Pulse or digital communications – Bandwidth reduction or expansion – Television or motion video signal
Reexamination Certificate
1999-01-19
2002-06-11
Diep, Nhon (Department: 2613)
Pulse or digital communications
Bandwidth reduction or expansion
Television or motion video signal
C348S500000
Reexamination Certificate
active
06404818
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a video transmission device and its method and more particularly, is suitably applied to a digital broadcasting system.
2. Description of the Related Art
A digital broadcasting system for multiplexing coded video and audio data to transmitting them through a satellite circuit has been proposed and become practical use. In this digital system, video data and also audio data are encoded, and by packetizing and multiplexing the coded video and audio data per fixed data unit, transport data (hereinafter, referred to as a transport stream) is formed and transmitted through such as a satellite wireless circuit.
Here, the digital broadcasting system will be described with reference to FIG.
1
. As shown in
FIG. 1
, a digital broadcasting system
1
is roughly comprised of a transmission device
2
to be set in a broadcasting station, a receiving device
3
and a television receiver
4
to be installed in each house. Transport stream data to be transmitted from the transmission device
2
is received by the receiving device
3
, and by sending out this to the television receiver
4
, broadcasting video and audio can be watched.
As shown in
FIG. 2
, in the transmission device
2
, firstly, video data S
1
to be transmitted is entered into a video encoder
5
, and audio data S
2
accompanying with the video data SI is entered into an audio encoder
6
. The video encoder
5
successively encodes the entered video data S
1
based on the MPEG
2
video encoding system described in the International Standards Regulation ITU-T Recommendation H.262 ISO/IEC13818-2, and outputs a stream of the resulting coded video data S
3
(generally, this is called as an elementary stream (ES)) to a packetizer
7
A. In the case of encoding the video data S
1
, the video encoder
5
applies an encoding processing with video data for several pictures, which are called as group of picture (GOP), as a coding unit, and by adding a header consisting of each parameter information at the time of encoding to the head of the coded video data, forms coded video data S
3
. Thus, a decoding processing can be conducted based on the parameter information of the header at the time of decoding.
As shown in
FIGS. 3A and 3B
, the packetizer
7
A, by connecting a fixed number of ES packets of coded video data S
3
encoded per GOP and adding a packetized elementary stream (PES) header to the head of the packet, PES-packets the coded video data S
3
and outputs the PES-packetized coded video data S
4
to a multiplexer
8
. Note that, data of the PES header consist of time information when reproducing and outputting the video data included in the PES packet at the receiving side (generally, called as presentation time stamp (PTS)), identification information showing the type of elementary stream included in the PES packet (generally, called as a stream ID), and the like. In this connection, such time information PTS is provided in the PES header, so that audio and video can be synchronized and reproduced at the receiving side.
On the other hand, the audio encoder
6
encodes the input audio data S
2
based on an audio encoding system described in the International Standards Regulation ITU-T Recommendation H.262 ISO/IEC13181-3 and outputs the resultant coded audio data S
5
to a packetizer
7
B. Note that, the audio encoder
6
encodes the audio data S
2
per fixed number of samples called as an audio frame in the same manner as in the case of video data shown in
FIG. 2
, and by adding a header comprising parameter information at the time of encoding to the head of the coded audio data, forms an ES-packetized coded audio data S
5
.
Moreover, the packetizer
7
B, by connecting a fixed number of ES packets of the coded audio data S
5
encoded per audio frame and adding the PES header to the head of the packet, PES-packetizes the coded audio data S
5
and outputs the PES-packetized coded audio data S
6
to the multiplexer
8
. The data of the PES header are approximately the same as in the case of video.
The multiplexer
8
transport-stream (TS)-packetizes the PES-packetized coded video data S
4
and coded audio data S
6
by dividing them per fixed data unit respectively, and by switching and outputting the TS packets of the video and audio at established intervals, multiplexes them to form a transport stream S
7
.
More specifically, as shown in
FIGS. 5A
,
5
B,
6
A and
6
B, the multiplexer
8
,,by dividing each PES packet of the coded video data S
4
and coded audio data S
6
per 184 bytes and adding a TS header of 4 bytes to each of their heads, forms a TS packet. In this case, the TS header is formed of synchronization information and packet identification information PID showing the type of data included in the TS packet. However, the data part of 184 bytes is not only comprised of PES data but in practice, also additional information is added and these additional information and PES data are adjusted to become 184 bytes altogether. Such data adjusting processing is generally called as a stuffing processing. In this connection, even when PES data are not enough, the stuffing processing is conducted so that data part becomes 184 bytes by adding dummy byte. Then, the multiplexer
8
forms a transport stream S
7
by multiplexing thus formed video TS packets onto thus formed audio TS packets.
In this connection, since proper packet identification information PID is added to the multiplexed video and audio TS packet per data, the receiving side can separate the TS packets based on the packet identification information PID to decode video and audio from one multiplexed transport stream.
Thus, the transport stream S
7
comprised of video and audio TS packets is transmitted to the succeeding transmission unit
9
. The transmission unit
9
, after forming a transmission signal by applying the modulation processing to the transport stream S
7
for transmitting, forms a transmission signal S
8
by applying a frequency conversion processing to the transmission signal of a stated band and transmits this toward the satellite (not shown) via an antenna
10
.
A transmission signal S
8
relayed via the satellite is received by the receiving device
3
shown in FIG.
1
and the receiving device
3
conducting a reverse processing of the transmission device
2
, so that the transmission signal S
8
is decoded to the original video and audio data. More specifically, the receiving device
3
applies the frequency conversion processing and demodulation processing to the received signal to restore the transport stream S
8
transmitted from the transmission device
2
. And then, the receiving device
3
separates video TS packets and audio TS packets based on the packet identification information PID and takes out coded video data and coded audio data from each TS packet separated, and applying the decoding processing to these data, restores video data and audio data transmitted. Thus, these restored video data and audio data are transmitted to the television receiver
4
, so that video and audio of the program sent from the transmitter
2
can be watched.
In the foregoing explanation, the transmission device
2
transmits video and audio data forming one program. However, in practice, the transmission device
2
transmits video and audio data of the plural number of programs in the form of one transport stream S
8
by TS-packetizing and multiplexing video and audio data of plural programs. Furthermore, in the case where text data are attached to the video data, the text data can also be transmitted in the form of one transport stream S
8
by being TS-packetized and multiplexed. In this connection, if the plural programs are multiplexed, the receiving side extracts TS packets of a desired program based on the packet identification information PID added to the TS packets and thus, the video and audio data of the desired program can be restored.
At this point, the processing in the case of multiplexing the plural programs will be described in detail in the followi
Diep Nhon
Frommer William S.
Sony Corporation
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