Which of the following tasks can be performed by a digital signal processor?
- sampling, but not encoding and compression, of analog audio
- encoding, but not sampling and compression, of analog audio
- sampling and compression, but not encoding, of analog audio
- sampling, encoding, and compression of analog audio
Sampling, encoding, and compression of analog audio can be performed by a digital signal processor (DSP). DSPs execute the steps required to convert an analog voice signal to digital packets, which allow voice data to traverse a Voice over IP (VoIP) network. There are four steps involved in converting analog audio data to digital audio data: sampling, quantization, encoding, and compression.
Sampling is the process of capturing an analog voice waveform at a rate of 8,000 times per second. Quantization is the process of assigning a voltage value to each audio sample. Encoding is the process of converting the quantized voltage data into a binary format. Compression is the process of replacing consecutive sets of repeating data with an equivalent mathematical expression that can be used to reconstruct the data pattern.
When analog audio is received by a DSP, the DSP samples and quantizes the analog audio data, encodes the data into binary format, and optionally, compresses it to conserve bandwidth. For example, Cisco Integrated Services Routers (ISRs) with DSP resources are used to process calls between Cisco Unified Communications Manager (UCM) and the public switched telephone network (PSTN).