JP4596277B2 - Encoding device, encoding method, decoding device, and decoding method - Google Patents

Description

The present invention relates to an encoding device, an encoding method, a decoding device, and a decoding method . For example, a moving image signal is recorded on a recording medium such as an optical disk or a magnetic tape, reproduced, and displayed, or a video conference system or a video phone system. It is suitable for use when a moving image signal is transmitted from a transmission side to a reception side via a transmission line, and is received and displayed on the reception side, such as in broadcasting equipment.

  For example, in a system that transmits a moving image signal to a remote place such as a video conference system and a video phone system, in order to efficiently use a transmission path, the line correlation of video signals and the correlation between frames are used. An image signal is compressed and encoded. FIG. 20 shows the configuration of a moving image encoding / decoding device that encodes and transmits a moving image signal and decodes it. The encoding device 1 encodes the input video signal VD and transmits it to the recording medium 3 as a transmission path. Then, the decoding device 2 reproduces the signal recorded on the recording medium 3, decodes it, and outputs it.

  In the encoding device 1, an input video signal VD is input to a preprocessing circuit 11, where it is separated into a luminance signal and a color signal (in this case, a color difference signal), and analog digital (A / D) converters 12, 13 respectively. In analog digital conversion. The video signal that has been converted to a digital signal by analog-digital conversion by the A / D converters 12 and 13 is input to the pre-filter 19 and subjected to filter processing, and then supplied to the frame memory 14 and stored therein. The frame memory 14 stores the luminance signal in the luminance signal frame memory 15 and the color difference signal in the color difference signal frame memory 16, respectively.

  The prefilter 19 performs processing for improving encoding efficiency and image quality. This is, for example, a noise removal filter, and for example, a filter for limiting the band. FIG. 26 shows a configuration of a two-dimensional low-pass filter as an example of the prefilter 19. FIG. 27A shows the filter coefficient of the two-dimensional low-pass filter, and FIG. 27B shows a 3 × 3 pixel block as an input. For a target pixel e, a surrounding 3 × 3 pixel block is extracted. On the other hand, the following formula

The output of the calculation is the output value of the filter for the pixel e. Actually, the output value after the filter process is output from the output OUT1, and the original pixel value not subjected to the filter process is output from the output OUT2 after a predetermined delay. In this filter, uniform filter processing is always performed regardless of the input image signal and regardless of the state of the encoder.

  The format conversion circuit 17 converts the image signal stored in the frame memory 14 into an input format of an encoder 18. The data converted into a predetermined format is supplied from the format conversion circuit 17 to the encoder 18 where it is encoded. Although this encoding algorithm is arbitrary, details of one example will be described later with reference to FIG. The signal encoded by the encoder 18 is output as a bit stream to the transmission path and recorded on the recording medium 3, for example.

  Data reproduced from the recording medium 3 is supplied to the decoder 31 of the decoding device 2 and decoded. The decoding (decoding) algorithm of the decoder 31 may be arbitrary, but it must be paired with the encoding algorithm. Details of one example will be described later with reference to FIG. The data decoded by the decoder 31 is input to the format conversion circuit 32 and converted to the output format.

  The luminance signal of the frame format is supplied to and stored in the luminance signal frame memory 34 of the frame memory 33, and the color difference signal is supplied to and stored in the color difference signal frame memory 35. The luminance signal and the color difference signal read out from the luminance signal frame memory 34 and the color difference signal frame memory 35 are supplied to the post filter 39 and subjected to the filtering process, and then digital digital (D / A) converters 36 and 37 respectively. It is converted into an analog signal, supplied to the post-processing circuit 38, and synthesized. The output video signal is output and displayed on a display such as a CRT (not shown).

  The post filter 39 performs a filter process for improving the image quality. Used to mitigate degradation caused by encoding an image. For example, it is a filter for removing noise generated in the vicinity of block distortion, steep edges, and quantization noise. There are various types of postfilters. For example, as shown in FIG. 26, a two-dimensional low-pass filter similar to that used for the prefilter 19 can be used.

  Next, high-efficiency encoding of moving images will be described. Conventionally, moving image data such as a video signal has an extremely large amount of information, and thus a recording medium having an extremely high data transmission speed has been required to record and reproduce it for a long time. Therefore, large-sized magnetic tapes and optical disks are required. Further, even when moving image data is communicated via a transmission line or used for broadcasting, the amount of data is too large, and there is a problem that communication cannot be performed using an existing transmission line as it is.

  Therefore, when recording a video signal on a smaller recording medium for a long time, or when using it for communication or broadcasting, there is provided means for efficiently recording and recording the video signal and decoding the read signal efficiently. It is essential. In order to meet such demands, a high-efficiency encoding method using correlation of video signals has been proposed, and one of them is the MPEG (Moving Picture Experts Group) method. This was discussed in ISO-IEC / JTC1 / SC2 / WG11 and proposed as a standard proposal, and is a hybrid system that combines motion compensated prediction coding and discrete cosine transform (DCT) coding. is there.

  Motion-compensated predictive coding is a method that uses correlation in the time axis direction of an image signal, predicts a currently input image from a signal that has already been decoded and reproduced, and transmits only the prediction error at that time. This is a method for compressing the amount of information necessary for encoding. In DCT coding, the signal power is concentrated on a specific frequency component using the intra-frame two-dimensional correlation of the image signal, and the information amount is compressed by coding only the concentrated distribution coefficient. Make it possible. For example, in a portion where the pattern is flat and the autocorrelation of the image signal is high, the DCT coefficients are concentratedly distributed to low frequency components. Therefore, in this case, it is possible to compress the information amount by encoding only the coefficients concentrated and distributed in the low band. Hereinafter, an example in the case of the MPEG2 system as an encoder will be described in detail, but the encoding system is not limited to the MPEG2 system, and can be similarly applied to an arbitrary encoding system.

  Next, the MPEG2 system will be described in detail. When line correlation is used, an image signal can be compressed by, for example, DCT processing. If the inter-frame correlation is used, the image signal can be further compressed and encoded. For example, as shown in FIG. 17, when frame images PC1, PC2, and PC3 are generated at times t1, t2, and t3, the difference between the image signals of the frame images PC1 and PC2 is calculated to generate PC12. Also, the difference between the frame images PC2 and PC3 is calculated to generate PC23. Usually, images of frames that are adjacent in time do not have such a large change. Therefore, if the difference between them is calculated, the difference signal has a small value. Therefore, if this difference signal is encoded, the code amount can be compressed.

  However, if only the differential signal is transmitted, the original image cannot be restored. Therefore, the image of each frame is set to one of the three types of I-picture, P-picture, and B-picture, and the image signal is compression-coded. That is, for example, as shown in FIG. 18, the image signals of 17 frames from F1 to F17 are set as a group of pictures (GOP) as one unit of processing. The image signal of the first frame F1 is encoded as an I picture, the second frame F2 is processed as a B picture, and the third frame F3 is processed as a P picture. The fourth and subsequent frames F4 to F17 are processed alternately as a B picture or a P picture.

  The I-picture image signal is transmitted as it is for one frame. In contrast, as shown in FIG. 18A, the P-picture image signal basically transmits a difference from the I-picture or P-picture image signal temporally preceding it. Further, as shown in FIG. 18B, for the B-picture image signal, a difference from the average value of both the temporally preceding frame and the succeeding frame is obtained, and the difference is encoded.

  FIG. 19 shows the principle of the method for encoding a moving image signal in this way. Since the first frame F1 is processed as an I-picture, it is transmitted as it is to the transmission path as transmission data F1X (intra-image coding). On the other hand, since the second frame F2 is processed as a B picture, the difference between the temporally preceding frame F1 and the average value of the temporally following frame F3 is calculated, and the difference is transmitted. It is transmitted as data F2X.

  However, there are four types of processing as the B-picture. The first process is to transmit the data of the original frame F2 as it is as the transmission data F2X (SP1) (intra coding), and is the same process as in the case of I-picture. The second process is to calculate a difference from a temporally subsequent frame F3 and transmit the difference (SP2) (backward predictive coding). The third process is to transmit a difference (SP3) from the temporally preceding frame F1 (forward prediction coding). Further, the fourth process is to generate a difference (SP4) between the average value of the temporally preceding frame F1 and the succeeding frame F3 and transmit this as transmission data F2X (bidirectional predictive coding). .

  Of these four methods, the method with the least amount of transmission data is employed. When the difference data is transmitted, a motion vector x1 (motion vector between frames F1 and F2) between the frame image (predicted image) whose difference is to be calculated (forward prediction) or x2 ( The motion vector between frames F3 and F2) (for backward prediction) or both x1 and x2 (for bidirectional prediction) are transmitted along with the difference data.

  Also, the P-picture frame F3 is obtained by calculating the difference signal (SP3) from this frame and the motion vector x3 using the temporally preceding frame F1 as a predicted image, and transmitting this as transmission data F3X (forward prediction code). ). Alternatively, the data of the original frame F3 is transmitted as it is as transmission data F3X (SP1) (intra coding). Which method is used for transmission is selected, as in the case of the B picture, in which the transmission data becomes smaller.

  Next, the configuration of the encoder 18 will be described with reference to FIG. The image data BD to be encoded is input to the motion vector detection circuit (MV-Det) 50 in units of macro blocks. The motion vector detection circuit 50 processes the image data of each frame as an I picture, a P picture, or a B picture according to a predetermined sequence set in advance. Whether the image of each frame input to the sequential is processed as a picture of I, P, or B is determined in advance (for example, as shown in FIG. 18, it is configured by frames F1 to F17. Group of pictures are processed as I, B, P, B, P,... B, P).

  Image data of a frame (for example, frame F1) processed as an I-picture is transferred from the motion vector detection circuit 50 to the front original image portion 51a of the frame memory 51 and stored, and a frame (for example, frame F2) processed as a B-picture. ) Is transferred to and stored in the original image portion 51b, and image data of a frame (eg, frame F3) processed as a P picture is transferred to and stored in the rear original image portion 51c.

  At the next timing, when an image of a frame to be further processed as a B-picture (frame F4) or a P-picture (frame F5) is input, the first P-picture (stored in the rear original image portion 51c until then) The image data of the frame F3) is transferred to the front original image portion 51a, the image data of the next B picture (frame F4) is stored (overwritten) in the original image portion 51b, and the next P picture (frame F5) is stored. The image data is stored (overwritten) in the rear original image portion 51c. Such an operation is sequentially repeated.

  The signal of each picture stored in the frame memory 51 is read out from the picture signal and is subjected to frame prediction mode processing or field prediction mode processing in a prediction mode switching circuit (Mode-SW) 52. Further, under the control of the prediction determination circuit 54, the calculation unit 53 performs calculation of intra-picture prediction, forward prediction, backward prediction, or bidirectional prediction. Which of these processes is performed is determined corresponding to a prediction error signal (a difference between a reference image to be processed and a predicted image corresponding thereto). Therefore, the motion vector detection circuit 50 generates the absolute value sum (or sum of squares) of the prediction error signal used for this determination.

  Here, the frame prediction mode and the field prediction mode in the prediction mode switching circuit 52 will be described. When the frame prediction mode is set, the prediction mode switching circuit 52 outputs the four luminance blocks Y [1] to Y [4] supplied from the motion vector detection circuit 50 to the subsequent calculation unit 53 as they are. . In other words, in this case, as shown in FIG. 23A, the data of the odd-numbered line and the data of the even-numbered line are mixed in each luminance block. In this frame prediction mode, prediction is performed in units of four luminance blocks (macro blocks), and one motion vector corresponds to the four luminance blocks.

  In contrast, in the field prediction mode, the prediction mode switching circuit 52 receives four signals input from the motion vector detection circuit 50 with the configuration shown in FIG. 23A, as shown in FIG. The luminance blocks Y [1] and Y [2] are constituted only by, for example, the odd field line dots, and the other two luminance blocks Y [3] and Y [4] are even fields. And output to the calculation unit 53. In this case, one motion vector corresponds to the two luminance blocks Y [1] and Y [2], and the other two luminance blocks Y [3] and Y [4] Are associated with one motion vector.

  The motion vector detection circuit 50 outputs the absolute value sum of the prediction errors in the frame prediction mode and the absolute value sum of the prediction errors in the field prediction mode to the prediction mode switching circuit 52. The prediction mode switching circuit 52 compares the absolute value sum of the prediction errors in the frame prediction mode and the field prediction mode, performs a process corresponding to the prediction mode having a small value, and outputs the data to the calculation unit 53. However, this processing is actually performed by the motion vector detection circuit 50. That is, the motion vector detection circuit 50 outputs a signal having a configuration corresponding to the determined mode to the prediction mode switching circuit 52, and the prediction mode switching circuit 52 outputs the signal as it is to the calculation unit 53 in the subsequent stage.

  In the frame prediction mode, the color difference signal is supplied to the arithmetic unit 53 in a state where odd field line data and even field line data are mixed, as shown in FIG. Further, in the field prediction mode, as shown in FIG. 23B, the upper half (four lines) of the color difference blocks Cb and Cr are the odd field color differences corresponding to the luminance blocks Y [1] and Y [2]. The lower half (four lines) is an even field color difference signal corresponding to the luminance blocks Y [3] and Y [4].

  In addition, the motion vector detection circuit 50 calculates the prediction error absolute value sum for determining whether the prediction determination circuit 54 performs prediction in the image, forward prediction, backward prediction or bidirectional prediction as follows. Is generated. That is, as the sum of the absolute values of the prediction errors of intra-picture prediction, the sum ΣAij | of the sum ΣAij of the macroblock signal Aij of the reference image and the sum Σ | Aij | of the absolute value | Aij | of the macroblock signal Aij Find the difference. Also, as the sum of the absolute values of the prediction errors of the forward prediction, the sum Σ | Aij−Bij of the absolute value | Aij−Bij | of the difference Aij−Bij between the macroblock signal Aij of the reference image and the macroblock signal Bij of the predicted image Find |.

  Also, the absolute value sum of the prediction errors of the backward prediction and the bidirectional prediction is obtained in the same manner as in the forward prediction (by changing the prediction image to a prediction image different from that in the forward prediction). These sums of absolute values are supplied to the prediction determination circuit 54. The prediction determination circuit 54 selects the smallest absolute value sum of prediction errors of forward prediction, backward prediction, and bidirectional prediction as the absolute value sum of prediction errors of inter prediction. Further, the absolute value sum of the prediction errors of the inter prediction and the absolute value sum of the prediction errors of the intra prediction are compared, and the smaller one is selected, and the mode corresponding to the selected absolute value sum is set to the prediction mode (P -mode). That is, if the sum of the absolute values of the prediction errors of intra prediction is smaller, the intra prediction mode is set. If the absolute value sum of the prediction errors of inter prediction is smaller, the mode with the smallest corresponding absolute value sum is set among the forward prediction, backward prediction, and bidirectional prediction modes.

  As described above, the motion vector detection circuit 50 is configured to use the macroblock signal of the reference image as a mode corresponding to the mode selected by the prediction mode switching circuit 52 in the frame or field prediction mode via the prediction mode switching circuit 52. The motion vector between the prediction image and the reference image corresponding to the prediction mode (P-mode) selected by the prediction determination circuit 54 out of the four prediction modes is detected and is variable length. The data is output to the encoding circuit (VLC) 58 and the motion compensation circuit (M-comp) 64. As described above, the motion vector having the minimum absolute value sum of the corresponding prediction errors is selected.

  The prediction determination circuit 54 sets an intra-frame (image) prediction mode (a mode in which motion compensation is not performed) as a prediction mode when the motion vector detection circuit 50 reads I-picture image data from the front original image portion 51a. The switch 53d of the calculation unit 53 is switched to the contact a side. As a result, the I-picture image data is input to the DCT mode switching circuit (DCT CTL) 55. In this DCT mode switching circuit 55, as shown in FIG. 24A or 24B, the data of the four luminance blocks is mixed with the odd-numbered and even-numbered lines (frame DCT mode). Alternatively, the state is set to one of the separated states (field DCT mode) and output to the DCT circuit 56.

  That is, the DCT mode switching circuit 55 compares the coding efficiency when DCT processing is performed with a mixture of odd field data and even field data, and the coding efficiency when DCT processing is performed in a separated state. Select a good mode. For example, as shown in FIG. 24A, the input signal has a configuration in which odd and even field lines are mixed, and the difference between the signal of the odd and even field lines adjacent to each other is calculated. Calculation is performed, and the sum (or sum of squares) of the absolute values is obtained.

  In addition, as shown in FIG. 24B, the input signal has a structure in which odd and even field lines are separated, and the signal difference between the odd and even adjacent odd field lines and the even field lines are separated. Is calculated, and the sum (or sum of squares) of the absolute values is calculated. Furthermore, both (absolute value sum) are compared, and a DCT mode corresponding to a small value is set. That is, if the former is smaller, the frame DCT mode is set, and if the latter is smaller, the field DCT mode is set. Data having a configuration corresponding to the selected DCT mode is output to the DCT circuit 56, and a DCT flag (DCT-FLG) indicating the selected DCT mode is output to the variable length coding circuit 58 and the motion compensation circuit 64.

  As is clear from comparison between the prediction mode in the prediction mode switching circuit 52 (FIG. 23) and the DCT mode in the DCT mode switching circuit 55 (FIG. 24), the data structure in each of the two modes is related to the luminance block. Are substantially identical. When the frame prediction mode (mode in which odd lines and even lines are mixed) is selected in the prediction mode switching circuit 52, the frame DCT mode (mode in which odd lines and even lines are mixed) is also selected in the DCT mode switching circuit 55. If the field prediction mode (the mode in which the odd field data and the even field data are separated) is selected by the prediction mode switching circuit 52, the DCT mode switching circuit 55 also uses the field DCT mode (odd field and even number). The mode in which the field data is separated is likely to be selected.

  However, this is not always the case. In the prediction mode switching circuit 52, the mode is determined so as to reduce the absolute value sum of the prediction errors, and in the DCT mode switching circuit 55, the coding efficiency is improved. The mode is determined. The I-picture image data output from the DCT mode switching circuit 55 is input to the DCT circuit 56, subjected to DCT processing, and converted into DCT coefficients. This DCT coefficient is input to the quantization circuit (Q) 57 and quantized with a quantization scale (QS) corresponding to the data accumulation amount (quantization control signal (B-full)) of the transmission buffer (Buffer) 59. Thereafter, it is input to the variable length coding circuit 58.

  The variable length encoding circuit 58 corresponds to the quantization scale (QS) supplied from the quantization circuit 57, and converts the image data (in this case, I-picture data) supplied from the quantization circuit 57 into, for example, a Huffman code. Is converted to a variable length code such as, and output to the transmission buffer 59. The variable length coding circuit 58 also indicates whether the quantization scale (QS) is set by the quantization circuit 57 and the prediction mode (intra-picture prediction, forward prediction, backward prediction, or bidirectional prediction is set by the prediction determination circuit 54. Mode (P-mode)), a motion vector (MV) from the motion vector detection circuit 50, and a prediction flag (P-FLG) indicating whether a frame prediction mode or a field prediction mode is set from the prediction mode switching circuit 52 , And a DCT flag output from the DCT mode switching circuit 55 (a flag (DCT-FLG) indicating whether a frame DCT mode or a field DCT mode has been set) is input, and these are also variable-length encoded.

  The transmission buffer 59 temporarily stores the input data and outputs data corresponding to the storage amount to the quantization circuit 57. When the remaining amount of data increases to the allowable upper limit value, the transmission buffer 59 increases the quantization scale (QS) of the quantization circuit 57 by the quantization control signal (B-full), thereby Reduce the amount of data. On the other hand, when the remaining amount of data decreases to the allowable lower limit value, the transmission buffer 59 reduces the quantization scale (QS) of the quantization circuit 57 with the quantization control signal (B-full). Increase the amount of quantized data. In this way, overflow or underflow of the transmission buffer 59 is prevented. The data stored in the transmission buffer 59 is read at a predetermined timing, output to the transmission path, and recorded on the recording medium 3, for example.

  On the other hand, the I-picture data output from the quantization circuit 57 is input to the inverse quantization circuit (IQ) 60 and inversely quantized corresponding to the quantization scale (QS) supplied from the quantization circuit 57. . The output of the inverse quantization circuit 60 is input to an inverse DCT (IDCT) circuit 61 and subjected to inverse DCT processing. Then, a block rearrangement circuit (Block Change) 65 outputs a block for each DCT mode (frame / field). Sorting is done. The output of the block rearrangement circuit 65 is supplied to and stored in the forward predicted image portion (FP) 63a of the frame memory 63 via the calculator 62.

  When the motion vector detection circuit 50 processes the image data of each frame sequentially input as, for example, I, B, P, B, P, B,..., The image data of the first input frame. After the image is processed as an I-picture, the image data of the next input frame is processed as a P-picture before the image of the next input frame is processed as a B-picture. This is because the B picture is accompanied by backward prediction, and therefore cannot be decoded unless the P picture as the backward predicted image is prepared first.

  Therefore, the motion vector detection circuit 50 starts processing the image data of the P picture stored in the rear original image portion 51c after the processing of the I picture. Similarly to the case described above, the absolute value sum of the inter-frame difference (prediction error) in units of macroblocks is supplied from the motion vector detection circuit 50 to the prediction mode switching circuit 52 and the prediction determination circuit 54. The prediction mode switching circuit 52 and the prediction determination circuit 54 predict the frame / field prediction mode or intra-picture prediction, forward prediction, backward prediction, or bidirectional prediction in accordance with the absolute value sum of the prediction errors of the P-picture macroblock. Set the mode.

  When the intra-frame prediction mode is set, the calculation unit 53 switches the switch 53d to the contact a side as described above. Therefore, this data is transmitted to the transmission line via the DCT mode switching circuit 55, the DCT circuit 56, the quantization circuit 57, the variable length coding circuit 58, and the transmission buffer 59, as with the I-picture data. Further, this data is supplied to and stored in the backward predicted image section (BP) 63b of the frame memory 63 via the inverse quantization circuit 60, the inverse DCT circuit 61, the block rearrangement circuit 65, and the arithmetic unit 62.

  In the forward prediction mode, the switch 53d is switched to the contact point b, and the image data (in this case, the I-picture image) stored in the forward prediction image portion 63a of the frame memory 63 is read out, and the motion compensation circuit 64 Motion compensation is performed in accordance with the motion vector output from the motion vector detection circuit 50. That is, the motion compensation circuit 64 corresponds to the read address of the forward prediction image unit 63a corresponding to the position of the macro block currently output by the motion vector detection circuit 50 when the prediction determination circuit 54 is instructed to set the forward prediction mode. The data is read from the position to be shifted by the amount corresponding to the motion vector to generate predicted image data.

  The predicted image data output from the motion compensation circuit 64 is supplied to the calculator 53a. The computing unit 53a subtracts the predicted image data corresponding to the macroblock supplied from the motion compensation circuit 64 from the macroblock data of the reference image supplied from the prediction mode switching circuit 52, and the difference (prediction error). Is output. The difference data is transmitted to the transmission line via the DCT mode switching circuit 55, the DCT circuit 56, the quantization circuit 57, the variable length coding circuit 58, and the transmission buffer 59. The difference data is locally decoded by the inverse quantization circuit 60 and the inverse DCT circuit 61 and input to the arithmetic unit 62 via the block rearrangement circuit 65.

  The calculator 62 is also supplied with the same data as the predicted image data supplied to the calculator 53a. The calculator 62 adds the predicted image data output from the motion compensation circuit 64 to the difference data output from the inverse DCT circuit 61. As a result, the original (decoded) P-picture image data is obtained. The P-picture image data is supplied to and stored in the backward predicted image unit 63b of the frame memory 63.

  The motion vector detection circuit 50 thus executes the B-picture processing after the I-picture data and the P-picture data are stored in the forward prediction image section 63a and the backward prediction image section 63b, respectively. The prediction mode switching circuit 52 and the prediction determination circuit 54 set a frame / field mode corresponding to the magnitude of the sum of absolute values of inter-frame differences in units of macroblocks. Set to one of prediction mode, backward prediction mode, or bidirectional prediction mode. As described above, in the intra-frame prediction mode or the forward prediction mode, the switch 53d is switched to the contact point a or b. At this time, the same processing as in the P-picture is performed, and data is transmitted.

  On the other hand, when the backward prediction mode or the bidirectional prediction mode is set, the switch 53d is switched to the contact c or d, respectively. In the backward prediction mode in which the switch 53d is switched to the contact point c, image data (in this case, a P-picture image) stored in the backward prediction image unit 63b is read out, and the motion compensation circuit 64 moves the motion vector. Motion compensation is performed corresponding to the motion vector output from the detection circuit 50. In other words, the motion compensation circuit 64 corresponds to the read address of the backward prediction image unit 63b corresponding to the position of the macro block currently output by the motion vector detection circuit 50 when the prediction determination circuit 54 is instructed to set the backward prediction mode. The data is read from the position to be shifted by the amount corresponding to the motion vector to generate predicted image data.

  The predicted image data output from the motion compensation circuit 64 is supplied to the calculator 53b. The computing unit 53b subtracts the predicted image data supplied from the motion compensation circuit 64 from the macroblock data of the reference image supplied from the prediction mode switching circuit 52, and outputs the difference. The difference data is transmitted to the transmission line via the DCT mode switching circuit 55, the DCT circuit 56, the quantization circuit 57, the variable length coding circuit 58, and the transmission buffer 59.

  In the bidirectional prediction mode in which the switch 53d is switched to the contact point d, image data (in this case, I-picture image) data stored in the forward prediction image unit 63a and image stored in the backward prediction image unit 63b (In this case, the image of the P picture) is read out, and motion compensation is performed by the motion compensation circuit 64 in accordance with the motion vector output from the motion vector detection circuit 50. That is, in the motion compensation circuit 64, when the setting of the bidirectional prediction mode is instructed by the prediction determination circuit 54, the motion vector detection circuit 50 now outputs the read addresses of the forward prediction image unit 63a and the backward prediction image unit 63b. Data is read out from the position corresponding to the position of the macroblock by the amount corresponding to the motion vector (in this case, two motion vectors are for the forward prediction image and the backward prediction image), and the prediction image data is generated. .

  The predicted image data output from the motion compensation circuit 64 is supplied to the calculator 53c. The computing unit 53c subtracts the average value of the predicted image data supplied from the motion compensation circuit 64 from the macroblock data of the reference image supplied from the motion vector detection circuit 50, and outputs the difference. The difference data is transmitted to the transmission line via the DCT mode switching circuit 55, the DCT circuit 56, the quantization circuit 57, the variable length coding circuit 58, and the transmission buffer 59. The B-picture image is not stored in the frame memory 63 because it is not a predicted image of another image.

  Note that, in the frame memory 63, the forward prediction image unit 63a and the backward prediction image unit 63b are subjected to bank switching as necessary, and the one stored in one or the other for a predetermined reference image is forward-predicted. It can be switched and output as an image or a backward prediction image. In the above description, the luminance block has been mainly described, but the color difference block is also processed and transmitted in units of macro blocks shown in FIGS. 23 and 24. As the motion vector when processing the color difference block, the motion vector of the corresponding luminance block is halved in the vertical and horizontal directions.

  Next, FIG. 25 shows a configuration of the decoder 31 of FIG. The encoded image data transmitted through the transmission path (recording medium 3) is received by a receiving circuit (not shown) or reproduced by a reproducing device, temporarily stored in a receiving buffer 81, and then decoded. The variable length decoding circuit (IVLC) 82 of the circuit 90 is supplied. The variable-length decoding circuit 82 performs variable-length decoding on the data supplied from the reception buffer 81 and outputs a motion vector (MV), a prediction mode (P-mode), and a prediction flag (P-FLG) to a motion compensation circuit (M− comp) 87. Also, the DCT flag (DCT-FLG) is output to the inverse block rearrangement circuit (Block Change) 88, the quantization scale (QS) is output to the inverse quantization circuit (IQ) 83, and the decoded image data is inversely quantized. Output to the circuit 83.

  The inverse quantization circuit 83 inversely quantizes the image data supplied from the variable length decoding circuit 82 in accordance with the quantization scale (QS) also supplied from the variable length decoding circuit 82, and performs an inverse DCT circuit (IDCT). ) 84. The data (DCT coefficient) output from the inverse quantization circuit 83 is subjected to inverse DCT processing by the inverse DCT circuit 84 and supplied to the computing unit 85 through the block rearrangement circuit 88. When the image data supplied from the inverse DCT circuit 84 is I-picture data, the data is output from the computing unit 85 and prediction of image data (P or B-picture data) to be input to the computing unit 85 later. In order to generate image data, the image data is supplied to and stored in the forward predicted image portion (FP) 86a of the frame memory 86. This data is output to the format conversion circuit 32 (FIG. 20).

  When the image data supplied from the inverse DCT circuit 84 is P-picture data that uses the image data of the previous frame as predicted image data and is data in the forward prediction mode, the forward predicted image portion of the frame memory 86 The image data of the previous frame (I-picture data) stored in 86a is read out, and motion compensation corresponding to the motion vector output from the variable length decoding circuit 82 is performed by the motion compensation circuit 87. . The arithmetic unit 85 adds the image data (difference data) supplied from the inverse DCT circuit 84 and outputs the result. This added data, that is, the decoded P-picture data is used as the backward prediction of the frame memory 86 to generate the predicted image data of the image data (B-picture or P-picture data) to be input later to the calculator 85. The image portion (BP) 86b is supplied and stored.

  Even in the case of the P-picture data, the data in the intra-picture prediction mode is stored in the backward predicted image unit 86b as it is without any particular processing by the computing unit 85, like the I-picture data. Since this P picture is an image to be displayed next to the next B picture, it is not yet output to the format conversion circuit 32 at this point in time (as described above, the P picture inputted after the B picture is B B Processed and transmitted before the picture).

  When the image data supplied from the inverse DCT circuit 84 is B-picture data, it is stored in the forward prediction image unit 86a of the frame memory 86 corresponding to the prediction mode supplied from the variable length decoding circuit 82. I-picture image data (in the case of forward prediction mode), P-picture image data stored in the backward prediction image portion 86b (in the case of backward prediction mode), or both of them (in the case of bidirectional prediction mode) And motion compensation corresponding to the motion vector output from the variable-length decoding circuit 82 is performed in the motion compensation circuit 87, and a predicted image is generated. However, when motion compensation is not required (in the case of intra-picture prediction mode), a predicted image is not generated.

  In this way, the data subjected to motion compensation by the motion compensation circuit 87 is added to the output of the inverse DCT circuit 84 in the arithmetic unit 85. This addition output is output to the format conversion circuit 32. However, since this added output is B-picture data and is not used for generating a predicted image of another image, it is not stored in the frame memory 86. After the B-picture image is output, the P-picture image data stored in the backward predicted image unit 86 b is read and supplied to the calculator 85 via the motion compensation circuit 87. However, motion compensation is not performed at this time.

  The decoder 31 does not show the circuits corresponding to the prediction mode switching circuit 52 and the DCT mode switching circuit 55 in the encoder 18 of FIG. 22, but the processing corresponding to these circuits, that is, the odd field and the even field. The motion compensation circuit 87 executes processing for returning the configuration in which the line signals are separated to the original mixed configuration as necessary. In the above description, the processing of the luminance signal has been described, but the processing of the color difference signal is performed in the same manner. However, in this case, the motion vector used is a luminance signal halved in the vertical and horizontal directions.

  By the way, in the moving picture coding apparatus 1 as described above with reference to FIG. 20, the prefilter 19 removes noise contained in the input picture signal and increases the coding efficiency in the coding apparatus 1 and information up to a predetermined amount. Used to reduce the amount. The post filter 39 is used to alleviate the degradation of the decoded image and improve the image quality. Here, consider the noise included in the image. There are various types of noise. For example, noise generated when passing through a transmission line, or granular noise peculiar to a film exists in a film source such as a movie.

  Noise included in such an image includes intentionally included noise and noise that is unintentionally generated and causes deterioration. The prefilter 19 reduces these noises without distinction. In addition, when an image signal is encoded, the high-frequency component of the image is reduced, and as a result, noise is reduced or the noise is changed to noise having a different property from the original noise. When noise is reduced in this way, if it is excessively reduced, an image having an impression different from that of the original image is obtained, and the image is deteriorated. This is particularly a problem with intentionally included noise.

  Therefore, according to this moving image encoding method, there is a problem that the prefilter 19 and the encoding device 1 excessively reduce noise, and on the contrary, deteriorate the image. Also, quantization noise occurs in the encoded image. This is particularly noticeable in the vicinity of the edge and is a major cause of image quality degradation.

The present invention has been made in view of the above, to restore the noise that was lost when decoding coded moving picture coding apparatus capable of improving the image quality of visually decoded moving image An encoding method, a decoding device, and a decoding method are proposed.

In the present invention for solving the above problems, in the encoding apparatus for encoding an image signal, a coding section for generating an encoded stream image signal by encoding the quantization to be used for encoding an image signal A noise characteristic information generating unit that generates noise characteristic information indicating characteristics of noise to be added when performing the filter processing by decoding the encoded stream in accordance with the scale and the filter coefficient when the image signal is filtered; and noise characteristic information generated by the noise characteristic information generation unit, and be provided and a transmission unit for transmitting the coded stream generated by the encoding unit.

According to the present invention, in an encoding method for encoding an image signal, the image signal is encoded according to a quantization scale used when the image signal is encoded and a filter coefficient when the image signal is filtered. decodes the generated coded stream generating noise characteristics information indicating characteristics of the noise to be added in performing the filter processing Te, generated noise characteristic information and the image signal generated by encoding the encoded stream transmission I tried to do it.

In the present invention, in a decoding apparatus that decodes an encoded stream obtained by encoding an image signal, the quantization scale used when the image signal is encoded and the filter coefficient used when the image signal is filtered are used. A receiving unit that receives noise characteristics information indicating characteristics of noise to be added when decoding the encoded stream and performing filter processing, and an encoded stream received by the receiving unit. A decoding unit that generates an image signal by decoding , and a noise amount that indicates a noise amount to be added when performing a filtering process on the image signal generated by the decoding unit according to the noise characteristic information received by the receiving unit a noise amount information generation unit for generating information, follow the noise amount information generated by the noise amount information generation section connexion, the decoding section It was provided a post filter unit that performs filter processing for adding noise to made the image signal.

According to the present invention, in a decoding method for decoding an encoded stream obtained by encoding an image signal, the quantization scale used when the image signal is encoded and the filter coefficient used when the image signal is filtered are used. connexion determined, and the noise characteristic information indicating characteristics of noise by decoding the encoded stream is added when performing the filter processing, it receives a coded stream, follow the receive One noise characteristic information connexion, coded stream Generate noise amount information indicating the amount of noise to be added when performing filter processing on the image signal generated by decoding and generate the received encoded stream according to the generated noise amount information Filter processing for adding noise to the processed image signal is performed.

Noise characteristic information is generated according to the quantization scale used when encoding the image signal and the filter coefficient used when filtering, and the noise characteristic information is encoded with the encoded bit stream generated by encoding the image signal. transmitted to the decoding side, to generate a noise amount information indicating the Supporting connexion noise amount to the noise characteristic information at the decoding side, the noise on the image signal generated by decoding the Supporting connexion coded bit stream to the noise amount information Perform additional filter processing. This makes it possible to reproduce noise components lost due to encoding. Further, deterioration such as quantization noise caused by encoding can be made inconspicuous.

As described above, according to the present invention, noise characteristic information is generated according to the quantization scale used when encoding the image signal and the filter coefficient used when performing the filter processing, and the noise characteristic information is converted into the image signal. It is transmitted to the decoding side together with the encoded bit stream generated by encoding, and the decoding side generates noise amount information indicating the noise amount according to the noise characteristic information, and decodes the encoded bit stream according to the noise amount information. By performing a filter process that adds noise to the image signal generated in this way, the noise component lost by encoding can be reproduced, and deterioration such as quantization noise caused by encoding is made inconspicuous. Thus, an encoding device, an encoding method, a decoding device, and a decoding method that can improve the image quality of a visually decoded moving image can be realized.

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

(1) First Embodiment FIG. 1 in which the same reference numerals are assigned to corresponding parts as in FIG. 20 shows a moving picture encoding apparatus and decoding apparatus according to the first embodiment of the present invention. In this embodiment, the encoder 18 determines the amount of noise to be added in the post filter 39 according to the encoding conditions and according to the characteristics of the filter used in the prefilter 19, and adds an additional noise characteristic signal NA indicating this. Is encoded. There are two noise characteristic determination methods for determining the additional noise characteristic signal NA. The first noise characteristic determination method is forcibly inputting and setting the additional noise characteristic signal NA from the outside, and the second noise characteristic determination method is based on various flags generated at the time of encoding. Is to determine.

  The configuration of the encoder 18 according to the first noise characteristic determination method is shown in FIG. The additional noise characteristic signal NA input from the outside is input to the variable length encoder 58. The variable length coder 58 performs variable length coding similar to the conventional one and also variable length codes the noise characteristic signal NA. The additional noise characteristic signal NA is recorded in user data in the bit stream. Since user data in the MPEG system or MPEG2 system can be set after the sequence, GOP, and picture header, the PST can be similarly set in units of sequence, GOP, and picture.

  FIG. 3 shows the syntax of the MPEG video. Extension data extension-data or user data user-data is recorded in extension / user data extension-and-user-data (i) with an underline in the figure. FIG. 4A and FIG. 4B show extension / user data extension-and-user-data (i) and extension data extension-data. When the user data start code user-data-start-code is recorded in the extension / user data extension-and-user-data (i), this indicates that the user data user-data is recorded next. . Next, FIG. 4C shows user data user-data. User data user-data is recorded in units of 8 bits. When "0000 0000 0000 0000 0000 0001" occurs, user data user-data is terminated.

  Next, the additional noise characteristic signal NA will be described. The additional noise characteristic signal NA is, for example, an 8-bit signal as shown in FIG. The additional noise characteristic signal NA is recorded in the user data user-data shown in FIGS. Characteristic 0 is the least amount of noise, and characteristic 255 is the most amount of noise. The process of adding noise using the additional noise characteristic signal NA will be described later.

  The additional noise characteristic signal NA can be set by user data user-data after the sequence, GOP, and picture header. Once the additional noise characteristic signal NA is set, the value is used until it is reset again. That is, the same noise is added until it is reset. The additional noise characteristic signal NA is first set by the sequence header. When resetting thereafter, any user data user-data after the sequence, GOP, or picture header may be set.

  Next, the configuration of the encoder 18 according to the second noise characteristic determination method is shown in FIG. The additional noise determination circuit 70 determines the amount of noise to be added in the post filter 39 (FIG. 1) from the quantization scale (QS) input to the variable length encoder 58 and the filter characteristics used in the prefilter 19 (FIG. 1). To do. The additional noise determination circuit 70 outputs a flag indicating the amount of noise added by the post filter 39 and an additional noise characteristic signal NA to the variable length encoder 58. The variable length coder 58 performs variable length coding on the additional noise characteristic signal NA as in the case of the first noise characteristic determination method.

  An example of a method for determining the additional noise characteristic signal NA in the second noise characteristic determination method will be described. The encoder 18 performs quantization. At this time, the smaller the quantization scale (QS), the smaller the amplitude of the signal can be encoded. Therefore, the smaller the quantization scale (QS) is, the more noise is transmitted in the original image. If the quantization scale (QS) is large, noise cannot be transmitted, and the decoded image is a flat image from which noise has been removed.

  In the encoding apparatus 1, the filter process is performed by the prefilter 19. There are various types of filter processing, and noise removal processing is one example. In addition to the noise removal filter, for example, a low-pass filter has an effect of reducing noise. The amount of noise that can be reproduced in the decoded image is determined by the degree of noise removal by the filter. That is, when the prefilter 19 hardly removes noise, the noise component included in the original image can be transmitted. However, when the prefilter 19 removes most noise, it is impossible to transmit noise. Become.

  Therefore, the additional noise characteristic signal NA is determined by the quantization scale (QS) and the degree of noise removal by the prefilter 19. That is, the greater the quantization scale (QS) and the greater the degree of noise removal of the prefilter 19, the greater the amount of noise added by the postfilter 39. Adding noise by the post filter 39 has an effect not only to restore noise lost during encoding but also to make deterioration such as quantization noise caused by encoding inconspicuous.

  This will be described with reference to FIG. Deterioration caused by encoding includes deterioration near the edge and block distortion. FIG. 8A shows an original image, and FIG. 8B shows that deterioration has occurred in the vicinity of the edge. In FIG. 8C, noise having the same level as noise generated by deterioration is added. It turns out that it becomes inconspicuous by adding noise.

  The quantization scale (QS) is a measure of the degree of such degradation. When the quantization scale (QS) is small, the deterioration is considered to be small, and when the quantization scale (QS) is large, the deterioration is considered to be remarkable. Therefore, from the viewpoint of making deterioration inconspicuous, the larger the quantization scale (QS) is, the more noise is added, and the smaller the quantization scale (QS) is, the less noise is added.

  FIG. 9 shows a method of determining the additional noise characteristic signal NA from the quantization scale (QS) and the filter characteristics F1 to FN of the prefilter 19. Here, the prefilter 19 is strong and weak, but a stronger filter removes more noise, and a weaker filter stores noise. FIG. 10 shows a specific example. F1 to FN are filter coefficients whose frequency characteristics are as shown in FIG. F1 is the weakest filter and FN is the strongest filter.

  Here, the syntax of the macro block header in the case of the MPEG system or the MPEG2 system is shown in FIG. As indicated by the underline in the figure, the quantization coefficient (quantizer-scale-code) is set in units of macroblocks. First, after encoding one frame, an average value MEAN-Q of quantization coefficients in one frame is obtained. FIG. 9 shows a method of determining the additional noise characteristic signal NA from the average value MEAN-Q of the quantization coefficient and the filter characteristics F1 to FN of the prefilter 19. In this way, the additional noise characteristic signal NA is determined.

  Next, the configuration of the decoder 31 (FIG. 1) in the first embodiment is shown in FIG. Both the first and second noise characteristic determination methods are decoded by the decoding circuit 90 shown in FIG. When the bit stream is input to the decoder 31, it is first input to the variable length decoding circuit 82, where the variable length encoding is solved. At this time, the additional noise characteristic signal NA recorded in the user data user-data is decoded and output to the post filter 39 (FIG. 1). The other operations of the decoder 31 are the same as those described in the prior art.

  The post filter 39 is shown in FIG. The noise generation circuit 39A generates random white noise. This can be realized, for example, by a circuit that generates an M series. The additional noise characteristic signal NA decoded by the decoder 31 is input to the additional noise determination circuit 39B. The additional noise determination circuit 39B determines the amount of noise added to the image signal according to the additional noise characteristic signal NA. The input image signal and the generated noise are input to the adder 39C and added. The output of the adder 39C is input to the D / A converters 36 and 37 (FIG. 1) as the output of the post filter 39.

  According to the above configuration, when a moving image signal is encoded, the amount of noise included in the image is detected, and the additional noise characteristic signal NA indicating the amount of noise is encoded and transmitted. Since the noise is added according to the additional noise characteristic signal NA indicating the amount of noise after the stream is decoded, the noise component lost by the encoding can be reproduced. In addition, by adding post-filter noise of the same level as the quantization noise generated by encoding, the degradation of quantization noise and the like can be made inconspicuous, thus improving the image quality of visually decoded moving images. Can do.

(2) Second Embodiment FIG. 13 in which the same reference numerals are assigned to the parts corresponding to those in FIG. 1 shows a moving picture coding apparatus and decoding apparatus according to a second embodiment of the present invention. The encoding device 1 is the same as the conventional one. As described in the first embodiment, the amount of noise to be added depends on the quantization scale (QS). Although the quantization scale (QS) is set in units of macro blocks, user data user-data can be transmitted only in units of sequences, GOPs, and pictures. In the second embodiment, the amount of noise to be added is determined on a macroblock basis.

  The decoder 31 in the second embodiment will be described with reference to FIG. 14 in which the same reference numerals are assigned to the parts corresponding to those in FIG. When the bit stream is input to the decoder 31, it is input to the variable length decoding circuit 82, and the variable length code is solved. At this time, the additional noise characteristic signal NA and the quantization scale (QS) recorded in the user data user-data are output to the post filter 39. The other operations of the decoder 31 are the same as those described in the prior art.

  A post filter 39 according to the second embodiment will be described with reference to FIG. In this embodiment, the additional noise characteristic signal NA and the quantization scale (QS) are input to the noise amount determination circuit 39D. The noise amount determination circuit 39D determines the amount of noise added in the post filter 39 from the additional noise characteristic signal NA and the quantization scale (QS). FIG. 16 shows a noise amount determination method. The determined noise amount NA ′ is output to the additional noise determination circuit 39B.

  The additional noise determination circuit 39B determines the noise to be added to the image signal as in the first embodiment. The input image signal and generated noise are input to the adder 39C and added. The output of the adder 39C is input to the D / A converters 36 and 37 (FIG. 1) as the output of the post filter 39. Other operations are the same as those in the first embodiment.

  According to the above configuration, when a moving image signal is encoded, the amount of noise included in the image is detected, and the additional noise characteristic signal NA indicating the amount of noise is encoded and transmitted. Reproducing the noise component lost by encoding by adding noise according to the additional noise characteristic signal NA and quantization scale (QS) indicating the amount of noise after decoding the stream I get out. In addition, by adding post-filter noise of the same level as the quantization noise generated by encoding, the degradation of quantization noise and the like can be made inconspicuous, thus improving the image quality of visually decoded moving images. Can do.

  The present invention can be widely used in an apparatus for recording and reproducing a moving image signal on a recording medium such as an optical disk or a magnetic tape, displaying it, a video conference system, a video phone system, a broadcasting device, and the like.

It is a block diagram which shows the structure of the moving image encoding / decoding apparatus of 1st Example by this invention. It is a block diagram which shows the structure of the encoder of the encoding apparatus of FIG. It is a chart which shows the syntax of the video of an MPEG system. 5 is a table showing extension of MPEG video syntax / user data. It is a table | surface which shows the syntax of the macro block of the video of an MPEG system. It is a chart which shows the contents of additional noise characteristic signal NA. It is a block diagram which shows the structure of the encoder of the encoding apparatus of FIG. FIG. 6 is a characteristic curve diagram for explaining an improvement in image quality by reproducing a noise component. It is a characteristic curve figure with which it uses for description of the determination method of an additional noise characteristic signal. It is a characteristic curve figure with which it uses for description of the frequency characteristic of a filter coefficient. It is a block diagram which shows the structure of the decoder of the decoding apparatus of FIG. It is a block diagram which shows the structure of the post filter of the decoding apparatus of FIG. It is a block diagram which shows the structure of the moving image encoding / decoding apparatus of 2nd Example by this invention. It is a block diagram which shows the structure of the decoder of the decoding apparatus of FIG. It is a block diagram which shows the structure of the post filter of the decoding apparatus of FIG. It is a characteristic curve figure with which it uses for description of the determination method of an additional noise characteristic signal. It is a basic diagram with which it uses for description of the principle of the highly efficient encoding of the moving image signal using a frame correlation. It is a basic diagram with which it uses for description of the picture type in the case of compressing a moving image signal. It is a basic diagram with which it uses for description of the principle of a moving image signal encoding method. It is a block diagram which shows the structure of the conventional moving image encoding / decoding apparatus. It is a basic diagram which shows the structure of image data as description of operation | movement of a format conversion circuit. FIG. 21 is a block diagram illustrating a configuration of an encoder in the moving image encoding / decoding device in FIG. 20. It is a basic diagram with which it uses for description of operation | movement of the prediction mode switching circuit of an encoder. It is a basic diagram with which it uses for description of operation | movement of the DCT mode switching circuit of an encoder. FIG. 21 is a block diagram showing a configuration of a decoder in the moving picture encoding / decoding apparatus in FIG. 20. FIG. 21 is a connection diagram illustrating a configuration of a two-dimensional low-pass filter as a prefilter / postfilter in the moving image encoding / decoding apparatus of FIG. 20. It is a basic diagram with which it uses for description of the coefficient of the two-dimensional low-pass filter of FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Encoding apparatus, 2 ... Decoding apparatus, 3 ... Recording medium (transmission path), 11 ... Pre-processing circuit, 12, 13 ... Analog digital (A / D) converter, 14, 33 ... ... Frame memory, 15, 34 ... Luminance signal frame memory, 16, 35 ... Color difference signal frame memory, 17, 32 ... Format conversion circuit, 18 ... Encoder, 19 ... Prefilter, 20 ... Storage device, 21 ... Coefficient determination circuit, 22... Coding rate determination circuit, 31... Decoder, 36 and 37... Digital analog (D / A) converter, 38. MV-Det), 51... Frame memory, 51 a... Original image portion, 51 b... Original image portion, 51 c. ... Calculation unit 54 ... Prediction determination circuit 55 ... DCT mode switching circuit (DCT CTL) 56 ... DCT circuit 57 ... Quantization circuit (Q) 58 ... Variable length coding circuit (VLC) , 59... Transmission buffer (60), 83... Inverse quantization circuit (IQ), 61, 84... Inverse DCT circuit (IDCT), 62, 85... Computing unit, 63, 86. , 63a, 86a... Prediction image (FP), 63b, 86b... Prediction image (BP), 64, 87... Motion compensation circuit (M-comp), 65, 88. Rearrangement circuit, 70... Additional noise determination circuit, 81... Reception buffer, 82... Variable length decoding circuit (IVLC).

Claims (12)

In an encoding device for encoding an image signal,
An encoding unit that encodes the image signal to generate an encoded stream;
According to the quantization scale used when the image signal is encoded and the filter coefficient when the image signal is filtered , the characteristics of noise to be added when the encoded stream is decoded and the filter process is performed. A noise characteristic information generating unit for generating noise characteristic information to be shown ;
The noise characteristic information and the noise characteristic information generated by the generating unit, the transmission unit and a comprises Ru marks Goka apparatus for transmitting the encoded stream generated by the coding unit. The noise characteristic information generation unit generates the noise characteristic information in units of macro blocks.
Encoding apparatus according to 請 Motomeko 1. The transmission unit multiplexes and transmits the noise characteristic information to the encoded stream
Encoding apparatus according to 請 Motomeko 1. The encoding unit generates the encoded stream according to the MPEG standard.
Encoding apparatus according to 請 Motomeko 1. The transmission unit transmits the noise characteristic information described in the user data area in the coded stream
Encoding apparatus according to 請 Motomeko 4. In an encoding method for encoding an image signal,
In accordance with the quantization scale used when the image signal is encoded and the filter coefficient used when the image signal is filtered, the encoded stream generated by encoding the image signal is decoded and the filter process is performed. Noise characteristic information indicating the characteristics of noise added at the time is generated, and the generated noise characteristic information and the encoded stream generated by encoding the image signal are transmitted .
It marks Goka way. In a decoding device for decoding an encoded stream obtained by encoding an image signal,
Noise added when performing the filtering process by decoding the encoded stream, determined according to the quantization scale used when the image signal is encoded and the filter coefficient when the image signal is filtered A receiving unit that receives the noise characteristic information indicating the characteristics and the encoded stream;
A decoding unit that decodes the encoded stream received by the receiving unit to generate an image signal;
Follow the noise characteristic information received by the receiving unit connexion, and the noise amount information generation section for generating a noise amount information indicating the amount of noise to be added in performing the filter processing on the image signal generated by the decoding unit ,
The noise amount information accordance connexion to the generated noise amount information by the generating section, decrypt device Ru comprising a post filter unit that performs filter processing for adding noise to the image signal generated by the decoding unit. The noise amount information generation unit generates the noise amount information in units of macro blocks.
Decoding apparatus according to 請 Motomeko 7. The noise characteristic information is multiplexed in the encoded stream,
The receiving unit acquires the noise characteristic information from the encoded stream.
Decoding apparatus according to 請 Motomeko 7. The encoded stream is a stream encoded according to the MPEG standard.
Decoding apparatus according to 請 Motomeko 7. The noise characteristic information is described in a user data area in the encoded stream,
The receiving unit acquires the noise characteristic information from a user data area in the encoded stream.
Decoding apparatus according to 請 Motomeko 10. In a decoding method for decoding an encoded stream obtained by encoding an image signal,
Noise added when performing the filtering process by decoding the encoded stream, determined according to the quantization scale used when the image signal is encoded and the filter coefficient when the image signal is filtered and noise characteristic information indicating a characteristic, receives the above coded stream, follow the receive One was the noise characteristic information connexion, added when performing the filter processing on the image signal generated by decoding the coded stream Decoding method for generating noise amount information indicating the amount of noise to be performed and adding noise to an image signal generated by decoding the received encoded stream according to the generated noise amount information .

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