This set of Embedded Systems Multiple Choice Questions & Answers (MCQs) focuses on “Codecs”.
1. From which of the following words does codecs is derived?
a) coder
b) decoder
c) coder-decoder
d) coder-encoder
View Answer
Explanation: The codec is derived coder-decoder and is coupled to perform the coding. It can support both analogue to digital conversion and digital to analogue conversion.
2. Which codec is used in digital audio?
a) A-law
b) µ-law
c) linear
d) PCM
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Explanation: In the linear codec, the relationship between the analogue and digital values are linear. This method is commonly used in digital audio communication.
3. Which of the following have the same quantisation step throughout the range?
a) linear
b) PCM
c) DPCM
d) ADPCM
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Explanation: The quantisation step is same throughout the dynamic range in the linear codec and thus any increase in the analogue value increases the digital value, that is, the overall performance is linear.
4. Which is used in the telecommunication applications which has a limited bandwidth of 300 to 3100 HZ?
a) linear codec
b) logarithmic codec
c) PCM
d) DPCM
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Explanation: The logarithmic codec is frequently used in the telecommunication system which have a limited bandwidth of 300 to 3100 Hz. this can provide an 8-bit sample at 8 KHz, which are used in the telephones. The commonly used are A-law and µ-law.
5. Which codec is used in the UK?
a) a-law
b) µ-law
c) linear codec
d) PCM
View Answer
Explanation: The a-law is a logarithmic codec which is commonly used in the UK whereas µ-law is used in the US.
6. What does PCM stand for?
a) pulse codec machine
b) pulse code modulation
c) peripheral code machine
d) peculiar code modulation
View Answer
Explanation: The linear codec is also known as pulse code modulation which is commonly used in the telecommunications industry.
7. Which of the following conversion is performed by using a lookup table?
a) DPCM
b) ADPCM
c) Between DPCM and ADPCM
d) Linear cdec and a-law
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Explanation: The conversion between a-law/µ-law and a linear digital signal or between µ-law and a-law is performed by a lookup table.
8. What does DPCM stand for?
a) differential pulse code modulation
b) data pulse code modulation
c) dynamic pulse code machine
d) dynamic pulse code modulation
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Explanation: The differential pulse code modulation is similar to pulse code modulation, but DPCM uses an encoded value which is the difference between the current and the previous sample.
9. Which of the following have a 16-bit digital dynamic range?
a) PCM
b) DPCM
c) linear codec
d) logarithmic codec
View Answer
Explanation: The differential pulse code modulation can improve the accuracy and resolution by having a 16-bit dynamic range. It works by the increasing dynamic range.
10. How many types of logarithmic codecs are used commonly?
a) 2
b) 3
c) 4
d) 5
View Answer
Explanation: There are two types of logarithmic codec which are commonly used. They are a-law which is used in UK and µ-law codec which is used in the US.
11. What does ADPCM stand for?
a) address differential pulse code modulation
b) adaptive differential pulse code modulation
c) address dynamic pulse code machine
d) adaptive dynamic pulse code modulation
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Explanation: The adaptive differential pulse code modulation is used in telecommunications and is based on non-linear quantisation values.
12. Which of the following uses a non-linear quantisation value?
a) PCM
b) DPCM
c) ADPCM
d) linear codec
View Answer
Explanation: The adaptive differential pulse code modulation is based on non-linear quantisation values. In the ADPCM, instead of using all bit for encoding, only a few bits are used for encoding which makes it non linear.
13. Which of the following works by increasing the dynamic range?
a) logarithmic codec
b) linear codec
c) DPCM
d) PCM
View Answer
Explanation: The differential pulse code modulation can improve the accuracy and resolution by having a 16-bit dynamic range. It works by the increasing dynamic range.
14. Which device can make the PWM operation easier?
a) timer
b) software
c) hardware
d) transistor
View Answer
Explanation: The timer can be used for making up the PWM waveform far more easier and faster and it will free the processor to do other things without affecting the timing.
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