CS代考 The high-frequency limit of human hearing extends to approximately 20 KHz,

The high-frequency limit of human hearing extends to approximately 20 KHz, but studies have shown that intelligible speech requires frequencies only up to 4 K Hz.
 Justify why the sampling rate for an audio Compact Disc (CD) is 44.1 kHz. What is the Nyquist rate for reliable speech communications?
 Why do you think people sound different on the phone from in person?
 Suppose intelligible speech requires 7 bits per sample. If the phone system is

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designed to just meet the requirements for speech (which is the case), what is the
maximum bit rate allowable over telephone lines?
 CDs use 16 bits per sample. What is the bit rate of music coming off a CD? Is a
modem connection fast enough to support streamed CD quality audio?
Consider a discrete time source emitting equiprobable symbols A, B, C.
 What is the entropy of the source (assume log23 = 1.585)
 Encoding the source output symbol by symbol, find the average bit length per
symbol. Give the example of a code achieving this.
 Encoding the source output in blocks of two symbols, how many bits/symbol are
required on an average. Give an example code achieving this.
Both subband coding and Subsampling seem to reduce sample sizes and attain compression.
 What is the main difference between them?
 What would motivate an encoding design to use subband as against subsampling?
 Explain how subband coding is used in MPEG1 audio
 Name the three modes of transmission in JPEG and classify them as closely as
you can as being “subband coding” or “subsampling”.
 What is the color gamut of a CRT screen?
 Why do most standards use the YCrCb color space instead of the RGB color
 Choose the color mode for each of the following types of projects:
(Your choices are 1-bit, 8-bit grayscale, RGB, and CMYK.)
a. You want to post a copy of your own artwork on your Web page.
b. You need to put a copy of your signature on your computer typed report c. You need to print the digital photograph of a pencil sketch of the map.

Suppose a camera has 450 lines per frame, 520 pixels per line, and 25 Hz frame rate. The color-subsampling scheme is 4:2:0, and the pixel aspect ratio is 16:9. The camera uses interlaced scanning, and each sample of Y, Cr, Cb is quantized with 8 bits.
 What is the bit-rate produced by the camera?
 Suppose we want to store the video signal on a hard disk, and, in order to save
space, re-quantize each chrominance (Cr, Cb) signals with only 6 bits per sample.
What is the minimum size of the hard disk required to store 10 minutes of video? Repeat the exercise (both questions) assuming color subsampling scheme 4:2:2.
 We have studied about constant bit rates (CBR) and variable bit rates (VBR) in class.
 Differentiate between CBR and VBR.
 Which one is normally preferable and why? Give your answer with regards to
throughput and quality.
 Classify the following as producing VBR or CBR?
 Huffman coding
 Lossless Mode of JPEG Compression
 MPEG1 Video
 A VBR video stream generates 420×320 pixels per frame at 20 frames per second, 8 bits per pixel. Consider a buffering strategy at the receiver with a 10 frame buffer to hold the frames so that they can be displayed at CBR. What is the minimum throughput (in Mbps) required from the network to display a video stream of 4 seconds.
In Video Encoding more compression is achieved by using block-based motion estimation and compensation. Let’s called this temporal compression.
 Define I, P and B frames used in MPEG.
 Qualitatively explain how much of compression is achieved for each type of

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