PRELIMINARY
CYW43340
5.4.4 Wideband Speech
The CYW43340 provides support for wideband speech (WBS) using on-chip Smart Audio technology. The CYW43340 can perform
subband-codec (SBC), as well as mSBC, encoding and decoding of linear 16 bits at 16 kHz (256 Kbps rate) transferred over the PCM
bus.
5.4.5 Packet Loss Concealment
Packet Loss Concealment (PLC) improves apparent audio quality for systems with marginal link performance. Bluetooth messages
are sent in packets. When a packet is lost, it creates a gap in the received audio bit-stream. Packet loss can be mitigated in several
ways:
■ Fill in zeros.
■ Ramp down the output audio signal toward zero (this is the method used in current Bluetooth headsets).
■ Repeat the last frame (or packet) of the received bit-stream and decode it as usual (frame repeat).
These techniques cause distortion and popping in the audio stream. The CYW43340 uses a proprietary waveform extension algorithm
to provide dramatic improvement in the audio quality. Figure 8 and Figure 9 show audio waveforms with and without Packet Loss
Concealment. Cypress PLC/BEC algorithms also support wideband speech.
Figure 8. CVSD Decoder Output Waveform Without PLC
Figure 9. CVSD Decoder Output Waveform After Applying PLC
5.4.6 Audio Rate-Matching Algorithms
The CYW43340 has an enhanced rate-matching algorithm that uses interpolation algorithms to reduce audio stream jitter that may
be present when the rate of audio data coming from the host is not the same as the Bluetooth audio data rates.
5.4.7 Codec Encoding
The CYW43340 can support SBC and mSBC encoding and decoding for wideband speech.
5.4.8 Multiple Simultaneous A2DP Audio Stream
The CYW43340 has the ability to take a single audio stream and output it to multiple Bluetooth devices simultaneously. This allows a
user to share his or her music (or any audio stream) with a friend.
5.4.9 Burst Buffer Operation
The CYW43340 has a data buffer that can buffer data being sent over the HCI and audio transports, then send the data at an increased
rate. This mode of operation allows the host to sleep for the maximum amount of time, dramatically reducing system current
consumption.
Document Number: 002-14943 Rev. *L
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