Classifications

• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
  • H04N19/00—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals
  • H04N19/10—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding
  • H04N19/134—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding characterised by the element, parameter or criterion affecting or controlling the adaptive coding
  • H04N19/167—Position within a video image, e.g. region of interest [ROI]
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
  • H04N19/00—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals
  • H04N19/10—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding
  • H04N19/169—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding characterised by the coding unit, i.e. the structural portion or semantic portion of the video signal being the object or the subject of the adaptive coding
  • H04N19/17—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding characterised by the coding unit, i.e. the structural portion or semantic portion of the video signal being the object or the subject of the adaptive coding the unit being an image region, e.g. an object
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
  • H04N19/00—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals
  • H04N19/30—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using hierarchical techniques, e.g. scalability
  • H04N19/37—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using hierarchical techniques, e.g. scalability with arrangements for assigning different transmission priorities to video input data or to video coded data
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
  • H04N19/00—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals
  • H04N19/60—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using transform coding
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
  • H04N19/00—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals
  • H04N19/60—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using transform coding
  • H04N19/63—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using transform coding using sub-band based transform, e.g. wavelets

Definitions

• the present invention relates to a method and to arrangement for coding and extracting regions of interest (ROI) in the transmission of still images and video images.
• the method and the arrangement are particularly well suited for transform- based coders, such as wavelets and DCT.
• the image In transmission of digitized still images from a transmitter to a receiver, the image is usually coded in order to reduce the amount of bits required for transmitting the image.
• bit quantity is usually reduced, because the capacity of the channel used is limited.
• a digitized image however, consists of a very large number of bits.
• transmission times will be unacceptably long for the majority of applications if it is necessary to transmit every bit of the image.
• Lossless methods i.e. methods exploiting the redundancy in the image in such manner as to enable the image to be reconstructed by the receiver without loss of information.
• Lossy methods i.e. methods that exploit the fact that not all bits are equally as important to the receiver.
• the image received is not identical to the original but looks sufficiently like the original image to the human eye, for instance.
• certain parts of the transmitted image are of more interest than the remainder of the image, and better visual quality of these parts of the image is therefore desired.
• a part is usually called the region of interest (ROI).
• ROI region of interest
• Applications in which this can be useful include, for example, medical databases or the transmission of satellite images.
• the present invention addresses the aforesaid problem of defining and transmitting regions of interest and background regions of mutually different qualities in the transmission of images.
• the basic concept of the invention in solving the problem is to transform the image and to define in said transform a mask that corresponds to the regions of interest and to the background regions.
• the region definition and the image transform are transmitted to a receiver capable of recreating the image with the quality desired in the predetermined regions.
• the solution involves dividing the image into the desired regions.
• the image is then transformed to some type of transform coefficients.
• a mask corresponding to the separate regions in the image is defined in the transform domain and the coefficients classified and assigned to different segments in accordance with the mask definition.
• the segments thus belong to the corresponding regions in the image.
• the segments and the coefficients are transmitted in a compressed state to a receiver that is capable of reproducing regions in the image on the one hand and of reproducing the actual image on the other hand with the desired image quality in the various regions.
• One advantage afforded by the invention is that several different regions of interest can be defined.
• Another advantage is that different regions can have several different degrees of image quality. Still another advantage is that only those parts of the image that are of vital interest to the user need be decoded, while avoiding decoding of the whole of the image.
• Figure 1 is a block schematic illustrating an inventive arrangement.
• Figure 2 is a flow chart illustrating part of an inventive method.
• Figure 3 is a flow chart illustrating a further part of an inventive method.
• Figure 4 is a diagram illustrating classification of transform coefficients.
• Figure 5 is a diagram for interlinking image segments in a bit stream.
• Figure 6 is a view of an image with object.
• Figure 7 is a graphic representation of the topology in Figure 6. DESCRIPTION OF PREFERRED EMBODIMENTS
• Figure 1 is an overview of an arrangement for coding and transmitting images.
• An image 3 of an object is stored in digital form in a digital camera 1, and the image presented on a screen 4.
• the screen is connected to a computer 2 which is programmed to divide the image 3 into objects or regions, of which a background region RI and regions of interest RI and Rn are shown.
• An image coder 5 in the computer 2 wavelet- transforms the image, while simultaneously compressing the image, and generates a compressed bit stream PS1.
• An operator at the image screen 4 defines the regions of interest R2 and Rn.
• the image coder includes means for creating a mask PS2 in accordance with the regions and defines separate parts, segments, of the bit streams with respect to the corresponding regions RI, R2 and Rn, with the aid of said mask.
• the definition also enables the regions RI, R2 , Rn in the form of said separate segments in the bit stream PS1 to be coded to different degrees of accuracy.
• a transmitter 6 sends the bit stream, including the definition of the positions and shapes of the regions R2 and Rn to a receiver 7 which is connected to a computer that includes an image decoder 8.
• the decoder decodes the bit stream PS1 and reproduces the mask definition PS2 and presents the image on an image display screen 9.
• the accuracy of the background RI is relatively poor, whereas each of the regions R2 and Rn has respectively a higher degree of accuracy.
• a segment is defined here as all of the coefficients in the transform domain that belong to a given object or the background in the image. The segment can then be divided further into subsets.
• a subset is defined here as a number of coefficients in a part of the transform domain (e.g. a subband in the case of the wavelet transform) which is required for the reconstruction and which belongs to a segment in the digitized image, see Figure 4.
• the coefficients are classified and can be assigned to individual segments.
• the segments are coded independently of one another to different levels of accuracy, which yields a bit stream for each segment. These segments are then joined together.
• the inventive encoding method will be described with reference to Figure 2.
• the digitized image 3 to be transmitted presents the background RI and the regions of interest R2 and Rn.
• the following procedural steps are carried out:
• step 21 Perform a transformation of the image 3 according to step 21.
• this transformation is performed with a wavelet transform or with a discrete cosine transform (DCT) .
• DCT discrete cosine transform
• step 2 Create a mask according to step 2 with the aid of information as to how the digitized image 3 shall be divided into the background RI and the objects R2 and Rn.
• the techniques described in Swedish Patent Applications SE 9703690-9 and SE 9800088-8 can be used to this end.
• the mask is created in the transform domain and describes which coefficients are required to reconstruct the different objects or the background. Different segments SGI, SG2 and SGn correspond to the background RI and the objects R2 and Rn.
• step 24 Code the segments independently of one another, according to step 24. This gives the number of bits needed for each subset.
• step 26 Concatenate the subset streams together with necessary substream information and header information, according to step 26. This requires a bit stream description, given below.
• the method enables the receiver to have immediate access to any parts of the image when so desired, as shown in Figure 3. This is possible because the information as to where different parts are found in the bit stream is known.
• step 32 Find and decode the required segment information
• a pointer is a set of symbols that defines the position of a bit or a byte in a bit stream or a file. Many ways of defining a pointer have been defined in computer science. Any one of these methods can be used here. A pointer can be defined implicitly by a specific bit stream composition rule. A pointer can be defined relative to an explicitly or implicitly determined position. A simple way of defining a pointer is to determine the number of bits between the requested position and a known reference point, such as the first bit in the bit stream, for instance.
• the topology descriptor, TOP is a set of symbols that defines the topological relationship between numbered objects and shapes. This is illustrated in Figure 6, in which four objects 01, 02, 03, 04 and four shapes SI, S2, S3 and S4 are shown.
• the topology of the image can be represented, e.g., as a tree graph as shown in Figure 7.
• the nodes and the edges of the tree graph can be coded in a data structure using well known methods.
• P_T0P is a pointer to a topology descriptor.
• a shape descriptor, Si defines the appearance of a closed boundary line of an object.
• the shape number, i is given by a topology descriptor.
• Many different shape coding techniques can be used. Examples of such methods are chain coding and shape coding methods in MPEG-4.
• Shape descriptors can be decoded independently of one another once their respective positions in the bit stream is known.
• P_Si is a pointer to a shape descriptor.
• a segment descriptor, Ti is a compressed set of symbols that encode a segment as described above.
• the segment includes an ordered set of subsets.
• the object number, i is given by a topology descriptor.
• P_Ti is a pointer to a segment descriptor.
• a subset descriptor, B ;j is an independently decodable subset, j , of a segment descriptor, T A , which describes, e.g., the coefficients that belong to a given subband, j , as described above.
• p_B ij is a pointer to a subset descriptor.
• segment descriptors ⁇ i r T , T k ... ⁇
• MT data structure
• p_MT is a pointer to a multiplexed segment descriptor.
• MT(i, j ,k) ⁇ B i0 , B j0 , B k0 , B il r B jX , B kl , B i2 , B j2 , B k2 ... ⁇
• the order of the symbols corresponds to the order in the bit stream 51, with symbols on the left being sent first. Subsets in a multiplexed stream may be excluded if they are known by the decoder.
• the stored bit stream or file structure should preferably include at least the following components:
• a group of segment descriptors with index ⁇ k,l,m... ⁇ can optionally be replaced with a multiplexed segment descriptor MT(k, l,m... ) N is the number of stored objects.
• the background is the object with index 0.
• a server receives a request for sending image data to a client.
• the image is stored with the server in the format described in the preceding passage.
• Part of the stored data structures may have already been sent to the receiving terminal.
• This section of the description describes a procedure for composing a bit stream with the server that handles the request.
• a simple request contains the following information:
• TOP is sent in response to a first request for image information.
• Subset descriptors that describe the objects requested to the defined accuracy.
• Subset descriptors that are already known to the decoder need not be sent. For instance, the user is aware of the subsets ⁇ B k0 , B kl , B k2 , B k3 ⁇ belonging .to segment k .
• Subset descriptors ⁇ B k5 , B k6 , B k7 ⁇ must be sent when object k is requested to accuracy 7.
• the original image is transformed with a wavelet transform.
• a mask is then created in the transform domain.
• This mask describes the coefficients that are required in the transform domain in order to reconstruct the region R52 and the background R53.
• the created mask is then used to classify the coefficients in the transform domain in two segments, one segment for the region and one segment for the background.
• the two segments are built up by a number of subsets. In the illustrated case, the number of subsets is the same as the number of subbands in the transform domain. The situation on hand is thus:
• a shape descriptor T r ⁇ B r#0 ,B r/1 , ... ,B r/no _ subbands ⁇ and a set of subset pointers ⁇ p_B r/0 ,p_B r/1 , ... ,p_B rrno _ subbands ⁇ .
• a segment descriptor T b ⁇ B b/0 ,B b/1 , ... ,B b , no _ subbands ⁇ and a set of subset pointers ⁇ p_B b#0 ,B b
• bit stream 51 4.
• the subsets are combined in the manner shown in the upper part of Figure 5, with the sub-bit streams 52 of the region being taken alternately with the sub-bit streams of the background.
• the TOP field is not required when the receiver is aware of the order in which the various parts of the image are set.
• the combined bit stream is then sent to the receiver.
• the decoder is now able to create the same mask as that described above.
• the decoder creates the segments with the underlying subsets .
• the decoder commences with decoding the combined bit stream and filling in the transmitted transform coefficients in the corresponding subsets.
• the image is transmitted and reconstructed.
• the aforedescribed is one way of using the proposed method.
• Other methods may be to combine (mix) the bit streams in another way. For instance, as shown in the bottom part of Figure 5, the region R52 may be transmitted first, followed by the background R53.
• Another example is one in which more than one region is found, as described with reference to Figure 6, wherewith these regions are combined in a number of different ways.
• the proposed method has the added advantage of enabling shape information to be sent only when needed.

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• Engineering & Computer Science (AREA)
• Multimedia (AREA)
• Signal Processing (AREA)
• Compression Or Coding Systems Of Tv Signals (AREA)
• Compression Of Band Width Or Redundancy In Fax (AREA)

Priority Applications (5)

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Cited By (13)

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Citations (1)

• 1998
  • 1998-06-18 SE SE9802193A patent/SE521021C2/sv unknown
• 1999
  • 1999-06-10 CA CA002335022A patent/CA2335022A1/en not_active Abandoned
  • 1999-06-10 WO PCT/SE1999/001024 patent/WO2000001153A1/en not_active Application Discontinuation
  • 1999-06-10 CN CNB998074810A patent/CN1135848C/zh not_active Expired - Lifetime
  • 1999-06-10 AU AU48120/99A patent/AU753304B2/en not_active Expired
  • 1999-06-10 JP JP2000557619A patent/JP2002519953A/ja not_active Withdrawn
  • 1999-06-10 EP EP99931683A patent/EP1106014A1/en not_active Withdrawn
  • 1999-06-10 KR KR1020007013975A patent/KR20010052710A/ko not_active Application Discontinuation

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