EVOLUTION OF PORTABLE AUDIO DEVICES

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    PHONAUTOGRAM

    Mechanical analog; sound waveform transcribed to paper or glass
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    Phonograph cylinder (Edison)

    Mechanical analog; hill-and-dale grooves, vertical stylus motion
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    Ediphone - Dictaphone

    Mechanical analog, The Ediphone and subsequent wax cylinders used in Edison's other product lines continued to be sold up until 1929 when the Edison Manufacturing Company folded
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    Electrical cut record

    Mechanical analog; electrically cut from amplified microphone signal, lateral grooves, horizontal stylus motion, discs at 7", 10", 12", most at 78 rpm
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    High Definition Compatible Digital (HDCD)

    Digital. Redbook compatible physical CD containing 20–24 bit information (uses linear pulse-code modulation (LPCM)
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    SILK

    Digital. Codec developed by Skype, extended into the Opus codec
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    DCP

    Digital. Auro-3D codec
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    OPUS

    Digital. OPUS-3D codec