CHAPTER 4

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1. To record your voice on your multimedia PC, you can use the sound recorder available on the Windows operating system. You can also use a more sophisticated software utility such as GoldWave (http://www.goldwave.com). You will have the options to select the sampling rate (8kHz, 16kHz, etc.) and the quantization levels (8 bits, 16 bits, etc.). GoldWave provides utilities to filter background noise, vary the pitch, and so on.

2. When you use a software package such as Microsoft's NetMeeting over a LAN, the video will be transmitted at very low bit rates, so the video appears jerky.

3. If the video is transmitted at the rate of 30 frames per second, with each frame divided into 640 × 480 pixels, and coding is done at 3 bits per pixel, the data rate is

   30 × 640 × 480 × 3 bits per second = 3 × 64 × 48 × 3kbps =27,648kbps = 27.648Mbps

4. The Indian Standard Code for Information Interchange (ISCII) is a standard developed by Department of Electronics (Ministry of Information Technology), Government of India. ISCII code is used to represent Indian languages in computers. Center for Development of Advanced Computing (CDAC) supplies the hardware and software for Indian language processing based on ISCII. You can obtain the details from the Web site http://www.cdacindia.com.

5. MP3 software can be obtained from the following sites:

   • http://www.dailymp3.com

   • http://www.mp3machine.com

   • http://www.mp3.com

6. To store 100 hours of voice, the memory requirement is given below if the coding is done using (a) PCM at 64kbps, (b) ADPCM at 32kbps, and (c) LPC at 2.4kbps.

   1. To store 100 hours of voice using PCM at 64kbps data rate, Total duration of voice conversation = 100 hours = 100 × 3600 seconds Memory requirement = 100 × 3600 × 64 kbps = 100 × 3600 × 8 Kbytes = 360 × 8 Mbytes = 2880Mbytes

   2. 1440Mbytes

   3. 100 × 3600 × 2.4kbps = 100 × 3600 × 0.3Kbytes = 36 × 3 Mbytes = 108Mbytes

7. If the music signal is band-limited to 15kHz, the minimum sampling rate required is twice the bandwidth. Hence,
   Minimum sampling rate = 2 × 15kHz = 30kHz
   If 12 bits are used to represent each sample, the data rate = 30,000 × 12 bits/ second = 360,000 bits per second = 360kbps.

8. The image is of the size 640 × 480 pixels. Each pixel is coded using 4 bits. To store the image,
   Memory requirement = 640 × 480 × 4 bits = 153.6Kbytes.

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