Multiplex communications – Communication techniques for information carried in plural... – Adaptive
Reexamination Certificate
1999-09-03
2003-07-08
Marcelo, Melvin (Department: 2663)
Multiplex communications
Communication techniques for information carried in plural...
Adaptive
C348S384100, C382S232000, C382S276000
Reexamination Certificate
active
06590902
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to compressed coded data transmitting systems, and more particularly to an apparatus for packetizing layer-coded video data and for transmitting it.
2. Description of the Related Art
In the transmission of video data, a system is known which divides coded data which contains DCT (Discreet Cosine Transform) components into low and high frequency component data and packetizes them individually in a H.261 encoding system which is an international standard for video conference, as described in JP-A-10-23418 laid-open on Jan. 23, 1998. In this invention, if data to be transmitted comprises low frequency components, a flag indicative of high priority is annexed to a packet for transmitting the data whereas if the data contains high frequency components, a flag indicative of low priority is annexed to the data for transmitting purposes. A gateway (which is a packet video speed converter capable of converting a video stream speed) disposed on a network discards the packets to which the flag indicative of low priority is annexed (high frequency component data) when the network becomes congested, alleviate the congested state of the network to thereby prevent a deterioration in the video quality.
For example, “Encoding, Transmitting, and Controlling System in Video Multicast”, The Journal of the Institute of Image Information and Television Engineers, Vol. 52, No. 6, pp. 863-870(1998-6) describes a layer-coded data transmission controlling system in which layer-coded video data is transmitted from a sever to a client in a multi-channel system using an IP address, transmit/receive code port numbers, etc. In this system, a total of six kinds of encoded data of low and high frequency components of respective I, P and B frame data, which an MPEG encoding system (Generic Coding of Moving Pictures and Associated Audio: Video, ISO/IEC 13818-2) which is an international standard prescribes for layering the video data, are transmitted from the sever to the client, using a plurality of channels. In order to reproduce the P frame data among the I, P and B frame data which the MPEG encoding system prescribes, the I frame data is required. In order to reproduce the B frame data, the I and P frame data are required. As a result, the respective decreasing significances are placed on the I, P and B frames in this order. The low frequency components of each frame which represent its basic contour are important compared to its high frequency components which represent the details of the frame. There are a total of six leveled significances, inclusive of those of the I, P and B frame structures. By transmitting those six leveled data, using a plurality of channels, only data for a layer which the client requests can be transmitted.
JP-A-6-339137 laid-open on Dec. 6, 1994 describes on its front page that “an image signal is packetized in packet assembling section 13 for each layer and is transmitted from transmitting section 14.”
JP-A-3-22780 laid-open on Jan. 31, 1991 describes on page 4, lower right column, line 18—page 5, upper left column, line 2 that “a first group of packets are formed of those image signal components, loss of which will cause a small extent of degradation of image quality and a second group of packets are formed of those image signal components, loss of which will cause a large extent of degradation of image quality, and a high priority is given to the second group of packets so that discard of the second group of packets is hardly effected.”
JP-A-2-58938 laid-open on Feb. 28, 1990 describes in its claim that “means for layer-structuring the coded information into basic blocks for decoding and into additional blocks for interpolating them and thereafter packetizing the resulting information for transmission”.
JP-A-2-86241 laid-open on Mar. 27, 1990 describes in its claim that “coded information is layer-structured into those portions which will exert small influence on the image quality and into those portions which will exert large influence on the image quality, and several blocks are formed into a packet for each portion”.
JP-A-6-125361 laid-open on May 6, 1994 discloses a speech packet communication system intended to suppress degradation of speech quality when a packet is discarded.
JP-A-4-83488 laid-open on Mar. 17, 1992 discloses use of the layer-coding technique and the burst error correction technique in an ATM image signal transmission.
Since video data of a plurality of layers are transmitted through a plurality of channels in the conventional system, channels whose number equals the product of the number of video programs to be transmitted and the number of program layers are required. Thus, a plurality of addresses and ports are be consumed to transmit one video program.
When packet discarding occurs due to congestion of the transmission network, disordered packet discarding would lead to discard of data important for video reproduction, which can greatly affect the video reproduction. It is preferable that as described above with reference to the prior art, the I, P and B frame structures and the significances of the frequency component data are used to positively discard the component data, starting with the least significant component data when the network is congested. When one-video program data of a plurality of layers is transmitted through one channel in packets where components data belonging to different layers, for example, the low and high frequency components data of the B frame, are present in a mixed state, a router which has a packet discarding function in the network cannot discard only the high frequency component data of the B frame.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a layer-coded video data transmitting apparatus where one-video program data of a plurality of layers is transmitted through one channel, and a router which has a packet discarding function in the transmission network can discard only specified layer data.
In order to solve the above problems, according to one aspect of the present invention, there is provided a layer-coded data transmitting apparatus for transmitting layer-coded data in a single channel, which apparatus packetizes layer-coded data so that a packet for transmitting the layer-coded data contains only data belonging to the same layer.
According to another aspect of the present invention, there is provided a layer-coded data transmitting apparatus for transmitting layer-coded data in a single channel, which apparatus divides into low and high frequency component data each of intra-coded image (hereinafter referred to as “I frame”) data, prediction-coded image (hereinafter referred to as “P frame”) data, and bidirectional prediction-coded image (hereinafter referred to as “B frame”) data, which a video signal compressing/encoding system prescribes; and transmits in different packets the respective low and high frequency component data of each of the I, P and B frame data.
According to still another aspect of the present invention, there is provided a layer-coded data transmitting apparatus for transmitting layer-coded data in a single channel, comprising means for converting data belonging to each of layers of an elementary stream (hereinafter refereed to as “ES”) to packetized elementary stream (hereinafter referred to as “PES”) data, and wherein the converting means converts the ES data so that only ES data belonging to the same layer is contained in a single PES packet. The apparatus further comprises means for packetizing the PES packet to a real time protocol (hereinafter referred to as “RTP”) packet for each layer data, so that only the RTP packet data belonging to the same layer is contained in a single RTP packet which transmits the RTP packet; means for packetizing the RTP packet to a user datagram protocol (hereinafter referred to as “UDP”) packet for each layer data, so that only the RTP packet data belonging to the same layer is contained in a single UDP packet which trasmits th
Ikezawa Mitsuru
Kameyama Tatsuya
Mimura Itaru
Suzuki Toshiaki
Yoshizawa Satoshi
Antonelli Terry Stout & Kraus LLP
Ferris Derrick W.
Hitachi , Ltd.
Marcelo Melvin
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