JP2003319278A - Receiver for digital broadcasting - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a receiver for digital broadcasting which does not display an image made significantly different from an original image due to image compensation which is performed when a reception state of digital broadcasting is degraded by some cause. <P>SOLUTION: An input bit monitor circuit 9 detects the input state of each of bits forming data of a video bit stream to which a transport stream outputted from a demodulation circuit 1 has been converted. A discrimination processing circuit 10 connected to the following stage of the input bit monitor circuit 9 discriminates whether the detected input state meets a prescribed state. When its memory volume is smaller than a prescribed certain value, the discrimination processing circuit 10 judges that the reception state is degraded and sends a corresponding video output control signal to a horizontal conversion circuit 8 and further sends a reset signal to each of a buffer memory 3, a video decoder 4, and an external frame memory 5. A compensation means is constituted which performs data compensation based on the discrimination result of the discrimination processing circuit 10 and outputs the result as a video signal when taking out stored data from the buffer memory 3 and the external frame memory 5. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a digital broadcast receiver that receives a digital broadcast transmitted using a wired transmission line or a wireless transmission line and outputs a predetermined video signal.

[0002] Television broadcasting performed by using a wired transmission line formed by a coaxial cable or an optical cable or a wireless transmission line performed by using a satellite wave or a terrestrial wave has hitherto been performed by AM modulation of an analog video signal. In addition, an analog broadcasting program that transmits a signal obtained by FM-modulating an audio signal at a predetermined carrier frequency has been the mainstream, but in recent years, analog video signals and audio signals have been digitized, and data after digital compression has been performed. The digital broadcast to send has started.

Such digital broadcasting is based on semiconductor technology,
This has been made possible by the remarkable progress in image and audio signal compression technology, and it is possible to broadcast more program programs within the frequency band of the same transmission line as compared with the conventional analog broadcasting. It becomes possible, and OFD
Adopting a digital transmission system such as the M system has many advantages such as high-quality broadcasting with little deterioration of transmission signals.

An image decoding circuit block for receiving this digital broadcast and obtaining a predetermined video signal is configured, for example, as shown in FIG. 4, and a transport stream output from the demodulation circuit 1 included in the tuner section. Is input to the demultiplexer 2 to be filtered into a video stream and an audio stream with an arbitrary program identifier (PID), the audio stream is output to an audio processing circuit (not shown), and the video bit stream is , External video bits are temporarily stored in the buffer memory 3.

The data stored in the buffer memory 3 are sequentially read by the video decoder 4 connected to the subsequent stage, and when the image compression / decompression standard is MPEG2, the macroblock of 16 × 16 pixels in the vertical and horizontal directions. Inverse quantization and inverse DCT processing (decoding) is performed with (MB) as one unit, and at the same time, pixel data is decoded through motion compensation (MC) processing.

This pixel data is again written in the external frame memory 5 in units of fields, the line conversion circuit 6 in the subsequent stage performs line conversion for scanning in which a macro block (MB) is one unit, and the vertical conversion circuit 7 in the subsequent stage. And the horizontal conversion circuit 8 performs interpolation processing such as vertical / horizontal up / down sampling processing and outputs the video output signal to an image monitor or a video recording device (not shown).

[0007] Here, when the receiving condition of the digital broadcast deteriorates due to the environment such as the weather, first, MPEG2
The error concealment function defined by the standard works,
Macro block (M
A portion where the data of unit B) is required from the reference image already obtained immediately before or before the current image based on the video output control signal output from the video decoder 4 to the horizontal conversion circuit 8. The data of is copied as it is and inserted.

When the reception state in the state where such compensation is performed is further deteriorated, the function of monitoring the buffer state of the external frame memory 5 on the side of the video decoder 4 operates and the data of the external frame memory 5 is stored. It informs that it is empty and cannot generate a video signal, so that the operation of the video decoder 4 itself is stopped.

[0009]

When decoding a compressed image signal used in a digital broadcast receiver, if the standard is MPEG2, an error concealment is provided in case a code error occurs. It is stipulated to be able to perform image correction by ment, and copy the data of the necessary part from the reference image already obtained at the time immediately before the current image or before that, and insert it,
Although it is possible to perform correction in units of a macro block (MB) formed by 16 pixels in the vertical direction and 16 pixels in the horizontal direction, such correction does not result in a small data bit loss or a code error. It is effective for small-scale, but it is not effective for large-scale occurrence such as frame or field unit, and when this is displayed as it is, macroblock noise is large on the screen. It occurs and an image far from the original image is reproduced.

Further, although the input is also monitored on the side of the video decoder 4, in this case, since the processing is performed when the buffer of the external frame memory 5 becomes empty, the monitor which is the final output is already used. Displays a screen that makes viewers feel uncomfortable.

Further, when the reception condition of the digital broadcast is poor, meaningless data is read from the frame memory and displayed on the screen due to the lack of the number of data which compose one picture. As a result, an image far from the original image is displayed.

On the other hand, when the reception state of the digital broadcast returns from the deteriorated state to the normal state, the image decoding by the video decoder 4 is started (restarted) when the data starts to be stored in the buffer memory 3, but at this time. Since it is too early, an image far from the original image is displayed.

Therefore, an object of the present invention is to provide a digital broadcast in which an image far from the original image is not displayed by the image processing performed when the receiving condition of the digital broadcast deteriorates for some reason. To provide a receiver.

[0014]

In order to solve the above-mentioned problems, the digital broadcast receiver according to the present invention adopts a characteristic structure as described below.

(1) Data of a video bit stream based on a transport stream output from a reception demodulator that receives a digital broadcast is temporarily stored in a buffer memory, the stored data is taken out from the buffer memory, and a video is output by a decoder. In a digital broadcast receiver that decodes and outputs a signal, bit detection means for detecting an input state of each bit forming a video bit stream output from the reception demodulator, and the bit detection means detected by the bit detection means A bit discriminating means for discriminating whether or not the input state satisfies a predetermined state and an image normally received immediately before the current image based on the discrimination result by the bit discriminating means when the stored data is taken out from the buffer memory. Compensation output as a video signal for processing to display or stop displaying images A digital broadcast receiver comprising a stage.

(2) The data of the video bit stream based on the transport stream output from the reception demodulator for receiving digital broadcasting is temporarily stored in the buffer memory, the stored data is taken out from the buffer memory, and the video is decoded by the decoder. In a digital broadcast receiver that decodes and outputs a signal, an error rate detection unit that detects a bit error rate included in the transport stream output from the reception demodulator, and a rate value detected by the error rate detection unit are An error rate discriminating means for discriminating whether or not a predetermined value is satisfied, and when the stored data is taken out from the buffer memory, the image normally received immediately before the current image is displayed based on the discrimination result by the error rate discriminating means. Video signal to be processed or to stop the image display A digital broadcast receiver comprising a compensating means for outputting.

(3) Data of a video bit stream based on a transport stream output from a reception demodulator that receives a digital broadcast is temporarily stored in a buffer memory, the stored data is taken out from the buffer memory, and a video is output by a decoder. In a digital broadcast receiver that decodes and outputs a signal, bit detection means for detecting an input state of each bit forming a video bit stream output from the reception demodulator, and the bit detection means detected by the bit detection means A bit discriminating means for discriminating whether the input state satisfies a predetermined state, a bit discriminating means for discriminating whether the level state detected by the bit detecting means satisfies a predetermined state, and the receiving demodulator Error rate to detect the bit error rate of the output transport stream An output unit, an error rate determination unit that determines whether or not the rate value detected by the error rate detection unit satisfies a predetermined value, and a determination result by the bit determination unit when the stored data is retrieved from the buffer memory. And a compensating means for outputting as a video signal for performing processing of displaying the image normally received immediately before the current image or stopping the image display based on the discrimination result by the error rate discriminating means. Receiver.

(4) A frame memory for storing the decoded decoded image is further provided, and when the judgment result of the bit judging means or the error rate judging means does not return to a predetermined state within a predetermined period, the decoder decodes. The digital broadcast receiver according to any of (1) to (3) above, wherein the processing is stopped and the data accumulated in the frame memory is erased.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below with reference to the drawings. First, a first embodiment will be described with reference to FIGS. 1 and 2. This form is a form in which the present invention is applied to a digital broadcast receiver that receives a digital broadcast transmitted using satellite radio waves. The basic configuration of the present embodiment is configured as shown in FIG. 1, and the input bit monitor circuit 9 and the discrimination processing circuit 1 are added to the configuration of the conventional example shown in FIG.
0 is additionally provided.

That is, in the digital broadcast receiver of this embodiment, the data obtained by converting the transport stream output from the demodulation circuit 1 for receiving the digital broadcast into the video bit stream by the demultiplexer 2 is stored in the buffer memory 3. The buffer memory 3 is temporarily stored, and the stored data is taken out from the buffer memory 3 to generate and output a video signal.

The input bit monitor circuit 9 which is the configuration added in the present embodiment is provided for each bit forming the data of the video bit stream obtained by converting the transport stream output from the demodulation circuit 1 by the demultiplexer 2. A bit detecting means configured to detect an input state.

The discrimination processing circuit 10 connected to the subsequent stage of the input bit monitor circuit 9 is a bit discrimination means,
This is to determine whether or not the input state detected by the input bit monitor circuit 9 satisfies a predetermined state. If the memory amount falls below a certain value, it is determined that the receiving state has deteriorated. The corresponding video output control signal is output to the horizontal conversion circuit 8.

When the reception state at that time does not recover within a certain period, the video decoder 4 is reset and the contents of the frame memory stored so far are cleared.

Further, when the stored data is taken out from the buffer memory formed by the buffer memory 3 and the external frame memory 5, the compensating means for compensating the data based on the discrimination result by the discrimination processing circuit 10 and outputting it as a video signal is constituted. Has been done.

Therefore, the detailed operation of the judgment and processing in the input bit monitor circuit 9 and the judgment processing circuit 10 is as shown in the operation diagram of FIG. 2, when the vertical synchronizing interrupt signal is generated, the data is read from the buffer memory 3 in step S0. Is performed as the video buffer read (VBL), and it is determined in step S1 whether or not the value is below the threshold.

When step S1 is No, it is determined that the normal reception state is established, and the compensation operation is not performed and the process ends (END).
If Yes, it is determined that the reception state has deteriorated, the process proceeds to step S2, and the video buffer counter F
1 is stepped, and at the same time, the process proceeds to step S3, where 3
It is determined whether or not one condition, that is, the condition that the video decoder reset flag is off, is satisfied during the operation of the video decoder 4 and the real-time decoding.

If No in step S3, it is determined that the reception state is normal and the operation is ended (END) without performing the compensation operation. If Yes, the reception state is deteriorated. The determination is made and the process proceeds to step S4.

This step S4 is to judge the degree of deterioration of the reception state, and there are three selection branches from the first state to the third state. The first state is the video buffer empty flag F2 in the buffer memory 3. Is 0, and the second state is that the video buffer empty flag F2 is 1 and the video buffer counter F1 is
Is whether it is equal to the threshold level,
The third state is a determination as to whether it is other than the above (when it is other than the determination of the first state and the second state).

When it is determined that the state is the third state, it is determined that the state is the normal reception state, and the compensation operation is not performed, and the process ends (END).

When it is determined in step S4 that the state is the first state, it is determined that the reception state has deteriorated, and steps S5 to S8 are simultaneously performed, and step S5 is performed.
The count value of the video buffer counter F1 is changed (reset) to 0 in step S6, and the determination processing circuit 1 is set in step S6.
The reset signal output from 0 is output as 1 to the buffer memory 3, the video decoder 4, and the external frame memory 5, the video output is turned off and the video display is turned off in step S7, and the video buffer empty flag F2 is output in step S8. Is set to 1.

On the other hand, when it is determined that the state is the second state, it is determined that the reception state has deteriorated, and steps S9 to S11 are simultaneously performed, and the count value of the video buffer counter F1 is set to 0 in step S9. The reset signal which is changed (reset) and is output from the discrimination processing circuit 10 in step S10 is output to the buffer memory 3, the video decoder 4, and the external frame memory 5 as 1, and the video output is turned off in step S11 to display the video. Is turned off.

Therefore, by detecting the deterioration state of reception and cutting off the transmission of the video output according to the degree of the state, or by displaying the normally received basic reference image immediately before the current image, the viewer It is possible to prevent the display of an unpleasant image, and depending on the degree of the deterioration state, forcibly resetting the video decoder and its related circuits so that they are stored in the buffer memory 3 and the external frame memory 5, respectively. By erasing odd data once and newly performing decoding by the video decoder 4,
It is possible to prevent an unnatural image from being displayed by referring to an image unrelated to the currently received data displayed in the past.

Next, a digital broadcast receiver according to a second embodiment of the present invention will be described with reference to FIG. This form is a form in which the present invention is applied to a digital broadcast receiver that receives a digital broadcast transmitted using satellite radio waves.
The basic configuration of this embodiment is configured as shown in FIG.
An input bit monitor circuit 11 and a discrimination processing circuit 12 are added to the configuration of the conventional example shown in FIG.

That is, in the digital broadcast receiver of this embodiment, the data obtained by converting the transport stream output from the demodulation circuit 1 for receiving the digital broadcast into the video bit stream by the demultiplexer 2 is stored in the buffer memory 3. The buffer memory 3 is temporarily stored, and the stored data is taken out from the buffer memory 3 to generate and output a video signal.

The input bit monitor circuit 11 having the configuration added in the present embodiment is provided for each bit forming the data of the video bit stream obtained by converting the transport stream output from the demodulation circuit 1 by the demultiplexer 2. In addition to having a bit detecting means for detecting an input state, an error rate detecting means for detecting a bit error rate of the transport stream output from the demodulation circuit 1 is included.

The discrimination processing circuit 12 connected to the subsequent stage of the input bit monitor circuit 11 has a bit discrimination means for discriminating whether or not the input state detected by the input bit monitor circuit 11 satisfies a predetermined state. An error rate discriminating means for discriminating whether or not the detected error rate value satisfies a predetermined value.

In the above-mentioned first embodiment, the deterioration of the reception state and its degree are detected and judged from the output of the demultiplexer 2, that is, the signal of the video bit stream input to the buffer memory 3. In the second embodiment, the bit error rate (BER) of the signal of the transport stream in the demodulation circuit 1 provided in the preceding circuit is actually used as one of the criteria for the judgment.

Therefore, the judgment and processing operations of the input bit monitor circuit 11 and the judgment processing circuit 12 are the operations of the first embodiment with the following operations added. That is, when the bit error rate detected by the input bit monitor circuit 11 is lower than the predetermined value, it is determined that the normal reception state is achieved, and the operation is ended without performing the compensation operation.

When the detected bit error rate is higher than the predetermined value and lower than the first upper limit value,
It is determined that the reception state has deteriorated, the count value of the video buffer counter F1 is changed (reset) to 0, and the reset signal output from the determination processing circuit 12 is set to 1 as the buffer memory 3, the video decoder 4, the external frame memory. 5, the video output is turned off, the video display is turned off, and the video buffer empty flag F2 is set to 1.

On the other hand, when it is determined that the detected bit error rate exceeds the predetermined value and exceeds the first upper limit value, it is determined that the reception state is further deteriorated, and the count value of the video buffer counter F1 is increased. The reset signal that is changed (reset) to 0 and output from the discrimination processing circuit 12 is output to the buffer memory 3, the video decoder 4, and the external frame memory 5 as 1, and the video output is turned off and the video display is turned off.

Therefore, the deterioration state of reception is detected in consideration of the detection result of the bit error rate, the transmission of the video output is interrupted according to the degree of the state, or the normal reception is performed immediately before the current image. By displaying the reference image, it is possible to prevent the viewer from seeing an offensive image,
Depending on the degree of deterioration, the video decoder and its related circuits are forcibly reset to erase the halfway data stored in each of the buffer memory 3 and the external frame memory 5, and a new video decoder is newly added. By performing the decoding according to No. 4, it is possible to avoid displaying an unnatural image by referring to an image that was displayed in the past and is not related to the currently received data.

Although the transmission line of the digital broadcast receiver in the above first and second embodiments is a case where the satellite radio wave is the transmission line, the present invention is not limited to this. It may be formed by a terrestrial radio wave such as a VHF band or a UHF band, or a wired transmission line formed by a coaxial cable, an optical cable, or the like.

[0043]

As is apparent from the above description, according to the present invention, a deterioration state of reception is detected, and depending on the degree of the state, transmission of video output is interrupted or immediately before the current image. By displaying the normally received basic reference image, it is possible to prevent the viewer from seeing an offensive image,
Also, depending on the degree of deterioration, by forcibly resetting the video decoder and its related circuits, the halfway data stored in the buffer memory is once erased, and new decoding is performed by the video decoder. It is possible to prevent an unnatural image from being displayed by referring to an image unrelated to the currently received data displayed in the past.

Therefore, it is possible to provide a digital broadcast receiver in which an image far from the original image is not displayed by image compensation performed when the receiving condition of the digital broadcast deteriorates for some reason. You can

[Brief description of drawings]

FIG. 1 is a block circuit diagram showing a schematic circuit configuration of a digital broadcast receiver according to a first embodiment of the present invention.

FIG. 2 is a diagram for explaining the operation of the digital broadcast receiver shown in FIG.

FIG. 3 is a block circuit diagram showing a schematic circuit configuration of a digital broadcast receiver according to a second embodiment of the present invention.

FIG. 4 is a block circuit diagram showing a schematic circuit configuration of a conventional digital broadcast receiver.

[Explanation of symbols]

1 Demodulation circuit 2 Demultiplexer 3 buffer memory 4 video decoder 5 External frame memory 6 line conversion circuit 7 Vertical conversion circuit 8 Horizontal conversion circuit 9, 11 Input bit monitor circuit 10, 12 Discrimination processing circuit

Claims (4)

[Claims] 1. Data of a video bit stream based on a transport stream output from a reception demodulator for receiving digital broadcasting is temporarily stored in a buffer memory, the stored data is taken out from the buffer memory, and a video signal is output by a decoder. In a digital broadcast receiver that decodes and outputs, a bit detection unit that detects an input state of each bit forming a video bit stream output from the reception demodulator; and the input detected by the bit detection unit. A bit discriminating means for discriminating whether or not a state satisfies a predetermined state, and when taking out stored data from the buffer memory,
And a compensating means for outputting as a video signal for performing processing for displaying an image normally received immediately before the current image or stopping the image display based on the discrimination result by the bit discriminating means. Digital broadcast receiver. 2. Data of a video bit stream based on a transport stream output from a reception demodulator for receiving digital broadcasting is temporarily stored in a buffer memory, the stored data is taken out from the buffer memory, and a video signal is output by a decoder. In a digital broadcast receiver that decodes and outputs, the error rate detection unit that detects a bit error rate of the transport stream output from the reception demodulator, and the rate value detected by the error rate detection unit are predetermined. Error rate determining means for determining whether or not a value is satisfied, and when extracting stored data from the buffer memory,
Compensation means for outputting as a video signal for performing processing of displaying the image normally received immediately before the current image or stopping the image display based on the discrimination result by the error rate discrimination means. Digital broadcast receiver to do. 3. Data of a video bit stream based on a transport stream output from a reception demodulator for receiving digital broadcasting is temporarily stored in a buffer memory, the stored data is taken out from the buffer memory, and a video signal is output by a decoder. In a digital broadcast receiver that decodes and outputs, a bit detection unit that detects an input state of each bit forming a video bit stream output from the reception demodulator; and the input detected by the bit detection unit. Bit discriminating means for discriminating whether or not a state satisfies a predetermined state, bit discriminating means for discriminating whether or not the level state detected by the bit detecting means satisfies a predetermined state, and output from the reception demodulator Rate detection for detecting bit error rate of transport stream Means, an error rate determination means for determining whether or not the rate value detected by the error rate detection means satisfies a predetermined value, and when extracting stored data from the buffer memory,
Output as a video signal for performing processing of displaying the image normally received immediately before the current image or stopping the image display based on the determination result by the bit determining means and the determination result by the error rate determining means. A receiver for digital broadcasting, comprising a compensating means. 4. A decoding process of the decoder, further comprising a frame memory for storing a decoded decoded image, when the judgment result of the bit judging means or the error rate judging means does not return to a predetermined state within a predetermined period. 4. The digital broadcast receiver according to claim 1, wherein the receiver is stopped and the data accumulated in the frame memory is erased.