JP4836027B2 - Digital broadcast receiving apparatus and digital broadcast reproduction method - Google Patents

Description

  The present invention relates to an apparatus for receiving a digital broadcast of a plurality of channels.

  In digital broadcasting, a differential encoding method is adopted in which a difference between successive images is extracted and the video data is compressed by sending the difference. An example of the differential encoding method is MPEG2 (Moving Picture Experts Group phase 2).

  In the differential encoding method, an independent image (hereinafter referred to as a “basic image”) that is basic and can be played back only by the data is sent at a certain point in time, and thereafter, only the difference between adjacent images is sent. It is done. Basic images are inserted at intervals. Therefore, reproduction of the differentially encoded video can be started only from the basic image.

  In digital broadcasting, MPEG2 data is broadcast as a TS (Transport Stream) packet sequence. A digital broadcast TS packet sequence includes sequence headers at intervals of 0.5 sec. This sequence header indicates the position of the basic image described above, and means that video can be reproduced therefrom.

  Therefore, when the user switches the channel of the digital broadcast receiving apparatus, it takes 0.5 sec at maximum to detect the position of this sequence header. In addition, unlike analog broadcasting, digital broadcasting requires processing such as A / D (analog / digital) conversion, error correction, deinterleaving, and Reed-Solomon accompanying the tuner.

  Therefore, in general digital broadcast receivers, the audio is stopped by performing mute processing such as fixed video or monochrome display until the user can play a new channel after switching the channel. . This mute time generally takes about 1 second, and this time is a stress for the user.

On the other hand, a configuration has been proposed in which a plurality of tuner units are provided, and each tuner unit performs tuning and accompanying processing for each of a plurality of channels, and selects one of the outputs (see Patent Document 1). ). This eliminates the need for new tuning and associated processing when switching channels, and shortens the time required for switching.
JP 2004-312504 A

  However, since the configuration disclosed in Patent Document 1 is a configuration that selects and outputs one of the TSs output from each tuner unit, the sequence header inserted at intervals of 0.5 sec as described above at the time of channel switching. It was necessary to detect and start playback from there. Therefore, the user waits for a maximum time of 0.5 sec, and it cannot be said that sufficient operability is ensured.

  Note that the switching time can be further shortened by providing a plurality of playback units for detecting sequence headers and playing back video, and selecting video signals output from the multiple playback units. However, such a configuration is not preferable because it increases the amount of hardware and increases costs.

  An object of the present invention is to provide a digital broadcast receiving apparatus that shortens the channel switching time.

A digital broadcast receiving apparatus according to one embodiment of the present invention includes :
A digital broadcast receiving apparatus for receiving a digital broadcast of a plurality of channels that is differentially encoded,
A plurality of capturing units for extracting at least one channel from the plurality of broadcast channels and acquiring data obtained from the signal;
The data acquired by any of the above-mentioned capturing units is played back and output, and at least the data of channels other than the playback output is temporarily stored for a predetermined time, and the old channel being played back is transferred to another new channel. When there is a request for switching, after the reproduction output of the data of the old channel is stopped, the newest channel data can be reproduced by using the new channel data temporarily stored. A switching unit that starts to output from the part,
By adding a bias to the feedback of a PLL circuit that generates a clock for reproduction until the delay caused by the switching unit starting to reproduce and output the new channel from past data at the time of channel switching is eliminated, And a speed adjustment unit for increasing the speed of reproduction output of the new channel.

  According to the present invention, it is not necessary to take a time from when a channel switching instruction as in the prior art is issued until a portion where playback of a new channel can be started is detected, and the channel can be switched in a short time.

  Embodiments for carrying out the present invention will be described in detail with reference to the drawings.

(First embodiment)
FIG. 1 is a block diagram showing a configuration of a digital broadcast receiving apparatus according to the first embodiment. Referring to FIG. 1, the digital broadcast receiving apparatus 10 includes a plurality of digital broadcast capture units 11 and 12, a data storage unit 13, and a video reproduction unit 14. The digital broadcast receiving apparatus 10 includes a plurality (here, two) of digital broadcast capturing units 11 and 12 so that a plurality of channels can be captured simultaneously.

  The digital broadcast capturing units 11 and 12 take out a signal of at least one channel from a digital broadcast including a plurality of channels, and send data obtained from the signal to the data storage unit 13. The video data included in this data is differentially encoded video data, and a plurality of images including a basic image are set as one unit, and a sequence header is added to each unit. Reproduction of the differentially encoded video data can be started only from the basic image.

  As a specific example, the digital broadcast capturing units 11 and 12 perform processing such as channel selection, A / D conversion, error correction, and deinterleaving, and send the obtained MPEG2 TS packet sequence to the data storage unit 13. The data transmitted in the TS packet sequence includes a sequence header indicating the position of the basic image.

  The data storage unit 13 stores a plurality of data from the plurality of digital broadcast capturing units 11 and 12 and sends the video data of one channel selected by the user for viewing to the video playback unit 14. .

  FIG. 2 is a diagram illustrating how TS packet sequences are switched at the time of channel switching. When the user is instructed to switch channels, the data storage unit 13 switches the data to be sent to the video reproduction unit 14 from the old channel data (TS packet sequence) to the new channel data (TS packet sequence). FIG. 2 shows an example of switching from 4 channels (4 ch) to 6 channels (6 ch). In this case, 4ch is the old channel and 6ch is the new channel.

  At the time of channel switching, the data storage unit 13 stops the TS packet sequence of the old channel (4ch), and then connects the TS packet sequence of the new channel (6ch) from the latest sequence header portion in the past. As a result, reproduction can be started from the beginning of the TS packet string of the new channel.

  The video playback unit 14 plays back the video data sent from the data storage unit 13. Specifically, the video reproduction unit 14 performs MPEG2 decoding on the TS packet sequence from the data storage unit 14 and performs D / A (digital / analog) conversion to reproduce the video. At the time of channel switching, since data of the new channel is connected and sent from the portion where playback can be started after the data of the old channel, switching can be performed in a short time without the need for mute.

  Next, the operation of the data storage unit 13 at the time of channel switching will be described. FIG. 3 is a flowchart showing the operation at the time of channel switching in the first embodiment.

  Referring to FIG. 3, the data storage unit 13 monitors the channel switching instruction from the user while sending the data of the channel selected by the user to the video reproduction unit 14 (step 101). When there is a switching instruction, the process returns to the most recent sequence header portion of the data of the new channel (step 102).

  Then, the data switching unit 13 stops sending the data of the old channel, and then starts to send the data of the new channel by connecting from the sequence header (step 103). When transmission of new channel data is started, the data storage unit 13 returns to step 101 and monitors a channel switching instruction from the user.

  As described above, according to this embodiment, the plurality of digital broadcast capturing units 11 and 12 capture the data of a plurality of channels and send the data to the data storage unit 13, and the data storage unit 13 switches the old channel at the time of channel switching. The data of the new channel is connected from the past portion where the reproduction can be started and sent to the video reproduction unit 14, and the video reproduction unit 14 reproduces the data from the data storage unit 13. This eliminates the need for muting from when a channel switching instruction is given to when a portion where playback of a new channel can be started is detected, and allows channel switching in a short time.

  In this embodiment, an example in which the present invention is applied to a digital broadcast adopting the MPEG2 standard has been shown. However, the scope of the present invention is not limited to this, and a plurality of differentially encoded channels are broadcast. It can be widely applied to the system. This also applies to each embodiment shown below. Examples of other data compression methods include MPEG4 and ITU-T H.264. H.264.

(Second Embodiment)
In the first embodiment, when switching channels, the old channel is always connected to the past sequence header of the new channel. The second embodiment differs from the first embodiment in that it selects whether to go back to the past sequence header or wait for the next sequence header according to the timing relationship between the switching instruction and the latest sequence header in the past. .

  The configuration of the digital broadcast receiving apparatus of the second embodiment is the same as that of the first embodiment shown in FIG. In the second embodiment, the operation of the data storage unit is different from that of the first embodiment.

  4 and 5 are diagrams for explaining the operation at the time of channel switching of the data storage unit. In digital broadcasting, sequence headers are inserted at intervals of 0.5 sec. Therefore, if there is a newest sequence header of the new channel in the past within 0.25 sec before the switching instruction, the data storage unit 13 of this embodiment starts to send to the video playback unit 14 from the sequence header, and before the switching instruction. If there is no past newest sequence header of the new channel within 0.25 sec, it waits until the next appearing sequence header and starts sending it to the video reproduction section 14 from there.

  Referring to FIG. 4, since there is a newest sequence header in the past of the new channel (6ch) within 0.25 sec before the instruction to switch the channel, transmission to the video reproduction unit 14 is started from there.

  On the other hand, referring to FIG. 5, since there is no past newest sequence header of the new channel (6ch) within 0.25 sec before the channel switching instruction, the sequence header that appears next starts to be sent to the video reproduction unit 14. . As described above, since the sequence header appears at intervals of 0.5 sec, if there is no newest sequence header in the past within 0.25 sec before the channel switching instruction, the next sequence header will be displayed within 0.25 sec after the switching instruction. Should appear.

  FIG. 6 is a flowchart showing the operation at the time of channel switching in the second embodiment. The data storage unit 13 of this embodiment controls a timer that counts 0.25 sec and uses the timer value. If there are a plurality of channels other than the channel being reproduced and each data is sent to the data storage unit 13, a plurality of timers are prepared for each channel.

  Referring to FIG. 6, in the initial state, the data storage unit 13 monitors the sequence headers of other channels while sending the channel selected by the user to the video reproduction unit 14 (step 201). Until the sequence header is first detected, the data storage unit 13 maintains the timer in a reset state (step 202). When the sequence header is first detected, the data storage unit 13 starts a timer count (step 203).

  Thereafter, the data storage unit 13 determines whether or not a new sequence header has been detected (step 204). If the sequence header is detected, the data storage unit 13 resets the timer, starts counting again (step 205), and returns to step 204.

  On the other hand, if a new sequence header has not been detected, the data storage unit 13 next determines whether or not there has been a channel switching instruction from the user (step 206). If there is no switching instruction, the data storage unit 13 returns to step 204.

  On the other hand, if there is a switching instruction, the data storage unit 13 refers to the timer for the new channel and determines whether it is within 0.25 sec since the previous reset (step 207). If it is not within 0.25 sec from the reset, the data storage unit 13 waits for the next sequence header (step 208) and selects it. If it is within 0.25 sec from the reset, the data storage unit 13 selects the previous sequence header (step 209).

  After the processing of step 208 or step 209, the data storage unit 13 stops sending the data of the old channel, and then starts sending the data of the new channel by connecting from the selected sequence header (step 210). ). When the transmission of the new channel data is started, the data storage unit 13 returns to step 204.

  In the first embodiment, the reproduction time of the new channel is delayed by a maximum of 0.5 sec. In the second embodiment, this delay is suppressed to 0.25 sec. On the other hand, in the second embodiment, the channel switching time is increased by a maximum of 0.25 sec. However, if this level is reached, the operability of the user is not impaired and stress does not occur.

(Third embodiment)
In the first embodiment, the reproduction time of the new channel is delayed from the reference by 0.5 sec at the maximum and by 0.25 sec at the maximum in the second embodiment. The delay of the new channel occurs regardless of the delay that occurred in the old channel and is not accumulated at every switching, so it will not be greater than 0.5 sec or 0.25 sec and can be left alone There is no substantial impact. However, since the playback is delayed from the original playback time, it is preferable to eliminate this delay. The digital broadcast receiving apparatus according to the third embodiment has a function of eliminating the reproduction time delay.

  FIG. 7 is a block diagram showing a configuration of a digital broadcast receiving apparatus according to the third embodiment. Referring to FIG. 7, the digital broadcast receiving apparatus 20 includes a plurality of digital broadcast capturing units 11 and 12, a data storage unit 13, a video reproduction unit 14, and a speed adjustment unit 21. The digital broadcast capturing units 11 and 12, the data storage unit 13, and the video reproduction unit 14 of the third embodiment are the same as those of the first embodiment shown in FIG.

  The speed adjustment unit 21 eliminates the delay of 0.5 sec at the maximum caused by the channel switching process by the data storage unit 13 by increasing the playback speed of the video playback unit 14. Note that the amount of delay caused by channel switching can be determined by how long the new channel starts to be output.

  FIG. 8 is a block diagram illustrating a configuration of a speed adjustment unit according to the third embodiment. Referring to FIG. 8, the speed adjustment unit 21 includes an input speed storage unit 31, a subtracter 32, a D / A conversion unit 33, a VCxO 34, a frequency division unit 35, a playback speed counter 36, and a delay control unit 37. Yes.

  The input speed storage unit 31 stores PCR (Program Clock Reference) information of the input TS.

  The subtractor 32 obtains the difference between the output of the input speed storage unit 31 and the output of the playback speed counter 36.

  The D / A converter 33 performs digital / analog conversion on the difference value obtained by the subtracter 32 and outputs a voltage signal.

  The VCxO 34 is an oscillator that changes the frequency based on the voltage level of the voltage signal from the D / A conversion unit 33, and its output is a clock used for video reproduction in the video reproduction unit 14. The speed at which the video playback unit 14 plays back the video is determined by this clock.

  The frequency divider 35 divides the clock from the VCxO 34. The frequency division ratio of the frequency divider 35 is 300.

  The playback speed counter 36 counts the playback speed based on STC (System Time Clock) obtained by frequency division by the frequency divider 35. However, the bias value from the delay control unit 37 is added to the counter value of the reproduction speed counter 36.

  When a delay due to channel switching occurs in the data storage unit 13, the delay control unit 37 gives the delay control unit 37 a bias value for increasing the playback speed of the video playback unit 14 and eliminating the delay. The bias value is a value within the range of the frequency control width in VCxO34, and the delay is eliminated by maintaining the state where the reproduction speed is increased within the range for a necessary time.

  As can be seen from the above description, the input speed storage unit 31, the subtractor 32, the D / A conversion unit 33, the VCxO 34, the frequency division unit 35, and the reproduction speed counter 36 constitute a PLL circuit that generates a reproduction clock. The delay control unit 37 increases the reproduction speed by applying a bias to the feedback of the PLL circuit.

  Assume that the oscillation frequency of the system clock and VCxO34 is 27 MHz. Further, assuming that the frequency control width of the VCxO 34 conforms to the MPEG standard, the frequency control is limited to a range of 27 MHz ± 810 Hz. In this case, it is possible to eliminate a delay of up to 810 clocks in 1 second. For example, if a delay of 0.5 sec, which is the maximum value, occurs, this corresponds to 450,000 clocks and is eliminated in about 556 sec.

  FIG. 9 is a flowchart illustrating the operation of the delay control unit according to the third embodiment. In this example, the delay control unit 37 performs processing using the parameter D for the delay time. Referring to FIG. 9, it is determined whether or not channel switching has occurred from the initial state (step 301) in which the delay time D is cleared (step 301).

  When channel switching occurs, the delay control unit 37 sets the generated delay time (generated delay) X to the delay time D (step 303).

  Whether channel switching has occurred in step 302 or after the processing in step 303, the delay control unit 37 determines whether or not the delay time D = 0 (step 304). If D = 0, the delay control unit 37 adds a predetermined bias value to the count value of the reproduction speed counter 36 (step 305), and subtracts the bias value from the delay time D (step 306).

  When D = 0 in step 304 or after the processing in step 306, the VCxO 34 is controlled (step 307), and the process returns to step 302.

  As described above, according to the present embodiment, when a delay associated with channel switching occurs in the data storage unit 13, the speed adjustment unit 21 increases the playback speed of the video playback unit 14 until the delay is eliminated. The delay caused by shortening the channel switching time can be finally eliminated.

(Fourth embodiment)
In the first to third embodiments, assuming a digital broadcast receiving apparatus capable of simultaneously recording a plurality of channels, the channel switching process is performed in the data storage unit in which the data of the plurality of channels is collected. However, the present invention is not limited to this configuration. As another configuration, the fourth embodiment is different from the first embodiment in that a video switching unit is provided with a channel switching process.

  Here, as an example, as in the first embodiment, when there is an instruction to switch channels, playback is performed retroactively to the latest sequence header in the past in the new channel. However, as in the second embodiment, it may be selected whether to go back to the past or wait for the next sequence header.

  FIG. 10 is a block diagram showing a configuration of a digital broadcast receiving apparatus according to the fourth embodiment. Referring to FIG. 10, the digital broadcast receiving apparatus 40 includes a plurality of digital broadcast capturing units 11 and 12, a data storage unit 41, and a video reproduction unit 42.

  The digital broadcast capturing units 11 and 12 are the same as those in the first embodiment shown in FIG. 1 except that data is sent to both the data storage unit 41 and the video reproduction unit 42.

  The data storage unit 41 has only a function of storing a plurality of data from the plurality of digital broadcast capturing units 11 and 12 and is not involved in channel switching.

  The video playback unit 42 receives a plurality of data from the plurality of digital broadcast capturing units 11 and 12, plays back the data of the channel selected by the user, and temporarily stores the data of other channels for 0.5 sec. Accumulate. In digital broadcasting, since a sequence header is inserted every 0.5 sec, the past newest sequence header always exists in the temporarily stored data for 0.5 sec.

  When the user gives an instruction to switch channels, playback of the old channel is stopped, and playback of the new channel is started from the portion of the new channel delimited by the latest sequence header in the past.

  Here, since an example is shown in which reproduction of a new channel is always started by tracing back to the latest sequence header in the past, data for 0.5 sec is accumulated. However, if it is configured to select whether to go back or wait for the next sequence header as in the second embodiment, data for 0.25 sec may be temporarily stored.

It is a block diagram which shows the structure of the digital broadcast receiver by 1st Embodiment. It is a figure which shows the mode of the switching of the TS packet sequence at the time of channel switching. It is a flowchart which shows the operation | movement at the time of the channel switching in 1st Embodiment. It is a figure for demonstrating the operation | movement at the time of the channel switching of a data storage part. It is a figure for demonstrating the operation | movement at the time of the channel switching of a data storage part. It is a flowchart which shows the operation | movement at the time of the channel switching in 2nd Embodiment. It is a block diagram which shows the structure of the digital broadcast receiver by 3rd Embodiment. It is a block diagram which shows the structure of the speed adjustment part in 3rd Embodiment. It is a flowchart which shows operation | movement of the delay control part in 3rd Embodiment. It is a block diagram which shows the structure of the digital broadcast receiver by 4th Embodiment.

Explanation of symbols

10, 20, 40 Digital broadcast receiver 11, 12 Digital broadcast capture unit 13, 41 Data storage unit 14, 42 Video playback unit 21 Speed adjustment unit 31 Input speed storage unit 32 Subtractor 33 D / A conversion unit 34 VCxO
35 Divider 36 Replay Speed Counter 37 Delay Controller 101-103, 201-210, 301-307 Steps

Claims (2)

A digital broadcast receiving apparatus for receiving a digital broadcast of a plurality of channels that is differentially encoded,
A plurality of capturing units for extracting at least one channel from the plurality of broadcast channels and acquiring data obtained from the signal;
The data acquired by any of the above-mentioned capturing units is played back and output, and at least the data of channels other than the playback output is temporarily stored for a predetermined time, and the old channel being played back is transferred to another new channel. When there is a request for switching, after the reproduction output of the data of the old channel is stopped, the newest channel data can be reproduced by using the new channel data temporarily stored. A switching unit that starts to output from the part,
By adding a bias to the feedback of a PLL circuit that generates a clock for reproduction until the delay caused by the switching unit starting to reproduce and output the new channel from past data at the time of channel switching is eliminated, And a speed adjusting unit for increasing the speed of reproduction output of the new channel. A digital broadcast reproduction method for receiving a digital broadcast of a plurality of differentially encoded channels and reproducing a user's desired channel,
Obtaining a plurality of data obtained from signals of a plurality of broadcast channels;
Replaying any acquired data and at least temporarily storing data of channels other than being replayed for a predetermined time;
When there is a request to switch from the old channel being played to another new channel, the step of stopping the output of the data of the old channel;
Using the data of the new channel that has been temporarily stored, and starting to output the data of the new channel from the portion where the latest reproduction can be started in the past;
By adding a bias to the feedback of the PLL circuit that generates the clock for reproduction until the delay caused by starting to reproduce and output the new channel from the past data at the time of channel switching, the reproduction of the new channel is performed. Increasing the speed of the digital broadcast reproduction method.

Images