FAQ/Is there a wideband support on snom phones

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Answer

Yes, speaking of wideband means supporting a wider audio frequency band of 7 kHz rather than the usual telephony freq. of 4 kHz. Its sampling rate therefore is 16 kHz rather than 8 kHz. The phone's software supports wideband by offering the G.722 codec but the hardware like mics, speakers, plastics (correct dimensions) etc. will only be wideband ready from the next production lot onwards.

Some information about the implemented wideband codec is mentioned in RFC 3551, section 4.5.2 given below, which is mostly about how its data should be sent in RTP:

RFC 3551: 4.5.2 G722

G722 is specified in ITU-T Recommendation G.722, "7 kHz audio-coding within 64 kbit/s". The G.722 encoder produces a stream of octets, each of which SHALL be octet-aligned in an RTP packet. The first bit transmitted in the G.722 octet, which is the most significant bit of the higher sub-band sample, SHALL correspond to the most significant bit of the octet in the RTP packet.

Even though the actual sampling rate for G.722 audio is 16,000 Hz, the RTP clock rate for the G722 payload format is 8,000 Hz because that value was erroneously assigned in RFC 1890 and must remain unchanged for backward compatibility. The octet rate or sample-pair rate is 8,000 Hz.

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