Multiplex communications – Communication techniques for information carried in plural... – Combining or distributing information via time channels
Reexamination Certificate
1998-03-25
2004-06-22
Kizou, Hassan (Department: 2662)
Multiplex communications
Communication techniques for information carried in plural...
Combining or distributing information via time channels
C370S538000, C370S395640, C348S423100, C348S844000
Reexamination Certificate
active
06754239
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a multiplexing apparatus and method, a transmitting apparatus and method, and a recording medium. More particularly, the present invention relates to a multiplexing apparatus and method, a transmitting apparatus and method, and a recording medium suitable for use, for example, in a situation where a bit stream of a digital signal formed from an image (moving image) signal and an audio signal is recorded on a recording medium such as a magneto-optical disk or a magnetic tape and is reproduced to be displayed on a display, or in a situation where such a bit stream is transmitted from a transmitting terminal to a receiving terminal over a transmission channel in a television conference system, a video telephone system, broadcasting apparatuses or the like, and is received at the receiving terminal to be displayed.
2. Description of the Related Art
FIG. 7
shows the configuration of an example of a conventional multiplexing/demultiplexing apparatus.
At a transmitting terminal, a digital image signal (video data) is supplied to a video encoder
101
, which compresses and encodes a bit stream of video data in accordance with a standard, e.g., ISO13818-2 (so-called MPEG (Moving Picture Experts Group) 2 video standard), ISO11172-2 (so-called MPEG1 video standard) or the like, and thereafter outputs the compressed and encoded data. A digital audio signal (audio data) is supplied to an audio encoder
102
, which compresses and encodes a bit stream of audio data in accordance with a standard, e.g., ISO13818-3 (so-called MPEG2 audio standard), ISO11172-3 (so-called MPEG1 audio standard) or the like, and thereafter outputs the compressed and encoded data. Another encoder
103
is supplied with digital data (other data) other than video data and audio data. The encoder
103
encodes and outputs the other data.
A bit stream compressed and encoded and thereafter output will be referred to as “elementary stream” as occasion demands.
Elementary streams of video data, audio data and other data respectively output from the video encoder
101
, the audio encoder
102
and the other encoder
103
are supplied to a multiplexer
104
. The multiplexer
104
multiplexes the elementary streams of video data, audio data, other data, and additional data (additional information) necessary in a time division multiplexing manner at a receiving terminal. A stream obtained by this multiplexing (hereinafter referred to as “multiplexed stream” as occasion demands) is recorded on a predetermined recording medium
105
or is transmitted through a predetermined transmission medium
106
.
At the receiving terminal, the multiplexed stream reproduced from the recording medium
105
or received through the transmission medium
106
is supplied to a demultiplexer
107
. The demultiplexer
107
separates the multiplexed stream into elementary streams of video data, audio data and other data, and additional data by referring to the additional data in the multiplexed stream. The elementary streams of video data, audio data and other data are respectively supplied to a video decoder
108
, an audio decoder
109
and another decoder
110
to be respectively decoded into video data, audio data and other data in certain formats.
The decoded video data is supplied to, for example, a display unit such as a cathode ray tube (CRT) or a liquid crystal display to be displayed. The decoded audio data is supplied to, for example, a speaker or the like to be output. The other data is supplied to, for example, a predetermined recording medium to be recorded.
With respect to the above-described multiplexing of elementary streams at a transmitting terminal, a standard model (system target decoder (STD)) corresponding to a decoder at a receiving terminal is supposed and time division multiplexing is performed so that decoding (decode processing) can be correctly performed in the STD.
FIG. 8
shows the configuration of an example of an STD in accordance with ISO13818-1 (so-called MPEG2 system) and ISO11172-1 (so-called MPEG1 system).
A multiplexed stream formed by time-division-multiplexing elementary streams is input to the STD. The multiplexed stream contains time information (clock reference) as additional data, and is input to the STD at a time corresponding to the time information. The multiplexed stream also contains multiplexing rate information MUX_rate as additional data, and is input to the STD at a data rate corresponding to this multiplexing rate information.
The multiplexed stream input to the STD is supplied to a switch
111
. The switch
111
selects one of input terminals of a video buffer
112
, audio buffers
113
1
to
113
N
and another buffer
114
to enable video data, audio data (N-channel audio data) or other data to be supplied to and stored in the corresponding buffer (video buffer
112
, audio buffers
113
1
to
113
N
) or buffer
114
).
Each of the elementary streams of video data, audio data (N-channel audio data) and other data respectively stored in the video buffer
112
, the audio buffers
113
1
to
113
N
and the other buffer
114
is instantly read out by a length corresponding to its predetermined decoded unit.
Such a decoded unit is called an access unit. With respect to video data, one frame, for example, is prescribed as an access unit. With respect to audio data, one audio frame, for example, is prescribed as an access unit. The length of one audio frame of audio data varies depending upon the sampling frequency at which the audio data was sampled.
The multiplexed stream also contains the decoding time of each access unit as additional data. Each of access units of video data, audio data and other data stored in the video buffer
112
, the audio buffers
113
1
to
113
N
and the other buffer
114
is instantly read out at the corresponding decoding time to be supplied to a decoder
115
, decoders
116
1
to
116
N
, or a decoder
117
. Video data decoded by the decoder
115
is output to a CRT display unit or the like via a reorder buffer
118
and a switch
119
.
Each access unit is read out according to the decoding time to ensure synchronization between the elementary streams. That is, for example, synchronization between images and corresponding sounds is ensured.
Each of access units into which the data is separated by the switch
111
is stored till a predetermined time (the above-mentioned decoding time) in the video buffer
112
, the audio buffers
113
1
to
113
N
or the other buffer
114
of the STD. These buffers will be referred to collectively as “STD buffer”. Accordingly, on the transmitting side, it is necessary to perform scheduling of time division multiplexing in order to prevent an overflow in the STD buffer (an excess of data accumulated in the STD buffer over the capacity of the STD buffer) or an underflow (failure to store one complete access unit in the STD buffer before the decoding time).
FIGS. 9A and 9B
show the formats of multiplexed streams prescribed in ISO13818-1, for example.
A multiplexed stream is obtained by time-division-multiplexing at least one elementary stream and is formed of a plurality of packets. That is, each of elementary streams is separated into packets, and the time of being input to the decoder (clock reference), the decoding time at which each access unit is decoded (displayed), etc., are added to the packets, thus forming a multiplexed stream.
In ISO13818-1, as shown in
FIGS. 9A and 9B
, a transport stream (
FIG. 9A
) and a program stream (
FIG. 9B
) are prescribed. A transport stream is a stream for use in transmission in an environment having such an influence as to cause errors such as a bit error and cell loss. For example, such a stream is used in transmission channels of asynchronous transfer mode (ATM) networks and digital broadcasting. A program stream is a stream for use in transmission in an environment with a reduced possibility of occurrence of errors. In particular, such a stream is used with a recording medium in the form of a disk or a tape.
As
Negishi Shinji
Oishi Noriaki
Tahara Katsumi
Kizou Hassan
Nguyen Hanh
Sonnenschein Nath & Rosenthal LLP
Sony Corpration
LandOfFree
Multiplexing apparatus and method, transmitting apparatus... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Multiplexing apparatus and method, transmitting apparatus..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Multiplexing apparatus and method, transmitting apparatus... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3365779