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 07:39:07 +0900
Hi Yilok,
Yes, iOS support wideband voice codec over BT HFP.
The sample rate is 16KHz.
But if you check the actual voice contents, it’s filtered by 3.5KHz cut-off.
No signal in 3.5KHz ~ 7KHz, that is expected with wideband speech codec.
The physical link is opened with the wideband standard,
bu the actual voice is all filtered out, providing just poor narrowband voice
quality.
You can check easily with iOS voice memos app.
Record your voice through airPods or any BT headset with Voice Memos.
The recorded voice sample m4a file, it has 16KHz sample rate, which represent
wideband.
But the spectral analysis on it shows no signal from 3.5KHz to 7KHz. All
filtered out.
> 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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