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Consider an uncompressed stereo audio signal of CD quality which is sampled at 44.1 kHz and quantized using 16 bits. What is required storage space if a compression ratio of 0.5 is achieved for 10 seconds of this audio?

  1. 172 KB
  2. 430 KB
  3. 860 KB
  4. 1720 KB
in Multimedia by Veteran (106k points) | 2.9k views

1 Answer

+10 votes
Best answer

My Answer: 861.33 KB

Explanation:
Use small k = 1000 and capital K = 1024.
Given sample frequency = 44.1 kHz = 44.1 * 1000 = 44100 bits per second
This is stereo audio signal, it will need 2 channels.
While converting to MP3 it will need 16 bits to represent 1 sound signal.
So, 
Bit Rate = 2 * 16 * 44100 = 1411200 bps

Given compression ratio = 0.5
Compressed Bit Rate will be = 705600 bps

For 10 seconds, data will be = 7056000 bits = 882000 Bytes = (861.33 * 1024) Bytes = 861.33 KB

 Reference: http://www.theaudioarchive.com/TAA_Resources_File_Size.htm

by Active (2.4k points)
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0
882 ?

Not in options.
0
I edited my answer after your comment. Actually I do not know why 860 KB answer is given in ISRO answer key. And my answer 882 KB that seems correct is not in options.
0
using k = 1000, and K = 1024.
0
Arjun Sir, its a great clarification about k and K. Thanks. By using this hint still I am getting 861.33 KB.
0
yes, thats a small change considering what all are asked in ISRO :)
0
It is 44100 'samples' per sec right?
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