JP2008205553A - Digital broadcast receiving apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a digital broadcast receiving apparatus capable of preventing the generation of display disturbance in an image at the time of automatically switching hierarchies such as 12-segment broadcast and one-segment broadcast. <P>SOLUTION: The digital broadcast receiving apparatus is provided with: a receiving part for receiving a digital broadcast signal transmitted by a plurality of hierarchies having respectively different quality; a hierarchy switching part for judging a receiving state, selecting one suitable hierarchy from the plurality of hierarchies and controlling switching; a decoding part for decoding an image signal of the selected hierarchy; a frame memory for storing the decoded result; a memory control part for controlling reading/writing from/in the frame memory; and an image display part for displaying an image read out from the frame memory. The hierarchy switching part switches hierarchies after completing the decoding of a picture or GOP in the decoding part, and the memory control part stops the updating of the frame memory up to the completion of decoding of the initial picture after hierarchy switching and supplies a final frame before the switching to the image display part. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a digital broadcast receiving apparatus, and more particularly to a technique for switching hierarchies according to various conditions.

  In terrestrial digital broadcasting, a broadcasting system based on hierarchical transmission is adopted in which a transmission band assigned to each broadcasting station is divided into a number of segments and a plurality of layers composed of one or more segments are simultaneously transmitted. In hierarchical transmission, the higher the number of segments that make up a hierarchy, the higher the quality of data that can be transmitted, but the weaker the reception by a moving body such as an automobile. Therefore, each broadcasting station plans to set up a plurality of hierarchies with different numbers of segments and provide services for fixed reception at home, etc., for mobile reception such as automobiles, or for mobile phone reception. Correspondingly, electrical manufacturers and the like are developing digital broadcast receivers that support terrestrial digital broadcasting by hierarchical transmission.

  When viewing images with a digital broadcast receiver mounted on a moving body such as an automobile, the receiving location changes due to movement, so the moving body may be in the shadow of a building or the distance from a radio tower or relay station. Or the reception level (electric field strength) of a digital broadcast signal changes. Further, in the case of a mobile object, the reception level is affected by the deterioration of the weather, high speed traveling, and the like. For this reason, in a digital broadcast receiving apparatus in a mobile body, the reception level may deteriorate during viewing, and the video may be interrupted or disturbed. At this time, the user must perform an operation to change the hierarchy to be received.

  In view of this, a digital broadcast receiving apparatus has been devised in which videos can be viewed without interruption by appropriately switching the hierarchy according to the reception level (see, for example, Patent Documents 1 and 2).

  According to these inventions, when the reception state is poor and the video is likely to be interrupted, it is possible to switch to a layer capable of receiving, and conversely, if the reception state is good, the layer can be switched to a higher quality layer for viewing.

However, in the above method, it is possible to avoid the interruption of reception itself, but no consideration is given to the video display disturbance associated with the layer switching process. As shown in FIG. 3, at the time of switching, processing such as hierarchy switching (stream switching), next header search, and next decoding of the first I picture (intra coded image) is performed from the display image immediately before switching. Blackout processing and the like are performed until the same picture is displayed. Since this blackout period reaches several tens to several hundreds of ms, the viewer feels uncomfortable.
JP 2003-274302 A Japanese Patent Laid-Open No. 10-191257

  SUMMARY OF THE INVENTION In view of the above problems, an object of the present invention is to provide a digital broadcast receiving apparatus that does not cause video display disturbance at the time of automatic layer switching between 12 segment broadcasting and 1 segment broadcasting.

  A digital broadcast receiving apparatus according to the present invention includes a receiving unit that receives digital broadcast signals transmitted at a plurality of layers having different qualities, and a layer that determines a reception state and selects and switches one appropriate layer from the plurality of layers. A switching unit; a decoding unit that decodes the video signal of the selected layer; a frame memory that stores the decoding result; a memory control unit that controls reading and writing of the frame memory; and an image read from the frame memory A video display section for displaying is provided.

  Particularly preferably, the hierarchy switching unit waits for completion of decoding of a picture or GOP in the decoding unit and switches the hierarchy.

  The memory control unit stops updating the frame memory until decoding of the first picture after layer switching is completed, and supplies the final frame before switching to the video display unit.

  According to the present invention, the blackout at the time of hierarchical switching can be eliminated and the freeze period can be reduced, so that the video quality can be improved.

  First, the configuration of the present embodiment will be described. FIG. 1 is a block diagram showing a configuration of an embodiment of a video receiving apparatus according to the present invention.

  In FIG. 1, a receiving unit 100 demodulates a received signal of a viewing channel to obtain video streams of two layers (12 segment broadcast and 1 segment broadcast) having different qualities, and notifies a current switching level to the layer switching unit. The layer switching unit 150 performs selection / switching control of which layer is viewed based on the reception state. The decoding unit 200 decodes the selected video stream, and the decoded video is stored in the frame memory 300. The video display unit 400 reads the video from the frame memory, performs display processing, and outputs the video.

  This frame memory has an area for storing a plurality of frames of video (for example, addresses: FM0 to FMn). In which area the decoding result is written, and from which area the frame to be passed to the video display unit is read. It is controlled by the memory control unit 350. In this embodiment, n = 3, that is, it has an area for 4 frames, and the address is circulated so that the write destination and the read source do not pass each other and the output order of the MPEG reference images is taken into consideration. Yes.

  Next, the switching sequence will be described. When it is determined that hierarchy switching is necessary, the hierarchical layer switching unit first notifies the decoding unit of a switching request. On the other hand, when the decoding of the last picture of the GOP currently being decoded is completed, the decoding unit notifies the hierarchy switching unit of switching permission. In the above operation, quick switching is required for channel switching by a general user operation, but in hierarchical automatic switching as in this implementation assumption, there is a certain likelihood of switching timing and efficient timing. This is because it is only necessary to change the mode.

  For example, in FIG. 3 (in the case of immediate switching to a switching request), it is not possible to output frames B8 and P9 that have been decoded. When this is switched in units of GOP (FIG. 2), B8 and P9 can be displayed because they are switched after the completion of decoding of B8, and the period of no display image at the time of switching can be minimized.

  When the hierarchy switching unit is notified of the switching permission from the decoding unit, the hierarchy switching unit is instructed to switch the layer to switch the layer, and the memory control unit is notified of the address update stop. When notified of the update stop, the memory control unit fixes the address of the write destination frame memory (FIG. 2: FM2) and fixes the read frame address to the last picture (FIG. 2: FM3).

  On the other hand, the decoding unit enters the header search of the stream after switching, and starts decoding the first I picture when the header is detected. When the decoding is completed, the memory control unit is notified of the decoding completion. Then, the memory control unit releases the fixed address, the video to be passed to the video display unit is switched, and the video display after layer switching is started.

  With the above hierarchical switching control, (1) since switching is performed at the GOP completion timing, the period when there is no frame to be discarded and there is no display image can be shortened. Is displayed as a freeze, so that the display quality of the video can be improved.

  As described above, the present invention can improve the video quality at the time of hierarchical switching between 12-segment broadcasting and 1-segment broadcasting, and therefore can be expected to be incorporated in a digital broadcast receiving apparatus such as an in-vehicle.

The block diagram which showed the structure of the Example of this invention Explanatory drawing which showed the video display process at the time of hierarchy switching by this invention Explanatory drawing showing the conventional video display processing at the time of layer switching

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Receiving part 150 Hierarchy switching part 200 Decoding part 300 Frame memory 350 Memory control part 400 Image | video display part

Claims (3)

A receiver for receiving digital broadcast signals transmitted at a plurality of layers having different qualities;
A hierarchy switching unit that determines a reception state and selects and switches one appropriate hierarchy from the plurality of hierarchies;
A decoding unit for decoding the video signal of the selected hierarchy;
A frame memory for storing the decoding result;
A memory control unit that controls reading and writing of the frame memory;
A video display unit for displaying video read from the frame memory;
A digital broadcast receiver characterized by comprising: The digital broadcast receiving apparatus according to claim 1, wherein the hierarchy switching unit switches the hierarchy after completion of decoding of a picture or a GOP in the decoding unit. 2. The digital broadcast reception according to claim 1, wherein the memory control unit stops updating the frame memory until the decoding of the first picture after layer switching is completed, and supplies the final frame before switching to the video display unit. apparatus.

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