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
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.
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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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