ISRO2015-67

Question

What is compression ratio in a typical mp3 audio files?

• A. 4:1
• B. 6:1
• C. 8:1
• D. 10:1

Answer 1

Audio is recorded in frequency = 44.1 KHz

While converting to Mp3 16 bits are used to represent one sound signal.

For sake of stereo 2 channels are used.

Hence

2 channels of 16bit audio at 44.1KHz = 2 x 16 x 44,100 = 1,411,200 bits/sec, or 172kbyte/sec

Compression is made at128kbit, or 16kbyte/sec

So, 172 / 16 = 10.75:1 compression

 

Ans is D

Answer 2

Answer (d)

 

Uncompressed audio as stored on an audio-CD has a bit rate of 1,411.2 kbit/s, so the bitrates 128, 160 and 192 kbit/s represent compression ratios of approximately 11:1, 9:1 and 7:1 respectively.

Comments

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