Display for displaying compressed video

A display is configured to display transformed video. The display includes a display unit comprising pixels. The display also includes a set of filter elements positioned adjacent to the display unit. The set of filter elements enable the display unit to display transformed video.

FIELD

This disclosure generally relates to displays. More particularly, the subject matter of this disclosure pertains to displays that are capable of displaying compressed video.

BACKGROUND

Conventional displays receive video signals which represent either still or moving images. Conventional displays require that the video signals be uncompressed in order to properly display the video.

Typically, video is stored or transmitted in compressed format such as Joint Photographic Experts Group (JPEG) format for still images and Moving Pictures Experts Group (MPEG) for moving images. For example, in JPEG compression, the image is down sampled from the original 12- or 14-bit data back to 8 bits before performing the JPEG compression. Then, a large set of calculations must be performed on the image data to compress the image. Accordingly, any compressed video signal must be decompressed before a conventional display may display the video. Thus, a separate processor or a processor in the display must decompress the video signal before the video may be displayed.

Indeed, some digital devices that include a display, such as a digital camera or cell phone, may include a separate digital signal processor or other form of processor in order to perform decompression, such as JPEG decompression. Therefore, support of the decompression algorithm can consume a large amount of time and power in such digital devices.

It may be desirable to reduce the amount of processing and power required for digital devices. Due to their popular acceptance, compressed video can be generated and handled by a wide variety of devices. For example, portable devices like video cameras, mobile phones, personal digital assistants (PDAs), digital media players such as I-Pods etc., are now capable of displaying video, such as JPEG images or MPEG images. However, these devices must also conserve space used by the components and the amount of power they consume (since they run on batteries). It may also be desirable to speed the processing related to decompression, such as, for security applications.

Accordingly, it would be desirable to systems and methods that efficiently implement decompression algorithms to display compressed video, such as a JPEG, image without the extra processing and hardware involved.

SUMMARY

Embodiments of the present teaching are directed to a display configured to display transformed video. The display comprises a display unit comprising pixels and a set of filter elements positioned adjacent to the display unit. The set of filter elements enable the display unit to display transformed video.

Embodiments also are directed to a display configured to display transformed video by transforming light emitted by a display unit. The display comprises a display unit comprising video divisions. The video divisions are arranged in blocks and each video division comprises sub-divisions. The display also includes a set of filter elements positioned adjacent to the display unit. Each filter element of the set of filter elements comprises sub-divisions corresponding to the sub-divisions in an adjacent video division.

Embodiments are also directed to a device which comprises a video source capable of providing a compressed video signal representing transformation values of a compression method. The device also comprises a display configured to display the compressed video signal based on the transformation values.

DETAILED DESCRIPTION

As noted above, in conventional displays, video, which includes still and moving images, is usually imputed to or stored in the displays in a compressed format, such as JPEG or MPEG. The display device uses “back-end” processing to decompress the video into a format that may be displayed by the display. Unfortunately, this type of “back-end” processing often requires the use of a separate digital signal processor or a separate computing device to perform the calculations necessary for the decompression algorithm. As such, conventional devices consume a large amount of power, take long times to decompress the video, and increase in size to accommodate additional hardware.

However, embodiments of the present teaching provide a display that implements “front-end” processing to perform part of a decompression or transformation algorithm when displaying video. In particular, the display uses transformation values of the compression or transformation algorithm directly as the video signal. The display includes a filter which converts the transformation values inputted to the display into the actual viewable video.

For example, a display may be composed of video divisions, such as pixels. Each division is subdivided into sub-divisions, such as sub-pixels. Each sub-division of display device generates light corresponding to a transformation coefficient of compressed video. The transformation coefficient may be a whole or partial coefficient. The number of sub-divisions corresponds to the number of transformation coefficients or partial coefficients used by the compression algorithm.

A set of filters or a filter with multiple divisions is positioned in front of the display. The filter (or filters) is divided into sub-divisions that correspond to the sub-divisions of the divisions of the display. Each sub-division of the filter has a transmissivity related to inverse transformation coefficients or partial coefficients of the compression or transformation algorithm. As such, the filter transforms the light generated by the display into an actual viewable video signal. Accordingly, the display device produces video without having to decompress or electronically transform the compressed or transformed video signal.

In addition, in order to simplify the display device, a reduced or compressed number of transformation coefficients or partial coefficients (such as 20) may be used. Also, sub-divisions across different divisions, but corresponding to the same inverse transformation coefficient or partial coefficient may be connected in parallel.

By using “front-end” processing, embodiments of the present teaching can be implemented using less power, less memory, and reduced physical size. In addition, such “front-end” processing may significantly reduce or even eliminate delays in displaying video and power consumption of a display. Thus, for example, the performance of small size, battery powered, camera and display systems such as cell phones, web cameras, digital cameras, and surveillance systems may be enhanced.

FIG. 1is a block diagram illustrating an exemplary display100consistent with embodiments of the present teaching. Display100may be any type of display capable of producing video, such as a still image or moving image, based on a video signal. For example, display100may be a liquid crystal display (LCD). It should be readily apparent to those of ordinary skill in the art that display100illustrated inFIG. 1represents a generalized schematic illustration and that other components may be added or existing components may be removed or modified.

Display100may be a stand alone display that receives video signals from an external device. For example, display100may be a monitor coupled to a computing device. Further, display100may be incorporated in a device that stores, receives, or captures compressed data. For example, display100may be a video screen in a cell phone or digital camera. One skilled in the art will realize that display100may be utilized with any type of device capable of producing, outputting, transmitting, or receiving video such as still images or moving images.

As illustrated inFIG. 1, display100includes a display unit102and a display control104. For example, if display100is an LCD, display unit102may include a light source such as a light emitting diode (LED) backlight. Further, if display100is an LCD, display unit102may include a liquid crystal panel that comprises video divisions such as pixels positioned in front of the light source. One skilled in the art will realize that display unit102may include any additional hardware, software, firmware, or combination thereof to produce video based on a video signal.

As illustrated inFIG. 1, display100also includes display control104. Display control104may include any hardware, software, firmware or combination thereof to control display unit102and to provide a compressed video signal to display unit102. One skilled in the art will realize that display unit104may include any additional hardware, software, firmware, or combination thereof to control display unit102and provide a compressed video signal to display unit102.

Display100also includes a filter106. Filter106may be positioned in front of display unit102to alter light generated by display unit102. Filter106may be integrated into display100. Likewise, filter106may be adapted to be attached and removed from display100. Filter106may be a single filter with multiple divisions. Likewise, filter106may be multiple individual filters.

Filter106may be composed of any material capable of changing properties of light passing through filter106. For example, filter106may be composed of a partially opaque optical material that changes the amount of light passing through filter106. One skilled in the art will realize that filter106may be composed of any known material capable of changing the properties of light.

Filter106(or filters) performs “front-end” processing on light emitted from display unit102. Filter106may perform part of a decompression or inverse transformation algorithm on a compressed or transformed video signal being displayed by display100. For example, the compression algorithm may be JPEG or MPEG.

To display compressed video, display unit102generates light based on the transformations values of the compression or transformation algorithm. Filter106performs “front-end” processing by receiving light from display unit102which represents transformation values. Filter106then performs a part of the decompression or inverse transformation algorithm on the light, representing the inverse transformation values, to produce actual viewable video.

As mentioned above, filter106may be composed of multiple divisions or filter106may be multiple individual filters. Each division of filter106(or individual filter) may be positioned adjacent to the video divisions of display unit102. For example, each division of filter106(or individual filter) may be positioned adjacent to a corresponding pixel in display unit102. Each division of filter106(or individual filter) may be configured to alter light generated by the corresponding division of display unit102.

Divisions of both filter106(or individual filter) and display unit102may also be further sub divided. In such a case, each sub-division of display unit102generates light corresponding to a compressed or transformed video signal. Each sub-division of display unit102generates light by receiving a specific transformation value of the compression or transformation algorithm. Each sub-division of filter106(or individual filter) is related to the respective transformation value of the corresponding sub-division of display unit102. As such, each sub-division of filter106(or individual filter) inverse transforms the light generated by the corresponding sub-division of display unit102into actual video. By this process, display100produces video without having to perform additional processing on the compressed or transformed video signal.

FIGS. 2-5illustrate an exemplary filter106which may be used in display100. Filter106may be configured to be used with transform encoding for video such as the JPEG compression algorithm for a still image or MPEG compression algorithm for moving images. Filter106alters the light output by display unit102such that the light corresponding to the transformation coefficients of the JPEG or other transformation algorithm output by display panel102is converted to actual viewable video. It should be readily apparent to those of ordinary skill in the art that filter106illustrated inFIGS. 2-5represents generalized schematic illustrations and that other components may be added or existing components may be removed or modified.

The JPEG algorithm is designed to compress either color or grey-scale digital images. Conceptually, JPEG compresses a digital image based on a mathematical tool known as the DCT and empirical adjustments to account for the characteristics of human vision.

The basic DCT can be expressed by the formula:

where p(m,n) represents the pixel values, either intensity or color.

JPEG applies the DCT to an elementary image area (called an “image block”) that are 8 pixels wide and 8 lines high. This causes the basic DCT expression to simplify to:

Therefore, in essence, JPEG uses the DCT to calculate the amplitude of spatial sinusoids that, when superimposed, can be used to recreate the original image.

In order to compress the data for an image, JPEG also combines a set of empirical adjustments to the DCT. The empirical adjustments have been developed through experimentation and may be expressed as a matrix of parameters that synthesizes or models what a human vision actually sees and what it discards. Through research, it was determined that a loss of some visual information in some frequency ranges is more acceptable than others. In general, human eyes are more sensitive to low spatial frequencies than to high spatial frequencies. As a result, a family of quantization matrices Q was developed. In a Q matrix, the bigger an element, the less sensitive the human eye is to that combination of horizontal and vertical spatial frequencies. In JPEG, quantization matrices are used to reduce the weight of the spatial frequency components of the DCT processed data, i.e., to model human eye behavior. The quantization matrix Q50represents the best known compromise between image quality and compression ratio and is presented below.

For higher compression ratios, poorer image quality, the Q50matrix can be multiplied by a scalar larger than 1 and clip all results to a maximum value of 255. For better quality images, but less compression, the Q50matrix can be multiplied by a scalar less than 1.

Therefore, the JPEG algorithm can be expressed as the following equation:

Of note, the application of the quantization matrix with the DCT essentially eliminates many of the frequency components of the DCT alone. The example below illustrates this phenomenon.

For clarity of presentation, the example is limited to a single 8×8 image block from a stock image. For example, suppose the image array I for a single image block is:

Initially, it is noted that all values in the I matrix are positive. Therefore, before continuing, the apparent DC bias in the image can be removed by subtracting a value, such as 128, from the matrix I. A new matrix I′ results and is provided below.

From matrix algebra, the application of the DCT to the image array I is equivalent to multiplying the DCT matrix T by the matrix I. The result may then be multiplied with the transpose of T. From the DCT definition, the elements of the T matrix can be calculated by the equation:

where i and j are row and column numbers from 0 to 7. For convenience, the T matrix is presented below.

Continuing now with JPEG, the DCT may be applied to the image matrix I′ by multiplying it with T on the left and the transpose of T on the right. Rounding the result, the following matrix I″ is obtained.

In order to consider the empirical data of human vision, each element of the I″ matrix is divided by the corresponding element of a quantization matrix and each result is rounded. For example, if quantization matrix Q50is used, the result I″ Q50is expressed below.

Of note, most of the elements in the result matrix round off to 0. In particular, only 19 of the 64 transformation coefficients are non-zero values. That is, JPEG has eliminated those components that were too small to overcome the human eye's lack of sensitivity to their spatial frequency.

If the quality level is dropped by using a quantization matrix, such as Q10, approximately only 7 nonzero coefficients remain. Likewise, if the quality level is increased by using a quantization matrix, such as Q90, approximately 45 coefficients remain. Therefore, for the most part, the JPEG algorithm utilizes relatively few of the 64 possible transformation coefficients of the DCT.

The number of terms that may bring a non-negligible contribution to the value of K(i,j) depends of the desired fidelity of the image. For example, only 10 to 30 of these 64 terms may bring a non-negligible contribution to the value of K(i,j), with 20 being the most common number. The JPEG algorithm obtains compression replacing the measurement and transmission of 64 pixel values (for each 8×8 tile) with the calculation and transmission of K(i,j) coefficient values. For example, if only 20 of these 64 terms bring a non-negligible contribution to the value of K(i,j), only these 20 coefficient values may be used to represent the image.

As discussed above, at the core of the JPEG algorithm is the division of the DCT coefficients of 8×8 tiles of the image of interest by the experimentally determined quantization values Q(i,j). To recover the actual image, the inverse Direct Cosine Transformation is applied to the K(i,j) coefficients.

The actual given value for a viewable pixel m,n would be given by:

p(m,n) is the pixel illumination for the image at the position m,n (within the 8×8 tile), Q(i,j) measures the eye sensitivity at the spatial frequencies i and j, and C(k) is given by:

Returning toFIG. 2, display100by use of filter106produces actual video by using a video signal composed of K(i,j) values. Filter106may be composed of divisions202(or filter106may be made up of separate individual filters202). Display unit102may be composed of multiple video divisions204, such as pixels. Divisions202of filter106(or individual filters) may be arranged to be matched up to video divisions204in display unit102. For example, divisions202(or individual filters) may be matched up with pixels in display unit102.

Video divisions204may be grouped into blocks. For example, video divisions204may be grouped into 8 video divisions by 8 video divisions block. Divisions202of filter106may also be grouped into blocks corresponding to the video division blocks. For example, division202may be grouped into a 8×8 division block204.

To properly display video using the transformation coefficients K(i,j), each division204of display unit102may be further divided into sub-divisions, such as sub-pixels.FIG. 3is a diagram illustrating exemplary sub-divisions of video divisions204in an 8×8 block208of video divisions. As illustrated inFIG. 3, each video division204may represent a pixel m,n in display102. Each video division204may be divided into sub-divisions302. Each sub-division302may represent physical divisions of display unit102. For example, if display unit102includes an LCD panel and light source, sub-divisions302may represent the physical LC cells or light source divisions of display unit102

The number of the sub-divisions302may be equal to the number of transformation coefficients or partial coefficients, for example JPEG coefficients K(i,j). For example, as illustrated inFIG. 3, a particular video division204may be sub-divided into 64 sub-divisions302. One skilled in the art will realize that the number of division is exemplary and that display unit102and filter106may be divided into any number of divisions and sub-divisions as required by the compression method.

Each division202of filter106(or individual filter), which corresponds to a video division204, may also be sub-divided.FIG. 4is a diagram illustrating an exemplary video division204and division202of filter106consistent with embodiments of the present teaching. As illustrated inFIG. 4, division202may be divided into sub-divisions304. Sub-divisions304may be aligned with individual video sub-divisions302, for example sub-pixels, of display unit102. For example, if display unit102includes an LCD panel and light source, sub-divisions304are aligned with the physical LC cells or light source divisions of display unit102.

Display100produces actual viewable video by outputting from display unit102light corresponding to transform coefficients K(i,j). Each sub-division302of display unit102is driven with the corresponding transform coefficient K(i,j). Then, filter106transforms the light emitted from display unit102into actual viewable video. To achieve this, sub-divisions302have a transmissivity related to the inverse transformation coefficient or partial coefficient. For example, if the JPEG compression algorithm is utilized, the transmissivity may be given as follows:

FIGS. 5A and 5Bare diagrams illustrating the transform coefficients supplied to display unit102and the transmissivity of the corresponding sub-divisions of filter106for a particular pixel m,n. As illustrated inFIG. 5A, sub-divisions302may be supplied with different transformation coefficients or partial coefficients. For example, the transform coefficients may be supplied to display unit102, for example, as follows:

As such, the corresponding sub-division304of filter106may have a transmissivity related to the inverse transform coefficients or partial coefficients in order to transform the light emitted by sub-divisions302into actual viewable video. For example, as illustrated inFIG. 5B, sub-division304corresponding to sub-division 0,0 may have a transmissivity proportional toC(0)C(O)Q(0,0).

Sub-division304corresponding to sub-division 1,0 may have a transmissivity proportional to

Sub-division304corresponding to sub-division 0,1 may have a transmissivity proportional to

Sub-division302corresponding to sub-division 0,2 may have a transmissivity proportional to

where m,n is the position of the division in the 8×8 block. Accordingly, the video output by display100after processing by filter106would appear as actual viewable video.

One skilled in the art will also realize that any transformation or compression/decompression algorithm may be utilized to determine the number of sub-division of video division204and the transmissivities of filter106. For example, the number of sub-division of video divisions204and the transmissivities of filter106may be related to transformation values in the MPEG algorithm.

FIGS. 2-4,5A, and5B illustrate 64 K(i,j) sub-divisions for each division (or individual filter). Display unit102and filter106may be divided into less sub-divisions such as 20. One skilled in the art will realize that display unit102and filter106may be divided into any number of sub-divisions depending on the desired number of transform coefficients or partial coefficients.

Since the video signal supplied to each corresponding sub-division in different divisions of a common 8×8 of display unit102represent the same transform coefficient or partial coefficient, all the sub-divisions having the same transform coefficient or partial coefficient may be connected in parallel in order to receive the same signal.FIG. 6is a schematic diagram illustrating a driving circuit600for supplying a video signal to sub-divisions302, for example sub-pixels, in different divisions, for example pixels m,n in a common 8×8 block. For example, driving circuit600may be utilized to supply K(0,1) to all sub-divisions 0,1 in pixels m,n in an 8×8 block. Sub-divisions302may be, for example, the individual LC cells if a LC panel is utilized. Driving circuit600may be included in display control104.

It should be readily apparent to those of ordinary skill in the art that driving circuit600illustrated inFIG. 6represents a generalized schematic illustration and that other components may be added or existing components may be removed or modified. Further, one skilled in the art will realize that display device100would have a driving circuit600for each different transform coefficient K(i,j).

As illustrated inFIG. 6, driving circuit600comprises an amplifier602and a transistor604coupled to amplifier602. Amplifier602amplifies the signal supplied, which corresponds to K(i,j), to sub-divisions302of display unit102. Transistor604controls when the video signal, which corresponds to K(i,j), is supplied to sub-divisions302of display102.

As illustrated inFIG. 6, transistor604is coupled in parallel to each sub-divisions i,j for different divisions m,n. For example, for sub-division 0,1, transistor604may be coupled to each sub-division 0,1 in all divisions204of an 8×8 block.

As illustrated inFIG. 6, sub-divisions304of filter106are placed in front of the corresponding sub-divisions302of display unit102. Accordingly, the video output by display100after inverse transforming by filter106would appear as actual viewable video.