Sub-Band Coding Implementation - Essay Example

?? Sub-band coding (SBC), a method used to en signals, is a more efficient form of transform coding strategy compared to other systems. The purpose of this paper is to describe a sub-band coding system intended for digitally encoded speech or audio signals. Details of the principles of two-band sub-band coding implementation were discussed. Then, an appraisal on why each step is used and how the sub-band coding is implemented in the laboratory were tackled. Finally, a solution to the SBC implementation was suggested. Index terms-- template, markup, discount I. INTRODUCTION The degree to which the bit rate can be reduced or compressed without impairing the quality of the decoded signal strongly determines the efficiency of an encoding technique. Typically, speech and audio signals have a high degree of redundancy which may be exploited to reduce the bit rate. In addition, the human auditory system possesses certain properties which may be useful in reducing the bit rate without compromising the quality of the decoded signal. 1 To take advantage of the aforementioned properties, a variety of techniques have been developed to efficiently represent speech and audio signals in digital form for either transmission or storage purposes. Since two different sub bands in each signal exist, the lower-frequency band and high-frequency band, and most of the energy in the signal is contained in the lower frequencies, it is possible to encode the lower-frequency band with more bits than the high-frequency band. Sub-band coding is a powerful approach where a speech or audio signal is broken down into several frequency bands and each band is digitally encoded separately. 2 II. Sub-Band coding implementation Figure 1 shows the basic configuration of the two- band sub-band design. The input signal represented as xi (n) is divided into two equally spaced frequency bands by low pass filter and high pass filter, represented as H1 and H2 respectively. After deviation, the sampling rate of each sub-band signal is reduced by a factor of 2. For instance, if the sampling rate for the input signal is Fs, then the sampling rate for each of the sub band after the deviation will be Fs/2. Reducing the signal by a factor of 2 follows every after frequency subdivision. By allocating a different number of bits per sample to the signal in the sub-bands, a reduction in the bit rate of the digitalized speech signal can be achieved. Meanwhile, the receiver converts the sub-band signals back to their original sampling rate by using the similar low pass and high pass filters as the input. The sum of two sub-band signals represented as xo (n) is the reconstructed signal of the input signal (Figure 1). Figure 1 After the input signal has been decomposed into two sub-band signals, each signal is then passed through the Quantizers. The resulting signals are represented as QL and QH in the figure above. Filter design is particularly important in achieving good performance in sub-band coding.2 III. implementing the system using sub-band coding A. Creating a New Paper For writing a paper from scratch using the IEEETRAN.DOT template, or creating an empty document in the template for cutting and pasting text from an existing file in some non-Word format, the following steps should be followed: 1. Copy IEEETRAN.DOT into the template’s directory, e.g., C:\MSoffice\Templates, so that it will be available from within Word. 2. Open Microsoft Word. 3. In the File menu, select New option. In the New dialog, select IEEETRAN.DOT. 4. IEEETRAN.DOT's startup macro will pop up a dialog box requesting to type in text for several of the paper’s elements. Some information may be typed in the box if all the information being asked is not yet available. In fact, the default text can be left in place for the meantime. These elements can always be edited later. Note that the macro will not be repeated when the user re-opens the document. The cursor should now be positioned near the top of the paper, indicating that the program is now ready to begin writing. 1 B. Converting an Existing Word Paper First, papers originally created in Word version 5 or earlier will have to be converted to Word 6 or 7 format in order to attach IEEETRAN.DOT. Note however that the converted paper still lack styles specific to IEEETRAN.DOT. Moreover, Word styles may not have been used at all to mark up the paper when it was created. In any case, some re-styling with IEEETRAN.DOT will have to be done in order to submit the Word file in compliance with these guidelines. To prepare the paper for re-styling, the following steps must be observed: 1. Copy IEEETRAN.DOT into the template’s directory, e.g., C:\MSoffice\Templates, so that it will be available from within Word. 2. Run Word and open the existing Word 6 or 7 document. 3. Under the File menu, select Templates…, the top of the resulting dialog box will show NORMAL.DOT, or perhaps another template, as the current attachment. 4. Click on the Attach… button. This will show the contents of the template directory. Double click on IEEETRAN.DOT. 5. Still in the Templates… dialog, click the checkbox marked “Automatically update styles,” then click OK. 6. Finally, run the Fix Page Layout macro from the IEEE Macros menu. After the above steps have been followed, the paper needs to be redefined using the style menu or the Re-style or Edit macro under IEEE Macros. However, styles in the existing paper that share exactly the same names under IEEETRAN.DOT, such as Heading 1, do not need to be re-styled anymore. IV. MATH Aside from IEEETRAN.DOT, the Microsoft Equation Editor or the MathType add-on must be used for all math objects in the paper. By definition, a math object is any equation or fragment containing mathematical symbols which include Greek characters, and super- and subscripts, that appear either in-line (in the flow of normal text) or as a display equation (in its own space between lines of text). Specifically, using Word fonts or character calls for in-line “quickies” such as single variables with super- or subscripts must be avoided. Preparing math-related elements with the equation editor or MathType allows the automatic conversion of most of the math objects in the paper to the in-house math format, TeX, while formatting math objects for the hard copy of the paper that will be submitted along with theWord file and ascii dump. The MathType add-on for Word is a commercial product that may or may not have been purchased already for the user’s own use. If MathType is available, it is encouraged to use it in all math objects as possible. If not, the Microsoft Equation Editor may be used, which is included in the Word program. V. MARKUP Markup is defined as the specific parts of a paper such as the title, headings, and lists among others. Each element is provided with an appropriate name. In addition, certain formatting instructions are associated with the assigned name such that the title text, for instance, always looks a certain way. In Word, the mechanism for associating an element name with its formatting conventions is called a style. Style names are located in the pull down style menu along the left hand side of the Word window. Basically, to change the style of a text, the area of a text or the entire sentence is highlighted. Then, the name of the style is selected on the style menu to apply the desired changes. The process described above does two things. First, highlighting the text associates the style name with the highlighted text. This connection is hidden within the Word file. Second, it applies the formatting rules associated with the style to the highlighted text. IEEETRAN.DOT offers an alternative method for applying certain styles (the Re-style or Edit macro), but it must be noted that highlighting followed by selecting a style from the styles menu can always be used to re-style. However, Re-style or Edit macro does not have all style names, only those that are most commonly used in IEEE journal papers. These style names are mostly unique to IEEETRAN.DOT. The advantage of using macro is that it allows the user to add or edit styles without first highlighting any text. If the style already exists, macro will find the first instance it has been used and automatically move the cursor over those words or texts. If the desired style has not been used before, macro will activate the style at the current cursor position, ready for the user’s input. In this case, it must be noted that the style will remain active until it will be turned off by selecting a different style or by moving the cursor to another text in the document. VI. IEEE PAPER STYLES A. Style Reference Below is an alphabetical reference for styles used in IEEE papers. Some styles such as Heading 1 are borrowed from Word's NORMAL.DOT; others are unique to IEEETRAN.DOT. It must be noted however, that paragraphs do not require special styling and should be left with the “Normal” style. Abstract -- Includes all text for the abstract. Formatting is 9-point bold italic. Authors -- Comprises the entire comma-delimited list of authors, starting from the principal author. This appears in frame centered on the page, and should appear after the Title. Depending on the length of the Titlle, this frame may have to be repositioned manually. Nested within this style may be one or more MemberType style areas. AuthorInfo -- AuthorInfo can be created with the Add Author Info macro, which contains details about the authors’ affiliation. This style should be unique within the paper. It produces a special footnote on the first page. This footnote possesses a non-printing symbol as its reference marker so as not to interfere with the numbering of regular footnotes later in the paper. Heading 1 -- Top-level heading. This is auto-numbered so the user shouldn't add Roman numerals of anymore. This appears centered on the column in smallcaps. Heading 2 -- Level-two heading. Also auto-numbered so the user no longer needs to add capital letters. Heading 3 -- Level-three heading. Auto-numbered so there is no need to add Arabic numerals manually. Note that only heading levels 1 through 3 are supported in IEEE style. IndexTerms -- Optional list of index terms or keywords. However, if no index terms are supplied, this style should be removed entirely. Lemma -- Heading (only) for a lemma. List Number-- Regular, numbered, and bulleted lists. This is used within Word normally. Each entire list receives the list style, and carriage returns within the list area define list items. MemberType – This is activated when there are many authors comprising the Author’s section. Each MemberType instance is preceded (and followed, if necessary) by a comma as part of the comma-delimited list of authors. References – This section lists the references cited in the paper, also called bibliography outside the IEEE. This refers to a special kind of numbered list. Note that there should be only one References style section in the paper. This is auto-numbered so that the user no longer needs to add numbering anymore. The entire section receives References style, and paragraphs within the area define individual references. Theorem -- Heading (only) for a theorem. This is derived from Heading 3. Title -- Full paper title which appears in 24-point Times New Roman type within a frame centered on the page. This should be the first item in the paper. Depending on the length of the Title contents, the Authors frame may have to be repositioned manually. B. Order of Appearance A list of IEEE-unique styles is provided below in order of appearance: Title Authors (including MemberType areas) AuthorInfo (special footnote) Abstract IndexTerms Heading 1 Heading 2 Heading 3 Acknowledgment References 1. R.E. Crochiere, “Sub-band coding'', Bell Syst. Tech. Journ., Vol. 60, No. 7, pp. 1633-1653, Sept. 1981. 2. John G. Proakis and Dimitris G. Manolakis, Digital Signal Processing Principles, Algorithms, and Applications. New Jersey: Prentice-Hall Inc., 1996, pp. 831,832 VII. IEEE MACROS A reference list of the four macros listed under the IEEE Macros menu that activates when a new document is created using IEEETRAN.DOT or IEEETRAN.DOT is attached to an existing Word document is provided below. Fix Page Layout -- Performs a number of formatting and page layout functions. This is usually run after attaching IEEETRAN.DOT to an existing Word paper, but it can be used at any time. Re-style or Edit – This allows the user to proceed to the next instance of the selected style, if it finds one. Otherwise, this restyles the text surrounding the current cursor position. If current cursor position is within an IEEE-unique style, this will prompt the user before re-styling. Add Author Info -- Creates the affiliation section of the authors as a special footnote on the first page. This macro is used to re-create a deleted author info area or add one for the first time. It must be noted that there should be only one instance of this style. Check Styles –This tells the user how many instances the styles that are supposed to be unique have appeared. For instance, something is wrong if a paper has three titles. But note that multiple style sections may sometimes be counted if the user has carriage returns within a single style area. Hence, carriage returns within these areas should be deleted. VIII. SUBMITTING YOUR PAPER As outlined in the general Transactions/Journals paper author’s guide, complete submission of the paper should include a hard copy and an ascii dump, including any graphics files and captions for figures. In addition, a copy of your Word binary file must be sent at the same time (via whatever medium). It is however, important to remember to keep the original copy of the documents, in case the paper needs to be retransmitted. Read More