Technologies for Packet-Based Voice Applications in C#.NET

Recognize PDF 417 in C#.NET Technologies for Packet-Based Voice Applications

2
Recognize PDF417 In C#.NET
Using Barcode reader for VS .NET Control to read, scan PDF-417 2d barcode image in .NET applications.
www.OnBarcode.com
PDF 417 Reader In C#
Using Barcode scanner for .NET framework Control to read, scan read, scan image in VS .NET applications.
www.OnBarcode.com
(fricatives and stop consonants) Fortunately, the predictor equation does not care if the sound source is periodic (buzz) or chaotic (hiss) This means that for each frame, the LPC encoder must decide if the sound source is buzz or hiss If it is buzz, estimate the frequency; in either case, estimate the intensity and encode the information so that the decoder can undo all these steps This methodology is how LPC-10 enhanced (LPC-10e), the algorithm described over a decade ago in Federal Standard 1015, works LPC-10e uses one number to represent the frequency of the buzz, and the number 0 is understood to represent hiss LPC-10e provides intelligible speech transmission at 2,400 bps27 The speed of 2,400 bps is not a toll-quality technology, but it does establish a lower target for reasonably intelligible speech over bandwidth-constrained networks Some enhancements are needed to improve quality One reason is that there are speech sounds that are made with a combination of buzz and hiss sources (for example, the initial consonants in this zoo and the middle consonant in azure ) Speech sounds like this will not be reproduced accurately by a simple LPC encoder Another problem is that, inevitably, any inaccuracy in the estimation of the formants means that more speech information is left in the residue The aspects of nasal sounds that do not match the LPC model (as discussed previously), for example, will end up in the residue Other aspects of the speech sound do not match the LPC model; side branches introduced by the tongue positions of some consonants and tracheal (lung) resonances are some examples26 Because of the issues discussed in the previous paragraph, the residue contains important information about how the speech should sound, and LPC synthesis without this information will result in poor-quality speech For the best results, you could just send the residue signal, and the LPC synthesis would sound fine Unfortunately, the motivation for using this technique is to compress the speech signal, and the residue signal takes just as many bits as the original speech signal, so this would not provide any compression Various attempts have been made to encode the residue signal in an efficient way, providing better-quality speech than LPC-10e without excessively increasing the bit rate The most successful methods use a code book The code book is a table of typical residue signals, which is set up by the system designers In operation, the analyzer compares the residue to all the entries in the code book, chooses the entry that is the closest match, and sends the code for that entry The synthesizer receives this code, retrieves the corresponding residue from the code book, and uses that to excite the formant filter This kind of scheme is called code-excited linear prediction (CELP) For CELP to work well, the code book must be big enough to include all the various kinds of residues If the code book is too big, it will be
Bar Code Scanner In C#.NET
Using Barcode decoder for Visual Studio .NET Control to read, scan bar code image in VS .NET applications.
www.OnBarcode.com
Bar Code Recognizer In C#
Using Barcode reader for .NET framework Control to read, scan read, scan image in .NET framework applications.
www.OnBarcode.com
Technologies for Packet-Based Voice Applications
PDF 417 Decoder In Visual C#
Using Barcode recognizer for VS .NET Control to read, scan PDF 417 image in Visual Studio .NET applications.
www.OnBarcode.com
PDF417 Reader In .NET Framework
Using Barcode decoder for ASP.NET Control to read, scan PDF-417 2d barcode image in ASP.NET applications.
www.OnBarcode.com
time consuming to search through, and it will require large codes to specify the desired residue The biggest problem is that such a system would require a different code for every frequency of the source (pitch of the voice), which would make the code book extremely large26,28 30 The problem just identified can be solved by using two small code books instead of one very large one One code book is fixed by the designers and contains just enough codes to represent one pitch period of residue The other code book is adaptive; it starts out empty and is filled in during operation, with copies of the previous residue delayed by various amounts Therefore, the adaptive code book acts like a variable shift register, and the amount of delay provides the pitch This is the CELP algorithm described in Federal Standard 1016 It provides reasonable-quality, natural-sounding speech at 4,800 bps Appendix A provides a mathematical treatment of the LPC vocoder CELP This section expands on the description of CELP coding provided in the previous section CELP is a well-known technique that synthesizes speech using encoded excitation information to excite an LPC filter This excitation information is found by searching though a table of candidate excitation vectors on a frame-by-frame basis LPC analysis is performed on input speech to determine the LPC filter parameters The analysis includes comparing the outputs of the LPC filter when it is excited by the various candidate vectors from the table or code book The best candidate is chosen based on how well its corresponding synthesized output matches the input speech frame After the best match has been found, information specifying the best code book entry and the filter are transmitted to the speech synthesizer The speech synthesizer has the same code book and accesses the appropriate entry in that code book, using it to excite the same LPC filter to reproduce the original input speech frame31 The code book is made up of vectors whose components are consecutive excitation samples Each vector contains the same number of excitation samples as there are speech samples in a frame In typical CELP coding techniques (see Figure 2-5), each set of excitation samples in the code book must be used to excite the LPC filter and the excitation results must be compared using an error criterion Normally, the error criterion used determines the sum of the squared differences between the original and synthesized speech samples resulting from the excitation information for each speech frame These calculations involve the convolution of each excitation frame stored in the code book with the perceptual weighting impulse response Calculations are performed by using vector and matrix operations of the excitation frame and the perceptual weighting impulse response31 A large number of computations must be performed The initial versions of CELP required approximately 500 million multiply-add operations per
PDF 417 Scanner In VS .NET
Using Barcode recognizer for .NET framework Control to read, scan PDF-417 2d barcode image in .NET applications.
www.OnBarcode.com
Decode PDF 417 In VB.NET
Using Barcode decoder for .NET Control to read, scan PDF-417 2d barcode image in VS .NET applications.
www.OnBarcode.com
UCC - 12 Recognizer In C#
Using Barcode recognizer for .NET framework Control to read, scan UCC - 12 image in VS .NET applications.
www.OnBarcode.com
Barcode Reader In C#.NET
Using Barcode reader for .NET framework Control to read, scan bar code image in .NET applications.
www.OnBarcode.com
PDF-417 2d Barcode Recognizer In Visual C#.NET
Using Barcode reader for .NET Control to read, scan PDF417 image in Visual Studio .NET applications.
www.OnBarcode.com
Matrix Barcode Recognizer In Visual C#.NET
Using Barcode decoder for .NET Control to read, scan Matrix 2D Barcode image in .NET framework applications.
www.OnBarcode.com
Decoding Intelligent Mail In Visual C#.NET
Using Barcode reader for .NET framework Control to read, scan Intelligent Mail image in VS .NET applications.
www.OnBarcode.com
Read EAN-13 Supplement 5 In None
Using Barcode scanner for Software Control to read, scan read, scan image in Software applications.
www.OnBarcode.com
UPC - 13 Reader In None
Using Barcode decoder for Office Excel Control to read, scan GS1 - 13 image in Microsoft Excel applications.
www.OnBarcode.com
Recognizing GTIN - 13 In Objective-C
Using Barcode recognizer for iPad Control to read, scan UPC - 13 image in iPad applications.
www.OnBarcode.com
Bar Code Scanner In VB.NET
Using Barcode scanner for .NET Control to read, scan barcode image in .NET applications.
www.OnBarcode.com
DataMatrix Recognizer In .NET Framework
Using Barcode recognizer for ASP.NET Control to read, scan Data Matrix ECC200 image in ASP.NET applications.
www.OnBarcode.com
PDF-417 2d Barcode Decoder In VB.NET
Using Barcode recognizer for Visual Studio .NET Control to read, scan read, scan image in .NET applications.
www.OnBarcode.com
ANSI/AIM Code 39 Reader In .NET
Using Barcode scanner for Visual Studio .NET Control to read, scan Code39 image in .NET applications.
www.OnBarcode.com
Copyright © OnBarcode.com . All rights reserved.