Comfort Noise Generation; Echo Cancellation; Recording Custom Tones - ZyXEL Communications VMG8924-B10D User Manual

• G.726 is an Adaptive Differential PCM (ADPCM) waveform codec that uses a lower bitrate than
standard PCM conversion. ADPCM converts analog audio into digital signals based on the difference
between each audio sample and a prediction based on previous samples. The more similar the
audio sample is to the prediction, the less space needed to describe it. G.726 operates at 16, 24, 32 or
40 kbps.
• G.729 is an Analysis-by-Synthesis (AbS) hybrid waveform codec that uses a filter based on information
about how the human vocal tract produces sounds. G.729 provides good sound quality and reduces
the required bandwidth to 8 kbps.
Voice Activity Detection/Silence Suppression
Voice Activity Detection (VAD) detects whether or not speech is present. This lets the VMG reduce the
bandwidth that a call uses by not transmitting "silent packets" when you are not speaking.

Comfort Noise Generation

When using VAD, the VMG generates comfort noise when the other party is not speaking. The comfort
noise lets you know that the line is still connected as total silence could easily be mistaken for a lost
connection.

Echo Cancellation

G.168 is an ITU-T standard for eliminating the echo caused by the sound of your voice reverberating in
the telephone receiver while you talk.
MWI (Message Waiting Indication)
Enable Message Waiting Indication (MWI) enables your phone to give you a message–waiting
(beeping) dial tone when you have a voice message(s). Your VoIP service provider must have a
messaging system that sends message waiting status SIP packets as defined in RFC 3842.
Custom Tones (IVR)
IVR (Interactive Voice Response) is a feature that allows you to use your telephone to interact with the
VMG. The VMG allows you to record custom tones for the Early Media and Music On Hold functions. The
same recordings apply to both the caller ringing and on hold tones.
Table 111 Custom Tones Details
LABEL
Total Time for All Tones
Maximum Time per Individual
Tone
Total Number of Tones
Recordable

Recording Custom Tones

Use the following steps if you would like to create new tones or change your tones:
Chapter 22 Voice
DESCRIPTION
900 seconds for all custom tones combined
180 seconds
5
You can record up to 5 different custom tones but the total time must be 900
seconds or less.
VMG8924-B10D/B30D User's Guide
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