Television – Two-way video and voice communication – Transmission control
Reexamination Certificate
2000-11-21
2003-11-11
Eng, George (Department: 2643)
Television
Two-way video and voice communication
Transmission control
C348S014010
Reexamination Certificate
active
06646674
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a TV telephone system having a plurality of TV telephone apparatuses communicating by video signals and audio signals via an Internet protocol network.
2. Related Art
In a TV telephone system of the past, communication by video and audio signals was conducted between TV telephone apparatuses via an internet protocol network such as an intranet or an internet.
In a TV telephone system, communication is conducted using video and audio signals, based for example on the Recommendation H.323 or H.225 of the International Telecommunication Union Telecommunication Standardization Sector (ITU-T).
A TV telephone apparatus used in a TV telephone system of the past is described below.
FIG. 6
of the accompanying drawings is a block diagram showing the example of the configuration of a TV telephone apparatus used in a TV telephone of the past.
The TV telephone apparatus
100
in this example of prior art conducts communication using a video signal and an audio signal via a network
114
, with a TV telephone apparatus (not shown in the drawing) having the same configuration as the TV telephone apparatus
100
.
As shown in
FIG. 6
, the TV telephone apparatus
100
of the prior art is formed by an audio I/O section
101
, an audio CODEC
102
, a receiving path delay section
103
, a video CODEC
104
, a video I/O section
105
, a user data application section
106
, a system controller
107
, a system controller unnumbered information (UI) section
111
, an H.225 layer section
112
, and a network interface
113
.
The audio CODEC
102
performs compression and encoding processing of an audio signal received from the audio I/O section
101
, so as to generate compressed audio data. The compressed audio data output from the audio CODEC
102
passes through the receiving path delay section
103
, the H.225 layer section
112
, the network interface
113
, and the network
114
and is transmitted to the other party's TV telephone apparatus.
The audio CODEC
102
performs decompression and decoding of compressed audio data received from the other party's TV telephone apparatus via the network
114
, the network interface
113
, the H.225 layer section
112
, and the receiving path delay section
113
, so as to play back the audio signal to the audio I/O section
101
, which outputs the audio signal output from the audio CODEC
102
to a speaker (not shown in the drawing) or the like.
At the audio CODEC
102
, compression/decompression and encoding/decoding processing are performed in accordance with any one of ITU-T Recommendations G.711, G.722, G.723, G.728, and G.729.
The video CODEC
104
performs interframe predictive decoding of a video signal captured by a video camera (not shown in the drawing) at the video I/O section
105
, so as to generate an output compressed image data. The compressed image data output from the video CODEC
104
is sent to the other party's TV telephone apparatus, via the receiving path delay section
103
, the H.225 layer section
112
, the network interface
113
, and the network
114
.
The video CODEC
104
performs decompression and decoding of compressed image data sent from the other party's TV telephone apparatus via the network
114
, the network interface
113
, the H.225 layer section
112
, and the receiving path delay section
103
, so as to generate a video signal and output to the video I/O section
105
, which displays the video signal output from the video CODEC
104
on a display (not shown in the drawing).
In the video CODEC
104
, interframe predictive coding of a video signal captured at the video I/O section
105
is performed, in accordance with any one of the ITU-T Recommendations H.261, and H.263, and the compressed video signal sent from the other party's TV telephone apparatus is expanded and decoded.
The ITU-T Recommendation H.261 (hereinafter referred to as simple H.261) is described below.
In H.261, intraframe coding (hereinafter referred to as INTRA) and interframe coding (hereinafter referred to as INTER) are both used as interframe predictive encoding.
Interframe predictive coding is coding in which data from an initial or previous frame is referenced when performing encoding processing, and intraframe coding is coding in which only data within the current frame is used in performing encoding processing.
For example, in the case in which there is little movement in the video signal captured by the video I/O section
105
, because there is a large correlation with respect to previous and subsequent frames, interframe coding is performed. However, in the case in which there is a large amount of movement captured in the video signal at the video I/O section
105
, because the correlation with respect to previous and subsequent frames is small, intraframe coding is used.
Thus, in H.261, in the case in which there is a large change between a frame being coded and an initial frame or a previous frame, intraframe coding, in which the data from the previous frame is not referenced, is performed. In coding other frames, the previous frame is referenced, and interframe coding is done.
In H.261, in the case of performing decompression and decoding of compressed image data that has been coded at the other party's TV telephone apparatus using inter frame coding, previous frame data is referenced when performing decompression and decoding, and in the case of performing decompression and decoding of compressed data that has been coded at the other party's TV telephone apparatus using intraframe coding decompression and decoding are performed using only the current frame.
H.263 is a partially improved version of H.261 for a general switched telephone network (GSTN) type of TV telephone system, and because features of interframe predictive coding and operation are very similar to H.261, it will not be described herein.
Therefore, compressed image data generated at the video CODEC
104
is a mixture of “INTRA” data without interframe predictive signals, obtained by intraframe coding and “INTER” data with interframe predictive signals, obtained by interframe coding.
The receiving path delay section
103
, in the case in which there is a offset between the audio signal at the audio I/O section
101
and the video signal at the video I/O section
105
, provides a delay so as to compensate for this offset by causing any one of the audio signal and the video signal to delay. The offset between the audio signal and the video signal is dependent upon communication condition over the transmission path between the TV telephone apparatus
100
and the TV telephone apparatus of the other party.
The user data application section
106
executes various applications that use the user data channel in the TV telephone apparatus
100
.
With respect to the compressed audio data output from the audio CODEC
102
and the compressed image data output from the video CODEC
104
, the H.225 layer section
112
adds an RTP (real time transfer protocol) header and performs UDP protocol processing (User Datagram Protocol), and also performs UDP protocol processing and removing the RTP header from compressed image data sent from the other party's TV telephone apparatus via the network
114
and the network interface
113
.
The UDP protocol is a connectionless type of protocol (RFC 768) that has been standardized by the IETF (Internet Engineering Task Force), and is a type of communication protocol for the IP network such as Internet and intranet.
Because of the simplicity of the UDP protocol, it features superior data communication throughput, and provides an advantage in improving the simultaneity of image communication, making it suitable, for use in real-time communication of both audio and video signals.
FIG. 7
of the accompanying drawings is a block diagram showing an example of the configuration of the H.225 layer section
112
of FIG.
6
.
In the configuration example shown in
FIG. 7
, the H.225 layer section
112
is formed by an RTP section
1
Eng George
Whitham Curtis & Christofferson, P.C.
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