is known that for an image with a high degree of difficulty, the luminance peak after encoding varies for each picture type, which causes visual deterioration called “flicker”. This flicker is observed as flickering when reproduced as a moving image, and becomes a visual disturbance.

  A method for reducing this kind of flicker is described in Japanese Patent Application Laid-Open No. H10-228707. An input image is analyzed for each block, a weighting coefficient is determined based on the analysis result, and the image quality for each block is controlled by multiplying the weighting coefficient by the wavelet transform coefficient.

Patent Document 2 suppresses flicker by removing random noise resulting from gain-up by improving filter characteristics in conjunction with gain-up under the belief that many flickers are likely to occur during gain-up. It is described to do. Patent Document 3 describes a technique for controlling the code amount and the strength of the smoothing process according to the gain in the camera.
JP 2001-326936 A International Publication No. WO 97/05745 JP 2007-134880 A

  FIG. 2 shows a flicker generation mechanism in an encoding method using both intraframe encoding and interframe encoding. FIG. 2A shows a temporal change in the level of the reproduction signal from the I picture. The horizontal axis indicates time (or frame), and the vertical axis indicates the playback video signal level. The peak luminance of the noise component superimposed on the flat video signal can be reconstructed to some extent by intra-frame coding. This is because, in the above-described code amount control algorithm, the code amount allocation to the I picture is larger than that of other picture types.

  FIG. 2B shows a temporal change in the level of a reproduction signal of an inter-frame encoded picture such as a P picture and a B picture. The horizontal axis indicates time (or frame), and the vertical axis indicates the playback video signal level. Since an image with high complexity has a low correlation between frames, the amount of difference information between frames of P pictures and B pictures increases in normal coding. As a result, the video signal is deteriorated due to encoding, and the luminance peak cannot be reconstructed. In FIG. 2B, there is a difference in peak luminance as compared to the I picture shown in FIG. As a result, as shown in FIG. 2C, luminance flicker occurs during moving image reproduction. The horizontal axis indicates time (or frame), and the vertical axis indicates the playback video signal level.

  However, not all that have a large difference in peak luminance are perceived as flicker. Human visual characteristics are more likely to detect degradation of images with less motion than degradation of images with greater motion. This is why the flat part of the still image is bothering. For this reason, the peak luminance difference cannot be detected in an image with a large motion, and it is less likely to feel flicker. If a difference in peak luminance occurs in an image that moves less than an image that moves, the image becomes noticeable as flicker.

  When the technique described in Patent Document 1 is applied to such flicker, flicker can be reduced in small units such as macroblocks. However, it is difficult to suppress the above-described peak luminance difference when viewed as the entire image.

  Moreover, the technique for changing the filter characteristics as described in Patent Document 2 is one of the general encoding distortion reduction techniques at low S / N, and a partial effect can be expected. However, in order to remove the luminance flicker as described above only by the filter, the filter strength must be sufficiently increased. When the filter strength is increased, the resolution is reduced and an afterimage is generated. On the contrary, the image quality is deteriorated.

  SUMMARY OF THE INVENTION The present invention solves such a conventional problem, and an object thereof is to provide an encoding device that outputs a high-quality encoded signal in which flicker is suppressed.

An encoding apparatus according to the present invention includes an encoding unit that encodes input moving image data including a plurality of frames by using intra-frame encoding and inter-frame encoding, and an encoding unit including a predetermined number of frames. Of the frames included in the coding unit, the intra-frame coded picture for performing intra-frame coding and the frame for performing inter-frame coding with respect to a frame that has not been coded among the frames included in the coding unit so that the code amount becomes the target code amount. A setting process for setting a target code amount for each of a plurality of picture types including an inter-coded picture is repeated in the order of frames in the encoding unit, and the encoding means performs the setting according to the target code amount set for each picture type. a code amount control means for controlling the code amount of the moving image data to be encoded for each frame, the moving image data encoded by said encoding means Goshi, local and local decoding means for outputting decoded data, wherein the feature detection means for detecting a plurality of frames of the complexity included in the input image data, wherein the motion amount plurality of between-frame in the input moving image data motion detection means for detecting respectively the frame, the said input video data by using the local decoded data and coding distortion calculation means for calculating a coding distortion amount of each of the plurality of the frames, the output of the character detector When the output of the movement detector, in accordance with an output of the encoding distortion calculating means, for each frame in the input moving image data, detects that the flicker occurs in the moving picture data encoded by said encoding means and a flicker detection means for said flicker detection means, when detecting that the flicker occurs, the frame And changes from the target code amount to a target code amount set by the setting processing each of the arm in the coded picture the interframe coded pictures.

  In the present invention, prior to encoding, an image in which flicker is likely to occur at the time of reproduction is detected, and the code amount ratio applied to the intra-frame encoded picture and the inter-frame encoded picture for such an image is changed. Thereby, encoded image data in which flicker is suppressed can be generated.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 shows a schematic block diagram of an embodiment of the present invention. FIG. 3 is a schematic diagram for explaining the target code amount in this embodiment.

  Image data constituting a moving image is input to the input terminal 10 from the outside in screen order, that is, frame order. The image data is blocked in a size corresponding to the encoding method. In MPEG, the block size is 16 pixels × 16 lines or 8 pixels × 8 lines. In this embodiment, the MPEG system is assumed, and the basic block size of the minimum size is 8 pixels × 8 lines, and the macro block is 16 pixels × 16 lines.

  The frame rearrangement device 12 rearranges the image data input from the input terminal 10 in units of frames in the order of picture types corresponding to the encoding type. The frame rearrangement device 12 outputs the rearranged image data of each frame to the adder / subtractor 14, the motion prediction motion compensation device 34, and the PSNR (Peak Signal to Noise Ratio) calculation device 46 in block order.

  The adder / subtractor 14 outputs the image data from the frame rearrangement device 12 to the orthogonal transformer 16 as it is in the case of intra-frame coding, that is, intra-frame coding (intra coding). The adder / subtracter 14 subtracts a motion-compensated prediction value, which will be described later, from the image data from the frame rearrangement device 12 during inter-frame prediction encoding, that is, inter-frame prediction encoding (inter-coding), and calculates a difference value. Output to the orthogonal transformer 16.

  The orthogonal transformer 16 orthogonally transforms the image data from the adder / subtractor 14 in units of macroblocks using an orthogonal transform method such as discrete cosine transform, and outputs transform coefficient data to the quantizer 18. The quantizer 18 quantizes the transform coefficient data from the orthogonal transformer 16 with a designated quantization scale. The variable length encoding device 20 encodes the quantized transform coefficient data from the quantizer 18 by a variable length encoding method such as Huffman encoding. Code data output from the variable length encoding device 20 is temporarily stored in the buffer 22 and then output to the outside from the output terminal 24. As will be described later, the amount of code data stored in the buffer 22 is referred to for code amount control.

  The output data of the quantizer 18 is decoded locally for interframe predictive coding using motion prediction and motion compensation. That is, the inverse quantizer 26 inversely quantizes the output data of the quantizer 18. The inverse orthogonal transformer 28 performs inverse orthogonal transform on the output data of the inverse quantizer 26. The output data of the inverse orthogonal transformer 28 is decoded image data (in the case of intra coding) or difference image data (in the case of inter coding). In the case of intra coding, the adder 30 outputs the output data of the inverse orthogonal transformer 28 as it is. In the case of inter coding, the adder 30 adds the predicted value to the output data of the inverse orthogonal transformer 28 and outputs the result. By this addition, the difference value is returned to the image value.

  The video buffer 32 temporarily stores locally decoded image data output from the adder 30 for a plurality of frames for motion prediction and motion compensation. The video buffer 32 has a storage capacity for several frames. The motion prediction motion compensation device 34 compares the image data of the current frame from the frame rearrangement device 12 with a reference frame for inter-frame prediction in the video buffer 32 and calculates a motion vector. Then, the motion prediction motion compensation device 34 calculates a predicted value that compensates for motion from the calculated motion vector. The calculated prediction value is supplied to the adder / subtractor 14 and is applied to the adder 30 via the switch 36 which is closed at the time of inter coding.

  Although illustration is omitted, the motion vector value calculated by the motion prediction motion compensator 34 is necessary for decoding. Therefore, the motion vector value calculated by the motion prediction motion compensation device 34 is supplied to the buffer 22, multiplexed with the code data, and output to the output terminal 24.

  The portion described so far has a structure well known in a moving image compression encoding apparatus that uses both intraframe encoding and interframe encoding for motion compensation.

  A characteristic part of the present embodiment, that is, a part related to code amount control and quantization control will be described.

  The code amount control device 38 refers to the code data amount stored in the buffer 22 and sets a target code amount for each picture. Specifically, the allocated bit amount for each picture in the GOP is distributed based on the bit amount for a picture that has not yet been encoded in the GOP including the allocation target picture. This distribution is repeated in the order of the encoded pictures in the GOP, and a picture target code amount is set for each picture.

  The quantization control device 40 determines the reference value of the quantization scale based on the capacity of the virtual buffer in order to match the target code amount of each picture with the actual generated code amount. For this purpose, the generated code amount in units of macroblocks output from the variable length encoding device 20 is fed back from the buffer 22 to the quantization control device 40.

  The quantization parameter used in the quantizer 18 is determined using Equation (11) based on the activity calculated by block feature detection (not shown) with respect to the reference value of the quantization scale. If this activity is a small value, the quantization parameter is reduced so that a large amount of code is allocated. The operation so far corresponds to Steps 1 to 3 described in the background art.

  In this embodiment, a frame feature detection device 42, a frame motion detection device 44, a PSNR calculation device 46, and a flicker detection device 48 are provided for reducing flicker. These actions will be described.

  The frame feature detection device 42 calculates the complexity of the image to be encoded from the image data from the input terminal 10 as the frame activity. In this embodiment, the amount of AC component of image data, preferably the amount of high frequency component, is employed as the complexity. Specifically, the image data for one screen is divided into blocks of a predetermined size, and the variance is calculated for each block. Then, a result obtained by adding the variance calculated in each block for the total number of blocks of the image is set as a high-frequency component amount. Instead of dispersion, frequency conversion such as DCT (Discrete Cosine Transform) or Hadamard Transform may be performed, and the frequency component may be substituted.

  The frame motion detector 44 correlates the image data from the input terminal 10 between adjacent frames, and calculates how much the entire image to be encoded has moved. Specifically, an image of one screen is divided into blocks of a predetermined size, and for each block, a coordinate shift amount that gives the highest correlation is calculated while shifting the coordinates of one image between adjacent screens. Then, the sum of the motion vector amounts calculated in each block in the screen is used as the inter-frame motion amount. This inter-frame motion amount indicates a global motion (global vector), and can be calculated by a method other than the method shown here.

  In the present embodiment, a PSNR calculation device 46 is provided as an encoding distortion amount calculation unit that calculates an encoding distortion amount from an input image and a locally decoded image. First, the PSNR calculation device 46 calculates the PSNR in units of macroblocks from the image data from the input terminal 10 and the locally decoded image data (output image data of the adder 30). Then, the PSNR calculation device 46 outputs the sum of the PSNR for each macroblock in the screen as the final PSNR. The PSNR calculated here is for an encoded image, that is, for an image input at least one before the image to be encoded.

  The flicker detection device 48 receives the frame activity from the frame feature detection device 42, the inter-frame motion amount from the frame motion detection device 44, and the PSNR from the PSNR calculation device 46. The flicker detection device 48 detects whether or not flicker is likely to occur in an image to be encoded in accordance with these three parameter values.

  As described above, the flicker occurrence condition is that the luminance peak value after encoding differs for each picture type and that the image has little motion. The condition of an image in which a luminance peak value after encoding is satisfied is that the following two conditions are satisfied: 1) the complexity of the image is high, and 2) the encoded image is deteriorated. The first condition means that the amount of high-frequency components calculated by the frame feature detection device 42 is high. The second condition means that the PSNR calculated by the PSNR calculation device 46 is low. Note that if either one of the conditions is not satisfied, it cannot be said that a luminance peak difference occurs. For example, an image containing a lot of high frequencies has a high image complexity and satisfies the first condition. However, when the bit rate is high, the encoded image is not deteriorated, so that there is no luminance peak difference. On the other hand, if the encoded image is degraded, the second condition is satisfied. However, when the bit rate is low, the encoded image deteriorates even if the complexity of the image is low. In this case, no luminance peak difference occurs. The condition of an image with little motion is that the amount of motion of the entire image is small, which means that the amount of motion between frames calculated by the frame motion detector 44 is small.

  The flicker detection device 48 may cause flicker in an image to be encoded from now on when the high frequency component amount is higher than the reference value, the PSNR is lower than the reference value, and the frame motion amount is less than the reference value. It is judged that is high. When the possibility of occurrence of flicker is high, the flicker detection device 48 instructs the code amount control device 38 to change the code amount distribution for each picture type, for example, to change the ratio so as not to cause a luminance peak difference due to encoding. To do.

  FIG. 3A shows an example of code amount distribution when the possibility of occurrence of flicker is not detected. FIG. 3B shows an example of code amount distribution when the possibility of occurrence of flicker is detected according to this embodiment. FIG. 3A shows an example of code amount distribution by a conventional TM5 code amount control algorithm.

  As shown in FIG. 3A, when the possibility of occurrence of flicker is low or low, the target code amount for I pictures that are intra-coded is large, and the target code amounts for P-picture and B-picture that are inter-coded Is set low. Due to this code amount distribution, as described above, the inter-coded picture is more deteriorated than the intra-coded picture, and the luminance peak cannot be reconstructed. As a result, a luminance peak difference occurs between the inter-coded picture and the intra-coded picture, and the picture looks like flicker.

  In the present embodiment, when the possibility of occurrence of flicker is detected, the flicker detection device 48 distributes the code amount distribution as shown in FIG. 3 (A) to the code amount control device 38 as shown in FIG. 3 (B). Instruct to change to quantity distribution. Specifically, the code amount of the I picture is decreased while the generated code amount of the P picture and B picture is increased while maintaining the entire generated code amount constant. The change of the code amount distribution can be realized by changing the coefficients Kp and Kb in the equation (3).

  The coefficients Kp and Kb may be changed stepwise or continuously according to each value of the frame activity, the interframe motion amount, and the PSNR. The parameter Kp for determining the code amount distribution for each picture type is normally 1.0 and Kb is 1.4. On the other hand, if the values of the coefficients Kp and Kb are reduced for an image where flicker is likely to occur, the target code amount of the inter-coded picture is increased, and the target code amount for the intra-coded picture is changed to be low. .

  Such a change in the target code amount makes it difficult to produce a luminance peak difference between picture types, and can reduce occurrence of flicker during reproduction.

  The detection area unit of the possibility of occurrence of flicker due to the activity, interframe motion amount and PSNR is reduced, and the target code amount is changed for each detection area unit.

  The operation of this embodiment will be described with reference to FIG. As shown in FIG. 4, an image of one screen (for example, one frame) is divided into a plurality of areas, and frame activity, interframe motion amount and PSNR are calculated for each area. Thereafter, the same determination as that performed for each frame is performed, and an area where flicker is likely to occur is determined.

  In FIGS. 4A and 4B, hatched areas are areas where flicker is determined to occur. In an intra-coded picture, as shown in FIG. 4A, the target code amount for an area where flicker is likely to occur is reduced. In the inter-coded picture, as shown in FIG. 4B, the target code amount for an area where flicker is likely to occur is increased. On the other hand, a normal target code amount is set for an area where it is determined that flicker is unlikely to occur. By performing such determination for each area and adjustment of the target code amount, it is possible to perform processing limited to areas where flicker is likely to occur.

  Each process in each embodiment described above may be realized by reading a program for realizing the function of each process from the memory and executing it by a CPU (central processing unit) of the computer.

  The memory accessed by the CPU includes a nonvolatile memory such as an HDD, an optical disk, and a flash memory, a recording medium such as a CD-ROM that can only be read, and a volatile memory other than the RAM. Or you may comprise from the computer-readable recording medium by these combination, and a writable recording medium.

  In addition, a program for realizing each processing function in each of the above-described embodiments is recorded on a computer-readable recording medium, and the program recorded on the recording medium is read into a computer system and executed. Processing may be performed. The “computer system” here includes an OS and hardware such as peripheral devices. The program read from the recording medium is executed by a CPU or the like provided in a function expansion board or function expansion unit of a computer, thereby including a case where part or all of the functions of the above-described embodiments are realized.

  The “computer-readable recording medium” refers to a portable medium such as an optical disk such as a CD-ROM or DVD, a semiconductor memory card, or a storage device such as a hard disk built in a computer system. Furthermore, the “computer-readable recording medium” refers to a program for a certain period of time, such as a server or client volatile memory (RAM) when the program is transmitted via a network such as the Internet or a communication line such as a telephone line. Includes what is being held.

  The program may be transmitted from a computer system storing the program in a storage device or the like to another computer system via a transmission medium or by a transmission wave in the transmission medium. Here, the “transmission medium” for transmitting the program refers to a medium having a function of transmitting information, such as a network (communication network) such as the Internet or a communication line (communication line) such as a telephone line.

  The program may be for realizing a part of the functions described above. Furthermore, what can implement | achieve the function mentioned above in combination with the program already recorded on the computer system, and what is called a difference file (difference program) may be sufficient.

  A program product such as a computer-readable recording medium in which the above program is recorded can also be applied as an embodiment of the present invention. The above program, recording medium, transmission medium, and program product are included in the scope of the present invention.

  The embodiment of the present invention has been described in detail with reference to the drawings. However, the specific configuration is not limited to this embodiment, and includes designs and the like that do not depart from the gist of the present invention.

It is a schematic block diagram of one Example of this invention. It is a schematic diagram explaining the mechanism of flicker generation. 4A and 4B are schematic diagrams of code amount distribution with respect to the presence / absence of occurrence of flicker, where (A) shows code amount distribution when there is no possibility of flicker occurrence, and (B) shows code amount distribution when there is a possibility of occurrence of flicker. Indicates. It is explanatory drawing in the case of determining the target code amount at the time of flicker generation in the area unit which divides | segments 1 screen.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Input terminal 12 ... Frame rearrangement device 14 ... Adder / Subtractor 16 ... Orthogonal transformer 18 ... Quantizer 20 ... Variable length encoding device 22 ... Buffer 24 ..Output terminal 26 ... inverse quantizer 28 ... inverse orthogonal transformer 30 ... adder 32 ... video buffer (frame memory)
34 ... Motion prediction motion compensation device 36 ... Switch 38 ... Code amount control device 40 ... Quantization control device 42 ... Frame feature detection device 44 ... Frame motion detection device 46 ... PSNR calculation device 48... Flicker detection device

Claims (9)

The input moving image data including a plurality of frames, and encoding means for encoding using the intra-frame coding and inter-frame coding,
An intra-frame code that performs intra-frame coding on a frame that has not yet been encoded among frames included in the coding unit so that the code amount of the coding unit including a predetermined number of frames becomes the target code amount. A setting process for setting a target code amount for each of a plurality of picture types including an encoded picture and an inter-frame encoded picture for performing inter-frame encoding is repeated in the order of frames in the encoding unit, and set for each picture type. Code amount control means for controlling the code amount of the moving image data encoded by the encoding means for each frame in accordance with a target code amount ;
Local decoding means for decoding moving image data encoded by the encoding means and outputting locally decoded data;
Feature detection means for detecting the complexity of each of a plurality of frames included in the input image data ;
Motion detection means for detecting a motion amount between frames in the input video data for each of the plurality of frames ;
Coding distortion calculation means for calculating a coding distortion amount of each of the plurality of frames using the input moving image data and the local decoded data ;
An output of said characteristic detection means, an output of said motion detecting means, in accordance with an output of the encoding distortion calculating means, for each frame in the input moving image data, flicker encoded moving image data by the encoding means and a flicker detection means for detecting that but occur,
It said flicker detection means, when detecting that the flicker occurs, changing the target code amount to a target code amount set by the setting processing each of said intra-frame coded picture the inter-frame coding picture An encoding device characterized by the above. The flicker detection means has a complexity detected by the feature detection means greater than its reference value, a motion amount between the frames detected by the motion detection means is less than its reference value, and calculates the distortion amount. The encoding apparatus according to claim 1, wherein when the encoding distortion amount calculated by the unit is larger than the reference value, it is determined that flicker occurs in the encoded image. The flicker detection unit , when detecting occurrence of the flicker , reduces the target code amount of the intra-frame coded picture and increases the target code amount of the inter-frame coded picture. Item 3. The encoding device according to Item 1 or 2. It said feature detection means, the encoding apparatus according to the alternating current component amount obtained by orthogonal transform of the input video data to any one of claims 1 to 3, characterized in that the said complexity. The feature detection unit calculates an AC component by orthogonally transforming a block obtained by dividing the input moving image data into a predetermined size, and calculates a sum of the AC components of all blocks as the complexity. Item 4. The encoding device according to any one of Items 1 to 3. The motion detection means calculates a correlation while shifting the coordinates of an image of one frame between adjacent frames of the input moving image data , and calculates a coordinate shift amount that maximizes the correlation as the motion amount. The encoding device according to any one of claims 1 to 5. For each block obtained by dividing the input moving image data in the screen, the motion detection unit calculates a coordinate shift amount that maximizes the correlation while shifting the coordinates of one image between adjacent frames , and calculates the calculated coordinate shift amount. The encoding apparatus according to claim 1, wherein a total sum of all the blocks is calculated as the motion amount. 8. The coding distortion amount calculating means is means for calculating a PSNR (Peak Signal to Noise Ratio) of the local decoded image from the input moving image data and the local decoded image. The encoding device according to claim 1.   9. The encoding apparatus according to claim 1, wherein the intra-frame encoded picture is an I picture, and the inter-frame encoded picture is a P picture or a B picture.

Images