JP5283466B2 - Receiving machine - Google Patents

Description

  The present invention relates to a receiver capable of receiving a multi-channel digital broadcasting service.

  MediaFLO (registered trademark) is known as a broadcasting service for portable terminals. MediaFLO is a multi-channel digital broadcasting service for mobile terminals, and distributes video and music using technology suitable for mobile environments. The air interface of MediaFLO is called FLO (Forward Link Only), and Orthogonal Frequency Division Multiplexing (OFDM) is adopted for the physical layer of FLO (see Non-Patent Documents 1 and 2).

  FIG. 1 is a diagram showing an FLO interlace configuration. FLO uses a bandwidth of 6 MHz, and the number of subcarriers is 4096. Of these 4096 subcarriers, the actual subcarriers used are 4000 excluding 96 guard subcarriers. MediaFLO divides 4000 subcarriers into groups called 8 interlaces. Each interlace is composed of 500 subcarriers selected every 8 out of 4000 subcarriers. Since one interlace is used as a pilot symbol, the remaining seven interlaces are used for data transmission. In MediaFLO, service (video, audio, subtitles, etc.) is assigned to a frequency band with one interlace as a minimum unit.

  FIG. 2 is a diagram illustrating an example of service allocation to interlace. The vertical axis interlace represents division on the frequency axis, and the horizontal axis represents division on the time axis. Each service of MediaFLO is carried on a logical channel called MLC (Multicast Logical Channel). An MLC is composed of one or more interlaces and one or more OFDM symbols. The ranges surrounded by thick lines in FIG. 2 represent different MLCs, and data such as video, audio, and subtitles is stored in each MLC. For example, a service (program) composed of one video and one audio is composed of two MLCs. Further, for example, in order to view a service including only the MLC indicated by the oblique lines in FIG. As described above, in MediaFLO, the service is divided into the time domain and the frequency domain, and only necessary MLCs are selectively decoded (intermittent reception), thereby reducing the power consumption of the receiving apparatus. Can be planned. In MediaFLO, all tuners can be received by a single tuner, so that it is possible to simultaneously decode a large number of MLCs and view a plurality of services simultaneously.

  FIG. 3 shows the frame structure of MediaFLO. The MediaFLO is composed of a superframe (1200 OFDM symbols) with a period of 1 second, and the superframe is divided into a TDM (Time Division Multiplexing) pilot, an OIS (Overhead Information Symbols), and four data frames. The OIS is a control channel and includes MLC arrangement information in the data frame. The receiver detects the superframe boundary by the TDM pilot, acquires the timing for demodulation, decodes the data of the OIS channel, and obtains information on the MLC (image, audio, etc.) constituting the selected channel. Confirm and demodulate and decode the MLC in each data frame.

  FIG. 4 is a diagram illustrating a configuration of a general MediaFLO receiver. The signal received by the antenna 100 receives the channel designated by the RF front end 101, undergoes OFDM demodulation and error correction decoding by the demodulator 102, and audio, video, character information, etc. by the media decoder 103 Is output to the AV output unit 106 such as a speaker or a monitor. Here, explanations such as decryption of encryption and reception of an electronic program guide are omitted.

FIG. 5 is a timing chart of the demodulator, media decoder, and AV output unit when channel (service) change is performed.
When changing a channel (service), the user presses a channel button or the like on the operation unit 105 to perform a channel change operation. The system control unit 104 detects the operation and determines the channel to be received next according to the content of the operation, instructs the demodulator 102 to demodulate the channel, and instructs the media decoder 103 to switch the channel. To do. The demodulator 102 reads the OIS information of the next superframe and starts demodulating data of the designated channel.
The media decoder 103 stops the decoding of the current channel, stops the audio output, and displays the screen (for example) as a black screen in order to inform the user that the user has performed the channel switching operation and started the channel switching. Switch to. Decoding is resumed from the next superframe data, and the decoded data is output to the AV output unit 106.

  As described above, in the case of MediaFLO, when a channel switching instruction is issued by the user, data demodulation starts from the next super frame, so that a maximum waiting time of one super frame occurs depending on the channel switching timing. Actually, the waiting time further increases depending on the decoding process of the video and audio and the position of the I frame of the video.

In order to reduce this waiting time, a MediaFLO receiver configured as shown in FIG. 6 can be considered.
In the case of MediaFLO, since data of a plurality of channels is broadcast in one band (6 MHz), only one RF front end and demodulator corresponding to the tuner unit is required. The demodulator 102 can output data of a plurality of channels. Therefore, a plurality of media decoders are prepared to simultaneously decode the data of a plurality of channels.
The media decoder 107 decodes the data of the currently selected channel. The media decoder 108 decodes the data of the channel predicted to be switched next by the user. Then, the AV output switching unit 109 outputs the data of the media decoder 107 that is the data of the currently selected channel.

FIG. 7 is a timing chart of the demodulator, media decoder, and AV output unit when the channel is changed.
When the channel is changed, the system control unit 104 determines the channel to be switched next from the operation of the operation unit 105 by the user. If the channel is already decoded by the media decoder 108, the AV output switching unit 109 is immediately selected. Is switched to the output of the media decoder 108, and the AV data of the channel after the switching is output.
At this time, the user predicts a channel to be switched next, and instructs the demodulator 102 and the media decoder 107 to demodulate and decode the data of the channel from the next superframe.
If the channel after the change is not a predicted channel, the same control as the channel switching operation of a general MediaFLO receiver is performed, and data processing of the channel expected to be switched next is also started.

  Thus, if a receiver as shown in FIG. 6 is used, the channel switching time can be shortened. For example, when the user switches the channel using the up / down button (zapping in one direction), the user frequently operates the up key or down key continuously, so it is easy to predict the channel to be switched next, and the effect is great. .

Patent Document 1 discloses a digital broadcast receiver that can shorten the switching time when switching channels.
JP 2003-274304 A Nikkei Electronics, December 17, 2007 issue, Digital TV Seminar, 1st MediaFLO, “Broadcast for mobiles that can coexist with 1Seg, accommodating over 20 channels in 6 MHz width” ITU Journal, Vol. 37, no. 5, (2007.5) "New broadcasting service for mobile phones using MediaFLO"

However, if a plurality of decoders are prepared in the MediaFLO receiver and the channels are decoded at the same time to attempt to shorten the channel switching time, there are the following problems.
In portable devices that operate on batteries, processing must be performed with limited CPU power, so simultaneous processing (reception and decoding) of multiple channels may not be possible. Since reception and decoding are always performed, power consumption increases compared to when one channel is received, and the usage time of the portable device is shortened.

  The present invention has been made in view of such problems, and an object of the present invention is to provide a receiver capable of shortening channel switching time and switching channels with less CPU power and less power consumption. It is to provide.

  In order to achieve the above object, a receiver according to the present invention includes a plurality of reception units that receive multi-channel data hierarchically encoded in a plurality of layers, and a layer code of each channel received by the plurality of reception units. A decoder corresponding to each receiving unit for decoding the digitized data, a display unit for displaying the data decoded by the decoder, an operation unit for performing channel selection operation by the user, and a first of the plurality of receiving units When the receiving unit receives the first channel, the decoder corresponding to the first receiving unit decodes the encoded data of all layers of the channel, and the decoded data is displayed on the display unit. When the channel selection operation of the second channel is performed by the operation unit, the first reception unit receives the second channel, and the decoder corresponding to the first reception unit has a specific hierarchy of the channel. And the decoded data is displayed on the display unit, the second receiving unit receives the third channel, and the decoder corresponding to the second receiving unit receives a specific hierarchy of the channel. And a control unit that controls to decode the encoded data up to the above.

  Preferably, the control unit controls the display unit to display data decoded by a decoder corresponding to the second reception unit when the channel selection operation of the third channel is performed by the operation unit.

  In addition, when a predetermined time elapses after the channel selection operation of the second channel is performed by the operation unit, the control unit causes the decoder corresponding to the first reception unit to encode the encoded data of all layers of the second channel. It is preferable to control so that the decoded data is displayed on the display unit.

  In addition, the control unit, when a channel selection operation for the second channel is performed by the operation unit, and a predetermined time elapses, a decoder corresponding to the second reception unit decodes the encoded data of the third channel. It is preferable to control to stop.

  Since the present invention receives and decodes only the encoded data of a limited layer for a certain period of time when switching channels, the channel switching time can be shortened and the channel switching can be performed with less CPU power and less power consumption. Can do.

Embodiments of the present invention will be described with reference to the drawings.
In MediaFLO, a hierarchical modulation scheme and two-layer encoding (hierarchical encoding) of a base component and an enhanced component are used. Basic video (for example, 15 frames / second) can be output only by receiving and decoding the base component, but higher quality video (for example, 30 frames / second) can also be obtained by receiving and decoding the enhanced component. ) Can be output.
In general, if the base component and the enhanced component have the same amount of data as in MediaFLO, the processing of one component is not performed, so that the demodulator and media decoder Processing is greatly reduced.
It should be noted that the basic video and the high-quality video are not limited to the above-described examples because they differ depending on the system design.

  The receiver according to the present invention, in a broadcasting system that transmits data such as video and audio by hierarchical modulation system and hierarchical encoding, when switching to a channel after switching for a certain period of time at the time of channel switching and further to the next. The data of the expected channel is received and decoded. Furthermore, when the plurality of channels are received and decoded, only the data of a specific layer is received and decoded.

FIG. 8 is a diagram showing the configuration of the receiver of the present invention. The receiver of the present invention is a receiver that receives multi-channel data hierarchically encoded in a plurality of layers. As shown in FIG. 8, an antenna 200 and an RF front end that receives multi-channel broadcast waves. 201, a demodulator 202 which outputs the data of each channel by OFDM demodulation and error correction decoding of the received broadcast wave, and extracts data such as voice, video and text from the data of each channel, and decodes each data A plurality of media decoders 207, 208, a system control unit 204 that controls the system such as channel switching, an operation unit 205 that performs channel switching (channel selection operation) by a user, decoded audio, video, AV output switching unit 209 for switching the output of text data, etc., and outputs audio, video, text data, etc. V output unit 206 (display unit, a speaker) and a.
The RF front end 201 and the demodulator 202 function as a plurality of receiving units that receive multi-channel data.
As a technical idea of the plurality of receiving units, a configuration for outputting one channel corresponds to one receiving unit. Therefore, when one chip set outputs one channel, this is used as one receiving unit, and when one chip set outputs a plurality of channels, the common point is that multiple channels are received. One function for separating and outputting channels is defined as one receiving unit.

In the system control unit 204, a first reception unit (not shown) of the plurality of reception units (RF front end 201 and demodulator 202) receives the first channel, and a decoder corresponding to the first reception unit is the first one. When the encoded data (base component and enhanced component) of all layers of one channel is decoded and the decoded data is displayed on the AV output unit 206, the channel selection operation of the second channel is performed by the operation unit 205. The first receiving unit receives the second channel, the decoder corresponding to the first receiving unit decodes the encoded data (base component) up to a specific layer of the second channel, and the decoded data is output to the AV output unit. 206, the second receiving unit (not shown) receives the third channel, and the decoder corresponding to the second receiving unit receives the third channel. It controls to decode the coded data (base component) to a specific hierarchy of tunnels. As described above, when one chip set receives multiple channels and separates each channel, the first and second receiving units are identical in that they receive broadcast waves, but are separated and output. Is different.
In addition, when the channel selection operation of the third channel is performed by the operation unit 205, the system control unit 204 controls the AV output unit 206 to display data decoded by the decoder corresponding to the second reception unit.
In addition, when a predetermined time elapses after the channel selection operation of the second channel is performed by the operation unit 205, the system control unit 204 causes the decoder corresponding to the first reception unit to perform encoded data (all layers of the second channel) Base component and enhanced component), and the decoded data is controlled to be displayed on the AV output unit 206.
In addition, the system control unit 204 stops the decoding of the encoded data of the third channel when the predetermined time has elapsed after the channel selection operation of the second channel is performed by the operation unit 205. Control to do.

FIG. 9 is a timing chart for explaining the operation of the embodiment 1 of the receiver of the present invention. In FIG. 9, chA (B) indicates that the base component of channel A is being processed, and chA (B + E) indicates that the base component and enhanced component of channel A are being processed.
At timing (1), the user has selected channel A, and the receiver receives the base component and enhanced component of channel A, decodes them, and outputs them to the AV output unit 206.

When the user operates the operation unit 205 and performs a channel switching operation at timing (2), the system control unit 204 detects the channel switching operation by the user, determines the channel B to be switched next, and Next, the channel C expected to be switched is determined. Furthermore, the system control unit 204 starts a channel switching monitoring timer and sets the demodulator 202 (receiving unit) to receive the base components of the channel B and the channel C from the boundary of the next superframe. By receiving only the base components of channel B and channel C in this way, the amount of computation of the CPU can be reduced and power consumption can be suppressed.
The media decoder 207 is set to stop decoding the current channel and decode only the base component of channel B from the next superframe. The media decoder 208 is set to decode the base component of channel C from the next superframe. For the AV output switching unit 209, in order to inform the user that the channel switching has started, the audio output is stopped and the screen is switched to a black screen (for example). This shortens the time for channel switching.

At timing (3), reception of base components of channel B and channel C is started, and decoding of the received data is started. Also, the AV output switch 209 is set to output AV data of the media decoder 207.
Channel B data is decoded, and channel B AV data is output from timing (4) when video data and audio data are prepared.

Thereafter, at the timing (5), the channel switching monitoring timer times out (TO). The system control unit 204 detects the timeout of the channel switching monitoring timer, and sets the demodulator 202 (reception unit) to receive the currently selected channel B base component and enhanced component from the next superframe. To do. Also, the media decoder 207 is set to decode the base component and the enhanced component from the next superframe, and the media decoder 208 is stopped to reduce power consumption.
At timing (6), reception and decoding of the base component and enhanced component of channel B are started and output to the AV output unit 206 as they are.

  FIG. 10 is a timing chart for explaining the operation of the embodiment 2 of the receiver of the present invention. At timing (1), the user selects channel A, and the receiving device receives the base component and enhanced component of channel A, decodes them, and outputs them to the AV output unit 206.

At timing (2), when the user operates the operation unit 205 and performs a channel switching operation, the system control unit 204 detects the channel switching operation by the user, determines the channel B to be switched next, and then Channel C expected to be switched to is determined. Furthermore, the system control unit 204 starts a channel switching monitoring timer and sets the demodulator 202 (receiving unit) to receive the base components of the channel B and the channel C from the boundary of the next superframe. Thus, by receiving only the base components of channel B and channel C, it is possible to reduce the calculation amount of the CPU and suppress power consumption.
The media decoder 207 is set to stop decoding the current channel and decode only the base component of channel B from the next superframe. The media decoder 208 is set to decode the base component of channel C from the next superframe. For the AV output switching unit 209, in order to inform the user that the channel switching has started, the audio output is stopped and the screen is switched to a black screen (for example). This shortens the time for channel switching.

At timing (3), reception of base components of channel B and channel C is started, and decoding of the received data is started. Also, the AV output switch 209 is set to output AV data of the media decoder 207.
Channel B data is decoded, and channel B AV data is output from timing (4) when video data and audio data are prepared.

Next, when the user operates the operation unit 205 to perform a channel switching operation at timing (5) before the channel switching monitoring timer times out, the system control unit 204 detects the channel switching operation by the user. The channel C to be switched next is determined, and the channel D that is expected to be switched next is determined.
The system control unit 204 restarts the channel switching monitoring timer, and sets the demodulator 202 (receiving unit) to receive the base components of the channels C and D from the next superframe boundary.
Also, it is confirmed whether or not the switching destination channel C has already been decoded. In this case, since the channel C is decoded by the media decoder 208, the AV output switching unit 209 is set to output the AV data of the media decoder 208. At this time, channel C is immediately switched to AV output.
Decoding is stopped for the media decoder 207, and the base component of channel D is set to be decoded from the next superframe.

At timing (6), reception of the base components of channel C and channel D is started, and decoding of the received data is started.
Thereafter, at the timing (7), the channel switching monitoring timer times out (TO). The system control unit 204 detects the timeout of the channel switching monitoring timer, and sets the demodulator 202 (receiving unit) to receive the currently selected channel C base component and enhanced component from the next superframe. .
Further, in order to suppress power consumption, the media decoder 207 is stopped, and the media decoder 208 is set to decode the base component and the enhanced component from the next superframe.
At timing (8), reception and decoding of the base component and enhanced component of channel C are started and output to the AV output unit 206 as they are.

  As described above, according to the present invention, only the base component of the channel predicted to be switched to the current channel and the next channel is received and decoded only for a certain period of time at the time of channel switching. As a result, the power consumption can be reduced, and if the next channel to be switched matches the predicted channel, the channel can be switched smoothly and immediately.

  In the above-described embodiment, the RF front end and the demodulator function as a plurality of receiving units, and the plurality of receiving units are configured by one RF front end and a demodulator. This may be a single receiver that receives multi-channel data. The reception unit may receive the first to third channels, and a decoder corresponding to each channel may be decoded. When there is a difference in the timing of receiving each channel, the receiving unit can save power without performing a receiving operation during that time. The plurality of receiving units may be configured with a plurality of RF front ends and a demodulator.

It is a figure which shows the interlace structure of FLO. It is a figure which shows the example of allocation of the service with respect to an interlace. It is a figure which shows the frame structure of MediaFLO. It is a figure which shows the structure of the receiver of general MediaFLO. It is a figure which shows the timing chart of a demodulator, a media decoder, and an AV output part when a channel change is performed. It is a figure which shows the structure of the receiver of MediaFLO provided with a some media decoder. It is a figure which shows the timing chart of a demodulator, a media decoder, and an AV output part when a channel change is performed. It is a figure which shows the structure of the receiver of this invention. It is a timing diagram explaining operation | movement of Example 1 of the receiver of this invention. It is a timing diagram explaining operation | movement of Example 2 of the receiver of this invention.

Explanation of symbols

100, 200 Antenna 101, 201 RF front end 102, 202 Demodulator 103, 107, 108, 207, 208 Media decoder 104, 204 System control unit 105, 205 Operation unit 106, 206 AV output unit 109, 209 AV output switcher

Claims (4)

A plurality of receiving units for receiving multi-channel data hierarchically encoded in a plurality of layers;
A decoder corresponding to each receiving unit for decoding the hierarchically encoded data of each channel received by the plurality of receiving units;
A display unit for displaying the data decoded by the decoder;
An operation unit for channel selection operation by the user,
The first receiving unit of the plurality of receiving units receives the first channel, the decoder corresponding to the first receiving unit decodes the encoded data of all layers of the channel, and the decoded data is displayed on the display When a channel selection operation for the second channel is performed by the operation unit, the first reception unit receives the second channel, and a decoder corresponding to the first reception unit receives the second channel. The encoded data up to a specific layer of the channel is decoded, the decoded data is displayed on the display unit, the second receiving unit receives the third channel, and a decoder corresponding to the second receiving unit A control unit that controls to decode the encoded data up to a specific layer of the channel;
Receiver with.   The control unit controls the display unit to display data decoded by a decoder corresponding to the second receiving unit when the channel selection operation of the third channel is performed by the operation unit. The receiver according to claim 1.   The control unit decodes the encoded data of all layers of the second channel when a predetermined time has elapsed after the channel selection operation of the second channel is performed by the operation unit. The receiver according to claim 1, wherein the receiver is controlled to display the decoded data on the display unit.   The control unit stops the decoding of the encoded data of the third channel when a predetermined time elapses after the channel selection operation of the second channel is performed by the operation unit. The receiver according to claim 3, wherein the receiver is controlled as follows.

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