Speech Coding EE 516 Spring 2009. Alex Acero. Acknowledgments. Thanks to Allen Gersho for some slides…. Outline. Quality vs Bit rate Types of speech coders Waveform Coding Speech production and vocoders Analysis by Synthesis VoIP. Voice Quality. Bandwidth is easily quantified
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Evolution of Speech Coder Performance
North American TDMA
Bit Rate (kb/s)
Each sample is encoded into an 8-bit PCM code word
=> 8000 x 8 bit/s
Notice that the frequency scale is logarithmic in this figure. Speech has in general higher power at the lower frequencies for sonorants and less power above 3.3kHz, as shown here.
Power spectrum densityVoiced Speech
Power spectrum densityUnvoiced Speech