Sampling
The conversion of a continuous signal to a discrete one.
Impulse sampling
Multiplying the signal with a series of Dirac pulses.
Natural sampling
Multiplying the signal with a series of rectangular pulses of the width v.
Redundancy
It is the amount of symbols or bits that can be removed from a message without loss of information. Removal of redundancy = lossless compression.
Irrelevancy
it is an insubstantial (waste) information that can be suppressed in a message (voice or video) so that the required quality of a signal is maintained.
DPCM (Differential Pulse Code Modulation)
DPCM calculates the difference between the predicted and instant value and quantizes it.
Vocoder
It examines speech and determines filter coefficients, voiced or
unvoiced sound, period of a quasi-periodic signal and sound level.
Aliasing
Overlapping of spectrum components.
What is a group of pictures (GOP) ?
It is a set of consecutive frames that can be decoded without any other reference frames.
What are the frame types ?
I-frame, P-frame, B-frame.
The pulse excitation methods include what ?
Multi Pulse Excitation (MPE), Regular Pulse Excitation (RPE), and Code Excited Linear Prediction (CELP)
What does Nyquist’s theorem specify?
Sampling must be at least twice the maximum frequency.
What is introduced by quantization?
Quantization noise.
Which transform is used in JPEG?
The Discrete Cosine Transform (DCT).
Which compression type removes redundancy without losing information?
A. Lossy
B. Loss-less
C. Hybrid
D. Transform
Answer: B
Which source coding technique uses non-uniform quantization?
A. DM
B. PCM
C. A-law and μ-law
D. Huffman coding
Answer: C – Used in PSTN
Which method predicts future samples to reduce bitrate?
A. ADM
B. DPCM
C. CELP
D. Huffman
Answer: B
What does JPEG use first in its pipeline?
A. Motion estimation
B. RGB → Y, R-Y, B-Y conversion
C. Bit allocation
D. Entropy coding
Answer: B
Which audio coding technique uses psychoacoustic masking?
A. PCM
B. MPEGx
C. DM
D. LZW
Answer: B
Which algorithm is adaptive entropy coding?
A. Huffman
B. LZW
C. JPEG
D. DPCM
Answer: B – LZW is adaptive.
