Voice API Programming Guide — June 2005 87
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8.Recording and Playback
This chapter discusses playback and recording features supported by the voice library. The
following topics are discussed:
•Overview of Recording and Playback. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87
•Digital Recording and Playback . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88
•Play and Record Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88
•Play and Record Convenience Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88
•Voice Encoding Methods. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89
•G.726 Voice Coder. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91
•Transaction Record . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92
•Silence Compressed Record . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93
•Recording with the Voice Activity Detector . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95
•Streaming to Board . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97
•Pause and Resume Play. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99
•Echo Cancellation Resource . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101
8.1 Overview of Recording and Playback
The primary voice processing operations provided by a voice board include:
•recording: digitizing and storing human voice
•playback: retrieving, converting, and playing the stored, digital information to reconstruct the
human voice.
The following features related to voice recording and playback operation are documented in other
chapters in this document:
•Controlling when a playback or recording terminates using I/O termination conditions is
documented in Section 6.1.2, “Setting Termination Conditions for I/O Functions”, on page 32.
•Controlling the speed and volume when messages are played back is documented in Chapter 9,
“Speed and Volume Control”.
•A method for increasing access speed for retrieving and storing voice prompts is documented
in Chapter 12, “Cached Prompt Management”.