JP2012090060A - Broadcast transmitting device, broadcast receiving device and broadcast transmitting/receiving system - Google Patents

Abstract

A broadcast transmission device, a broadcast reception device, and a broadcast transmission / reception system capable of reducing the delay time when switching channels without newly preparing a broadcast signal.
There is one video as a broadcast program, and the video is sub-sampled into four videos by a sub-sampling unit 11 so that the size becomes 1/4. Next, encoding is performed by the encoding units 12a to 12d. The encoded video data is shown in units of frames, and the old and new frames are numbered sequentially to indicate the new and old. Encoding is performed so that the appearance timings of key frames differ between the respective video data at regular intervals. The encoded video data is multiplexed by the multiplexing unit 13. The multiplexed data is sent to the transmission unit 14, and the transmission unit 14 transmits the multiplexed data as a broadcast signal.
[Selection] Figure 3

Description

  The present invention relates to a broadcast transmission apparatus, a broadcast reception apparatus, and a broadcast transmission / reception system for digital broadcasts including terrestrial digital broadcasts.

  In recent years, digitalization such as terrestrial broadcasting and satellite broadcasting has been progressing, and it has already been possible to view it. In addition, one-segment broadcasting can be viewed on mobile phones. Therefore, viewing of digital broadcasting has become common.

  Since this digital broadcasting handles a large amount of data, a technique for compressing data is used. For example, a system called MPEG-2 is used in terrestrial digital broadcasting.

  In MPEG-2, video is handled in units of still images called frames. Since a video is a frame in which still images are continuously played back, there are many cases where a continuous frame has a high correlation. Therefore, in MPEG-2, the data amount is reduced by a method using this correlation. In encoding using the correlation of frames, the amount of data is reduced by referring to frames before and after the frame to be encoded and only encoding the difference information.

  When performing decoding, first, a frame serving as a reference source is detected and decoded. This reference frame is called a key frame. The key frame is an independent frame that does not refer to other frames, and can be decoded alone. For frames other than the key frame, the difference information is decoded, and the information of the original frame is obtained by adding the key frame information to the information. That is, if there is no information about the key frame to be referred to, it cannot be decrypted.

  Therefore, when decoding a video, first, a key frame is detected. Therefore, a delay time corresponding to the time for waiting for detection of the key frame is generated.

  To solve this problem, a low-resolution video receiving tuner that is not normally used in a digital broadcast receiving apparatus that supports a hierarchical coding system that simultaneously transmits two types of video with different resolutions using different modulation systems. A receiving apparatus is disclosed that reduces the delay that occurs at the time of channel switching by using the signal at the time of channel switching (Patent Document 1).

  This receiving apparatus includes a tuner for receiving normal-resolution video and a tuner for receiving low-resolution video. Normally, a tuner for receiving normal video is used when viewing a program. If there is a channel switching operation, the delay time that occurs at the time of switching is reduced by switching the tuner to receive low-resolution video and outputting low-resolution video until normal-resolution video output begins. I am trying.

JP 2001-285736 A

  However, in the above method, since it is necessary to transmit a low resolution video signal separately from the normal resolution video signal, the amount of data to be transmitted is increased, and the efficiency of data transmission is deteriorated. In addition, a receiving unit that receives a low-resolution signal is required for the receiving apparatus.

  SUMMARY OF THE INVENTION In view of the above problems, the present invention has an object to provide a broadcast transmission device, a broadcast reception device, and a broadcast transmission / reception system capable of reducing the delay time when switching channels without newly preparing a broadcast signal. And

The present invention is a broadcast transmission device for transmitting a broadcast signal of a digital broadcast,
Sub-sampling means for sub-sampling one video into a plurality of videos, encoding means for encoding the plurality of sub-sampled videos so that the appearance timings of key frames are different, and encoded video data It comprises a multiplexing means for multiplexing with other data, and a transmission means for transmitting the multiplexed broadcast signal.

  Here, the encoding means is characterized in that key frame appearance timings of a plurality of subsampled videos are shifted at a constant interval.

Further, the present invention is a broadcast receiving device that receives a broadcast signal of a digital broadcast,
Broadcast receiving means for receiving a broadcast signal in which one video is subsampled into a plurality of videos, and the plurality of videos are encoded and multiplexed so that the key frame appearance timings are different, and the received broadcast signal is converted into each video data. Separating means for separating the image data, decoding means for detecting a key frame from the separated video data, decoding using the detected key frame, and video synthesizing means for synthesizing the decoded video and outputting the synthesized video These are provided.

Here, the decoding means is a video whose earliest key frame is detected among the plurality of received video data during a period until the key frame is detected from all of the plurality of video data included in the received broadcast signal. Decrypt from the data,
The video synthesizing means synthesizes video when a key frame is detected from video data different from the video data.

  Furthermore, the present invention is a broadcast transmission / reception system comprising the broadcast transmission device and the broadcast reception device.

  According to the present invention, the broadcast transmission apparatus subsamples video, encodes each video so that the appearance timing of key frames of each video data is different, and multiplexes and transmits the encoded video data. The broadcast receiving apparatus extracts a plurality of video data from the received signal, detects a key frame, and performs video synthesis based on the key frame. Therefore, as compared with the case of one video, the appearance of the key frame is accelerated, the waiting time for detecting the key frame is shortened, and the delay time at the time of channel switching caused thereby can be shortened.

  In particular, in a broadcast transmitting device, in a plurality of sub-sampled videos, the appearance timing of key frames is shifted at regular intervals, or in a broadcast receiving device, the video decoded first from the video data in which the key frame is detected. By selecting as an output, the delay time at the time of channel switching can be further shortened compared to the case of one video before subsampling.

  In addition, since the video is subsampled, the data amount of each video is smaller than before the subsampling. Therefore, the buffering time at the time of decoding is shortened, and the delay time caused thereby can be shortened.

It is a block diagram which shows one Embodiment of the broadcast transmission apparatus which concerns on this invention. It is a block diagram which shows one Embodiment of the broadcast receiver which concerns on this invention. It is a schematic diagram which shows the flow of the video encoding in a broadcast transmission apparatus. It is a figure which shows the subsampling outline | summary of an image | video. It is a schematic diagram which shows the flow of the video decoding in a broadcast receiver. It is a figure which shows the example of the encoding of the subsampled image | video per frame. It is a figure which shows the example of the decoding process of the image | video at the time of channel switching.

  Embodiments of the present invention will be described below with reference to the accompanying drawings.

  FIG. 1 is a block diagram showing an embodiment of a broadcast transmitting apparatus according to the present invention. The broadcast transmission / reception system of the present invention is configured by combining this broadcast transmission apparatus and a broadcast reception apparatus described later. The block diagram of FIG. 1 shows only the part related to the image necessary for explaining the features of the present invention.

  1 includes a subsampling unit 11 that subsamples video, encoding units 12a, 12b, 12c, and 12d that encode subsampled video, and a multiplexing unit 13 that multiplexes encoded data. , A transmitter 14 for transmitting the multiplexed broadcast signal, and an antenna 15 for transmission.

  In the broadcast transmitting apparatus 10, the subsampling unit 11 subsamples a plurality of videos before encoding one video. Here, for example, the sub-sampling is performed on four videos so that the size becomes 1/4. Each video is encoded by the encoding units 12 a to 12 d, multiplexed with other data by the multiplexing unit 13, and then transmitted from the transmission unit 14 via the antenna 15.

  FIG. 2 is a block diagram showing an embodiment of a broadcast receiving apparatus according to the present invention. As in FIG. 1, only the part related to the video is shown. The broadcast receiving apparatus 20 in FIG. 2 includes an antenna 21 for receiving a broadcast signal, a broadcast receiving unit 22 for receiving the broadcast signal, and separation for separating the received broadcast signal into a plurality of subsampled video data and other data. 23, a decoding unit 24a, 24b, 24c, 24d for decoding the separated video data, and a synthesis unit 25 for synthesizing the decoded video.

  In the broadcast receiving device 20, the signal transmitted from the broadcast transmitting device 10 is received by the broadcast receiving unit 22 through the antenna 21, and the broadcast signal is separated into a plurality of video data and other data by the separating unit 23. As for the video data, each of the four video data included in the received broadcast signal is decoded by the decoding units 24a to 24d, the decoded video is synthesized by the synthesis unit 25, and a synthesized video is output.

  Here, an outline of video processing in the broadcast transmitting apparatus 10 will be described with reference to FIG. FIG. 3 shows an outline of the flow from video sub-sampling, encoding, and multiplexing in the broadcast transmitting apparatus 10.

  First, there is one video as a broadcast program, and the video is sub-sampled into four videos by the sub-sampling unit 11 so that the size becomes 1/4. The subsampled video is shown as video A, video B, video C, and video D.

  Next, encoding is performed by the encoding units 12a to 12d. The encoded video data is shown in units of frames, and the old and new frames are numbered sequentially to indicate the new and old. For example, in the encoded video A data, A1 is the oldest temporally encoded frame, and A9 is the latest temporally encoded frame. In addition, encoding is performed so that the appearance timing of key frames differs between each video data at a constant interval. In FIG. 3, encoding is performed so that each frame appears with a delay of two frames, and a frame corresponding to a key frame is indicated by a bold frame. How to determine the appearance timing of the key frame will be described later.

  The encoded video data is multiplexed by the multiplexing unit 13. The multiplexed data is sent to the transmission unit, and the transmission unit 14 transmits the multiplexed data as a broadcast signal.

  Subsampling will be described with reference to FIG. The sub-sampling is performed by dividing the luminance information and color difference information of the pixels constituting the video into information of the sub-sampled videos A, B, C, and D and recombining them. In FIG. 4, the pixel information of the video is divided by a matrix, and the information is distributed depending on whether the row and the column are odd or even. Specifically, in the video before sub-sampling, information on odd lines such as the first and third lines is information on video A and information on video B, and information on even lines such as the second and fourth lines is video. C information and video D information. The odd columns are divided into information for images A and C, and the even columns are divided as information for images B and D. Therefore, for example, the information of the video A is information corresponding to odd rows and odd columns (a11, a12,..., A21, a22,...). By dividing and recombining the information distributed in this way, four sub-sampled images of images A, B, C, and D are created. The pixel information dividing method is not limited to the above.

  Next, the video data processing of the broadcast signal received by the broadcast receiving device 20 will be described with reference to FIG. FIG. 5 shows a flow from separation of received video data to restoration of the original video in the broadcast receiving device 20. Similar to FIG. 3, the video is distinguished as video A, video B, video C, and video D.

  First, the receiving unit 22 receives a broadcast signal. Next, the received video data is sent to the separation unit 23, and is separated into video data A, video data B, video data C, and video data D by the separation unit 23. Each video data is decoded by the decoding units 24a to 24d. In the case of FIG. 5, since the key frame is detected earliest from the video data A, the video A can be decoded earliest. Next, key frames are detected in the order of video data B, C, and D, and sequentially decoded. The four decoded videos are synthesized by the synthesis unit 25 and output.

  Next, the appearance timing of the key frame when encoding the subsampled video will be described with reference to FIG. FIG. 6 shows an example in which the subsampled video is encoded and the data is shown in units of frames. The encoded video data is distinguished as video data A, video data B, video data C, and video data D.

  The four videos are encoded so that the appearance timings of the key frames are different from each other. Here, the key frame appearance interval of each video data is 8 frames, and the key frame appearance timing of another video is determined based on the encoding of video A.

  First, in the encoding of the video A, the first appearing frame A1 is set as a key frame. And the appearance timing at that time is set to Ta. Since the appearance interval of the key frame is 8 frames, the key frame next to A1 is A9. Thereafter, a frame that appears every 8 frames may be used as a key frame. Next, the key frame appearance timing of each video data of video B, video C, and video D is determined. Since the video is sub-sampled into four, the appearance timing of each video is delayed by ¼ of the appearance interval of the key frame, so that a constant interval is set between the four video data. That is, if the appearance interval of key frames is T, the key frame appearance timings in the other three video data can be expressed as Ta + 1 / 4T, Ta + 2 / 4T, and Ta + 3 / 4T, respectively. Since the appearance interval of the key frames is 8 frames, it may be delayed by 2 frames from the appearance timing of A1. Therefore, the key frame of video B is B3, the key frame of video C is C5, and the key frame of video D is D7. Thereafter, similarly, a frame that appears every 8 frames may be used as a key frame.

  By the method as described above, the key frame appearance timing between the four video data can be encoded so as to be different at a constant interval. Note that the appearance interval of key frames is not limited to eight frames.

  Next, processing when a channel switching operation is performed in the broadcast receiving apparatus 20 will be described with reference to FIG. Video data of a broadcast signal transmitted by the broadcast transmitting apparatus 10 is encoded by the above-described method, for example, with a structure as shown in the upper part of FIG.

  Assume that the viewer performs a channel switching operation at an arbitrary timing. The broadcast receiving apparatus 20 selects and receives the broadcast signal after channel switching at that timing. In FIG. 7, it is assumed that reception is started at the timing shown in the upper part of the figure. The broadcast receiving apparatus 20 receives data after A2 as the broadcast signal of the program after switching. The video data received by the broadcast receiving unit 22 is separated into four video data A, B, C, and D by the separation unit 23. The video output first after the channel switching is the video decoded from the video data in which the key frame is detected earliest among these video data. In FIG. 7, the frame No. 2 (A2, B2, C2, D2) of each video data is separated as the first frame. However, since these frames are not key frames, no video data can be decoded at this point. Next, data of frame number 3 is obtained. Here, the key frame (B3) is detected earliest from the video data B, and the video data B can be decoded. Therefore, video B decoded from video data B is output. At this time, only video B is decoded, so that the synthesis unit 25 does not synthesize it with another video, and only video B is enlarged and output.

  Next, the key frame (C5) is detected from the video data C after the video data B, and the video data C can be decoded. In this case, the video B and the video C decoded by the decoding units 24b and 24c are synthesized by the synthesis unit 25, and the synthesized video is output. Thereafter, the same applies to the case where a key frame is detected from the video data D and A, and the video decoded by the detection of the key frame is sequentially synthesized by the synthesis unit 25 and the synthesized video is output. Eventually, a composite image synthesized from all four images is output.

  When the channel switching operation is performed by the viewer by the above method, the video decoded from the video data in which the key frame is detected earliest is output from the four video data. The four videos are encoded by delaying the appearance timing of each key frame by 1/4 of the appearance interval. For this reason, the interval at which the key frame is detected from any of the video data is two frames, which is ¼ compared to the case of one video before sub-sampling. Therefore, the key frame detection waiting time can be shortened to ¼ at maximum, and the delay time due to waiting for key frame detection can be shortened. In addition, since the key frame detection waiting time can be shortened to ¼ at the maximum, the detection timing of the key frame is earlier than the case of one video before sub-sampling, thereby receiving the key frame and the difference frame and the video. Can be quickly decoded. For this reason, the time required for buffering can be shortened, and the resulting delay time can also be shortened.

  The broadcast receiving device 20 may be able to grasp the reception status of the broadcast signal. In this case, for example, when the reception situation is bad and it is impossible to decode a part of the video, the video that can be output may be preferentially output.

  Further, the broadcast receiving apparatus 20 may be used in combination with a recording apparatus for recording video, and it records four subsampled videos individually, and synthesizes and outputs the video during playback. May be. According to this method, when a recorded program is reproduced, operations such as rewinding and fast-forwarding can be performed more finely than before. For example, when a rewinding operation is performed, it is assumed that past videos are displayed one after another from the currently viewed video at regular intervals with reference to key frames. Since the appearance frequency of key frames is greatly increased by recording four images, the image being operated is displayed more smoothly than before, and the operation can be performed in finer time units. Furthermore, if, for example, three of four recorded sub-sampled videos are deleted, the recording information of the program itself is kept although the image quality is low, and the capacity of the recording device can be secured.

  The broadcast transmission / reception system is not limited to a system that transmits and receives video data using radio waves such as terrestrial broadcasting. For example, it may be used for a broadcasting service such as IPTV (Internet Protocol Television) for viewing video using a terminal such as a dedicated set-top box via a network. In this case, the subsampled video data is transmitted to the user's terminal via the network, and is decoded and synthesized on the terminal side and output. The terminal side only needs to be compatible with the IPTV service, and may be, for example, an IPTV compatible TV or an IPTV compatible PC with a set-top box function.

  The broadcast transmission / reception system may be used for a broadcast service that provides video using a general network such as the Internet. For example, OTT-IPTV (Over The Top-IPTV) that provides video over a network to terminals such as limited set-top boxes, televisions, PCs, and game consoles that satisfy a specific use It may be a service. In this case, the subsampled video is transmitted to the user's terminal via the network, and decoded and synthesized on the terminal side and output.

  The broadcast transmission / reception system may be used for a broadcast service that provides video using both broadcast and network. For example, a service such as HBB-TV (Hybrid Broadcast Broadband TV) may be used in which video data is transmitted and received by radio waves, data content such as text is acquired by a network, and synthesized and reproduced on the terminal side. In this case, the subsampled video data is transmitted to the user's terminal using either or both of radio waves and the network, and is received, decoded, combined, and output on the terminal. For example, one of the subsampled video data is transmitted using radio waves, and the remaining three video data are transmitted using a network. In this case, a terminal that can output a video with sub-sampling resolution can synthesize the sub-sampled video and output a video with the resolution before sub-sampling. Even a terminal that supports only video output of the above can be output by receiving and decoding subsampled video data transmitted using radio waves.

  The present invention is not limited to the above-described embodiments, and embodiments obtained by combining technical means disclosed in the embodiments are also included in the technical scope.

DESCRIPTION OF SYMBOLS 10 Broadcast transmission apparatus 11 Subsampling part 12a, 12b, 12c, 12d Encoding part 13 Multiplexing part 14 Transmission part 15 Antenna 20 Broadcast receiving apparatus 21 Antenna 22 Broadcast receiving part 23 Separation part 24a, 24b, 24c, 24d Decoding part 25 Synthesizer

Claims (5)

A broadcast transmission device for transmitting a broadcast signal of a digital broadcast,
Subsampling means for subsampling one video into a plurality of videos;
Encoding means for encoding a plurality of subsampled videos so that the appearance timing of keyframes differs from each other;
A multiplexing means for multiplexing the encoded video data together with other data;
A transmission means for transmitting the multiplexed broadcast signal;
A broadcast transmission apparatus comprising:   2. The broadcast transmission apparatus according to claim 1, wherein the encoding unit shifts key frame appearance timings of a plurality of subsampled videos at regular intervals. A broadcast receiving device for receiving a broadcast signal of a digital broadcast,
Broadcast receiving means for receiving a broadcast signal in which one video is subsampled into a plurality of videos, and the plurality of videos are encoded and multiplexed such that the key frame appearance timings are different;
Separating means for separating the received broadcast signal into each video data;
Decoding means for detecting a key frame from the separated video data and performing decoding using the detected key frame;
Video synthesizing means for synthesizing the decoded video and outputting the synthesized video;
A broadcast receiving apparatus comprising: The decoding means decodes from the video data in which the key frame is detected earliest among the plurality of received video data during a period until the key frame is detected from all of the plurality of video data included in the received broadcast signal. And
4. The broadcast receiving apparatus according to claim 3, wherein the video synthesizing unit synthesizes video when a key frame is detected from video data different from the video data. The broadcast transmission device according to claim 1 or 2,
The broadcast receiving device according to claim 3 or 4,
A broadcast transmission / reception system comprising:

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