Pulse or digital communications – Bandwidth reduction or expansion – Television or motion video signal
Reexamination Certificate
1998-07-17
2001-02-27
Le, Vu (Department: 2713)
Pulse or digital communications
Bandwidth reduction or expansion
Television or motion video signal
C375S240030
Reexamination Certificate
active
06195388
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to an apparatus and method for transmitting a plurality of multiplexed video programs over a channel of allowing for a constant bit rate (CBR), and particularly to an encoding apparatus and its method for multiple video programs transmission in which the sum of the bit rates of all the multiplexed video programs is constant, but each of the video programs allows for a variable bit rate (VBR) by synchronously controlling each of video encoders by means of a central controller.
2. Description of the Prior Art
Generally, when a plurality of video programs are transmitted through a single channel of allowing for only the CBR, each of them is encoded independently by it's own video encoder at the CBR compression, and then is multiplexed to transmit the aggregate bit stream.
Such a prior art will now be explained in detail with reference to FIG.
1
.
FIG. 1
shows a blockdiagram of a video encoding apparatus for transmitting multiple video programs. The video encoding apparatus includes an encoding unit
110
for encoding video programs received from each of video sources
1
to video sources N according to bit rate control by means of respective bit rate controllers
121
,
123
, and
125
, a bit rate controlling unit
120
for controlling bit rates of the respective encoders
111
,
113
, and
115
according to buffer informations from the respective buffer
131
,
133
, and
135
, a buffer unit
130
for storing outputs of the respective encoders
111
,
113
, and
115
and transferring them to a multiplexer (MUX)
140
, the MUX
140
for multiplexing the outputs of the respective buffers
131
,
133
, and
135
, and a network interface
150
for transmitting the output of the MUX
140
through a channel of allowing for a CBR transmission.
In the prior art apparatus shown in
FIG. 1
, every encoder
111
,
113
, or
115
includes independently buffers
131
,
133
, and
135
and bit rate controller
121
,
123
, and
125
to execute independent coding for compression.
There are, however, two main shortcomings with independent coding at a constant bit rate. First, the program content can vary significantly from program to program as well as within a program. This variation can lead to large fluctuations in picture quality among programs and within a program, so that a picture of an acceptable picture quality can not be provided with all users fairly. Second, if bandwidth is allocated in order to guarantee the acceptable picture quality with respect to all video programs, unnecessarily wide bandwidth may be allocated to video program having simple picture. That is, when the same rate is used for all types of pictures regardless content, bandwidth or channel capacity is effectively wasted, so that the number of programs capable of transmitting over a single channel is reduced.
SUMMARY OF THE INVENTION
An object of the present invention is to provide an encoding apparatus and its method for multiple video programs transmission in which the sum of the bit rates of all the multiplexed video programs is constant, but each of the video programs allows for a variable bit rate by synchronously controlling each of video encoders of respective video programs transmitted over a constant bit rate channel by means of a central controller.
To achieve the above object, the present invention discloses a video encoding apparatus for multiple video programs transmission comprising a plurality of encoding means for encoding each of a plurality of video programs received from external; multiplexing means for multiplexing outputs of the plurality of encoding means; storing means for temporarily storing and transmitting signal multiplexed by the multiplexing means; and central controlling means for receiving monitoring informations necessary for control from the plurality of encoding means and informations with respect to storing means fullness from the storing means and providing quantization parameters to be applied to respective pictures to be now encoded with the respective encoding means.
According to another aspect of the present invention, the invention discloses a video encoding method for multiple video programs transmission comprising the steps of allocating a total amount of bits to be allocated to all pictures to be encoded per every frame frequency; receiving a plurality of monitoring informations from respective encoders and estimating a plurality of estimating values of bit generating amounts and a plurality of estimating values of distortions corresponding to quantization parameters to be applied to present frames of respective programs to be encoded; estimating a target distortion to be generated when all the programs jointly coded according to the total target amount of bits maintains closest picture qualities; and selecting quantization parameters to be used for encoding so that distortions generated from the respective programs which are encoded is closest to a target distortion, and encoding the respective program pictures using the selected quantization parameters.
First, a principle of encoding video programs according to the present invention will now be explained.
For the encoded picture to maintain a certain picture quality, its bit amount to be used for coding shall vary as their respective picture complexities. The variable bit rate (VBR) compression can maintain the picture quality of the encoded picture more uniform than the constant bit rate (CBR) compression, since bit rates from the encoders can vary according to an amount of bit requested by the picture.
Further, generally, since decreasing effect on distortion according to increases in the amount of bit in case of the complex picture is larger than that of the simple picture, the VBR compression can provide more improved picture quality than the CBR compression.
In this respect, it is known that the VBR compression is more effective than the CBR compression. Nevertheless, only the CBR compression has to be used in the application of transmitting an picture information through the conventional channel allowing for only the CBR.
With new video compression tehcnology, such as MPEG-2 (moving picture expert group-2), and digital transmission technology, it allows for multi-program transmission environment in which the multiple video programs are delivered synchronously through a conventional transmission channel band. Such an environment is, for example, digital satellite broadcast, cable TV, and digital terrestrial broadcast.
In such a multi-program transmission environment, advantage of the VBR compression is obtained by transmitting the multiple video programs at the VBR compression, and a method to execute such a VBR compression may consider a statistical multiplexing method and joint coding method which is proposed in the present invention.
In this case, the statistical multiplexing is generally used in an asynchronous transfer mode (ATM), and is based on the fact that if a plurality of VBR video traffics are received at network, the sum of all the bit rates is substantially constant. When the VBR video programs are statistically multiplexed to transmit it through the CBR channel, however, if the number of video programs multipleded is small, it is doubtful to obtain multiplexing effects, and if the respective programs synchronously produce bitstreams at high bit rate, many cell losses are occurred. Since all of channel capacity can not be used to prevent such cell loss, use efficiency of the channel is decreased.
In the joint coding, bit rates of the respective video programs are variable by synchronously controlling video encoders of producing respective video programs compressed at the VBR by means of a central controller, but the sum of the bit rates of all the multiplexed video programs is constant.
Therefore, this joint coding method is effective in case of multiplexing small number of the video programs, which is different from the statistical multiplexing, and all the channel bandwidth can be used, so that this
Ahn Chie Teuk
Choi Jae Gark
Hong Sung Hoon
Electronics and Telecommunications Research Institute
Jacobson Price Holman & Stern PLLC
Le Vu
LandOfFree
Apparatus and method for encoding multiple video programs does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Apparatus and method for encoding multiple video programs, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Apparatus and method for encoding multiple video programs will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2585522