A graphics processing unit (GPU) is a dedicated graphics rendering device that may be used with, for example, personal computers, workstations, or game consoles. GPUs are very efficient at manipulating and displaying computer graphics. GPUs contain multiple processing units that that concurrently perform independent operations (e.g., color space conversion at pixel level). Their highly parallel structure may make them more effective than a typical central processing unit (CPU) for a range of complex algorithms. A GPU may implement a number of graphics primitive operations in a way that makes running them much faster than drawing directly to the screen with the host CPU.
General purpose programming on a GPU is becoming an effective and popular way to accelerate computations, and serves as an important computational unit in conjunction with a CPU. In practice, a large number of existing general purpose processing kernels (e.g., texture processing, matrix and vector computation) may be optimized for running on a GPU. However, the GPU has some hardware constraints and structural limitations. For example, the GPU has no global variable concept and can't use several global variables to save temporal data on the fly. Accordingly, the GPU may not efficiently handle some commonly used reduction operations (e.g., average and sum computations over a bunch of data elements).
The features and advantages of the various embodiments will become apparent from the following detailed description in which:
Feature extraction may be performed on by downscaling a frame (e.g., 720×576 pixels) into smaller blocks in a hierarchical fashion and extracting the features for the blocks. The frame is eventually reduced to 1 pixel and the pixel is an average value for the frame.
A blocked method entails downsizing the frame in large blocks using large filters. For example, a 720×576 pixel frame may be downsized to a 20×18 pixel image using a 36×32 filter shader and then the 20×18 pixel image may be downscaled into a single pixel using a 20×18 filter shader. This method requires only a few steps (e.g., two downsizing events) but the steps may require significant memory access time. Utilizing such a method on a GPU that has a plurality of independent processing units (pipelines), may result in one pipeline hogging access to memory resulting in other pipelines stalling.
A filter loop method entails utilizing one filter shader several times to continually downsize the frame a certain amount and then once the image has been reduced to a certain size utilizing a second filter shader to reduce to 1 pixel. This method uses multiple pixel buffers for each frame to hold the various downsized versions. For example, a 2×2 filter may be used to ¼ the image 5 times thus reducing the image to 22×18 pixels. The 22×18 pixel image may then be downsized to 1 pixel using a 22×18 filter shader. This example may require 5 pixel buffers to store the various downsized images (each ¼ sized image).
The filter loop method requires six downsizing operations for each frame and requires five additional pixel buffers to capture the downsized images. The critical path in the filter loop method is the downsizing utilizing the 22×18 filter shader.
A pipeline texture approach overlaps down scaling operations for various frames to increase parallelism. Multiple filtering steps are merged into a single filtering step so that multiple (e.g., 8) continuous frames with different size will be down scaled together. Initially a texture buffer that is larger (e.g., 2 times) than a fame is initialized. The texture buffer may include two sides, one side for storing a new frame and a second side for storing downscaled frames. A frame is read into the texture buffer. The texture buffer is then downsized and the downsized image is shifted. This process continues so that filtering operations are downscaling multiple frames at once. Once the operation is in steady state (the texture buffer is full) performing a single down scale is enough to obtain the final result.
The process of downsizing is continually repeated. Each downsized operation downsizes a new frame and the downsized images in the right side of the texture buffer together. It takes seven ¼ downsizing operations to reduce a frame to a single pixel. The right side of the texture buffer can hold seven downscaled images. When full, the texture buffer holds a total of eight frames in varying downscaled versions and downscales each of these images together. The value after the 7th downsizing operation is one pixel and represents the expected average value for the frame.
When a downsize operation is performed it reduces 7 images (various stages of seven different frames) together and redraws the images on the right side and then draw a new frame on the left side. Accordingly, when the pipeline texture method is in steady state each reduction operation will produce a result for one frame.
Utilizing the pipeline texture method on a GPU enables processing multiple computations for multiple frames at the same time. Such processing could not be performed on a CPU without sophisticated programming and SIMD optimization.
The texture buffer embodiments described above discussed the buffer being twice as long as a frame in length (e.g., 720×576 to 1440×576) but is not limited thereto. Rather the buffer could be extended by height (e.g., 720×1152) without departing from the scope. Moreover, the embodiments showed a new frame being drawn to the left and downsized frames being drawn to the right but is not limited thereto. Rather, the new frame could be drawn to the right with downsized frames drawn to the left, the new frame could be drawn to the top and downsized frames drawn below, or new frames could be drawn to the bottom and downsized frames drawn above without departing from the scope. It is simply the fact that one downsizing operation is being performed on everything in the buffer and then the downsized images are redrawn to next location in buffer.
Although the disclosure has been illustrated by reference to specific embodiments, it will be apparent that the disclosure is not limited thereto as various changes and modifications may be made thereto without departing from the scope. Reference to “one embodiment” or “an embodiment” means that a particular feature, structure or characteristic described therein is included in at least one embodiment. Thus, the appearances of the phrase “in one embodiment” or “in an embodiment” appearing in various places throughout the specification are not necessarily all referring to the same embodiment.
An embodiment may be implemented by hardware, software, firmware, microcode, or any combination thereof. When implemented in software, firmware, or microcode, the elements of an embodiment are the program code or code segments to perform the necessary tasks. The code may be the actual code that carries out the operations, or code that emulates or simulates the operations. A code segment may represent a procedure, a function, a subprogram, a program, a routine, a subroutine, a module, a software package, a class, or any combination of instructions, data structures, or program statements. A code segment may be coupled to another code segment or a hardware circuit by passing and/or receiving information, data, arguments, parameters, or memory contents. Information, arguments, parameters, data, etc. may be passed, forwarded, or transmitted via any suitable means including memory sharing, message passing, token passing, network transmission, etc. The program or code segments may be stored in a processor readable medium or transmitted by a computer data signal embodied in a carrier wave, or a signal modulated by a carrier, over a transmission medium. The “processor readable or accessible medium” or “machine readable or accessible medium” may include any medium that can store, transmit, or transfer information. Examples of the processor/machine readable/accessible medium include an electronic circuit, a semiconductor memory device, a read only memory (ROM), a flash memory, an erasable ROM (EROM), a floppy diskette, a compact disk (CD-ROM), an optical disk, a hard disk, a fiber optic medium, a radio frequency (RF) link, etc. The computer data signal may include any signal that can propagate over a transmission medium such as electronic network channels, optical fibers, air, electromagnetic, RF links, etc. The code segments may be downloaded via computer networks such as the Internet, Intranet, etc. The machine accessible medium may be embodied in an article of manufacture. The machine accessible medium may include data that, when accessed by a machine, cause the machine to perform the operations described in the following. The term “data” here refers to any type of information that is encoded for machine-readable purposes. Therefore, it may include program, code, data, file, etc.
All or part of an embodiment may be implemented by software. The software may have several modules coupled to one another. A software module is coupled to another module to receive variables, parameters, arguments, pointers, etc. and/or to generate or pass results, updated variables, pointers, etc. A software module may also be a software driver or interface to interact with the operating system running on the platform. A software module may also be a hardware driver to configure, set up, initialize, send and receive data to and from a hardware device.
An embodiment may be described as a process which is usually depicted as a flowchart, a flow diagram, a structure diagram, or a block diagram. Although a flowchart may describe the operations as a sequential process, many of the operations can be performed in parallel or concurrently. In addition, the order of the operations may be re-arranged. A process, is terminated when its operations are completed. A process may correspond to a method, a function, a procedure, a subroutine, a subprogram, etc. When a process corresponds to a function, its termination corresponds to a return of the function to the calling function or the main function.
The various embodiments are intended to be protected broadly within the spirit and scope of the appended claims.