JP3671980B2 - Video signal encoding device, video signal encoding method, portable terminal device, and video signal encoding program - Google Patents

Description

  The present invention relates to an apparatus and method for encoding an input video signal (hereinafter also referred to as an input video signal), and more particularly to an apparatus and method suitable for a mobile phone, a videophone system, and the like. About.

  In a conventional video encoding method, a moving image that has been filtered prior to encoding by a pre-filter having a plurality of characteristics is encoded in one or more modes, and the encoded moving image is encoded. Encoding difficulty is calculated from the encoding mode, the generated code amount tabulated for each coding mode, and the quantization step width tabulated for each coding mode, and the calculated coding difficulty, A filter characteristic coefficient is calculated from an arbitrarily set encoding output rate, and a plurality of filter characteristics in the prefilter are selected based on the calculated filter characteristic coefficient (for example, the following patents) See literature.)

JP 2002-247576 A (page 1-9, FIG. 1)

  As described above, in the conventional video encoding method, when selecting the prefilter characteristics, the encoding mode of the encoded image, the generated code amount totaled for each encoding mode, and the total for each encoding mode are calculated. Since the encoding difficulty level is calculated from the quantization step width and the filter characteristic coefficient is calculated from the encoding difficulty level and the encoding output rate, the calculation of the filter characteristic coefficient is complicated, and the filter characteristic The amount of calculation until the coefficient is calculated increases.

  For this reason, the burden on the arithmetic unit constituted by the CPU or the like increases, and the power consumption also increases. The problem of power consumption is particularly important when the number and size of power sources such as batteries that can be mounted are inevitably limited due to limitations due to the size of the device itself such as a mobile phone. It is a serious problem.

  The present invention has been made to solve the above-described problems, and provides a video signal encoding device capable of controlling the characteristics of a prefilter without performing complicated calculations.

The video signal encoding apparatus of the present invention is
Based on the filter characteristic control data, a pre-filter that outputs a predetermined frequency component in the input video signal as current image data,
Encoding means for encoding the current image data;
Filter control means for outputting the filter characteristic control data set based on the encoding parameter output by the encoding means,
The pre-filter is
A low-pass filter that outputs a low-frequency component in the input video signal;
A first gain controller that corrects the low frequency component and outputs a corrected low frequency component based on the filter characteristic control data;
A second gain controller that corrects the input video signal and outputs a corrected video signal based on the filter characteristic control data;
The pre-filter outputs a predetermined frequency component in the input video signal based on the corrected low frequency component or the corrected video signal.

  According to the present invention, it is possible to determine the characteristics of the prefilter according to the amount of code generated in the encoding means without performing complicated calculations.

  In addition, since a complicated calculation as described above is not used, a burden on a calculation unit including a CPU or the like is reduced, so that power consumption can be reduced.

  In addition, the pre-filter configuration is configured so that high frequency components in the input video can be adaptively suppressed according to the code amount, thereby suppressing an increase in the code amount and high quality with less deterioration such as block distortion. It is possible to obtain a simple image.

Embodiment 1 FIG.
Hereinafter, the present invention will be described based on illustrated embodiments.
FIG. 1 is a block diagram showing a video signal encoding apparatus according to the first embodiment.
In FIG. 1, an input video signal is input to a pre-filter 101, and a predetermined frequency component is extracted. Hereinafter, a predetermined frequency component in the input video signal is also referred to as current image data.

  The current image data extracted by the prefilter 101 is output to the frame memory 102. The frame memory 102 is constituted by a recording unit such as a semiconductor memory, a magnetic disk, or an optical disk device.

  The current image data recorded in the frame memory 102 is output to the encoding means 116 for each macroblock shown in FIG. 2, and is encoded by the encoding means 116. It should be noted that the encoding in the encoding means 116 is performed by any conversion method as long as the encoding method uses an orthogonal transform that converts an image included in the input video signal into the frequency domain, such as DCT, wavelet transform, and Amadal transform. You may go.

  Hereinafter, in the first embodiment, a case where encoding is performed by MPEG4 which is one of encoding methods using DCT will be described.

  The encoding means 116 to which the current image data is input outputs a bit stream corresponding to the encoded current image data. Further, the encoding unit 116 outputs one or two encoding parameters among the plurality of encoding parameters corresponding to the encoding to the filter control unit 117. The encoding parameters are parameters related to the encoding process, such as quantization parameters, inter / intra ratio, bitstream code amount, target bit rate, and the like.

  Here, the inter / intra ratio is a ratio between the number of macroblocks subjected to intra coding within one frame and the number of macroblocks subjected to inter coding. In a frame where intra coding is performed, intra coding is performed in all macroblocks. Therefore, the value of the inter / intra ratio of a frame on which intra coding is performed is 0. However, in a frame in which inter coding is performed, not all macro blocks are subjected to inter coding, but a macro block in which inter coding is performed and a macro block in which intra coding is performed are mixed. Become.

  Generally, when intra coding is performed, the amount of codes increases. Therefore, when the ratio of macroblocks to which inter coding is performed increases in a frame in which inter coding is performed, the value of the inter / intra ratio increases and the code amount decreases. On the other hand, when the ratio of macroblocks to which inter coding is performed decreases, the value of the inter / intra ratio decreases and the code amount increases. Thus, since the inter / intra ratio and the code amount have a correlation, the inter / intra ratio can also be handled as a coding parameter indicating increase / decrease in the code amount.

  Also, the quantization parameter is a coefficient that becomes a denominator of the arithmetic processing described later. When the quantization parameter value increases, the bitstream code amount decreases, and when the quantization parameter value decreases, the bitstream code. The amount increases. Thus, since the quantization parameter and the code amount have a correlation as described above, the quantization parameter can also be handled as a coding parameter indicating increase / decrease of the code amount.

  Furthermore, the target bit rate can be treated as an encoding parameter. That is, when the target bit rate value is large, the quantization parameter value is small, and as a result, the code amount of the bit stream is large. On the other hand, when the value of the target bit rate is small, the value of the quantization parameter increases, and as a result, the code amount of the bit stream decreases. Thus, since the target bit rate also has a correlation with the code amount, the target bit rate can also be handled as an encoding parameter indicating increase / decrease of the code amount.

  The filter control means 117 outputs filter characteristic control data K for controlling the characteristics of the prefilter 101 to the prefilter 101 based on one encoding parameter output from the encoding means 116.

  The pre-filter 101 outputs a predetermined frequency component in the input video signal based on the filter characteristic control data K.

Here, the operation of the encoding means 116 will be described.
As described above, the current image data divided for each macroblock is input from the frame memory 102 to the encoding unit 116. Then, the current image data is input to the subtracter 103 and the motion detection unit 113 in the encoding unit 116.

  When intra coding is performed in the coding unit 116, the current image data input to the subtracter 103 is output to the DCT unit 104 without being subjected to calculation by the subtracter 103. The current image data input to the DCT unit 104 is subjected to DCT in the DCT unit 104 and then output to the quantization unit 105. Hereinafter, the current image data subjected to DCT is referred to as DCT data.

  The quantization means 105 to which the DCT data is input quantizes the DCT data in accordance with the quantization parameter Qp output from the code amount control means 115, and the quantized DCT data is inversely quantized means 108, And output to the DC / AC prediction means 106. Here, the quantization parameter Qp is a parameter determined on the basis of the code amount of the bit stream output from the variable-length encoding means 107 described later.

  Hereinafter, the quantized DCT data is referred to as quantized data.

  The quantized data output from the quantizing unit 105 is decoded by an inverse quantizing unit 108 and an inverse DCT unit 109.

  More specifically, the quantized data is inversely quantized by the inverse quantization means 108 to become DCT data, which is output to the inverse DCT means 109. The DCT data is subjected to inverse DCT by the inverse DCT means 109. The decoded current image data (hereinafter, the decoded current image data is referred to as decoded current image data). Then, the decoded current image data is output to the adder 110.

  The decoded current image data is recorded in the memory 111 via the adder 110. Note that when the intra encoding is performed by the encoding unit 116, the adder 110 does not perform an operation on the decoded current image data. Therefore, the current image data output from the inverse DCT means 109 is recorded in the memory 111 as it is.

  On the other hand, the DC / AC predicting means 106 to which the quantized data is inputted from the quantizing means 105, the DC coefficient in the quantized data corresponding to the current image data and the image one frame period before the current image data. The difference between the quantized data corresponding to the data (hereinafter referred to as previous image data) and the DC coefficient is calculated, and the data corresponding to the difference (hereinafter referred to as DC difference data) is variable length encoding means 107. Output to. Also, the DC / AC prediction means 106 calculates difference data (hereinafter, the difference data for the AC coefficient is referred to as AC difference data) for the AC coefficient in the quantized data in the same manner as the DC coefficient, and the AC. The difference data is output to the variable length encoding means 107. When the DC / AC prediction means 106 outputs the DC difference data and the AC difference data, the DC / AC prediction means 106 also outputs additional information such as a quantization parameter Qp to the variable length coding means 107.

  In the variable length coding unit 107, variable length coding is performed on the DC difference data, the AC difference data, and the additional information output from the DC / AC prediction unit 106. Then, the variable length coding unit 107 outputs a bit stream corresponding to the data subjected to variable length coding.

  On the other hand, when the encoding unit 116 performs inter encoding, data corresponding to the difference between the current image data from the subtractor 103 and the predicted image data output from the predicted image creation unit 112 (hereinafter referred to as difference image). Data is output), and DCT, quantization, and variable-length coding are performed on the difference image data as in the case of performing the intra coding. When performing inter coding, the DC / AC coefficient prediction unit 106 does not perform the calculation of the DC difference data and the AC difference data, and corresponds to the difference image data output from the quantization unit 105. The quantized data (hereinafter referred to as quantized differential image data) is output to the variable length coding means 107 as it is.

  Here, the predicted image data is generated from the motion vector detected by the motion detection means 113 based on the previous image data and the current image data, and the pre-decoding image data recorded in the memory 111. Image data. Therefore, the difference image data is data corresponding to an error between the current image data and the predicted image data. Here, the pre-decoding image data is decoded image data corresponding to the image data one frame period before the current image data.

  The current image data is encoded by the encoding means 116 by the processing procedure as described above.

  By the way, generally, when the movement of an object or the like displayed in an image corresponding to an input video signal is fast, or for a frame in which a scene change has occurred, the code amount of the bit stream output from the variable length encoding unit 107 is It will increase.

  When the code amount increases, since the entire code amount needs to be controlled, the code amount control means 115 corresponds to the code amount in order to decrease the code amount corresponding to the frame after the scene change. A larger quantization parameter Qp is output, and the quantization means 105 is controlled. In the case of MPEG4, the quantization parameter Qp takes a value from 1 to 31.

  In general, image data subjected to DCT is decomposed into frequency components, and quantized in the order of low frequency components to high frequency components. Thus, when quantization is performed in order from the low frequency component, the high frequency component in the image data and the frequency component close to the high frequency component tend to be suppressed. Therefore, as described above, if the quantization parameter Qp is increased to reduce the code amount corresponding to the frame after the scene change, not only the high frequency component but also the middle frequency component may be removed. If even the intermediate frequency component is removed as described above, the spatial degradation such as block distortion that occurs during DCT or quantization increases in the displayed image, and the image quality deteriorates. End up.

  Therefore, in order to suppress an increase in the code amount corresponding to the frame in which the scene change has occurred and to reduce the quantization parameter Qp corresponding to the frame after the scene change, the prefilter 101 configured as shown in FIG. As shown in FIG. 1, it is installed at the front stage of the frame memory 102. As a result, it is possible to remove a high-frequency component from the input video signal in advance, and as a result, it is possible to control an appropriate code amount as a whole, and to prevent deterioration in image quality in a frame after a scene change.

  In FIG. 3, the input video signal is input to the low-pass filter 201. Then, the low frequency filter 201 outputs a low frequency component in the input video signal to the first gain controller 202. Of the frequency components in the input video signal, which frequency component is handled as the low frequency component can be arbitrarily set. For example, it can be arbitrarily determined by setting an appropriate sampling frequency (fs / 2) for the low-pass filter 201 and giving an appropriate characteristic (for example, FIG. 4). In the low-pass filter having the characteristics shown in FIG. 4, a frequency component smaller than the sampling frequency (fs / 2) in the input video signal is output to the first gain controller 202, and the frequency component is output with respect to the output. Is multiplied by the gain corresponding to, and the multiplied low frequency component is output to the adder 204.

  On the other hand, the input video signal is also input to the second gain controller 203.

  Filter characteristic control data K is input from the filter control means 117 to the second gain controller 203 and the first gain controller 202, and the gain of the first gain controller 202 is set to (K). Gain controller 203 is set to (1-K). The filter characteristic control data K is a value of 0 ≦ K ≦ 1.

  The gain of the first gain controller is set in the filter characteristic control data K, the low frequency component in the input video signal is corrected, and the gain of the second gain controller is set to (1-K). Thus, the input video signal is corrected. When K = 1 is set as the gain of the first gain controller, the low frequency component in the input video signal is not attenuated, and K = 0 is set as the gain of the first gain controller. When set, the input video signal is not attenuated. Therefore, the correction includes a case where the low-frequency component in the input video signal or the input video signal is not corrected.

  Hereinafter, the low frequency component output from the first gain controller 202 is also referred to as a corrected low frequency component, and the input video signal output from the second gain controller 203 is also referred to as a corrected video signal.

  In the prior art, the filter characteristic coefficient corresponding to the filter characteristic control data K is set by calculating the encoding difficulty level using a plurality of encoding parameters. In this case, as described in the section of the prior art, since the calculation is complicated, the amount of calculation is large, and the burden on the calculation unit is large. Therefore, problems such as an increase in power consumption occur. Therefore, in the first embodiment, the filter control unit 117 is provided with a data table composed of the quantization parameter Qp and the filter characteristic control data K, and the quantization according to the code amount generated in the encoding unit 116 is performed. The filter characteristic control data K is output from the data table based on the parameter Qp. 5 and 6 are examples of the data table.

  By using the data table as described above, the characteristics of the pre-filter 101 can be set without performing complicated calculations, so that the calculation speed can be improved and the power consumption can be reduced.

When the characteristics shown in FIG. 4 are given to the low-pass filter 201 and the data in the data table is set as shown in FIG. 5, the characteristics of the prefilter change as shown in FIG.
When the quantization parameter Qp is small (in the case of Qp ≦ 8 in FIG. 5), 0 is given to the first gain controller 202 as the filter characteristic control data K, and the pre-filter 101 receives an input video signal. Is output as is. On the other hand, when the quantization parameter Qp is large (in the case of Qp ≧ 25 in FIG. 5), 1 is given to the first gain controller 202 as the filter characteristic control data K, and the prefilter 101 is low-pass. The output of the filter 201 is output as it is.

  If the quantization parameter Qp is medium (9 ≦ Qp ≦ 24 in FIG. 5), the first gain controller 202 is set to 1/4 as the filter characteristic control data K, or When 1/2 is given and the filter control data K is 1/4, a video signal in which a high frequency component in the input signal (frequency component cut in the low-pass filter) is attenuated to 3/4 is output from the pre-filter 101. Is output. When the filter control data K is ½, a video signal in which a high frequency component in the input signal is attenuated to ½ is output from the pre-filter 101.

  That is, according to the pre-filter 101, the high frequency in the input video signal is output in accordance with the code amount generated in the encoding means 116 without the low frequency component of the input video signal output from the low pass filter 201 being attenuated. The component can be adaptively attenuated.

  In the above description, Qp ≦ 8 when the quantization parameter Qp is small, Qp ≧ 25 when the quantization parameter is large, and 9 ≦ Qp ≦ 24 when the quantization parameter is medium, but the magnitude of the quantization parameter Qp is large or small. Can be arbitrarily set according to the characteristics of a device or the like in the video signal encoding apparatus.

  Further, the filter characteristic control data K may be updated for each macroblock or for each Video Object Plane (hereinafter referred to as VOP). When the filter characteristic control data K is updated for each VOP, the filter control data K corresponding to the macroblock to be encoded first in each VOP is encoded for all macroblocks in the VOP. It may be a fixed value until is completed.

  In the first embodiment, the data table is used in order to simplify the determination of the filter characteristic control data K. However, the data table is also obtained by using simple functions such as those shown in FIGS. It has been found by the inventors' experiment and the like that the filter characteristic control data K can be determined with the same amount of calculation as that of the reference.

  In the first embodiment, the filter characteristic control data K is determined based only on the quantization parameter Qp among the plurality of encoding parameters according to the encoding in the encoding unit 116. The encoding parameter used when determining the data only needs to have a relationship with the amount of code generated in the encoding means 116. For example, an inter / intra ratio or a target bit rate can be used, The code amount itself can also be used. Further, the filter characteristic control data K may be determined based on the quantization parameter and the inter / intra ratio, and the filter characteristic control data K may be determined based on the code amount and the inter / intra ratio. Further, the filter characteristic control data K may be determined based on the target bit rate and the quantization parameter, or the target bit rate and the code amount.

  Furthermore, a coding mode may be used instead of the inter / intra ratio. That is, the intra coding mode of the intra-frame coding mode, the forward prediction coding mode, and the intra coding mode of the bidirectional coding prediction mode are set as one of the coding parameters. The filter characteristic control data K may be determined based on the activation parameter. Note that a target bit rate and a code amount may be used as an encoding parameter combined with the encoding mode.

  In the first embodiment, MPEG4 has been described as an example. However, the encoding performed by the encoding unit 116 is not limited to this, and for example, MPEG1, MPEG2, H.264, and the like. Encoding may be performed according to H.263.

  As described above, in the video signal encoding apparatus according to the first embodiment, the characteristics of the prefilter are determined according to the code amount generated in the encoding means by a simple method without performing complicated calculations. Is possible.

  In addition, since a complicated calculation as described above is not used, a burden on a calculation unit including a CPU or the like is reduced, and power consumption can be reduced.

  Furthermore, since the pre-filter configuration can adaptively suppress high-frequency components in the input video signal according to the code amount, the increase in the code amount is suppressed, and high-quality with little deterioration such as block distortion is suppressed. An image can be obtained.

Embodiment 2. FIG.
In general, an input video signal may include a noise component, and if an input video signal containing the noise component is encoded, a wasteful code amount corresponding to the noise component is generated. Resulting in.

  Since the prefilter 101 in the first embodiment determines the filter characteristic control data K so as to remove the high-frequency component when the amount of code generated by the encoding unit 116 increases, it is useless corresponding to the noise component. When the code amount is generated, a high-frequency component that does not need to be removed is removed, and the displayed image may be deteriorated.

  In view of this, the video signal encoding apparatus according to the second embodiment effectively suppresses the noise component by providing a noise reduction filter in the pre-filter 101, and a wasteful code amount is generated in the encoding unit 116. It suppresses.

  In the second embodiment, except for the configuration of the prefilter, the other components are the same as those in the first embodiment, and thus the description of the other components and the operation thereof is omitted. In the second embodiment, the input video signal input to the pre-filter is referred to as current image data, and the image data one frame period before the current image data is referred to as previous image data.

  FIG. 11 shows an internal configuration of the prefilter 101 according to the second embodiment. As shown in FIG. 11, the prefilter 101 according to the second embodiment includes a noise reduction filter 301 before the internal prefilter 302. The configuration of the internal prefilter 302 in the second embodiment is the same as that of the prefilter in the first embodiment.

  FIG. 12 shows the internal configuration of the noise reduction filter 301 in FIG.

  In FIG. 12, current image data is input to a first subtracter 401 and a second subtracter 403. The first subtracter 401 receives the previous image data recorded in the frame memory 102, and calculates a difference between the current image data and the previous image data (hereinafter, the difference is referred to as difference data). The Then, the difference data is output to the scaling means 402.

  The scaling unit 402 compares the difference data with the threshold value Th input from the filter control unit 117. If the difference data is smaller than the threshold value Th, the difference data is used as it is. Or, it is corrected and output to the second subtractor 403. On the other hand, when the difference data is larger than the threshold value Th, the difference data is not output.

  The threshold value Th is output from the filter control means 117 based on the encoding parameter in the encoding means 116, similarly to the filter characteristic control data K in the first embodiment. For example, the threshold value Th may be output from the data table provided with the threshold value Th corresponding to the quantization parameter as shown in FIG. The threshold value Th may be output by calculating with a function as shown in FIG. When the threshold value Th is determined by the calculation, it goes without saying that the filter control data K in the functions shown in FIGS. 8 to 10 is replaced with the threshold value Th.

  Further, the characteristic of the scaling means 402 is that when the difference data is smaller than the threshold value Th, the difference data is output as it is or after being corrected, and the difference data is larger than the threshold value. May have any characteristic that does not output the difference data. Therefore, for example, the characteristics of the scaling means 402 can be as shown in FIGS.

  The difference data output from the scaling means 402 is subtracted from the current image data in the subtractor 403 and output to the low pass filter 201 in the internal prefilter 302.

  For example, in the scaling means 402 having the characteristics as shown in FIG. 14 or FIG. 15, when the input difference data is smaller than the threshold value Th_i, the difference data is subtracted from the current image data. Data, that is, data having the same value as the previous image data is output from the noise reduction filter 301 to the low-pass filter 201.

  On the other hand, when the input difference data is larger than the threshold value Th_i and smaller than the threshold value Th_j, the current image data corrected according to the output of the scaling means 402 is sent from the noise reduction filter 301. Output to the low-pass filter 201. When the input difference data is equal to or greater than the threshold value Th_j, there is no output from the noise reduction filter, so that the current image data is output to the low-pass filter 201 as it is.

  Further, when the scaling means 402 having the characteristics as shown in FIG. 16 is used, the following image data is output from the noise reduction filter 301 to the low-pass filter 201.

  That is, when the input difference data is smaller than the threshold value Th_k, data obtained by subtracting the difference data from the current image data, that is, data having the same value as the previous image data is output to the low-pass filter 201. When the threshold value Th_k is exceeded, the current image data is output to the low-pass filter 201 as it is.

  FIG. 17 is an example of an image corresponding to the image data output from the noise reduction filter 301. Note that FIG. 17 is an enlarged image in order to more clearly show the influence of noise components in the image.

  17A shows an image corresponding to the previous image data, FIG. 17B shows an image corresponding to the current image data, and FIG. 17C shows an image corresponding to the image data output from the noise reduction filter 301.

  When the noise component is suppressed by the noise reduction filter 301, image flicker due to the influence of the noise component as seen in, for example, part A in (b) is added to the data output from the noise reduction filter 301. The corresponding image (c) has been removed.

  As described above, in the video signal encoding apparatus according to the second embodiment, since the noise reduction filter is provided, noise components in the input video signal can be removed prior to encoding. It is possible to suppress generation of a useless code amount corresponding to the noise component in the converting means, and it is possible to obtain the same effect as in the first embodiment.

Embodiment 3 FIG.
FIG. 18 is a block diagram showing a video signal encoding apparatus according to the third embodiment.
In the third embodiment, the filter control means 117 and the code amount control means 115 in the first embodiment or the second embodiment are integrally configured as a code amount control means 115a. The components other than the code amount control means 115a and the operation thereof are the same as those in the first embodiment or the second embodiment.

  The code amount control means 115a outputs the quantization parameter Qp in the quantization means 105 according to the code amount output from the variable length coding means 107, as in the first embodiment or the second embodiment. The filter characteristic control data K corresponding to the quantization parameter Qp is output to the prefilter 101.

  As described above, in the video signal encoding apparatus according to the third embodiment, the filter control means 117 and the code amount control means 115 in the first and second embodiments are configured integrally. The configuration of the video signal encoding device can be simplified, and the same effects as those of the first embodiment or the second embodiment can be obtained.

Embodiment 4 FIG.
In the video signal encoding apparatus according to the first to third embodiments, when a target compression rate, bit rate, and the like are set based on the code amount generated by the encoding unit 116, the video signal encoding device inputs the encoding unit 116. The compression rate or the like cannot be changed until the encoding of the current image data is completed.

  Therefore, for example, in a system that distributes the bit stream that is the output of the encoding means in real time, if some trouble occurs in the transmission path and it becomes impossible to send the bit stream at the current rate, the video signal Although it is necessary to lower the target bit rate in the encoding device, the video signal encoding device in the first to third embodiments cannot cope with such a case. Therefore, even if a bit stream corresponding to the input video signal is output, there is a problem that the bit stream is not distributed.

  Therefore, the video signal encoding apparatus according to the fourth embodiment can input parameters relating to code amount control such as compression rate and bit rate from the outside to the code amount control means 115 or the filter control means 117. In addition, by making it possible to change the target compression rate, etc., regardless of the encoding stage, based on the compression rate, bit rate, etc. input from the outside, the above-described problems can be solved. It is a solution. In the following description, a case where a bit rate is given as an external input will be described.

  FIG. 19 is a block diagram showing a video signal encoding apparatus according to the fourth embodiment. Note that the components other than the code amount control unit 115b in the encoding unit 116 and the operation thereof are the same as those of the encoding unit 116 in the first to third embodiments, and thus description thereof is omitted.

  The bit rate is input from the outside to the code amount control means 115b and the filter control means 117a in FIG.

  The code amount control unit 115b to which the bit rate is input sets the quantization parameter Qp to the quantization unit 105 and the filter control unit 117a in accordance with the bit rate and the code amount output from the variable length encoding unit 107. Output.

  The filter control means 117a outputs filter characteristic control data K to the prefilter 101 based on the bit rate and the quantization parameter Qp. When determining the quantization parameter Qp in the code amount control means 115b, a data table composed of the quantization parameter, the bit rate, and the code amount may be used, or an appropriate function Qp = f (Bit rate, code amount) may be used. The filter control means 117a may determine the filter characteristic control data K by the same method as the code amount control means 115b.

  The number of the data tables is not necessarily one, and a plurality of the data tables may be provided in the quantization unit 105 or the filter control unit 117a, and the data table may be selected according to the bit rate. For example, when a data table as shown in FIGS. 20A and 20B is provided, if the bit rate is high, a larger quantization parameter or filter characteristic control data K is determined according to the data table of FIG. On the other hand, when the bit rate is low, a smaller quantization parameter or filter characteristic control data K can be output by the data table as shown in (b).

  Further, at least one of the functions shown in FIGS. 8 to 10 is set in the filter control means 117a, and the quantization parameter Qp or the filter characteristic control data K is calculated by the function, It may be output.

  In the video encoding apparatus in which the filter control unit 117a and the code amount control unit 115b are integrally configured as in the third embodiment and the code amount control unit 115c is used, as shown in FIG. The bit rate may be input to the code amount control means 115c.

  As described above, in the video signal encoding device according to the fourth embodiment, the target bit in the video signal encoding device regardless of the encoding stage of the image data according to the bit rate input from the outside. In addition to controlling the rate, it is possible to control the prefilter so as to adapt to the bit rate. Furthermore, the same effects as those of the first to third embodiments can be obtained.

1 is a block diagram showing a video signal encoding device in Embodiment 1. FIG. It is a figure which shows the macroblock in a flame | frame. 3 is a block diagram showing a configuration of a prefilter in the first embodiment. FIG. It is a figure which shows an example of the characteristic of the low-pass filter 201 in FIG. It is a figure which shows an example of a data table. It is a figure which shows an example of a data table. FIG. 6 is a diagram illustrating an example of prefilter characteristics in the first embodiment. It is a figure which shows an example of the function which determines filter characteristic data. It is a figure which shows an example of the function which determines filter characteristic data. It is a figure which shows an example of the function which determines filter characteristic data. 6 is a diagram showing a configuration of a prefilter in Embodiment 2. FIG. 6 is a diagram illustrating a configuration of a noise reduction filter according to Embodiment 2. FIG. It is a figure which shows an example of the data table comprised from threshold value Th. 10 is an example of characteristics of scaling means in the second embodiment. 10 is an example of characteristics of scaling means in the second embodiment. 10 is an example of characteristics of scaling means in the second embodiment. 10 is a diagram illustrating an example of an image corresponding to image data output from a noise reduction filter according to Embodiment 2. FIG. FIG. 10 is a block diagram illustrating a video signal encoding device according to Embodiment 3. FIG. 10 is a block diagram showing a video signal encoding apparatus in a fourth embodiment. It is a figure which shows an example of a data table. FIG. 10 is a block diagram showing a case where the video signal encoding device is simplified in the fourth embodiment.

Explanation of symbols

  101 pre-filter, 102 frame memory, 116 encoding means, 201 low-pass filter, 302 low-pass filter, 301 noise reduction filter, 115 code amount control means, 115a code amount control means, 115b code amount control means, 115c code amount control means, 117 Filter control means, 117a Filter control means, 117b Filter control means.

Claims (9)

Based on the filter characteristic control data, a pre-filter that outputs a predetermined frequency component in the input video signal as current image data,
Encoding means for encoding the current image data;
Filter control means for outputting the filter characteristic control data set based on the encoding parameter output by the encoding means,
The pre-filter is
A low-pass filter that outputs a low-frequency component in the input video signal;
A first gain controller that corrects the low frequency component and outputs a corrected low frequency component based on the filter characteristic control data;
A second gain controller that corrects the input video signal and outputs a corrected video signal based on the filter characteristic control data;
The video signal encoding apparatus, wherein the prefilter outputs a predetermined frequency component in the input video signal based on the corrected low frequency component or the corrected video signal. The first gain controller attenuates the low frequency component based on the filter characteristic control data, and outputs the attenuated low frequency component as a corrected low frequency component,
2. The video signal according to claim 1, wherein the second gain controller attenuates the input video signal based on the filter characteristic control data and outputs the attenuated input video signal as a corrected video signal. Encoding device. When the filter characteristic control data value is K (0 ≦ K ≦ 1),
The video signal encoding apparatus according to claim 1 or 2, wherein the gain of the first gain controller is K, and the gain of the second gain controller is 1-K. 4. The video signal encoding apparatus according to claim 1, wherein the pre-filter adds and outputs the corrected low-frequency component and the corrected video signal. 5. With a noise reduction filter that outputs a noise-suppressed video signal that suppresses noise components in the input video signal,
5. The video signal encoding apparatus according to claim 1, wherein the pre-filter outputs a predetermined frequency component in the noise-suppressed video signal. 6. The noise reduction filter compares the difference data between the current image data and the previous image data of one frame before the current image data with a threshold value corresponding to an encoding parameter, and the difference data is the threshold value. 6. The video signal encoding apparatus according to claim 5, wherein the current image data is corrected when the value is smaller than the value. A frequency component output step of outputting a predetermined frequency component in the input video signal as current image data based on the filter characteristic control data;
An encoding parameter output step of performing encoding processing of the current image data, outputting a bit stream corresponding to the current image data generated by the encoding processing, and outputting an encoding parameter;
A control data output step for outputting the filter characteristic control data set based on the encoding parameter,
The frequency component output step includes
A low frequency component output step of outputting a low frequency component in the input video signal;
A first frequency component correction step of correcting the low frequency component and outputting a corrected low frequency component based on the filter characteristic control data;
A second frequency component correction step of correcting the input video signal and outputting a corrected video signal based on the filter characteristic control data,
The video signal encoding method, wherein the frequency component output step outputs a predetermined frequency component in the input video signal based on the corrected low frequency component or the corrected video signal. A portable terminal device comprising the video signal encoding device according to any one of claims 1 to 6. A frequency component output step for outputting a predetermined frequency component in the input video signal as current image data based on the filter characteristic control data;
An encoding parameter output step for performing encoding processing of the current image data, outputting a bit stream corresponding to the current image data generated by the encoding processing, and outputting an encoding parameter;
A control data output step for outputting the filter characteristic control data set based on the encoding parameter,
The frequency component output step includes
A low frequency component output step for outputting a low frequency component in the input video signal;
A first frequency component correcting step for correcting the low frequency component and outputting a corrected low frequency component based on the filter characteristic control data;
A second frequency component correction step for correcting the input video signal and outputting a corrected video signal based on the filter characteristic control data;
The video signal encoding program characterized in that the frequency component output step outputs a predetermined frequency component in the input video signal based on the corrected low frequency component or the corrected video signal.

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