Pulse or digital communications – Bandwidth reduction or expansion – Television or motion video signal
Reexamination Certificate
1999-08-02
2002-06-18
Kelley, Chris (Department: 2613)
Pulse or digital communications
Bandwidth reduction or expansion
Television or motion video signal
Reexamination Certificate
active
06408025
ABSTRACT:
BACKGROUND OF THE INVENTION
Field of the Invention
The invention lies in the electronics field and, more specifically, in the field of electronic video signal processing.
The coding of video signals in accordance with the picture coding standards H.261, H.263, MPEG1 and MPEG2 is based on a block-oriented discrete cosine transform (DCT). These methods generally use the principle of block-based picture coding.
A further approach to picture coding is the so-called principle of object-based picture coding. In such object-based picture coding, the original pictures are segmented in accordance with the objects that appear in the scene, and those objects are coded separately.
Reference will be had, in the following, to
FIG. 2
, which provides a general illustration of a configuration for picture coding and picture decoding.
A camera K records object pictures. The camera K may be, for example, any desired analog camera K which records pictures of a scene and either digitizes the pictures in the camera K or else transmits them in analog form to a first computer R
1
, in which then either the digitized pictures B are processed or the analog pictures are first converted into digitized pictures B and the digitized pictures B are processed.
The camera K may also be a digital camera K with which digitized pictures B are recorded directly and are fed to the first computer R
1
for further processing.
The first computer R
1
may also be configured as a dedicated configuration which is used to carry out the method steps described below, for example as a dedicated computer card installed in a computer.
The first computer R
1
should be understood generally to mean any unit which can perform video signal processing in accordance with the method described below, for example including a mobile terminal (mobile telephone).
The first computer R
1
has a processor unit P which is used to carry out the method steps of picture coding or of picture decoding that are described below. The processor unit P is coupled for example via a bus BU to a memory SP in which the video data are stored.
In general, the methods described below can be realized either using software or using hardware or else partly using software and partly using hardware.
Once picture coding has been effected in the first computer R
1
and the compressed video data have been transmitted via a transmission medium TM to a second computer R
2
, picture decoding is carried out in the second computer R
2
.
The second computer R
2
may have the same structure as the first computer R
1
, that is to say the memory SP which is coupled via the bus BU to the processor unit P.
FIG. 3
gives a more detailed illustration of a possible configuration in the form of a basic circuit diagram for picture coding and/or for picture decoding which can be used in the context of block-based picture coding and, in some instances, as explained below, in the context of object-based picture coding.
In block-based picture coding methods, a digitized picture B is divided into, typically square, blocks having a size of 8×8 pixels BP or 16×16 pixels BP. Those subdivided blocks are fed to the configuration for picture coding.
Usually, coding information is uniquely assigned to a pixel, for example brightness information (luminance values) or color information (chrominance values).
In the block-based picture coding methods, a distinction is made between various picture coding modes.
In the so-called intra-picture coding mode, in each case the entire picture with the entire coding information assigned to the pixels of the picture is coded and transmitted (I picture).
In the so-called inter-picture coding mode, in each case only the difference picture information between two chronologically succeeding pictures is coded and transmitted (P picture, B picture).
In order to change over between the intra-picture coding mode and the inter-picture coding mode, two switch units SE are provided. In order to carry out the inter-picture coding mode, a subtraction unit S is provided in which the difference in the picture information of two succeeding pictures B is formed. The entire picture coding is controlled by means of a picture coding control unit ST. The picture blocks BB or difference picture blocks BB to be coded are in each case fed to a transform coding unit DCT, in which transform coding, for example the discrete cosine transform (DCT), is applied to the coding information assigned to the pixels.
In general, however, it is possible to carry out any desired transform coding, for example a discrete sine transform or else a discrete Fourier transform.
The spectral coefficients formed by the transform coding are quantized in a quantization unit Q and fed to a non-illustrated picture coding multiplexer for example for channel coding and/or for entropy coding. In an internal reconstruction loop, the quantized spectral coefficients are subjected to inverse quantization in an inverse quantization unit IQ and to inverse transform coding in an inverse transform coding unit IDCT.
Furthermore, in the case of inter-picture coding, picture information of the respective chronologically preceding picture is added in an adder unit AE. The pictures reconstructed in this way are stored in a frame memory SP. A unit for motion compensation MC is illustrated symbolically in the frame memory SP in order to simplify the illustration.
Furthermore, a loop filter LF is provided which is connected to the memory SP and also to the subtraction unit S.
In addition to the video data to be transmitted, a mode flag p is fed to the picture coding multiplexer. The flag designates the type of coding, i.e., it specifies in each case whether intra or inter-picture coding has been performed.
Furthermore, quantization indices q for the spectral coefficients are fed to the picture coding multiplexer.
A motion vector v is also assigned in each case to a picture block and/or a macroblock having four picture blocks, for example. The motion vector v is also fed to the picture coding multiplexer.
Furthermore, an information item f for the activation or deactivation of the loop filter LF is provided.
After the transmission of the picture information via the transmission medium TM, the transmitted data can be decoded in the second computer R
2
. For this purpose, a picture decoding unit is provided in the second computer R
2
and, for example, has the structure of the reconstruction loop of the configuration illustrated in FIG.
2
.
In the case of object-based picture coding methods, each picture object is firstly split into blocks having a fixed size, for example likewise 8×8 pixels. After this splitting, some of the resulting picture blocks are located completely within a picture object BO. This situation is illustrated in FIG.
4
. The picture B contains at least one picture object BO, which is bounded by an object edge OK of the picture object BO. Furthermore, picture blocks BB having 8×8 pixels BP are illustrated. Picture blocks BB which contain at least part of the object edge OK are designated as edge picture blocks RBB below.
Picture blocks BB which are located completely within the picture object BO after the splitting operation can be coded in a manner following the above-mentioned block-based picture coding methods using a customary block-based discrete cosine transform. However, the edge picture blocks RBB are partly filled with picture information and have to be coded using a special method.
Two fundamental approaches exist to date for coding the edge picture blocks RBB.
Reference is first had to ISO/IEC JTC1/SC29/WG11, MPEG-4 Video Verification Model Version 5.0 Doc. N1469, November 1996, pp. 55-59. That document discloses supplementing the picture information of the picture object BO within the edge picture block RBB by means of a suitable extrapolation method of the coding information to the area of the complete edge picture block RBB. This procedure is referred to as padding. The supplemented area is then coded using a customary two-dimensional discrete cosine transform.
As an al
Greenberg Laurence A.
Kelley Chris
Locher Ralph E.
Siemens Aktiengesellschaft
Stemer Werner H.
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