Differential pulse-code modulation (DPCM) is a lossy data compression technique that removes redundancy in messages like voice or video to reduce the bit rate of transmitted data without serious degradation. It exploits linear prediction theory by performing prediction on quantized message samples in the transmitter instead of the original samples. This differential quantization approach caters to both waveform encoding in the transmitter, which requires quantization, and decoding in the receiver, which must process a quantized signal using the same predictors in both.

1. DIFFERENTIAL PULSE-
CODE MODULATION
(DPCM)
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2. Cont’d
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3. Differential pulse-code modulation
(DPCM)
• Exploits the use of lossy data compression to remove the redundancy inherent in a
message signal, such as voice or video, so as to reduce the bit rate of the
transmitted data without serious degradation.
• In effect, increased system complexity is traded off for reduced bit rate,
therefore reducing the bandwidth requirement of PCM.
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4. DPCM…
• DPCM, the scheme to be considered for channel-bandwidth conservation,
exploits the idea of linear prediction theory with a practical difference:
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In the transmitter, the linear prediction is performed on a quantized version of the
message sample instead of the message sample itself, as illustrated

5. DPCM…
• The resulting process is referred to as differential quantization.
• The motivation behind the use of differential quantization follows from two
practical considerations:
• In order to cater to both requirements in such a way that the same structure is
used for predictors in both the transmitter and the receiver.
• The transmitter has to perform prediction error filtering on the quantized version
of the message signal rather than the signal itself,
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1. Waveform encoding in the transmitter requires the use of quantization.
2. Waveform decoding in the receiver, therefore, has to process a quantized signal.

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8. DPCMTransmitter
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9. DPCM Receiver
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From the foregoing analysis, we thus observe that, in a noise-free environment, the linear predictors in the
transmitter and receiver of DPCM operate on the same sequence of samples, mq,n
It is with this point in mind that a feedback path is appended to the quantizer in the transmitter

10. DELTA MODULATION
(NEXT)
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