Camera noise, compression distortions and blur Deinterlacing and scaling for upconversion requires taking into account the degradations of the input (such as camera noise, compression artifacts and blurs) in order not to enhance them. The worst degradations often come from MPEG 2 and MPEG 4 compression. Upconverting such videos while removing the distortions, without adding worse artifacts, are difficult problems.

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<p>The fundamental building-blocks forming a wireless network As illustrated in <i>Fig 1</i> , a typical wireless network comprises a number of elements. At the front end” of the network is the network administration software (the <i>Administrator</i> ) running on a host computer. This software is first used to configure the other elements forming the network (telling them who they are” and what they do”). Following configuration, the administrator is used to monitor the values being presented to the network from external sensor devices and to control actuators (relays, switches, etc.) that can affect the outside environment.</p>

Camera noise, compression distortions and blur Deinterlacing and scaling for upconversion requires taking into account the degradations of the input (such as camera noise, compression artifacts and blurs) in order not to enhance them. The worst degradations often come from MPEG 2 and MPEG 4 compression. Upconverting such videos while removing the distortions, without adding worse artifacts, are difficult problems.

The book goes on to say that: in some applications, an RTOS comprises only a kernel, which is the core supervisory software that provides minimal logic, scheduling, and resource management algorithms. . . On the other hand, an RTOS can be a combination of various modules, including the kernel, a file system, networking protocol stacks, and other components required for a particular application. . .”

This definition illustrates one of the problems in defining an RTOS. Some people refer to the kernel, the basic task scheduler, as the RTOS while others refer to the kernel plus hardware drivers plus services as the RTOS. Those who followed the Microsoft anti-trust legal proceedings will remember that this same question came up there. When Microsoft added a file editor and a calculator and – specifically – a Web browser, did these constitute applications on top of the operating system, as the government insisted, or did they constitute additional functionality for the OS as Microsoft insisted? The answer is not simple and many reasonable people continue to disagree. For our purposes, we will refer to the RTOS as simply the task manager or kernel. The drivers and applications, though very important, will be considered to be separate.


Do You Need An RTOS? If your SoC will be running more than one task then it needs an RTOS. If your SoC will run only one task, then most likely you would not need an SoC but could simply create a hardware state machine in Verilog or VHDL to implement the single task.

While it is theoretically possible to create the RTOS in hardware, the effort is difficult, there are few if any tools to support it, and it is very difficult to make changes during development and particularly to systems in the field. These are all the reasons why software is useful and why systems are migrating to processor-based SoCs.

One argument that you must be careful to avoid is the one that says the processor in your SoC is doing only one thing so there is no need for an RTOS. This argument is often heard when describing multiprocessor SoCs – those with multiple small processors, each handling a single piece of hardware or a single small task. The CEO of a company that produces configurable processors – someone who should have known better – made this argument at a recent talk. If your SoC contains multiple processors, each handling one task, the processors by definition are actually handling more than one task. Each processor is handling the task to which it is assigned plus the task of communicating with the other processors. All SoCs need some kind of RTOS. The question is which RTOS and whether to build, buy, or use a third, more recent, option – synthesize.


Purchasing an RTOS Many commercial companies offer RTOSes that have been designed and debugged for you. These are often called off-the-shelf” RTOSes. There are generally two kinds of off-the-shelf RTOS – ones where you purchase object code that has been compiled for the processor you will be using, and ones where you receive the source code and compile the code to your processor. These are described in further detail below.

Object Code: A traditional off-the-shelf RTOS consists of code that has been written, compiled, debugged, and tested by a company that then sells the object code. The main reason for selling object code is that this protects the intellectual property of the company because the object code is extremely difficult to reverse engineer. It also means that the customer relies on the vendor to do a good job and to support the code when there are problems.


The traditional method of charging for these kinds of RTOSes is with an upfront fee and a royalty. In other words, the vendor receives a certain amount of money to hand over the code to the customer and support it during system development; the vendor subsequently receives a little money for each system that the customer ships containing the RTOS. With the availability of embedded Linux, which is open source, the object code model is becoming less popular.

Open Source: Especially since the introduction of Linux, and later the introduction of real-time versions of Linux intended for embedded systems, users are often no longer willing to pay royalties and want their software for free. Of course there is no such thing as a free lunch. Companies do not stay in business by giving away free goods. Open source RTOSes may be free to download, but there is usually a steep learning curve.

The deflate standard is in contrast to lossy compression techniques that are often used in audio and video decoders where human perception of potential data loss is leveraged to improve the compression efficiency. Popular compression algorithms such as MPEG, JPEG, and MP3 are examples of lossy compression.

How deflate” works Compression using deflate is performed on a block-by-block basis. Uncompressed blocks can be an arbitrary length up to 64K bytes long. The algorithm uses a sliding 32K byte window to examine the data stream for repeating patterns. The sliding window is often referred to as the history window, or history table, and may cross block boundaries. When a character string matches a pattern previously detected in the 32KB window, the string is replaced with a pointer representing the backward distance of the matching string in the history table, and the length of the matching string. The matched strings are limited to a maximum of 258 bytes in length and substitution only occurs for strings of length greater than three bytes. When a matching string is not found, the original byte, called a literal, is left in the compressed data stream. The resulting output of this compression step is a series of literals and length/distance pairs (See Figure 1).

Huffman trees are a very bit-efficient mechanism for encoding this information. Huffman encoding is used to encode the literals as well as the lengths and distances and uses the rate of occurrence of a particular symbol to define a unique variable-length bit code. Two Huffman tables are used in the deflate algorithm: one to encode the lengths and literals and the other to encode the distance values. The two Huffman tables themselves are encoded (compressed) using Huffman encoding and the resulting Huffman tables are pre-pended to the compressed data stream to form the compressed block output of a deflate- compliant compressor. The Huffman tables generated for any one compressed block are independent of the previous block's Huffman tables.

Where deflate” is usedWhile the deflate algorithm's compression efficiency is variable based on the uncompressed data stream, common benchmarks using text-based files show compression ratios in the 2.5:1 to 3.5:1 range. Compression of this magnitude has clear operational advantages in both storage and data networking.

Understanding clocks: In the timing analyzer, sampling is under direction of a single internal clock. That makes things very simple. However, in the world of microprocessors, a system may have several clocks.”

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