Re: iOS Bluetooth HFP speech codec bandwidth
Re: iOS Bluetooth HFP speech codec bandwidth
- Subject: Re: iOS Bluetooth HFP speech codec bandwidth
- From: Woo-Suk Lee <email@hidden>
- Date: Fri, 09 Nov 2018 08:35:04 +0900
Hi Yilok,
Yes, iOS supports WideBand voice codec over HFP.
But the problem is the voice signal seems to be filtered out with 3.5KHz
cut-off,
resulting poor narrowband voice quality.
Please check airPods with iOS built-in Voice Memos.
The recorded sample m4a file has 16KHz sample rate, which means WideBand.
But the spectral analysis on it shows just 20Hz ~ 3.5KHz, narrowband voice,
no signal from 3.5KHz to 7KHz, that is expected with a WideBand codec.
And the same happens with the cellular voice call.
Thanks!
> On 9 Nov 2018, at 4:55 AM, Yilok Wong <email@hidden> wrote:
>
> Hi Woo-Suk, iOS 12.1 and iPhone 6s supports wideband voice over Bluetooth HFP.
>
> As long as wideband voice is enabled and supported on the network and your
> two cellular devices, you should see the wideband spectrum over Bluetooth.
>
>
> Feel free to reach out to me offline if you’d like to debug your setup
> further.
>
> Yilok
>
>> On Nov 2, 2018, at 5:56 AM, Woo-Suk Lee <email@hidden
>> <mailto:email@hidden>> wrote:
>>
>> 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!
>>
>> <iOS Voice Rec Bluetooth.jpg>
>>> On 1 Nov 2018, at 1:12 PM, yinweixu <email@hidden
>>> <mailto:email@hidden>> wrote:
>>>
>>> I may not be able to solve it for you.
>>>
>>>
>>> ------------------ Original ------------------
>>> From: "Woo-Suk Lee"<email@hidden <mailto:email@hidden>>;
>>> Date: Thu, Nov 1, 2018 12:08 PM
>>> To: "yinweixu"<email@hidden <mailto:email@hidden>>;
>>> Cc: "bluetooth-dev"<email@hidden
>>> <mailto: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
>>>> <mailto: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!
>>>
>>>
>>
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