How to configure Opus in HD Voice for Android

[Raju S N]

Hi,

I am using WebRTC Opus codec for the OTT Voip application.

Voice stream is coming great and works well in Wifi and mobile networks.

Looking at HD voice quality used by service providers like Skype, Whatsapp, Viber, etc.

But, when evaluated the quality of the voice output on Android devices, it doesn't sound like HD voice.

After googling found some links to change the Opus parameters in SDP, but this did not result in HD voice.

Original SDP for Opus (configured for 32 and 48)

a=fmtp:111 minptime=10; useinbandfec=1

Edited SDP for Opus (configured for 32 and 48)

a=fmtp:111 minptime=10; useinbandfec=1; maxaveragebitrate=131072; stereo=1; sprop-stereo=1

In both the cases, around 3049 (1 minute) packets are transmitted and did not result in HD.

Can anyone please suggest how to achieve HD voice quality with Opus and WebRTC on Android ?

Thanks

Raju

[Henrik Andreasson]

How do you define "HD voice quality" and what tools are you using to measure the output audio quality?

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[Raju S N]

Hi,

We used two methods for evaluating the voice call.

First, is an automated test done using Voip quality assessment (Commercial tool) for calculating MOS score & Mouth to Ear Delay.

Second, is a listening testing done with group of ten people. Following parameters are used to access the quality and based on the user inputs for loudness & clarity.

This test is conducted with Opus-48 Kbps, Opus-32 Kbps and commercial offerings. Based on user inputs, we arrived at the fact that the voice quality is not HD.

Listening Quality

Listening Effort Scale

Loudness-preference scale

Degradation Category Rating

Distorted

Electronic feedback

Background Noise

Muffled speech

Echo

Definitely the Quality of Voice call with commercial offerings was Loud and we can hear much more than just the voice of the remote person, to say that it is a HD call.

Thanks,

Raju

On Wednesday, December 21, 2016 at 5:20:25 PM UTC+5:30, Henrik Andreassson wrote:

How do you define "HD voice quality" and what tools are you using to measure the output audio quality?

On Wed, Dec 21, 2016 at 12:35 PM, Raju S N <samudr...@gmail.com> wrote:

Hi,

I am using WebRTC Opus codec for the OTT Voip application.

Voice stream is coming great and works well in Wifi and mobile networks.

Looking at HD voice quality used by service providers like Skype, Whatsapp, Viber, etc.

But, when evaluated the quality of the voice output on Android devices, it doesn't sound like HD voice.

After googling found some links to change the Opus parameters in SDP, but this did not result in HD voice.

Original SDP for Opus (configured for 32 and 48)

a=fmtp:111 minptime=10; useinbandfec=1

Edited SDP for Opus (configured for 32 and 48)

a=fmtp:111 minptime=10; useinbandfec=1; maxaveragebitrate=131072; stereo=1; sprop-stereo=1

In both the cases, around 3049 (1 minute) packets are transmitted and did not result in HD.

Can anyone please suggest how to achieve HD voice quality with Opus and WebRTC on Android ?

Thanks

Raju

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[Henrik Andreasson]

Thanks for the explanation. Since the overall quality depends on many things, such as the device, the audio processing, the codec, and the network, there are much more than just codec settings affecting the perceived quality.

WebRTC on Android uses 48k sampling rate in both directions on most modern devices. Some older, and in combination with BT headset, only supports 16k. Hence, by default and in combination with Opus, the audio bandwidth should be high enough to qualify as HD.

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