Reduce Opus CPU load on low-powered Android devices

How to reduce Open CPU load.

Read time 2 minutes

Last updated 8 months ago

Warning

Modifying Opus settings to reduce CPU load might negatively impact voice quality.

If you need to reduce the Vivox CPU load for lower-power Android devices, the Vivox SDK exposes the

vx_opus_set_complexity

method to set the algorithmic complexity of the codec to another value. The Vivox SDK uses a default complexity value of 9, but you can set this down to 0 to reduce the CPU usage. The lower the value, the more the audio quality is negatively affected. For example, in a speech signal test where the complexity value was decreased to 0, the encoding time decreased to 39% of the default settings (Complexity: 9, Bandwidth: Auto).

It is also possible to use the

vx_opus_set_bandwidth

method to change the audio bandwidth that Opus uses. If you pass the

vx_opus_bandwidth::opus_bandwidth_nb

value, this also reduces the CPU usage, but might have a significant negative impact on audio quality. Lowering the audio bandwidth makes the audio signal sound duller by discarding high frequency content.

Note that reducing complexity has more impact on CPU use reduction than changing the audio bandwidth. For example, a speech signal test with a complexity of 0 combined with

vx_opus_bandwidth::opus_bandwidth_nb

got the lowest CPU time of 27% of the CPU time of the default settings (Complexity: 9, Bandwidth: Auto).

If either of these methods do not reduce CPU use enough, you can use the Siren14 codec, which takes 14% of the CPU time of Opus at its default settings. To use the Siren14 codec, perform either of the following actions:

Note

These updates affect the audio quality for all session participants. This is because when you change the codec of a client, all participants also switch to that codec.

When you initialize the SDK, update
```
vx_sdk_config_t
```
to set the
```
default_codecs_mask
```
field to
```
VIVOX_VANI_SIREN14
```
.
When you create your connector object, update the
```
vx_req_connector_create_t
```
request to set
```
default_codec
```
to
```
VIVOX_VANI_SIREN14
```
.

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