Linear Predictive Coding (LPC)

In summary, Linear Predictive Coding (LPC) is a process used for reducing the bandwidth in speech coding, particularly in mobile communications systems. This is achieved by fitting a function to the sound of the speech in small time intervals and storing the difference between the measured sound and the function in a smaller number of bits. This results in a reduction of the required bandwidth for transmission. The specific details and techniques involved in this process may vary, such as using the Levinson-Durbin algorithm or other coding schemes.
  • #1
jeejou
11
0
Hello everyone,

Question : One version of Linear Predictive Coding (LPC) has been adopted as a standard for speech compression in mobile communications systems. How Linear Predictive Coding (LPC) can reduce the bandwidth in this speech coding ?

Can someone please help me with this question. All I can find in the net is "LPC is the process used for reducing the bandwidth in speech coding". I would like to know how the process is undertaken ? Can someone give me pointers/clue/lectures ?

Thank you in advance.
 
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  • #2
Wikipedia is (usually) your friend http://www.engineer.tamuk.edu/SPark/chap7.pdf
 
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  • #3
Hi there mgb_phys,

I went through the webpage earlier. Unfortunately it does not say how exactly the LPC reduce the bandwidth. I mean the version of the LPC is VSELP, right ? But, what are the processes involved ? Does the Levinson-Durbin algorithm can be matched to answer the question ? Or there is another technique ? I AM CONFUSED! Anyway, THANKS A LOT FOR THE HELP.
 
  • #4
I'm not an expert but generally fo rthese sort of things.

suppose you have a signal that is say 16bits, but it isn' random - your voice can't suddenly change 86dB in a 1/20,000 second. You can fit a function of what the sound is going to do in the next smll time interval and then store in say 8bits, the difference between the measured sound and the function. Then to play it back just add the 8bit offset to the function. You need a couple of other codes to say when the function has changed.
Since you only need 8bits instead of 16 you have halved the bandwidth.

The details of the coding scheme I don't know.
 

1. What is Linear Predictive Coding (LPC)?

Linear Predictive Coding (LPC) is a signal processing technique used for speech and audio processing. It is a mathematical tool that is used to model the vocal tract in order to analyze and synthesize speech signals. LPC is commonly used in speech recognition, speech compression, and speech synthesis.

2. How does Linear Predictive Coding work?

LPC works by analyzing a speech signal and estimating the coefficients of a mathematical filter that best describes the vocal tract. These coefficients are then used to predict future speech samples. The prediction errors are then quantized and transmitted or stored, making it possible to reconstruct the original speech signal.

3. What are the advantages of using Linear Predictive Coding?

Linear Predictive Coding offers several advantages in speech and audio processing. It allows for efficient compression of speech signals, making it possible to transmit or store speech signals with less data. It also enables the reconstruction of high-quality speech signals, which is useful for speech recognition and synthesis applications. Additionally, LPC is a robust technique that can handle noisy and varying input signals.

4. What are the limitations of Linear Predictive Coding?

While LPC is a powerful tool, it does have some limitations. One limitation is that it assumes a linear and time-invariant vocal tract, which may not always be the case. This can lead to inaccuracies in the predicted speech signal. Additionally, LPC is sensitive to quantization errors, which can affect the quality of the reconstructed speech signal.

5. How is Linear Predictive Coding used in speech recognition?

LPC is used in speech recognition by analyzing the coefficients of the mathematical filter to identify the features of a speech signal. These features are then compared to a database of known speech patterns to recognize and understand the spoken words. LPC is also used to remove noise from the speech signal, improving the accuracy of the speech recognition system.

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