JP2006060358A - Digital broadcast receiver - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a digital broadcast receiver capable of performing an appropriate MPEG noise reduction processing without lowering the picture quality that video originally has. <P>SOLUTION: The broadcast receiver is provided with: a front end which receives a broadcast signal and performs tuning and demodulation; a decoder which extracts a desired video stream and a desired audio stream outputted from the front end; a video decoder which decodes the extracted video stream and outputs a video signal; an MPEG noise reducing filter which has a plurality of characteristics switched; and a means of holding characteristic information of the filter, thereby switching the filter characteristics according to a broadcasting system, a broadcasting station, program contents, the size of video, etc., to reduce noise of the video signal. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a digital broadcast receiver and noise removal technology.

  Conventionally, a digital broadcast receiver is generally configured as shown in FIG. FIG. 9 is a block diagram showing a configuration of a digital broadcast reception set top box (STB), which is an example of a standard digital broadcast receiver.

  A conventional digital broadcast receiver will be described below with reference to FIG. Reference numeral 10 denotes an antenna, 20 denotes a front end for tuning and demodulation, 30 denotes a transport decoder, 40 denotes a video decoder, 50 denotes an audio decoder, 60 denotes a video output unit, and 70 denotes an audio output unit.

The operation of the conventional digital broadcast receiver of FIG. 9 configured as described above will be described below. A broadcast signal received by the antenna 10 is input to the front end 20. The front end 20 tunes to the target broadcast frequency and performs demodulation using a demodulation method corresponding to the broadcast method. The data output from the front end 20 is normally in the MPEG2-TS format and is input to the transport decoder 30. The transport decoder 30 extracts the video and audio streams of the target program from the MPEG-TS and outputs them. The video stream output from the transport decoder 30 is input to the video decoder 40 and decoded as video data.
The decoded video data is input to the video output unit 60, converted into an analog or digital video signal, and output. Similarly, the audio stream output from the transport decoder 30 is input to the audio decoder 50 and decoded as audio data. The decoded audio data is input to the audio output unit 70, converted into an analog or digital audio signal and output.

Digital broadcast images are usually broadcast after being compressed using the inter-frame and intra-frame correlation by the MPEG method. In the case of the MPEG2 standard, discrete cosine transform (DCT) is performed in a unit called a block of 8 horizontal pixels and 8 vertical pixels in a frame, and then data of high frequency components is removed and then variable length coding (VLE) is performed. Compressed by In the case of luminance between frames, a motion compensation type compression method is adopted in which a difference between frames is compressed using a motion vector in units of 16 macro blocks and 16 vertical pixels, that is, a macro block of 4 blocks.
When the compression ratio is increased, block noise that makes the block boundary look like a mosaic due to compression in units of blocks or macroblocks, and high frequency components are cut after DCT As a result, mosquito noise becomes conspicuous around the portion where the signal level has changed greatly.
For these noises, an MPEG noise reduction filter that filters according to the degree of change in luminance or color difference signal level at the boundary of the block or filters the periphery of the detected contour is used. There is a way. A configuration example of a digital broadcast receiving set top box (STB) using this is shown in FIG. The difference from FIG. 9 is that an MPEG noise reduction filter 100 is added, and the video data output from the video decoder 40 is input to the MPEG noise reduction filter 100 to perform block noise and mosquito noise reduction processing. Then, it is input to the video output unit 50.
JP 2002-232890 A

  However, since the block noise and mosquito noise reduction filter is a low-pass filter that removes unnecessary high-frequency noise components in principle, in the digital broadcast receiver of FIG. There is a problem in that the sharpness of the original video is lost because the video is also processed for video that does not require much MPEG noise reduction processing.

  Therefore, an object of the present invention is to provide a digital broadcast receiver capable of performing appropriate MPEG noise reduction processing without degrading image quality on various types of digital broadcast images. is there.

The present invention is a broadcast receiver for receiving a broadcast signal composed of a compressed stream,
From a front end that receives a broadcast signal, performs tuning and demodulation, a decoder that extracts a desired video stream and audio stream output from the front end, a video decoder that decodes the extracted video stream, and a video decoder Based on the filter characteristic information, the noise reduction filter for reducing the noise of the output video signal, the filter characteristic holding means for holding the filter characteristic information of the noise reduction filter corresponding to the video signal, and the noise removal effect of the noise reduction filter A broadcast receiver comprising control means for setting.

  Accordingly, it is possible to perform appropriate noise removal processing on various types of digital broadcast images.

  The present invention further includes an input means for selecting a desired video stream, and changes the noise removal effect setting of the noise reduction filter to filter characteristic information corresponding to the desired video stream based on the input of the input means. And a broadcast receiver characterized by comprising control means.

  As a result, it is possible to set an appropriate noise removal effect only by selecting a desired video stream by the input means, and when the image is decoded by the decoding unit or the like, the transfer rate and motion The configuration for detecting the quantity is unnecessary.

  Furthermore, the present invention further comprises a communication port for communicating with the filter characteristic information server via the network, and the filter characteristic information holding means holds the filter characteristic information acquired from the external server device via the communication port. Is a broadcast receiver characterized by

  This makes it possible to obtain corresponding filter characteristic information from an external server device even for a new type of digital broadcast video having filter characteristic information not held in the filter characteristic holding means. Therefore, it is possible to perform a noise removal process.

  ADVANTAGE OF THE INVENTION According to this invention, the characteristic of a noise removal filter can be switched, the digital broadcast receiver which can perform an appropriate noise removal easily, without deteriorating the image quality of the image | video to receive can be provided.

  Hereinafter, as an example of a digital broadcast receiver according to the present invention, a digital broadcast reception set top box (STB) and its MPEG noise reduction method will be described.

  A first embodiment of the digital broadcast receiver and MPEG noise reduction method of the present invention will be described with reference to FIG. In FIG. 1, 10 is an antenna, 20 is a front end for tuning and demodulation, 30 is a transport decoder, 40 is a video decoder, 50 is a video output unit, 60 is an audio decoder, 70 is an audio output unit, and 101 is MPEG noise. With the reduction filter, it is possible to set at least two types of parameters such as detection sensitivity such as block noise and mosquito noise, filter strength, cutoff frequency, and the like. Reference numeral 110 denotes at least two types of filter characteristic information for determining the operation characteristics of the MPEG noise reduction filter, 120 denotes filter characteristic holding means for holding the filter characteristic information 110, and 130 denotes control means.

  The operation of the digital broadcast receiver of FIG. 1 configured as described above will be described below.

A broadcast signal received by the antenna 10 is input to the front end 20. The front end 20 tunes to the target broadcast frequency and performs demodulation using a demodulation method corresponding to the broadcast method. The data output from the front end 20 is normally in the MPEG2-TS format and is input to the transport decoder 30. The transport decoder 30 extracts the video and audio streams of the target program from the MPEG-TS and outputs them. The video stream output from the transport decoder 30 is input to the video decoder 40 and decoded as video data.
The decoded video data is input to the MPEG noise reduction filter 101, subjected to reduction processing such as block noise and mosquito noise, and then input to the video output unit 50, converted into an analog or digital video signal and output. Is done. Similarly, the audio stream output from the transport decoder 30 is input to the audio decoder 50 and decoded as audio data. The decoded audio data is input to the audio output unit 70, converted into an analog or digital audio signal and output.

  At this time, the control unit 130 sets the MPEG noise removal filter 101 based on the filter characteristic information 110 stored in the filter characteristic information holding unit 120. In the present invention, it has been found that the following method is appropriate for the rule for setting the filter characteristic information 110 in the MPEG noise removal filter 101.

  The first is a method of switching the filter characteristics depending on the broadcast system to be received. For example, for multi-channel broadcasting, the bit rate per channel is low and contains a lot of noise. For CS digital broadcasting, noise is actively removed, and for BS digital broadcasting with high bit rate and high image quality. It is conceivable to set so as not to perform much noise removal. In this way, by changing the filter characteristic information for each broadcasting system, it becomes possible to change the noise removal effect of an appropriate noise reduction filter for each broadcasting system, and for a broadcasting system that does not require noise reduction. As a result, it is possible to prevent image quality deterioration due to noise reduction processing.

  The second is a method of switching the filter characteristics depending on the receiving broadcast station. Since the amount of generated noise differs depending on the MPEG encoding processing equipment used in each broadcasting station, it is conceivable to strongly remove noise from a broadcasting station that generates a lot of noise. Thus, by changing the filter characteristic information for each broadcasting station, it is possible to change the noise removal effect of the appropriate noise reduction filter for each broadcasting station, and for broadcasting stations that do not require noise reduction. As a result, it is possible to prevent image quality deterioration due to noise reduction processing.

  The third is a method of switching filter characteristics depending on the type of broadcast program. In digital broadcasting, in addition to video and audio streams, program information used in an electronic program guide (EPG) or the like is transmitted as SI, so that program genre information can be obtained. By using this, it is conceivable to perform strong noise removal in a sports program where movement is intense and noise is likely to occur. Thus, by changing the filter characteristic information for each program, it is possible to change the noise removal effect of an appropriate noise reduction filter for each program, and for programs that do not require noise reduction, It becomes possible to prevent deterioration in image quality due to noise reduction processing.

  The fourth is a method of switching the filter characteristics depending on the size of the video. For example, in BS digital broadcasting, there are cases where broadcasting is switched between HD broadcasting of 1 channel or SD broadcasting of 3 channels depending on the time zone, but when HD 1080i and SD 480i are compared, the difference in resolution is about 6 : 1, the bit rate per resolution is higher for 480i and noise is less likely to occur. The video size information is contained in a sequence header in the video stream, and it is considered that noise removal is performed in accordance with this information. Thus, by changing the filter characteristic information for each video size, it is possible to change the noise removal effect of the appropriate noise reduction filter for each video size, and noise reduction is unnecessary. With respect to a video signal having a video size, it is possible to prevent image quality deterioration due to noise reduction processing. In addition to HD broadcasting or SD broadcasting, a configuration may be used in which discrimination is made by LDTV (Low Definition Television, for portable terminals).

  The fifth is a method of switching the filter characteristics depending on the frame rate. For example, in BS digital broadcasting, even when the same SD broadcasting is used, when comparing 480i and 480p, the frame frequency of 480i is 59.94 [Hz], and the frame frequency of 480p is 29.97 [ Hz], the frame rate of 480p is twice that of 480i, and noise is likely to occur. Using this, it is conceivable that noise removal is performed more positively for 480p than for 480i. As described above, the necessary noise removal effect differs depending on the frame rate depending on the frame rate. Therefore, by changing the filter characteristic information for each frame rate, the noise removal effect of the appropriate noise reduction filter can be changed for each frame rate. In addition, it becomes possible to prevent deterioration in image quality due to noise reduction processing for frame rate data that does not require noise removal.

  According to the present embodiment, MPEG noise removal can be performed without degrading the image quality of the received video by switching the characteristics of the MPEG noise removal filter by the method as described above. It is also possible to use a combination of these methods. For example, a more accurate noise reduction effect of the noise reduction filter can be set by combining broadcast station and program information.

  Next, noise removal processing when a desired program is selected will be described with reference to FIG. 2 to FIG. 6 as an example of changing the filter characteristics depending on the type of program, which is the third control method. To do. FIG. 2 is a flowchart for explaining the processing of the broadcast receiver when a desired program is input by the user via the input means. In S101, the user receives a selection signal for a desired program via the input means. Next, the program selected from S102 to S105 is identified. If the program cannot be identified through S102 to S105, the process is terminated. On the other hand, when the desired program selected through the input means is recognized through the processing from S102 to S105, the filter characteristic information corresponding to the program is acquired in S106. This filter characteristic information will be described later with reference to FIG. Next, after obtaining filter characteristic information corresponding to the program in S106, the noise removal processing is set by setting the noise removal effect of the noise removal unit in S107.

  Next, filter characteristic information will be described with reference to FIG. As shown in FIG. 3, the filter characteristic information holding means 120 in FIG. 1 holds filter characteristic information 110 regarding the transfer rate and motion amount corresponding to the program. For example, in the case of program A, the transfer rate is 13 Mbps, the amount of motion is identified, for example, in five stages, and in the case of program A, it is 2. Similarly, in the case of program B, the transfer rate is 9 Mbps and the amount of motion is 4, in the case of program C, the transfer rate is 21 Mbps, the amount of motion is 1, and in the case of program D The transfer rate is 15 Mbps, and the amount of motion is 2. In the five stages indicating the amount of movement, the largest amount of movement is set to 5, and the smallest amount of movement is set to 1.

  Next, FIG. 4 shows the relationship between the noise removal effect calculated based on the filter characteristic information in FIG. 3, the transfer rate, and the motion amount. In FIG. 4, the vertical axis represents the noise removal effect of the video data by the noise removal unit, and the horizontal axis represents the transfer rate of the video signal transferred to the noise removal unit. Further, in FIG. 4, the noise removal effect is changed in consideration of the influence of the motion amount of the video signal. For example, in the case of the program A, since the transfer rate is 13 Mbps and the amount of motion is 2, the noise removal effect falls within the “weak” region. Similarly, when the program selected by the user is program B, since the transfer rate is 9 Mbps and the amount of motion is 4, the noise removal effect is in the “strong” region. Furthermore, when the program selected by the user is program C, the transfer rate is 21 Mbps and the amount of motion is 1, so the noise removal effect corresponds to the “OFF” region. Furthermore, when the program selected by the user is program D, the transfer rate is 15 Mbps and the amount of motion is 2, so the noise removal effect corresponds to the “medium” region.

  Next, with reference to FIG. 5, the setting of the noise removal effect in the noise reduction filter 101 based on the noise removal effect derived from the filter characteristic information 110 held in the filter characteristic information holding unit 120 described above will be described. As shown in FIG. 5, the noise removal effect can be classified into four types of “OFF”, “weak”, “medium”, and “strong” based on the relationship between the transfer rate and the amount of motion described above. Here, in FIG. 5, when “OFF (no noise reduction processing is performed by the noise reduction filter)”, a signal “00” is output to the noise reduction filter. Similarly, in the case of “weak” (weak noise reduction processing is performed by the noise reduction filter), a signal “01” is output to the noise reduction filter. Further, in the case of “medium (medium noise reduction processing by the noise reduction filter is performed)”, a signal “10” is output to the noise reduction filter. Further, in the case of “strong” (intensity noise reduction processing is performed by the noise reduction filter), a signal “11” is output to the noise reduction filter.

  Next, the operation of the noise reduction filter 101 that receives the above-described signal from the control signal will be described with reference to FIG. First, the noise reduction filter 101 outputs a signal indicating the degree of the noise removal effect output from the control unit 130 in S201. Next, in S202 to S205, it is detected whether the signal indicating the degree of the noise removal effect is 00, 01, 10, or 11.

  Furthermore, when the signal indicating the noise removal effect is 00 in S202, the noise reduction filter 101 cancels the noise reduction filter 101, and thereby the video signal is displayed without performing noise removal in the noise reduction filter. The data is output to the output processing unit 50. As a result, the video signal is output to the video output processing unit 50 without causing deterioration in image quality due to noise removal when the compression rate is low or the video signal has a small amount of motion (S206).

  On the other hand, when it is detected in S203 that the signal indicating the degree of the noise removal effect is 01, the noise removal effect in the noise reduction filter 101 is set to be weak, thereby reducing the weakness with respect to the video signal. The noise is removed (S207). Similarly, if the signal indicating the noise removal effect is 10 in S204, the noise reduction effect in the noise reduction filter 101 is set to a medium noise removal effect, so that the image signal is moderate. The noise is removed (S208). Further, in S205, when it is detected that the signal indicating the degree of the noise removal effect is 11, the noise removal effect in the noise reduction filter in the noise reduction filter 101 is set to the strength, so that the video signal is processed. Intensity noise removal is performed (S209).

  As described above, by storing the filter characteristic information 110 relating to the bit rate and the motion amount for each program in the filter characteristic information holding unit 120, noise removal can be performed with an appropriate noise removal effect corresponding to each program. Further, when the compression rate is low or the video signal has a small amount of motion, it is possible to prevent image quality deterioration due to noise removal.

  Furthermore, in the present invention, as shown in FIG. 7, it is possible to select the filter characteristic information 110 based on the information input by the input means 135. Specifically, for example, when the user selects the program B by the input means 135, the selection signal is input from the input signal to the digital broadcast receiver. Next, the control means 130 of the digital broadcast receiver extracts the program B information of the filter characteristic information 110 in the filter characteristic information holding means 120. Next, based on the filter characteristic information of FIG. 3, as shown in FIG. 4, it is calculated that a strong noise removal effect is necessary for the program B. Next, the control means 130 outputs eleven signals to the noise removal filter 101 as shown in FIG. Furthermore, the control means 130 sets the noise removal effect of the noise removal filter 101 to strength as shown in FIG. Thereby, it is possible to set the noise removal effect of the noise removal filter 101 to the intensity for the video signal of the program B.

  With such a configuration, it is possible to change the noise removal effect of the noise reduction filter 101 based only on information input from the user via the input means, and a configuration for detecting information related to the transfer rate or motion amount is provided. There is no need, and the configuration of the digital broadcast receiver can be simplified. Furthermore, in the present invention, the noise removal effect of the noise reduction filter can be set based on the selection signal input by the input unit 135, and it is not necessary to detect information such as the transfer rate from the received stream. Therefore, even when a stream to be broadcast is not received, the noise removal effect of the noise reduction filter can be set independently, and the stream processing time can be shortened.

  Next, a second invention will be described with reference to FIG. The second embodiment will explain a method for acquiring the filter characteristic information described above.

  A second embodiment of the digital broadcast receiver and MPEG noise reduction method of the present invention will be described with reference to FIG. 8, 10 is an antenna, 20 is a front end for tuning and demodulation, 30 is a transport decoder, 40 is a video decoder, 50 is an audio decoder, 60 is a video output unit, 70 is an audio output unit, and 101 is MPEG noise. 110, 111 are at least two types of filter characteristic information for determining the operation characteristics of the MPEG noise reduction filter, 121 is a filter characteristic holding means for holding the filter characteristic information 110, 131 is a control means, 140 is a communication port, Reference numeral 200 denotes a network, and 210 denotes a filter characteristic information server.

  The operation of the digital broadcast receiver of FIG. 8 configured as described above will be described below. Since only a part of the operation is different from the first embodiment, the description of the same operation is omitted.

The filter characteristic information server 210 stores the latest filter characteristic information 111. The control unit 131 instructs the communication port 140 to download the filter characteristic information 111 from the filter characteristic information server 210 via the network 200 periodically or by user operation. The filter characteristic information 110 in the filter characteristic information holding unit 121 is updated with the acquired filter characteristic information 111.
As a result, the MPEG noise reduction filter 101 adds a parameter for a newly opened broadcast station when the filter characteristic information 110 is provided for each broadcast station, or improves the encoding algorithm on the broadcast station side, etc. It is possible to perform optimum MPEG noise reduction processing while responding to changes in the environment, such as taking measures to reduce the strength of the MPEG noise reduction filter 101 when occurrence is suppressed. become.

  Note that the transfer rate and motion amount information of each program can be extracted from information included in the broadcast signal, in addition to the method of holding the information in advance in the filter characteristic information holding means. Even in this case, it can be realized only by extracting the transfer rate information from the broadcast signal. For example, it is more than the configuration in which the transfer rate and the amount of motion are detected when the decoding unit decodes the image. This can be realized with a simple configuration.

As described above, according to the present invention, the characteristics of the MPEG noise removal filter can be switched to perform MPEG noise removal without degrading the image quality of the received video, and the digital broadcast receiver and the digital broadcast reception function are provided. It can also be applied to recording equipment.

1 is a block diagram showing the configuration of a digital broadcast receiver according to a first embodiment. Flowchart of processing of the digital broadcast receiver according to the first embodiment The figure which shows the filter characteristic information of each program concerning 1st Embodiment The figure which shows the relationship between the transfer rate concerning 1st Embodiment, the amount of motion, and the noise removal effect The figure which shows the setting of the noise removal effect concerning 1st Embodiment The flowchart which shows the setting method of the noise removal effect concerning 1st Embodiment. 1 is a block diagram of a digital broadcast receiver according to a first embodiment. Block diagram of a digital broadcast receiver according to the second embodiment Block diagram showing the configuration of a conventional digital broadcast receiver Block diagram showing the configuration of a conventional digital broadcast receiver

Explanation of symbols

10 antenna 20 front end 30 transport decoder 40 video decoder 50 video output unit 60 audio decoder 70 audio output unit 100, 101 MPEG noise reduction filter 110, 111 filter characteristic information 120, 121 filter characteristic information holding unit 130, 131 control unit 135 Input means 140 Communication port 200 Network network 210 Filter characteristic information server

Claims (10)

A broadcast receiver for receiving a broadcast signal composed of a compressed stream,
A front end for receiving the broadcast signal and performing tuning and demodulation;
A decoder for extracting a desired video stream and audio stream output from the front end;
A video decoder that decodes the extracted video stream and outputs a video signal;
A noise reduction filter for reducing noise of the video signal;
Filter characteristic holding means for holding filter characteristic information of the noise reduction filter corresponding to the video signal;
A broadcast receiver comprising: control means for setting a noise removal effect of the noise reduction filter based on the filter characteristic information. A broadcast receiver for receiving a broadcast signal composed of a compressed stream,
A front end for receiving the broadcast signal and performing tuning and demodulation;
A decoder for extracting a desired video stream and audio stream output from the front end;
A video decoder that decodes the extracted video stream and outputs a video signal;
A noise reduction filter for reducing noise of the video signal;
Input means for inputting a selection signal for selecting the desired video stream;
And a control means for setting a noise removal effect of the noise filter based on the selection signal. The broadcast receiver further includes filter characteristic holding means for holding filter characteristic information of the noise reduction filter corresponding to the video signal,
Filter characteristic information in which the filter characteristic information corresponding to the desired video stream held in the filter characteristic holding unit is detected based on the input selection signal and the setting of the noise removal effect of the noise reduction filter is detected The broadcast receiver according to claim 2, wherein the broadcast receiver is changed based on The filter characteristic information indicates a noise removal effect that varies depending on a broadcast system of the broadcast signal, and the control means removes noise from the noise reduction filter corresponding to the broadcast system of the broadcast signal based on the filter characteristic information. 4. The broadcast receiver according to claim 1, wherein an effect is set. The filter characteristic information indicates a noise removal effect that varies depending on the broadcast station of the broadcast signal, and the control means removes noise from the noise reduction filter corresponding to the broadcast station of the broadcast signal based on the filter characteristic information. The broadcast receiver according to claim 1, wherein an effect is set. The filter characteristic information indicates a noise removal effect that varies depending on the program of the broadcast signal, and the control means performs the noise removal effect of the noise reduction filter corresponding to the program of the broadcast signal based on the filter characteristic information. 6. The broadcast receiver according to claim 1, wherein the broadcast receiver is set. The filter characteristic information indicates a noise removal effect that varies depending on the size of the video broadcast by the broadcast signal, and the control means determines the size of the video broadcast by the broadcast signal based on the filter characteristic information. The broadcast receiver according to claim 1, wherein a noise removal effect of the noise reduction filter corresponding to the height is set. The filter characteristic information indicates a noise removal effect that varies depending on a frame rate of the broadcast signal, and the control means removes noise of the noise reduction filter corresponding to the frame rate of the broadcast signal based on the filter characteristic information. The broadcast receiver according to claim 1, wherein an effect is set. 9. The broadcast receiver according to claim 1, wherein the noise reduction filter reduces noise caused by MPEG compression. 10. The broadcast receiver according to claim 1, further comprising a communication port for communicating with a filter characteristic information server via a network, wherein the filter characteristic information holding means is acquired from the external server device via the communication port. A broadcast receiver characterized by retaining filter characteristic information.

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