Multiplex communications – Communication over free space – Combining or distributing information via time channels
Reexamination Certificate
1999-06-24
2004-01-20
Yao, Kwang Bin (Department: 2664)
Multiplex communications
Communication over free space
Combining or distributing information via time channels
C370S529000
Reexamination Certificate
active
06680931
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a data multiplex broadcasting system in which a plural kinds of data are multiplexed to be transmitted, and, in particular, to a data multiplex broadcasting system suitable for recognizing a start of broadcasting of a particular content on the receiving side.
2. Description of Related Art
In RDS (Radio Data System) and DAB (Digital Audio Broadcasting), programme-associated information or independent information is multiplexed into audio information to be broadcasted. In RDS and DAB, audio information is sent being multiplexed with information called M/S (Music/Speech) flag which indicates whether the content of the audio information in question belongs to the category of music or the category of speech. On the receiving side, by referring to this flag, it is easy to recognize a point of time at which a broadcast of a piece of music starts after speech of a speaker in a broadcast programme, for example. In other words, by referring to this M/S flag, it is easy to record a piece of music broadcasted during a broadcast programme, onto an audio recording device such as an MD (Mini Disk) recorder from the beginning of the music piece in question.
In the case of RDS, when a programme is broadcasted, information associated to the contents of the programme is subjected to multiplex modulation as RDS signal, and various services can be supplied to radio listeners based on the RDS signal demodulated on the receiving side.
This RDS signal is obtained by using a subcarrier of 57 kHz outside the frequency band of the FM-modulated wave, and by subjecting this subcarrier to amplitude modulation with coded information data signal associated to programme contents. This amplitude-modulated subcarrier is subjected to frequency modulation onto a main carrier and then broadcasted.
In
FIG. 14
, RDS signal is repeatedly multiplexed and transmitted by groups each of which consists of 104 bits. Each group consists of 4 blocks, and each block includes 26 bits. More particularly, the block consists of 16 bits of an information word and 10 bits of a check word.
Further, each group is classified into 16 types, Type
0
through Type
15
, depending on its contents. In addition, for each type of group, one of two versions, A and B, is defined.
For example,
0
A group is defined as basic tuning and switching information, and includes a programme identification code (PI code), a traffic-information-programme identification code (TP code), programme station code (PS code), and the like.
Information indicating whether contents of a broadcast belong to the category of music or the category of speech is included in a second block of
0
A group,
0
B group and
15
B group, and a fourth block of
15
B group. This information is called M/S (Music/Speech) flag, as described above. When the value of M/S flag is 0, it shows that the current broadcast contents belong to the category of “speech”, and, when its value is 1, it shows the current broadcast contents belong to the category of “music”. M/S flag is assigned, for example, to 13th bit
521
of the second block in FIG.
14
.
On the receiving side, by receiving and demodulating this RDS signal, and by extracting M/S flag included in the
0
A group,
0
B group or
15
B group, it is possible to recognize whether the current broadcast contents belong to the category of speech or to the category of music. Accordingly, by continuously monitoring this M/S flag, it is possible to recognize a point of time at which a broadcast of a piece of music starts after speech of a speaker in a broadcast programme, for example. Accordingly, it is possible to record apiece of music by an audio recording device such as an MD player, from the beginning of the music.
On the other hand, in the case of DAB, it is also possible to multiplex and transmit information similar to that in RDS. DAB is digital audio broadcasting in which Orthogonal Frequency Division Multiplex system (OFDM system) is employed to carry out multiplex modulation, and audio information is encoded in accordance with MPEG Layer II (International Standard system ISO/IEC 11172-3 Layer II).
In
FIG. 15
, an audio frame of DAB has a frame length of 24 ms, and is slightly different from a frame of MPEG. PAD (Programme Associated Data) included in this audio frame is for transmitting information associated with the programme. Utilizing this PAD, it is possible to transmit information such as a programme name, a record number, dynamic range control information, and the like. Further, PAD includes M/S (Music/Speech) flag that indicates whether broadcast contents belong to the category of music or the category of speech.
Accordingly, in the case of DAB, by extracting PAD included in an audio frame and referring to the content of M/S flag included in PAD, on the receiving side, it is also possible to recognize a point of time at which a broadcast of a piece of music starts after speech of a speaker, for example, similarly to RDS. Thus, it is possible to record a piece of music from the beginning by an audio recording device such as an MD player.
SUMMARY OF THE INVENTION
As described above, M/S flag indicates whether broadcast contents on the air belong to the category of music or the category of speech. In other words, it is a flag showing a category of broadcast contents on the air. However, use of M/S flag causes following problems in record control in an audio recording device such as an MD player.
Namely, when a plurality of music pieces are successively broadcasted, and it is desired to record a particular music piece out of these music pieces, the record control using M/S flag is not applicable to that situation. Accordingly, an operator must start a recording operation on the audio recording device in a timing synchronized a point of time at which that particular piece of music is actually started to be broadcasted. On that occasion, if the recording operation deviates from the actual point of time when the broadcast of the music piece is started to be transmitted, it is probable that failure such as so-called “headless” may be caused.
Further, as described above, even if plural pieces of music are to be successively broadcasted immediately after speech in a broadcast, it is possible to utilize M/S flag for automatic start of recording in synchronization with start of broadcasting the first piece of music. However, it is impossible to automatically stop recording operation in synchronization with a start of broadcast of a music piece next to the first-broadcasted one. In other words, it is impossible to record only the first music piece. Accordingly, an operator must stop recording of the audio recording device in synchronization with an actual end of broadcasting of the music piece which is being recorded.
The present invention has been made taking the above situation into consideration. An object of the present invention is to make it possible to easily recognize divisional point of respective content elements on the receiving side, even when the content elements of the same category are successively broadcasted. In detail, an object of the present invention is to provide a data multiplex broadcasting method, a switcher, a data multiplex transmitting device, a receiving device, a system controller, and a recording device which are able to support easy recognition of divisional point of respective content elements on the receiving side when the content elements of the same category are successively broadcasted.
To attain the above object, in the data multiplex broadcasting method of the present invention, information which can specify a start or end of each content element is multiplexed to data expressing broadcast contents and broadcasted when each content element of the broadcast contents belongs to the same category.
In detail, in the case that broadcast data expressing broadcast contents is formed of a plurality of successive element data, each of which expresses a content element belonging to the same category, a code whose state
Aigasa Yuichi
Oomori Yoshio
Denon Ltd.
Dickstein , Shapiro, Morin & Oshinsky, LLP
Emdadi Kamran
Yao Kwang Bin
LandOfFree
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