User's Manual

Chapter 17: Bluetooth I/O
136 APx500 User’s Manual
APx as A2DP source:
•48 kHz
•44.1 kHz
•32 kHz
•16 kHz
APx as A2DP sink:
•48 kHz
•44.1 kHz
•32 kHz
•16 kHz
AAC
The AAC codec is fixed at MPEG-2/4, AAC-LC,
44.1 kHz, 2 channels.
By default, variable bit rate (VBR) is set. You can dese-
lect variable bit rate to enforce fixed bit rate.
SBC
You can choose to support any or all of the following
sample rates for the SBC codec:
APx as A2DP source:
•48 kHz
•44.1 kHz
•32 kHz
•16 kHz
APx as A2DP sink:
•48 kHz
•44.1 kHz
•32 kHz
•16 kHz
Additionally, you can choose to support any or all of
the following channel modes:
•Joint Stereo
•Stereo
•Dual Channel
•Mono
Clock Recovery
Bluetooth A2DP Sink Clock Recovery
Clock Recovery: Fixed (the default) does not attempt
to algorithmically correct transmission errors, but sets
the A2DP sink sample rate at the negotiated rate. This
provides stable frequency measurements, but may
occasionally be subject to glitches due to packet loss
or buffer overruns. Generally, we recommend using
the Fixed setting, particularly when using the aptX Low
Latency codec.
Clock Recovery: (Auto) engages an A2DP sink algo-
rithm that compensates for RF packet loss or sample
rate drift between source and sink. Ideally, this com-
pensation is unnoticed by the listener, providing a
pleasant listening experience; it will, however, create
small but measurable sample rate and audio fre-
quency variations.
A/V Sync Delay
A/V Sync Delay
AV Sync Delay features are not supported
by the Legacy Bluetooth Option.
This feature of A2DP allows the sink device to notify
the source device of any rendering delay, enabling the
source device to compensate for the delay.
For example, a source device may provide video to a
television monitor via a hard-wired connection, but
route the audio through a Bluetooth A2DP connection
to speakers or headphones. Any delay in the audio
path will cause the audio to lag the video. If the source
device is informed of the rendering delay in the sink
device, it can delay the video stream by that amount
and maintain proper synchronization between video
and audio.
A2DP Source
When A2DP Source is selected, you can choose Enter
A/V Sync Delay into DUT Delay to apply the delay
reported by the remote sink device to the APx DUT
Delay feature.
The delay value entered into DUT Delay is updated
each time the remote device reports a new delay
value.
The Bluetooth Monitor will indicate the delay reported
from the remote sink device. If the remote device does
not support this feature, the monitor entry will read
“N/A”.
A2DP Sink
When A2DP Sink is selected, APx provides an A/V
Sync Delay value for the remote device to read.
For Report A/V Sync Delay you can choose either
•(Auto)
Auto reports the current delay in the Bluetooth
chip internal to the APx, which will vary with config-
uration and connection.
or
•Custom
Custom allows you to enter an arbitrary delay
value for the remote source device to read. The
range is 100 ns to 1.6 s.