JP2006339872A - Digital broadcast receiver - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a digital broadcast receiver capable of preventing a user from being uncomfortable due to video display with low image quality as much as possible and reducing the power consumption. <P>SOLUTION: A CPU 11 discriminates whether or not a picture that can be acquired is a normal picture (step S1). When the acquired picture is the normal picture, ordinary decode processing is executed (step S2). On the other hand, when the acquired picture is not the normal picture, the CPU 11 discriminates whether or not an estimated discomfort value is within a prescribed threshold value (step S3), and when no operation for stopping the decode by a user is executed within the threshold value (NO in step S4), temporary decoding is executed (step S2). When the estimated discomfort value exceeds the prescribed threshold value (NO in step S3), decoding is temporarily stopped (step S6). <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a digital broadcast receiving apparatus that receives a digital broadcast.

In a digital broadcasting system that employs MPEG or the like for compressing and encoding video data, for example, the period until the reception state recovers when it is determined that the reception state deteriorates is acquired in the past as shown in FIG. There is a technique for performing provisional decoding using the stored decoded data (see Patent Document 1 and Patent Document 2).
JP-A-10-336684 JP 2004-112654 A

  However, in such a conventional technique, although the display of the received video is continued, the quality of the displayed video may be very low, and if a new I picture cannot be obtained, a video that cannot be viewed is displayed to the user. May cause discomfort. The decoder is operating for such low-quality video display.

  In view of the above circumstances, the present invention provides a digital broadcast receiving apparatus that can prevent a user from feeling uncomfortable due to low-quality video display and can reduce power consumption as much as possible. Objective.

  In order to solve the above problems, the digital broadcast receiving apparatus of the present invention generates an independent frame and an accompanying frame by demodulating the received digital broadcast wave, and decodes these frames to generate video data. In the apparatus, even if a proper frame cannot be obtained, the provisional decoding is continued. On the other hand, when the estimated unpleasant value based on the lapse of time since the provisional decoding has started becomes a predetermined value, the decoding is temporarily stopped. It is characterized by being configured to stop automatically.

  With the above configuration, since the decoding is stopped when the estimated unpleasant value becomes a predetermined value, it is possible to prevent the user from feeling unpleasant due to low-quality video display and to consume power. Can be reduced.

  In the digital broadcast receiving apparatus having the above-described configuration, the elapsed time may be determined by subtracting the acquisition time of the independent frame acquired last time from the current time. Alternatively, the elapsed time may be determined by subtracting the acquisition time of the associated frame acquired last time from the current time.

  In the digital broadcast receiving apparatus having these configurations, the decoding that has been temporarily stopped is resumed when it is determined that broadcast reception is possible based on information provided from a tuner that receives the digital broadcast. It may be.

  In the digital broadcast receiving apparatus configured as described above, the estimated unpleasant value may be obtained by a curve equation that indicates a higher value as time elapses after the provisional decoding is started.

  The digital broadcast receiving apparatus having these configurations may be configured as a portable type or a mobile type that receives terrestrial digital broadcasts.

  According to the present invention, it is possible to prevent the user from feeling uncomfortable due to low-quality video display as much as possible, and to reduce the power consumption.

  A digital broadcast receiver according to an embodiment of the present invention will be described below with reference to FIGS.

  The tuner 1 extracts a signal having a specific frequency from the received high frequency digital modulation signal. Further, the tuner 1 includes a demodulation circuit, a deinterleave circuit, an error correction circuit, and the like, thereby demodulating the selected digital modulation signal and outputting a transport stream.

  The demultiplexer (DEMUX) 2 separates the transport stream received from the tuner 1 into a stream such as a video stream or an audio stream and section data.

  The audio decoder 3 decodes the encoded signal output from the demultiplexer 2, further performs D / A conversion to generate an audio signal, and supplies the audio signal to an audio output unit (speaker or the like) (not shown). The video decoder 4 decodes an input encoded signal to obtain a quantization coefficient and a motion vector, performs inverse DCT conversion, motion compensation control based on the motion vector, and the like to generate video data, and the video data is framed. Supply to buffer 5. The frame buffer 5 holds the latest one frame of video data. The drawing processing unit 6 reads the video data from the frame buffer 5 and adjusts the size and resolution of the image, and synthesizes the OSD (on-screen display) video and the received video. The video is displayed on a monitor (for example, a liquid crystal display panel) (not shown) by the video signal output from the drawing processing unit 6.

  An operation button or the like (not shown) is connected to the I / O circuit 7. The communication I / F 12 is connected to a telephone function unit (a mobile phone function unit if configured as a mobile device) or a LAN function unit (a wireless LAN function unit if configured as a mobile device). . The ROM 9 stores an operation program for the CPU 11 and the like.

  Further, for example, video data for decoding when reception is impossible is stored in the RAM 10 (for example, the latest video data for one frame is stored). When the reception is impossible, the CPU 11 reads the video data stored in the RAM 10 and supplies it to the video decoder 4 as an IDR frame (described later).

  By the way, in terrestrial digital broadcasting, as described above, a broadcast signal is composed of a transport stream (Transport Stream) made up of fixed-length data called a transport stream packet (Transport Stream Packet). Each TS packet is assigned a PID based on data such as video data and audio data, and the demultiplexer 2 separates the data based on the PID.

  In terrestrial digital broadcasting for mobile phones, IEEE H.264 is used as a video encoding system. H.264 is adopted. H. H.264 includes an IDR frame (independent frame) and a non_IDR frame (accompanying frame). It is guaranteed that decoding can be performed normally when decoding from the IDR frame, and it is necessary to reliably decode the IDR frame. become.

  Here, when the received radio wave condition has deteriorated, if a new IDR frame cannot be acquired, as described in the conventional section, a video that cannot be viewed may be displayed. The gist of the present invention is that when the received radio wave condition deteriorates (when a normal picture cannot be acquired), the technique described in the conventional section, that is, a process for presenting a good video as much as possible (provisional decoding) On the other hand, the estimated unpleasant value (discomfort caused by continuing to watch low-quality video) that the user would feel after starting this provisional decoding, and this estimated unpleasant value became a predetermined value Sometimes, as shown in FIG. 3, the decoding is stopped.

  A process for preventing the user from becoming uncomfortable due to the provisional decoding will be described below with reference to the flowchart of FIG. The CPU 11 determines whether or not the acquired picture is a normal picture (step S1). Such a determination can be made based on information on error correction from the tuner 1, information notified from the video decoder 4, and the like. If it is a normal picture, a normal decoding process is executed (step S2). On the other hand, if it is not a normal picture, the CPU 11 determines whether or not the estimated discomfort value is within a predetermined threshold (step S3), and if it is within the threshold and there is no decoding stop operation by the user (NO in step S4). Then, provisional decoding is executed (step S2). When the decoding stop operation is performed, the decoding is stopped (step S5).

  If the estimated discomfort value exceeds a predetermined threshold (NO in step S3), decoding is temporarily stopped (step S6). For example, if there is a decoding start / stop control port in the LSI that constitutes the decoders 3 and 4, the decoding is temporarily stopped by applying (or not applying) a predetermined voltage to the port. The The video output to the monitor is stopped by the decoding pause. When the CPU 11 temporarily stops decoding, the CPU 11 determines the recovery of the broadcast wave receivable state based on information on the electric field strength, C / N ratio, error correction, etc. of the received radio wave from the tuner 1 (step S7). . Then, the decoding is temporarily stopped until the broadcast wave can be received. When the broadcast wave can be received, a picture is acquired from the demultiplexer 2 and the decoding is resumed (steps S1 and S2).

  Next, the estimated unpleasant value will be described. For example, the discomfort function F (t) is defined as follows, the estimated discomfort value is F (T), and the constant k is a threshold value.

F (t) = 50 · (1-cos (θ · t))
However,
0 <θ <π / (2 · t)
T = (current time) − (time when the latest independent frame was acquired)
Decoding pause when F (T)> k

  The unpleasant function F (t) is a curve equation that increases as t increases (as time elapses from the start of provisional decoding). The above θ and k may be changed according to the situation of the apparatus in which the present invention is used. For example, when the digital broadcast receiving apparatus is configured as a portable terminal, it is considered that the spec cannot be expected so much, so θ is set large and k is set small. Since the formula using the above trigonometric function is based on simple four arithmetic operations, the load on the terminal is small. Conversely, when the digital broadcast receiving apparatus is configured as a stationary apparatus, it is considered that specifications can be expected, so θ is set small and k is set large. Note that by determining θ and k based on the specifications, T ′ when F (T)> k is obtained. Therefore, it is possible to determine whether or not the estimated unpleasant value has become a predetermined value simply by determining whether or not the elapsed time T since the start of provisional decoding has exceeded T ′. When θ and k are variable, the digital broadcast receiver needs to have the above formula. Of course, a table may be used instead of a formula.

  In the above example, the time at which the latest independent frame is acquired is used in the calculation of T. However, the present invention is not limited to this. The T may be calculated using the time when the latest accompanying frame is acquired. Further, the unpleasant function is not limited to the formula using the trigonometric function. The discomfort curve may be set using one or more other functions.

  Further, the digital broadcast receiving apparatus is not limited to being configured as a mobile phone with a TV function, but may be configured as a portable or mobile digital broadcast receiving apparatus. Further, it may be a stationary terrestrial digital broadcast receiver.

1 is a block diagram showing a digital broadcast receiver according to an embodiment of the present invention. It is the flowchart which showed the processing content. It is explanatory drawing of a decoding stop. It is explanatory drawing of provisional decoding.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Tuner 2 Demultiplexer 4 Video decoder 6 Drawing process part 10 RAM
11 CPU

Claims (6)

In a digital broadcast receiver that generates independent data and accompanying frames by demodulating received digital broadcast waves and generates video data by decoding these frames, provisional decoding is continued even if an appropriate frame cannot be obtained. On the other hand, when the estimated unpleasant value based on the passage of time since the start of the provisional decoding becomes a predetermined value, the decoding is temporarily stopped. apparatus. 2. The digital broadcast receiving apparatus according to claim 1, wherein the elapsed time is determined by subtracting the acquisition time of the independent frame acquired last time from the current time. 2. The digital broadcast receiving apparatus according to claim 1, wherein the elapsed time is determined by subtracting the acquisition time of the accompanying frame acquired last time from the current time. 4. The digital broadcast receiving apparatus according to claim 1, wherein the digital broadcast receiving apparatus is temporarily stopped when it is determined that broadcast reception is possible based on information provided from a tuner that receives the digital broadcast. A digital broadcast receiving apparatus configured to resume decoding which has been performed. 5. The digital broadcast receiving apparatus according to claim 1, wherein the estimated unpleasant value is obtained by a curve equation that indicates a higher value as time elapses after starting the provisional decoding. A digital broadcast receiver characterized by the above. 6. The digital broadcast receiving apparatus according to claim 1, wherein the digital broadcast receiving apparatus is configured as a portable type or a mobile type that receives terrestrial digital broadcasts.

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