Pulse or digital communications – Bandwidth reduction or expansion – Television or motion video signal
Reexamination Certificate
2001-06-18
2004-07-20
Diep, Nhon (Department: 2613)
Pulse or digital communications
Bandwidth reduction or expansion
Television or motion video signal
Reexamination Certificate
active
06765963
ABSTRACT:
BACKGROUND
This invention relates generally to the field of the multimedia applications. More particularly, this invention relates to a new frame type, apparatus and method for using same to provide for access of a video stream.
Multimedia applications that include audio and streaming video information have come into greater use. Several multimedia groups have established and proposed standards for compressing/encoding and decompressing/decoding the audio and video information. The examples are MPEG standards, established by the Motion Picture Expert Group and standards developed by ITU-Telecommunications Standardization.
The following are incorporated herein by reference:
G. Bjontegaard, “H.26L Test Model Long Term Number 6 (TML-6) draft0”, document VCEG-L45, ITU-T Video Coding Experts Group Meeting, Eibsee, Germany, Jan. 9-12, 2001. Keiichi Hibi, “Report of the Ad Hoc Committee on H.26L Development”, document Q15-H-07, ITU-T Video Coding Experts Group (Question 15) Meeting, Berlin, Aug. 3-6, 1999. Gary S. Greenbaum, “Remarks on the H.26L Project: Streaming Video Requirements for Next Generation Video Compression Standards”, document Q15-G-11, ITU-T Video Coding Experts Group (Question 15) Meeting, Monterey, Feb. 16-19, 1999. G. Bjontegaard, “Recommended Simulation Conditions for H.26L”, document Q15-I-62, ITU-T Video Coding Experts Group (Question 15) Meeting, Red Bank, N.J., Oct. 19-22, 1999. ATM & MPEG-2 Integrating Digital Video into Broadband Networks by Michael Orzessek and Peter Sommer (Prentice Hall Upper Saddle River N.J.).
Video sequences, like ordinary motion pictures recorded on film, comprise a sequence of still images, and the illusion of motion is created by displaying consecutive images at a relatively fast rate. For example, the display rate are between five and thirty frames per second. Because of the relatively fast frame rate, the images in consecutive frames tend to be similar. A typical scene recorded by a camera comprises some stationary elements, such as, for example, background scenery and some moving parts. The moving parts may take many different forms, for example, the face of a news reader, moving traffic, and so on. Alternatively, the camera recording the scene may itself be moving, in which case all elements of the image have the same kind of motion. In many cases, this means that the overall change between one video frame and the next is rather small. Of course, this depends on the nature of the movement, the rate of the movement, i.e., the amount of change from one frame to the next.
The purpose of the video coding is to remove the redundancy in the image sequence so that the encoded data rate is commensurate with the available bandwidth to transport the video sequence while keeping the distortion between the original and reconstructed images as small as possible. The redundancy in video sequences can be categorized into spatial and temporal redundancy. Spatial redundancy refers to the correlation between neighboring pixels in a frame while temporal redundancy refers to correlation between neighboring frames.
FIGS. 1A-1C
illustrate the type of encoded/compressed video frames that are commonly utilized for video standards.
FIG. 1A
depicts an Intra-frame or I-type frame
200
. The I-type frame or picture is a frame of video data that is coded exploiting only the spatial correlation of the pixels within the frame without using information from the past or the future and is utilized as the basis for decoding/decompression of other type frames.
FIG. 1B
is a representation of a Predictive-frame or P-type frame
210
. The P-type frame or picture is a frame that is encoded/compressed using motion compensated prediction from I-type or P-type frames of its past, in this case, I.sub.
1
200
. That is, previous frames are used to encode/compress a present given frame of video data.
205
a
represents the motion compensated prediction information to create a P-type frame
210
. Since in a typical video sequence the adjacent frames in a sequence are highly correlated, higher compression efficiencies are achieved when using P-frames.
FIG. 1C
depicts a Bi-directional-frame or B-type frame
220
. The B-type frame or picture is a frame that is encoded/compressed using a motion compensated prediction derived from the I-type reference frame (
200
in this example) or P-type reference frame in its past and the I-type reference frame or P-type reference frame (
210
in this example) in its future or a combination of both. B-type frames are usually inserted between I-type frames or P-type frames.
FIG. 2
represents a group of pictures in what is called display order I.sub.
1
B.sub.
2
B.sub.
3
P.sub.
4
B.sub.
5
P.sub.
6
.
FIG. 2
illustrates the B-type frames inserted between I-type and P-type frames and the direction which motion compensation information flows.
A system for P-frame encoding and decoding is provided and is shown in
FIGS. 3 and 4
. Referring to
FIGS. 3 and 4
, a communication system comprising an encoder
300
of
FIG. 3 and a
decoder
400
of
FIG. 4
is operable to communicate a multimedia sequence between a sequence generator and a sequence receiver. Other elements of the video sequence generator and receiver are not shown for the purposes of simplicity. The communication path between sequence generator and receiver may take various forms, including but not limited to a radio-link.
Encoder
300
is shown in
FIG. 3
coupled to receive video input on line
301
in the form of a frame to be encoded I(x, y), called the current frame. By (x, y) we denote location of the pixel within the frame. In the encoder the current frame I(x,y) is partitioned into rectangular regions of M×N pixels. These blocks are encoded using either only spatial correlation (intra coded blocks) or both spatial and temporal correlation (inter coded blocks). In what follows we concentrate on inter blocks.
Each of inter coded blocks is predicted using motion information from the previously coded and transmitted frame, called reference frame and denoted as R(x,y), which at given instant is available in the frame memory
350
of the encoder
300
. The motion information of the block may be represented by two dimensional motion vector (&Dgr;x(x,y), &Dgr;y(x,y)) where &Dgr;x(x,y) is the horizontal and &Dgr;y(x,y) is the vertical displacement, respectively of the pixel in location (x,y) between the current frame and the reference frame. The motion vectors (&Dgr;x( ), &Dgr;y( )) are calculated by the motion estimation and coding block
370
. The input to the motion estimation and coding block
370
are current frame and reference frame. The motion information is provided to a Motion Compensated (MC) prediction block
360
. The MC prediction block is also coupled to a frame memory
350
to receive the reference frame. In the MC block
360
, the motion vectors for each inter block together with the reference frame are used to construct prediction frame P(x, y):
P
(
x, y
)=
R
(
x+&Dgr;x
(
x,y
),
y+&Dgr;y
(
x,y
)).
Notice that values of the prediction frame are calculated only for inter blocks. For some pixels (x,y) which belong to intra blocks these values will not be calculated. It is also possible to use more than one reference frame. In such case different blocks may use different reference frames.
Subsequently, the prediction error E(x, y), i.e., the difference between the current frame and the prediction frame P(x, y) is calculated by:
E
(
x, y
)=
I
(
x, y
)−
P
(
x, y
).
In transform block
310
, the prediction error for each K×L block is represented as weighted sum of a transform basis functions f.sub.ij(x, y),
E
(
x
,
y
)
=
∑
i
=
1
K
∑
j
=
1
L
c
.
s
u
b
.
e
r
r
(
i
,
j
)
f
.
s
u
b
.
i
j
(
x
,
y
)
.
The weights c.sub.err(i,j), corresponding to the basis functions are called prediction error coefficients. Coefficients c.sub.err(i,j) can be calculated by performing so call
Karczewicz Marta
Kurceren Ragip
Diep Nhon
Nokia Corporation
Shaw Steven A.
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