Re: iOS Bluetooth HFP speech codec bandwidth

Subject: Re: iOS Bluetooth HFP speech codec bandwidth
From: Woo-Suk Lee <email@hidden>
Date: Fri, 02 Nov 2018 21:56:11 +0900

Again, I’ve run the test with airPod + iPhone 6S iOS 12.1.

Using built-in iOS Voice Memos app, I’ve recoded test sample through airPod.

The spectral analysis result for the recorded sample is as below.

With airPods, the sampling frequency of the recoded sample m4a file is 16KHz,

which means the HFP over Bluetooth is using the wide band voice codec.

However, the actual voice spectrum only has the narrow band signal, resulting poor voice quality.

It seems that the latest iOS has problem in dealing with wide band voice over Bluetooth HFP.

I thought it’s a Bluetooth receiver or sink device problem.

But after checking with airPods, I think the latest iOS is doing something wrong.

As I remember, the older version of iOS doesn’t have the problem.

It might be possible the latest iOS just cuts off the signal with the narrow band filter even for the wide band codec.

This is a major design flaw.

And if anyone experiences the same issue, please post and share the issue so that Apple would fix it shortly.

Thanks!

On 1 Nov 2018, at 1:12 PM, yinweixu <email@hidden> wrote:

I may not be able to solve it for you.

------------------ Original ------------------
From:  "Woo-Suk Lee"<email@hidden>;
Date:  Thu, Nov 1, 2018 12:08 PM
To:  "yinweixu"<email@hidden>;
Cc:  "bluetooth-dev"<email@hidden>;
Subject:  Re: iOS Bluetooth HFP speech codec bandwidth

What I mentioned is the generic voice call, not a voip application.
It’s just support 8KHz Narrow Band Speech over Bluetooth, even with Apple airPod.

On 1 Nov 2018, at 12:31 PM, yinweixu <email@hidden> wrote:

[AVAudioSession.sharedInstance setCategory:AVAudioSessionCategoryPlayAndRecord withOptions:AVAudioSessionCategoryOptionMixWithOthers | AVAudioSessionCategoryOptionAllowBluetooth error:nil];
[AVAudioSession.sharedInstance setMode:AVAudioSessionModeDefault error:nil];
[AVAudioSession.sharedInstance setActive:YES error:nil];

------------------ Original ------------------
From: "Woo-Suk Lee";
Date: 2018年11月1日(星期四) 中午11:07
To: "bluetooth-dev";
Subject: Re: iOS Bluetooth HFP speech codec bandwidth

Hello,

It seems that the latest iOS doesn’t support wide band speech codec over Bluetooth HFP.

As I tested airPod and other Bluetooth headset supporting HFP1.6 wide band speech codec with the test setup below,

airPod or BT receiver —> iOS —> voice call —> Android (Galaxy S8) —> Voice call recording

It just shows the narrow band speech, which has signals over 20~3KHz only.

And the two test setup below show the same result with the full 7KHz bandwidth.

iPhone built-in mic —> iOS —> voice call —> Android (Galaxy S8) —> Voice call recording

BT receiver —> Android(Galaxy S8) —> voice call —> Android (Galaxy S8) —> Voice call recording

It seems the current iOS doesn’t support Wideband Voice Codec over Bluetooth HFP.
Anyone exeriencing the same issue?

Thanks!

 _______________________________________________
Do not post admin requests to the list. They will be ignored.
Bluetooth-dev mailing list      (email@hidden)
Help/Unsubscribe/Update your Subscription:

This email sent to email@hidden

Follow-Ups:
- Re: iOS Bluetooth HFP speech codec bandwidth
  - From: Yilok Wong <email@hidden>

Next by Date: Re: iOS Bluetooth HFP speech codec bandwidth
Next by thread: Re: iOS Bluetooth HFP speech codec bandwidth
Index(es):
- Date
- Thread