Pulse or digital communications – Bandwidth reduction or expansion – Television or motion video signal
Reexamination Certificate
2002-05-14
2003-12-02
Lee, Young (Department: 2613)
Pulse or digital communications
Bandwidth reduction or expansion
Television or motion video signal
Reexamination Certificate
active
06658060
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a digital data transmission apparatus for multiplexing and transmitting digital data including video data and audio data, and a transmission method thereof. More particularly, the present invention relates to a digital data transmission apparatus for multiplexing and transmitting the digital data in an active video period of a television signal, and a transmission method thereof.
BACKGROUND ART
At present, there is generally employed the SMPTE-295M standard, i.e., Serial Digital Interface (below, referred to as “SDI”) standard as transmission method of digital video signals in broadcasting stations of all the countries in the world. It is known that the SDI standard is prescribed by the SMPTE (Society of Motion Picture and Television Engineers), and provides that digital data including video data and audio data are converted into serial data to be transmitted.
Referring to
FIG. 13
, a concrete description will be given to a digital data transmission method under the above-described known SDI standard. It is noted that a description will be given to a transmission method corresponding to television signals of the NTSC system in the following description.
FIG. 13
is an explanatory diagram showing a configuration of one frame in the SDI standard. It is noted that a straight line H of
FIG. 13
represents a horizontal pixels of a television signal, and each numeric value on the straight line H represents a pixel number. A straight line V of the same figure represents a vertical line of a television signal, and each numeric value on the straight line V represents a line number.
As shown in
FIG. 13
, in the SDI standard, one frame period is divided into a horizontal blanking period, and a vertical blanking period, an optional blanking period and an active video period in each field of a first field and a second field constituting the one frame.
The horizontal blanking period is prescribed by the section of horizontal pixels of which the pixel numbers range from 1440 to 1715. The horizontal blanking period is provided with EAV (End of Active Video) and SAV (Start of Active Video) on its top portion and end portion, respectively. In the horizontal blanking period between the EAV and SAV, ancillary data such as audio data and user data can be transmitted.
In the active video period, video data of 1440 pixels are multiplexed on every line to be transmitted as the serial data by a predetermined clock frequency. It is noted that one pixel is comprised of 8 bits or 10 bits of video data.
The optional blanking period is a period which is included in the vertical blanking period. However, the optional blanking period can arrange and transmit video data in the same manner as in the active video period.
The use of the SDI standard enables the transmission of 4:2:2-component television signals of one channel not through analog transmission system, ensuring the prevention of degradation in the signals.
On the other hand, in the case where the video data obtained from digitization of video signals were processed as they were, the video data were increased in amount of data, so that the video data were required very high data rate (transmission rate). Accordingly, when the above-described video data were recorded on a recording medium such as magnetic tape, it was impossible to ensure a sufficient recording time.
In contrast, the handling of the video data by performing compression thereof in such manner that visual image degradation is not recognized by bit rate reduction has been known as effective technique. Concretely, there is a DV format prescribed by the HD digital VCR Committee (High Definition Video Cassette Reorder Committee), and described in “Specifications of Consumer-Use Digital VCRs using 6.3 mm magnetic tape” as the one in which the bit rate reduction of a video signal is applied to a home digital VTR.
In the DV format, data compression is performed in two modes according to television signals by means of bit rate reduction based on DCT (Discrete Cosine Transform). Concretely, in the DV format, a standard television signal is compressed to 25 Mbps data, while a high-definition television signal is compressed to 50 Mbps data. The compressed video data are recorded on the magnetic tape with interleaved audio data, VAUX data which are data ancillary to the video data, AAUX data which are data ancillary to the audio data, and sub-code data and the like. In the case where the data compressed in the 25 Mbps mode are recorded on the magnetic tape, the data for one frame are divided into 10 tracks of the magnetic tape to be recorded. Also, in the case where the data compressed in the 50 Mbps mode are recorded on the magnetic tape, the data for one frame are divided into 20 tracks of the magnetic tape to be recorded. It is noted that, as for the concrete information the above-described VAUX data, AAUX data and sub-code data show, it is described in, for example, the technology of “digital recording and reproducing apparatus” disclosed in Japanese Laid-Open Patent Publication No. 7-226022.
When the video data compressed by the bit rate reduction such as the DV format are transmitted using the above-described SDI standard, in the prior art, the compression of the video data has been required to be once decompressed back into a base band signal. Because in the SDI standard, there is prescribed the transmission method of not the compressed video data but the non-compressed video data which have not been compressed. Further, the SDI standard is intended to transmit the video data of the one channel, and hence it has no provisions for the transmission method for transmitting multi-channel video data. For this reason, for example, transmission of compressed multi-channel video data between recording and reproducing apparatuses by the use of the SDI standard has required that a transmission line was provided for every channel, and further that at least a decoder and an encoder were provided at the transmission line on the transmitting side and the receiving side, respectively.
Examples of a conventional digital data transmission method to overcome the forgoing problems include the technology of “digital data transmission method” disclosed in Japanese Laid-Open Patent Publication No. Hei 9-46705. The object of the conventional digital data transmission method is to transmit multi-channel video signals compressed by, for example, the DV format, utilizing the existing transmission lines comprised of coaxial cables.
Here, a concrete description will be given to a conventional digital data transmission method with reference to FIG.
14
.
FIG. 14
is an explanatory diagram showing a method for multiplexing and transmitting digital data of six channels using the SDI standard in a conventional digital data transmission method.
As shown in
FIG. 14
, in the conventional digital data transmission method, the active video period is divided into units of 240 pixels (words), so that six transmission areas are formed on the SDI standard. Six channels
1
,
2
,
3
,
4
,
5
, and
6
are assigned to the six transmission areas, respectively. In each of the channels
1
through
6
, digital interface data (below, referred to as “DIF data”) for the one frame are arranged. Specifically, the DIF data are comprised of a plurality of a DIF block, and the DIF data are arranged in the transmission area so that three DIF blocks are multiplexed on every line. The DIF data are also comprised of the video data compressed to the 25 Mbps based on the DV format, the interleaved audio data, the VAUX data, the AUUX data and the sub-code data.
With the conventional digital data transmission method, in the case where the data compression is performed in the 25 Mbps mode as shown in the same figure, it is possible to multiplex the DIF data up to a maximum of the six channels of the channels
1
through
6
and transmit them on the SDI standard. Also, in the case where the data compression is performed in the 50 Mbps mode, two transmission areas can be assigned per one channe
Morishige Kazuma
Muraoka Hidefumi
Nakagawa Yukio
Otaka Hideki
Tanaka Shinya
Akin Gump Strauss Hauer & Feld L.L.P.
Lee Young
Matsushita Electric - Industrial Co., Ltd.
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