Patent Application
20070003215
This application claims the benefit of priority of Japanese Application No. 2005-189157 filed Jun. 29, 2005 and Japanese Application No. 2006-75861 filed Mar. 20, 2006, the disclosure of which also is entirely incorporated herein by reference.
The present invention relates to a digital broadcasting receiving device and a digital information receiving device, which have a recording function, and a playback method.
A digital broadcasting recording-and-playback device is disclosed in JP-A-2001-094948, in which video information of a received program is recorded and played back with respect to a recording medium. In the digital broadcasting recording-and-playback device, in the case that broadcasting time of a scene to be played back on a display device is delayed from current time due to pause by a user, when catch-up playback is instructed by the user, the broadcasting time is read out from the recording medium by TS (Transport Stream) indicating the scene and compared with current time given by a current time acquisition unit using a comparison unit. Playback speed is controlled by a playback speed control unit such that playback speed in fast-forward playback is close to playback speed in normal playback as the broadcasting time approaches the current time.
Since a broadcasting program contains not only video information but also audio information, a request that the audio information is desired to be confirmed even in the fast-forward playback is given, in addition, in the case of change from fast-forward playback to current broadcasting, a sense of discomfort felt by a user at the boundary between them is required to be mitigated also for the audio information. For example, when audio frequency is abruptly changed, since the user feels the sense of discomfort, such a difficulty is necessary to be solved.
It is necessary to provide a digital broadcasting receiving device and a digital information receiving device, in which a fast-forward playback function can be improved, and a playback method.
One aspect of the invention is configured such that in the case where digital information containing an audio stream is received, when an instruction of pause of looking and listening of the digital information is inputted, received digital information is stored, and when an instruction of canceling the pause is inputted, while the digital information is stored, fast-forward playback of the stored digital information is performed with playback speed of the stored digital information being changed in several stages. In this aspect, when the playback speed of the stored digital information is changed, audio frames of the audio stream are decoded with a thinning level of the audio frames being changed.
Embodiments of the present invention will be described in detail based on the following figures, wherein:
An example of a digital broadcasting receiving device having a recording function is described using drawings.
A control section 101 includes CPU (Central Processing Unit) and the like, and controls overall the digital broadcasting receiving device 100. An operational section 102 includes a plurality of keys including a number key and a function key, and receives an instruction from a user. In a stationary digital broadcasting receiving device, an infra-red ray reception section may be provided to configure the operational section 102 with remote control.
A channel select section 103 is a tuner for selecting a channel of digital broadcasting, and demodulates received digital broadcasting via a broadcast reception antenna 104, and then outputs digital data. The demodulation includes error correction using an error-correction code contained in the broadcasting. A radio communication section 105 is a modem for performing radio communication in a CDMA (Code Division Multiple Access) method and the like via a transmission and reception antenna for communication 106.
A memory section 107 is a memory for storing an operation program of the control section 101 and the like. A program storage section 108 is a memory for recording and storing a received digital broadcasting program. A program information storage section 109 is a memory for storing program information such as EPG (Electric Program Guide) of a program to be recorded. The EPG may be transmitted through the digital broadcasting, or may be acquired via internet and the like by using a radio communication line network.
Each of the memory section 107, program storage section 108, and program information storage section 109 may be a separate memory such as RAM, (Random Access Memory), or the memory section 107, storage section 108 and the like may be provided in a memory. Alternatively, a removable, external memory medium may be used. For example, the program storage section 108 may be configured by the external memory medium, and the memory section 107 and the like other than that may be configured by RAM. The program storage section 108 may be configured by the external memory medium, and a plurality of media can be exchanged to be used, thereby a large number of digital broadcasting program data can be stored.
A video decoding section 110 is a decoder for decoding compressed video data, and a display section 111 is a display such as a liquid crystal monitor for displaying a video image decoded by the video decoding section 110. An audio decoding section 112 is a decoder for decoding compressed audio data, and an audio output section 113 is a speaker for outputting an audio sound decoded by the audio decoding section 112. The display section 111 may be in a method of a touch panel in which a user can input a letter, a numeral, or user instruction by touching a screen of the display using a pen or a finger. Thus, the user properly uses the operational section 102 or the display section 111 depending on a use condition or information to be inputted. Alternatively, the user may use only the display section 111 and thus omit the operational section 102.
When the digital broadcasting is received via the broadcast reception antenna 104 and the channel select section 103, it is temporally stored in the memory section 107. The temporally stored digital broadcasting data are separated into compressed video data and compressed audio data by the control section 101. The compressed video data are decoded by the video decoding section 110, and then displayed by the display section 111. The compressed audio data are decoded by the audio decoding section 112, and outputted as audio sound by the audio output section 113. When the digital broadcasting program is recorded, the digital broadcasting data are stored in the program storage section 108.
The digital data received via the transmission and reception antenna for communication 106 and the radio communication section 105 are temporally stored in the memory section 107. The temporally stored digital data are separated by the control section 101. In the case of characteristic data such as a mail, the data are displayed by the display section 111, and in the case of audio data such as a call, the data are outputted as audio sound by the audio output section 113. By control of the control section 101, data stored in the memory section 107 and the like are read out, and transmitted as digital data via the radio communication section 105 and the transmission and reception antenna for communication 106.
When reception of the digital broadcasting is started (step 201), video data are displayed on the display section 111, and audio data are outputted from the audio output section 113, and consequently the broadcasting is looked and listened (step 202). When a stop instruction is inputted during looking and listening of the broadcasting (step 203), the control section 101 performs processing of finishing reception of the broadcasting (step 204).
The control section 101 detects whether a pause instruction is inputted or not (step 205). When looking and listening are paused during looking and listening of the broadcasting, recording is started (step 206), and data are sequentially recorded and stored in the program storage section 108. If looking and listening are neither stopped nor paused during the looking and listening of broadcasting, the looking and listening are continued.
During the pause, the control section 101 waits cancel of the pause (step 207). When cancel of the pause can be detected in the step 207, a mode of playback after the pause is determined (step 208). The digital broadcasting receiving device 100 has two modes of a time-shift playback mode where broadcasting data recorded at normal playback speed are played with constant time difference between current broadcasting and broadcasting data that are played, and a fast-forward playback mode where fast-forward playback of the recorded broadcasting data is performed such that the broadcasting data which are played catch up with the current broadcasting.
When the playback mode after the pause is the time-shift playback mode in the step 208, data that have been recorded are played while the current broadcasting is recorded (step 209). When looking and listening are stopped during looking and listening of playback data (step 210), the control section 101 finishes the recording (step 211), and then performs processing of finishing reception of the broadcasting (step 212) and then finishes the looking and listening of playback data (step 213).
When the playback mode after the pause is the fast-forward playback mode in the step 208, processing is shifted to processing of fast-forward playback of data that have been recorded while the current broadcasting is recorded (step 214). Detail of the fast-forward playback processing is described later using
Here, the fast-forward playback is described.
In a compression method of video data according to a simple profile of the MPEG4 (Moving Pictures Expert Group 4: a compression coding technique of data containing moving pictures and audio sound standardized by International Organization for Standardization (ISO/IEC14496)) standard, 1 GOP includes an I picture (Intra Picture) that can independently generate an image frame without having any other reference image, and a plurality of P pictures (Predictive Pictures) that generate image frames with reference to reference images in the front.
While the reference image is necessary for independently generating the P picture, since the reference image is not necessary for the I picture, the I picture can be played back independently, and only the I pictures are sequentially displayed, thereby fast-forward playback of the video stream can be carried out at any optional playback speed. In the embodiment, all the I pictures or I pictures for every several I pictures are displayed with an interval of fixed time, so that the fast-forward playback of the video stream is performed.
Audio data include a plurality of audio frames, and 1 audio frame includes data of 1024 samples. When sampling frequency is 48 kHz, duration (playback duration) during which 1 audio frame can be played back is 21.3 ms (1024 samples/48 kHz). Here, the sampling frequency during playback is increased to 64 kHz, duration during which 1 audio frame can be played back is 16 ms (1024 samples/64 kHz), and consequently playback can be performed at 1.33 times speed (64 kHz/48 kHz=21.3 ms/16 ms). The sampling frequency during playback is optionally increased, thereby playback can be performed at any optional speed.
In the embodiment, when the audio stream including the plurality of audio frames that have been received is inputted into the audio decoding section 112, audio frames are appropriately thinned from the plurality of audio frames, thereby fast-forward audio playback is performed.
In this way, according to the embodiment, since audio sampling frequency during playback is not different from that during recording, playback of audio sound without the sense of discomfort can be performed. Since the audio streams are thinned, it is feared that noise may be generated and clearness may be somewhat reduced at places where the audio frames are thinned, however, a thinning method in such a level that one audio frame is thinned for every four audio frames is practically not problematic for practically played audio sound.
Table 1 is an example of control data showing a relationship between a thinning level in the case of catching up with current broadcasting, and playback speed, playback speed depending on time difference to current broadcasting, and duration. Such control data as shown in Table 1 are stored in the memory section 107, and the control section 101 controls playback speed based on the control data. For example, when audio data are played back from a state of a delay of 10 minutes (600 seconds), playback is started at 1.3333 times speed, and when audio data are played back from a state of a delay of 5 minutes (300 seconds), playback is started at 1.2308 times speed.
In the example, there are 11 kinds of playback speed from 1.3333 times speed where 1 frame is thinned for every 4 frames to 1.0294 times speed where 1 frame is thinned for every 35 frames, in addition to 1.0 times speed where any audio frames are not thinned.
The audio frames are thinned, for example, in the following way. When 3 frames are thinned for every 16 audio frames in No. 9, 1 audio frame is thinned in first 5 audio frames, then 1 audio frame is further thinned in next 6 audio frames, and then 1 audio frame is still further thinned in next 5 audio frames. In the case of playback speed in No. 10, 1 audio frame is thinned in first 5 audio frames, then 1 audio frame is further thinned in next 5 audio frames, and then 1 audio frame is further thinned in next 5 audio frames, and then 1 audio frame is still further thinned in next 5 audio frames. In the case of playback speed in No. 11, 1 audio frame is thinned in first 4 audio frames, then 1 audio frame is further thinned in next 4 audio frames, and then 1 audio frame is still further thinned in next 5 audio frames.
When first delay time of 10 minutes (600 seconds), 11 stages of playback speed, and duration T (sec) in each playback speed are assumed to be given, since the total sum of delay time and duration is equal to the total sum of products of respective stages of playback speed multiplied by duration, equation (1) is established.
600+T×11=T×Σ(1.0294+ +1.3333) (equation 1)
From the equation (1), duration T (sec) for each playback speed is as follows.
T=600/(Σ(1.0294+ +1.3333)−11)=600/(12.9230−11)=312 (equation 2)
Time for catching up is 3432 sec (about 57 min) from (equation 3).
312×11=3432 (equation 3)
Since human sensibility has a property that even if the number of stages of change is the same, the change is hardly sensed in the case that a rate of change is constant compared with the case that a range of change is constant, a thinning level is adjusted such that a rate of change in playback speed is approximately constant (2.08% to 2.94%) in Table 1.
While playback speed is changed in 11 kinds of levels in addition to 1.0 times speed in Table 1, it is not restrictive, and playback may be performed at 1.5 times speed where 1 frame is thinned for every 3 frames, or 2.0 times speed where 1 frame is thinned for every 2 frames. Moreover, the thinning level may be changed finely compared with the example shown in Table 1. In this case, since the playback speed is changed more smoothly, a sense of discomfort of a user due to change in speed can be reduced. Conversely, when the thinning level is controlled more roughly, since the number of controlling the playback speed is decreased, load on a control program can be reduced. However, in order to restrain the load on the control program while reducing the sense of discomfort of the user, the rate of change in playback speed is preferably set to be 2.08% to 2.94% as the example of Table 1.
While duration for each playback speed is made constant in the example of Table 1, the duration may be changed for each playback speed. For example, the duration may be lengthened with increase in playback speed, so that time for catching up with current broadcasting may be reduced.
In the example of Table 1, when time difference to current broadcasting exceeds 512 sec, playback is performed at 1.333 times speed until time difference reaches 512 sec, however, when the time difference exceeds, for example, 10 min (600 sec), playback may be performed at 1.5 times speed where 1 frame is thinned for every 3 frames, or 2.0 times speed where 1 frame is thinned for every 2 frames. By performing control in this way, time for catching up with current broadcasting can be reduced.
A relational expression indicating a relationship between delay time, and the number of stages of playback speed and duration at each playback speed may be stored in the memory section 107 instead of control data, so that the control section 101 calculates the playback speed based on the relational expression.
In the example, when video playback speed is changed in accordance with audio playback speed, a time interval of video frames outputted into the display section 111 is changed. For example, when the number of frames to be displayed for 1 sec is assumed to be 15, the time interval of the video frames, is 66.66 ms (1 sec/15) at 1.0 times speed (standard state). Playback is performed with the time interval of the video frames being shortened, by which video playback speed can be increased. Time intervals of video frames corresponding to respective kinds of audio playback speed in Table 1 are shown in Table 2.
When fast-forward playback is started (step 601), the control section 101 detects time difference between time at a point of recording and time of current broadcasting, and calculates playback speed using the control data or the relational expression stored in the memory section 107 (step 602), and then plays back data that have been recorded at a calculated playback speed while continuing recording (step 603).
The control section 101 determines whether the time at the point of recording (time when recording data that are played back were recorded) corresponds to time of current broadcasting (step 604). Processes of the steps 602 and 603 are sequentially repeated until the time at the point of recording corresponds to the time of current broadcasting (until catching up with the current broadcasting). Playback speed is gradually decreased during that, and sequentially approaches 1.0 times speed. When the time at which recording data that are played back were recorded corresponds to the time of the current broadcasting, recording is finished (step 605), and the current broadcasting that is received is outputted to the display section 111 and the audio output section 113 (step 606).
When looking and listening are stopped during looking and listening of broadcasting (step 607), the control section 101 finishes reception of broadcasting (step 608).
In the embodiment, since control is performed such that the rate of change in playback speed is approximately constant, the sense of discomfort felt by the user in the boundary when fast-forward playback is changed into current playback can be mitigated.
Table 3 shows an example of control data in the case that sampling frequency during playback is also changed concurrently with the playback speed such that playback speed can be continuously changed.
For example, when playback speed is changed from 1.333 times speed to 1.300 times speed, frequency is temporally changed from 48 kHz that is original frequency to 49.231 kHz, so that the playback speed is made to be 1.333 times speed. Then, the sampling frequency is gradually changed from 49.231 kHz to 48 kHz, thereby playback speed is continuously shifted to 1.300 times speed. The sampling frequency during playback is gradually changed in this way, by which audio playback speed can be continuously changed to 1.0 times speed.
In the example of Table 3, to avoid obstacle in a sense of hearing, a pitch of playback speed is set such that the rate of change in sampling frequency is at most 2.973% that is half the 2**( 1/12)=1.05946 times (a rate of change of 5.946%) as a pitch of a sound (frequency) to a next scale (half tone) in the equal temperament scale.
The control section 101 controls a clock signal generation section 701 so that a specified sampling frequency is generated from the clock signal generation section 701 and supplied to the audio decoding section 112. Moreover, the clock signal generation section 701 provides a clock signal for determining operational frequency of the video decoding section 110, so that the control section 101 can control the clock signal generation section 701 to change the operational frequency of the video decoding section 110.
In the embodiment, the operational frequency of the video decoding section 110 is increased by using such a function, thereby processing capability of the video decoding section 110 is improved, and consequently fast-forward playback is realized, which is not playback of only the I pictures, but playback that displays all the frames including P pictures. It will be obvious that when the video decoding section 110 has originally sufficient processing capability, the fast-forward playback can be realized without increasing the operational frequency of the video decoding section 110.
While video playback speed is changed in accordance with audio playback speed in the embodiment, the audio playback speed may be changed in accordance with video playback speed.
While audio frames are thinned when data are inputted into the audio decoding section to reduce load on the audio decoding section in the embodiment, the thinning can be realized by thinning PCM (Pulse code modulation) data generated when data are outputted from the audio decoding section. In this case, while the load on the audio decoding section is not reduced, the same advantage is given in a sense of changing the playback speed.
While the digital broadcasting includes terrestrial digital broadcasting and digital broadcasting via an artificial satellite, they are the same in the light of digital broadcasting through wireless transmission, and therefore the embodiments of the invention can be applied to either of them. Moreover, it is obvious that the embodiments of the invention can be applied even to digital broadcasting through a wired cable television.
As described hereinbefore, a digital broadcasting receiving device and a digital information receiving device, in which a fast-forward playback function can be improved, and a playback method can be provided.
The foregoing invention has been described in terms of preferred embodiments. However, those skilled, in the art will recognize that many variations of such embodiments exist. Such variations are intended to be within the scope of the present invention and the appended claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2006-075861 | Mar 2006 | JP | national |
| 2005-189157 | Jun 2005 | JP | national |
