Assignment 4

The assignment is due Friday, May 8, 5 pm EDT, to be submitted via CourseWorks.

Some of the questions below are research questions, where you are asked to find information about a particular issue. You may use the Engineering Library, any text books you have, one of the paper from the class readings, or the web to come up with answers. Be sure to cite your sources. Generally, a paragraph or two should be sufficient to answer the question. There is no need to write a tutorial.

Problems

1. For a sine wave representing a tone of 1500 Hz, show the content of a 10 ms audio packet in G.711 (mu-law), sampled at 8 kHz. Illustrate the phases of sampling and companding (G.711) by tabulating and graphing the samples.
2. Sample the following sine waves at 1 kHz: 0.4 kHz, 1.4 kHz, 2.4 kHz and show the results.
3. Huffman coding: Using Dr. Jekyll and Mr. Hyde, compute the letter frequencies, ignoring the difference between upper-case and lower-case letters, but preserving punctuation and spaces. (a) Construct a Huffman code for this set of letters and draw the encoding tree. (b) Using the same all-lower-case text, compress it using gzip or zip. Compare the compression ratios.
4. Convert the hexadecimal RGB value #efefef and #121212 to YUV (YCrCb).
5. Compute the DCT coefficients of the 8x8 matrix below:

   20 20 20 20 20 20 20 20
    0  0  0  0  0  0  0  0
   20 20 20 20 20 20 20 20
    0  0  0  0  0  0  0  0
   20 20 20 20 20 20 20 20
    0  0  0  0  0  0  0  0
   20 20 20 20 20 20 20 20
    0  0  0  0  0  0  0  0
   

   Quantize the resulting coefficients in the same manner as the JPEG example and compute the inverse. What can you observe?
6. Modify the audio program to include an RTP header with the right time stamp and sequence number. Compile and use rtpdump to display the result for a second or two. (You do not have to support RTCP.)