Abstract:
A method and apparatus for sample adaptive offset without sign coding. The method includes selecting an edge offset type for at least a portion of an image, classifying at least one pixel of at least the portion of the image into edge shape category, calculating an offset of the pixel, determining the offset is larger or smaller than a predetermined threshold, changing a sign of the offset based on the threshold determination; and performing entropy coding accounting for the sign of the offset and the value of the offset.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a continuation of U.S. patent application Ser. No. 13/671,670, filed Nov. 8, 2012, which claims the benefit of United States Provisional Application No. 61/557,040, filed Nov. 8, 2011 and United States Provisional Application No. 61/585,806, filed Jan. 12, 2012, all of which are incorporated herein by reference in their entirety. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    Embodiments of the present invention generally relate to a method and apparatus for sample adaptive offset without sign coding, which maybe used for high efficiency video coding. 
         [0004]    2. Description of the Related Art 
         [0005]    Sample adaptive offset (SAO) was introduced for the next generation video coding standard called high efficiency video coding (HEVC).  FIG. 1  is an embodiment depicting a block diagram for decoding Architecture of high efficiency video coding with adaptive loop filtering (ALF) and sample adaptive offset. As shown in  FIG. 1 , SAO is applied after deblocking filtering process, usually, before adaptive loop filtering (ALF). 
         [0006]    SAO involves adding an offset directly to the reconstructed pixel from the video decoder loop in  FIG. 1 . The offset value applied to each pixel depends on the local characteristics surrounding that pixel. There are two kinds of offsets, namely band offset (BO) and edge offset (EO). BO classifies pixels by intensity interval of the reconstructed pixel, while EO classifies pixels based on edge direction and structure. In certain cases, the number of pixels increases but the number of bands stays the same. As a result, the system becomes less efficient. 
         [0007]    Therefore, there is a need for an improved method and/or apparatus for a more efficient image and video coding using hierarchical sample adaptive band offset. 
       SUMMARY OF THE INVENTION 
       [0008]    Embodiments of the present invention relate to a method and apparatus for sample adaptive offset without sign coding. The method includes selecting an edge offset type for at least a portion of an image, classifying at least one pixel of at least the portion of the image into edge shape category, calculating an offset of the pixel, determining the offset is larger or smaller than a predetermined threshold, changing a sign of the offset based on the threshold determination; and performing entropy coding accounting for the sign of the offset and the value of the offset. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]    So that the manner in which the above recited features of the present invention can be understood in detail, a more particular description of the invention, briefly summarized above, may be had by reference to embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments of this invention and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments. 
           [0010]      FIG. 1  is an embodiment depicting a block diagram for decoding architecture of high efficiency video coding with adaptive loop filtering and sample adaptive offset; 
           [0011]      FIG. 2  is a block diagram of a digital system; 
           [0012]      FIG. 3  is a block diagram of a video encoder; 
           [0013]      FIG. 4  is a block diagram of a video decoder; 
           [0014]      FIG. 5  is an embodiment depicting band offset group classification; 
           [0015]      FIG. 6  is an embodiment depicting edge offset pixel classification patterns; 
           [0016]      FIG. 7  is an embodiment depicting a flow diagram of a method for encoding procedure using a reconstructed signal; 
           [0017]      FIG. 8  is an embodiment depicting a flow diagram for a method for region adaptive offset compensation decoding; and 
           [0018]      FIG. 9  is an embodiment depicting a flow diagram of a method for general region adaptive offset compensation encoding. 
       
    
    
     DETAILED DESCRIPTION 
       [0019]      FIG. 2  is a block diagram of a digital system.  FIG. 2  shows a block diagram of a digital system that includes a source digital system  200  that transmits encoded video sequences to a destination digital system  202  via a communication channel  216 . The source digital system  200  includes a video capture component  204 , a video encoder component  206 , and a transmitter component  208 . The video capture component  204  is configured to provide a video sequence to be encoded by the video encoder component  206 . The video capture component  204  may be, for example, a video camera, a video archive, or a video feed from a video content provider. In some embodiments, the video capture component  204  may generate computer graphics as the video sequence, or a combination of live video, archived video, and/or computer-generated video. 
         [0020]    The video encoder component  206  receives a video sequence from the video capture component  204  and encodes it for transmission by the transmitter component  208 . The video encoder component  206  receives the video sequence from the video capture component  204  as a sequence of pictures, divides the pictures into largest coding units (LCUs), and encodes the video data in the LCUs. An embodiment of the video encoder component  206  is described in more detail herein in reference to  FIG. 3 . 
         [0021]    The transmitter component  208  transmits the encoded video data to the destination digital system  202  via the communication channel  216 . The communication channel  216  may be any communication medium, or combination of communication media suitable for transmission of the encoded video sequence, such as, for example, wired or wireless communication media, a local area network, or a wide area network. 
         [0022]    The destination digital system  202  includes a receiver component  210 , a video decoder component  212  and a display component  214 . The receiver component  210  receives the encoded video data from the source digital system  200  via the communication channel  216  and provides the encoded video data to the video decoder component  212  for decoding. The video decoder component  212  reverses the encoding process performed by the video encoder component  206  to reconstruct the LCUs of the video sequence. 
         [0023]    The reconstructed video sequence is displayed on the display component  214 . The display component  214  may be any suitable display device such as, for example, a plasma display, a liquid crystal display (LCD), a light emitting diode (LED) display, etc. 
         [0024]    In some embodiments, the source digital system  200  may also include a receiver component and a video decoder component and/or the destination digital system  202  may include a transmitter component and a video encoder component for transmission of video sequences both directions for video steaming, video broadcasting, and video telephony. Further, the video encoder component  206  and the video decoder component  212  may perform encoding and decoding in accordance with one or more video compression standards. The video encoder component  206  and the video decoder component  212  may be implemented in any suitable combination of software, firmware, and hardware, such as, for example, one or more digital signal processors (DSPs), microprocessors, discrete logic, application specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), etc. 
         [0000]      FIG. 3  is a block diagram of a video encoder.  FIG. 3  shows a block diagram of the LCU processing portion of an example video encoder. A coding control component (not shown) sequences the various operations of the LCU processing, i.e., the coding control component runs the main control loop for video encoding. The coding control component receives a digital video sequence and performs any processing on the input video sequence that is to be done at the picture level, such as determining the coding type (I, P, or B) of a picture based on the high level coding structure, e.g., IPPP, IBBP, hierarchical-B, and dividing a picture into LCUs for further processing. The coding control component also may determine the initial LCU CU structure for each CU and provides information regarding this initial LCU CU structure to the various components of the video encoder as needed. The coding control component also may determine the initial prediction unit and TU structure for each CU and provides information regarding this initial structure to the various components of the video encoder as needed.
 
The LCU processing receives LCUs of the input video sequence from the coding control component and encodes the LCUs under the control of the coding control component to generate the compressed video stream. The CUs in the CU structure of an LCU may be processed by the LCU processing in a depth-first Z-scan order. The LCUs  300  from the coding control unit are provided as one input of a motion estimation component  320 , as one input of an intra-prediction component  324 , and to a positive input of a combiner  302  (e.g., adder or subtractor or the like). Further, although not specifically shown, the prediction mode of each picture as selected by the coding control component is provided to a mode selector component and the entropy encoder  334 .
 
         [0025]    The storage component  318  provides reference data to the motion estimation component  320  and to the motion compensation component  322 . The reference data may include one or more previously encoded and decoded CUs, i.e., reconstructed CUs. 
         [0026]    The motion estimation component  320  provides motion data information to the motion compensation component  322  and the entropy encoder  334 . More specifically, the motion estimation component  320  performs tests on CUs in an LCU based on multiple inter-prediction modes (e.g., skip mode, merge mode, and normal or direct inter-prediction) and transform block sizes using reference picture data from storage  318  to choose the best motion vector(s)/prediction mode based on a rate distortion coding cost. To perform the tests, the motion estimation component  320  may begin with the CU structure provided by the coding control component. The motion estimation component  320  may divide each CU indicated in the CU structure into prediction units according to the unit sizes of prediction modes and into transform units according to the transform block sizes and calculate the coding costs for each prediction mode and transform block size for each CU. The motion estimation component  320  may also compute CU structure for the LCU and PU/TU partitioning structure for a CU of the LCU by itself. 
         [0027]    For coding efficiency, the motion estimation component  320  may also decide to alter the CU structure by further partitioning one or more of the CUs in the CU structure. That is, when choosing the best motion vectors/prediction modes, in addition to testing with the initial CU structure, the motion estimation component  320  may also choose to divide the larger CUs in the initial CU structure into smaller CUs (within the limits of the recursive quadtree structure), and calculate coding costs at lower levels in the coding hierarchy. If the motion estimation component  320  changes the initial CU structure, the modified CU structure is communicated to other components that need the information. 
         [0028]    The motion estimation component  320  provides the selected motion vector (MV) or vectors and the selected prediction mode for each inter-predicted prediction unit of a CU to the motion compensation component  322  and the selected motion vector (MV), reference picture index (indices), prediction direction (if any) to the entropy encoder  334   
         [0029]    The motion compensation component  322  provides motion compensated inter-prediction information to the mode decision component  326  that includes motion compensated inter-predicted PUs, the selected inter-prediction modes for the inter-predicted PUs, and corresponding transform block sizes. The coding costs of the inter-predicted prediction units are also provided to the mode decision component  326 . 
         [0030]    The intra-prediction component  324  provides intra-prediction information to the mode decision component  326  that includes intra-predicted prediction units and the corresponding intra-prediction modes. That is, the intra-prediction component  324  performs intra-prediction in which tests based on multiple intra-prediction modes and transform unit sizes are performed on CUs in an LCU using previously encoded neighboring prediction units from the buffer  328  to choose the best intra-prediction mode for each prediction unit in the CU based on a coding cost. 
         [0031]    To perform the tests, the intra-prediction component  324  may begin with the CU structure provided by the coding control. The intra-prediction component  324  may divide each CU indicated in the CU structure into prediction units according to the unit sizes of the intra-prediction modes and into transform units according to the transform block sizes and calculate the coding costs for each prediction mode and transform block size for each PU. For coding efficiency, the intra-prediction component  324  may also decide to alter the CU structure by further partitioning one or more of the CUs in the CU structure. That is, when choosing the best prediction modes, in addition to testing with the initial CU structure, the intra-prediction component  324  may also chose to divide the larger CUs in the initial CU structure into smaller CUs (within the limits of the recursive quadtree structure), and calculate coding costs at lower levels in the coding hierarchy. If the intra-prediction component  324  changes the initial CU structure, the modified CU structure is communicated to other components that need the information. Further, the coding costs of the intra-predicted prediction units and the associated transform block sizes are also provided to the mode decision component  326 . 
         [0032]    The mode decision component  326  selects between the motion-compensated inter-predicted prediction units from the motion compensation component  322  and the intra-predicted prediction units from the intra-prediction component  324  based on the coding costs of the prediction units and the picture prediction mode provided by the mode selector component. The decision is made at CU level. Based on the decision as to whether a CU is to be intra- or inter-coded, the intra-predicted prediction units or inter-predicted prediction units are selected, accordingly. 
         [0033]    The output of the mode decision component  326 , i.e., the predicted PU, is provided to a negative input of the combiner  302  and to a delay component  330 . The associated transform block size is also provided to the transform component  304 . The output of the delay component  330  is provided to another combiner (i.e., an adder)  338 . The combiner  302  subtracts the predicted prediction unit from the current prediction unit to provide a residual prediction unit to the transform component  304 . The resulting residual prediction unit is a set of pixel difference values that quantify differences between pixel values of the original prediction unit and the predicted PU. The residual blocks of all the prediction units of a CU form a residual CU block for the transform component  304 . 
         [0034]    The transform component  304  performs block transforms on the residual CU to convert the residual pixel values to transform coefficients and provides the transform coefficients to a quantize component  306 . The transform component  304  receives the transform block sizes for the residual CU and applies transforms of the specified sizes to the CU to generate transform coefficients. 
         [0035]    The quantize component  306  quantizes the transform coefficients based on quantization parameters (QPs) and quantization matrices provided by the coding control component and the transform sizes. The quantize component  306  may also determine the position of the last non-zero coefficient in a TU according to the scan pattern type for the TU and provide the coordinates of this position to the entropy encoder  334  for inclusion in the encoded bit stream. For example, the quantize component  306  may scan the transform coefficients according to the scan pattern type to perform the quantization, and determine the position of the last non-zero coefficient during the scanning/quantization. 
         [0036]    The quantized transform coefficients are taken out of their scan ordering by a scan component  308  and arranged sequentially for entropy coding. The scan component  308  scans the coefficients from the highest frequency position to the lowest frequency position according to the scan pattern type for each TU. In essence, the scan component  308  scans backward through the coefficients of the transform block to serialize the coefficients for entropy coding. As was previously mentioned, a large region of a transform block in the higher frequencies is typically zero. The scan component  308  does not send such large regions of zeros in transform blocks for entropy coding. Rather, the scan component  308  starts with the highest frequency position in the transform block and scans the coefficients backward in highest to lowest frequency order until a coefficient with a non-zero value is located. Once the first coefficient with a non-zero value is located, that coefficient and all remaining coefficient values following the coefficient in the highest to lowest frequency scan order are serialized and passed to the entropy encoder  334 . In some embodiments, the scan component  308  may begin scanning at the position of the last non-zero coefficient in the TU as determined by the quantize component  306 , rather than at the highest frequency position. 
         [0037]    The ordered quantized transform coefficients for a CU provided via the scan component  308  along with header information for the CU are coded by the entropy encoder  334 , which provides a compressed bit stream to a video buffer  336  for transmission or storage. The header information may include the prediction mode used for the CU. The entropy encoder  334  also encodes the CU and prediction unit structure of each LCU. 
         [0038]    The LCU processing includes an embedded decoder. As any compliant decoder is expected to reconstruct an image from a compressed bit stream, the embedded decoder provides the same utility to the video encoder. Knowledge of the reconstructed input allows the video encoder to transmit the appropriate residual energy to compose subsequent pictures. To determine the reconstructed input, i.e., reference data, the ordered quantized transform coefficients for a CU provided via the scan component  308  are returned to their original post-transform arrangement by an inverse scan component  310 , the output of which is provided to a dequantize component  312 , which outputs a reconstructed version of the transform result from the transform component  304 . 
         [0039]    The dequantized transform coefficients are provided to the inverse transform component  314 , which outputs estimated residual information which represents a reconstructed version of a residual CU. The inverse transform component  314  receives the transform block size used to generate the transform coefficients and applies inverse transform(s) of the specified size to the transform coefficients to reconstruct the residual values. 
         [0040]    The reconstructed residual CU is provided to the combiner  338 . The combiner  338  adds the delayed selected CU to the reconstructed residual CU to generate an unfiltered reconstructed CU, which becomes part of reconstructed picture information. The reconstructed picture information is provided via a buffer  328  to the intra-prediction component  324  and to an in-loop filter component  316 . The in-loop filter component  316  applies various filters to the reconstructed picture information to improve the reference picture used for encoding/decoding of subsequent pictures. The in-loop filter component  316  may, for example, adaptively apply low-pass filters to block boundaries according to the boundary strength to alleviate blocking artifacts causes by the block-based video coding. The filtered reference data is provided to storage component  318 . 
         [0041]      FIG. 4  shows a block diagram of an example video decoder. The video decoder operates to reverse the encoding operations, i.e., entropy coding, quantization, transformation, and prediction, performed by the video encoder of  FIG. 3  to regenerate the pictures of the original video sequence. In view of the above description of a video encoder, one of ordinary skill in the art will understand the functionality of components of the video decoder without detailed explanation. 
         [0042]    The entropy decoding component  400  receives an entropy encoded (compressed) video bit stream and reverses the entropy coding to recover the encoded PUs and header information such as the prediction modes and the encoded CU and PU structures of the LCUs. If the decoded prediction mode is an inter-prediction mode, the entropy decoder  400  then reconstructs the motion vector(s) as needed and provides the motion vector(s) to the motion compensation component  410 . 
         [0043]    The inverse scan and inverse quantization component  402  receives entropy decoded quantized transform coefficients from the entropy decoding component  400 , inverse scans the coefficients to return the coefficients to their original post-transform arrangement, i.e., performs the inverse of the scan performed by the scan component  308  of the encoder to reconstruct quantized transform blocks, and de-quantizes the quantized transform coefficients. The forward scanning in the encoder is a conversion of the two dimensional (2D) quantized transform block to a one dimensional (1D) sequence; the inverse scanning performed here is a conversion of the 1D sequence to the two dimensional quantized transform block using the same scanning pattern as that used in the encoder. 
         [0044]    The inverse transform component  404  transforms the frequency domain data from the inverse scan and inverse quantization component  402  back to the residual CU. That is, the inverse transform component  404  applies an inverse unit transform, i.e., the inverse of the unit transform used for encoding, to the de-quantized residual coefficients to produce the residual CUs. 
         [0045]    A residual CU supplies one input of the addition component  406 . The other input of the addition component  406  comes from the mode switch  408 . When an inter-prediction mode is signaled in the encoded video stream, the mode switch  408  selects predicted PUs from the motion compensation component  410  and when an intra-prediction mode is signaled, the mode switch selects predicted PUs from the intra-prediction component  414 . 
         [0046]    The motion compensation component  410  receives reference data from storage  412  and applies the motion compensation computed by the encoder and transmitted in the encoded video bit stream to the reference data to generate a predicted PU. That is, the motion compensation component  410  uses the motion vector(s) from the entropy decoder  400  and the reference data to generate a predicted PU. 
         [0047]    The intra-prediction component  414  receives reference data from previously decoded PUs of a current picture from the picture storage  412  and applies the intra-prediction computed by the encoder as signaled by the intra-prediction mode transmitted in the encoded video bit stream to the reference data to generate a predicted PU. 
         [0048]    The addition component  406  generates a decoded CU by adding the predicted PUs selected by the mode switch  408  and the residual CU. The output of the addition component  406  supplies the input of the in-loop filter component  416 . The in-loop filter component  416  performs the same filtering as the encoder. The output of the in-loop filter component  416  is the decoded pictures of the video bit stream. Further, the output of the in-loop filter component  416  is stored in storage  412  to be used as reference data. 
         [0049]    There are two kinds of offsets, namely band offset (BO) and edge offset (EO). BO classifies pixels by intensity interval of the reconstructed pixel, while EO classifies pixels based on edge direction and structure. For BO, the pixel is classified into one of two categories, the side band or central band, as shown in  FIG. 5 .  FIG. 5  is an embodiment depicting band offset group classification. 
         [0050]      FIG. 6  is an embodiment depicting edge offset pixel classification patterns. For edge offset, the pixels can be filtered in one of four directions, as shown in  FIG. 6 . For each direction, the pixel is classified into one of five categories based on the value of c, where c is the intensity value of the current reconstructed pixel. The category number can be calculated as sign(p 0 −p 1 )+sign (p 0 −p 2 ), where p 0  is current pixel and p 1  and p 2  are neighboring pixels. 
         [0000]      c &lt;2 neighboring pixels; 
         [0000]      c &lt;1 neighbor &amp;&amp; c ==1 neighbor;
 
         [0000]      c &gt;1 neighbor &amp;&amp; c ==1 neighbor;
 
         [0000]      c &gt;2 neighbors; and 
         [0000]      none of above (c =either neighbor). 
         [0051]    On the encoder side, the SAO is LCU-based processing to estimate the offsetsfor a LCU. Each LCU is allowed to switch between BO and EQ. Thus, the encoder can signal the following to the decoder for a LCU: 
         [0000]      sao_type_idx =type of SAO 
         [0000]      sao_offset =sao offset value 
         [0052]    Table 1 describes in more detail type of SAO or speciation of NumSaoClass: 
         [0000]                                                      TABLE 1                       sao_type_idx   NumSaoCategory   Edge type (informative)                                        0   0   Not applied           1   4   1D 0-degree edge           2   4   1D 90-degree edge           3   4   1D 135-degree edge           4   4   1D 45-degree edge           5   16   Central band           6   16   Side band                        
For each LCU, a sao_type_idx is signaled followed by offset values for each category.
 
         [0053]    In one embodiment, a method and/or apparatus compensates for quantization error using the reconstructed signal by adding offset to each pixel.  FIG. 7  is an embodiment depicting a flow diagram of a method  700  for encoding procedure using a reconstructed signal. The method starts at step  702  and proceeds to step  704 . At step  704 , the method  700  selects the type for a give region (e.g. LCU). At step  706 , the method  700  classifies each pixel into categories. At step  708 , the method  700  calculates the offset. At step  710 , the method  700  determines if the category is positive. If the category is positive, the method  700  proceeds to step  712 , wherein the method  700  determines if the offset is less than zero. If the offset is less than zero, the method  700  proceeds to step  714 , wherein the offset is set to zero and proceeds to step  716 . If the offset is not less than zero, the method  700  proceeds to step  716 . 
         [0054]    If the category is determined to be not positive in step  710 , the method proceeds to step  718 , wherein the method  700  determines if the offset is greater than zero. If the offset is greater than zero, the method  700  proceeds to step  714  wherein the offset is set to zero and the method  700  proceeds to step  716 . If the offset is not greater than zero, the method  700  proceeds to step  720 , wherein the offset is set to a negative value and the method  700  proceeds to step  716 . At step  716 , the method  700  performs determines the entropy coding of offset information. The method  700  ends at step  722 . Steps  708 - 716  maybe performed for each category. 
         [0055]    As shown in  FIG. 7 , an image or a video frame is divided into regions. A quad-tree structure can be used to divide regions. Or a fixed-size block, e.g., LCU, can be used. For each region edge offset type is selected according to edge structure in the region. Each pixel is classified into predefined categories. The category is defined according to the sign of difference between the current reconstructed pixel value and that of neighboring ones as described in the previous section. The offset for each category can be calculated by taking the average of differences between the original pixel and the reconstructed one which fall into each category. 
         [0056]    Accordingly, the level of the current pixel and neighboring pixel will form different shapes for each category, as shown in  FIG. 6 . In case of category  1  and category  2 , the level of current pixel is lower than the neighboring ones. Therefore, the offset value tends to have plus sign. On the other hand, in case of category  3  and  4 , the level of current pixel is higher than the neighboring ones. Therefore, the offset value tends to have minus sign. However, when the sign of the offset is reversed, this means that the difference between the current pixel and neighboring ones becomes larger, which may potentially cause visual artifact. Thus, the sign of the offset is restricted according to category. Specifically, for category  1  and  2 , or “+” category, the offset is set larger than or equal to 0. If it is smaller than 0, it is set to 0. On the other hand, category  3  and  4 , or “−” category, the offset is set as 0 or negative one. If it is larger than 0, it is set to 0. In this way, the visual artifact can be effectively removed. 
         [0057]    Since the sign is determined according to category, there is usually no need to include sign information into bitstream. Therefore, the absolute value of the sign is usually entropy coded. Hence, avoiding the use of coding sign information, coding efficiency improvement is achieved. In one embodiment, such a solution may be used with band offset, in which sign value may be coded and included into bitstream. 
         [0058]      FIG. 8  is an embodiment depicting a flow diagram for a method for region adaptive offset compensation decoding. The method  800  starts at step  802  and proceeds to step  804 , wherein the method  800  determines the entropy coding of type information for a given region. At step  806 , the method  800  determines the entropy coding of offset information. At step  808 , the method  800  determines if the category is positive. If the category is positive, the method  800  proceeds to step to step  812 . If the category is not positive, the method  800  proceeds to step  810  and then proceeds to step  812 . At  810 , the method  800  sets the offset to a negative value. At step  812 , the method  800  adds the offset to each pixel according to the category. The method  800  ends at step  814 . Steps  806 - 810  maybe performed for each category. 
         [0059]    In one embodiment, after decoding offset value for each category, its sign is determined according to the category. For “+” category offset, there is no sign change. For “−” category offset, the decoded value is converted into negative one with same absolute value. Usually, after deriving the offset values, the value is added to the reconstructed pixel value according to its category. 
         [0060]    In one embodiment, such a solution may be incorporated into an encoder with sign coding. For example, for “+” category offset, the offset values may be restricted to be in the range of [ 0 , max_abs_offset] in the encoder side, where max_abs_offset is the maximum absolute value of offset allowed in the encoder side. Hence, a “+” sign is usually encoded. On the contrary, for “−” category offset, the offset values may be restricted to be in the range of [-max_abs_offset,  0 ] and usually encode a “−” sign. 
         [0061]    In general, other restriction may be imposed on the range of offset values, for example, [-c, max_abs_offset] and [-max_abs_offset, c] for “+” category and “−” category, respectively, where c is zero or positive value (much) less than max_abs_offset. 
         [0062]      FIG. 9  is an embodiment depicting a flow diagram of a method  900  for general region adaptive offset compensation encoding. Method  900  starts at step  902  and proceeds to step  904 . At step  904 , the method  900  selects a type for a region. At step  906 , the method  900  calculates the offset. At step  910 , the method  900  determines if the category is positive. If the category is not positive, the method  900  proceeds to step  912 , wherein the method  900  determines if the offset is greater than a positive value of a threshold. If the offset is greater, then the method  900  proceeds to step  914 , wherein the offset is set to be a positive value of the threshold and proceeds to step  920 . If it is not greater, the method  900  proceeds to step  920 . If the category is positive, the method  900  proceeds to step  916 , wherein the method  900  determines if the offset is less than a negative value of the threshold. If the offset is less, then the method  900  proceeds to step  918 , wherein the offset is set to be a negative value of the threshold and proceeds to step  920 . If it is not less, the method  900  proceeds to step  920 . At step  920 , the method  900  determines the entropy coding of sign and the absolute value of the offset. The method  900  ends at step  922 . 
         [0063]    While the foregoing is directed to embodiments of the present invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.