Hi Aledis,
I assume that data path of your use-case is like following:
MediaRecoder <= AMR_WB encoder <= AudioFlinger <= Codec on plarform <=
Mic;
Now, I get some question for you:
1). Does AMR_WB support samplerate above 34kHz (17 x 2 kHz)?
2). Does AudioFlinger apply the samplerate above 34kHz (17 x 2 kHz)?
3). Does Codec Chip apply the samplerate above 34kHz for recording?
In a word, you must ensure the samplerate of all data path is above
34kHz, in order to get what you want.
Then some suggestion:
1). Use the format of PCM (RAW audio data) to check if you can get
data above 34kHz;
Remember set the samplerate to 44.1kHz if you can set.
2). Check if AMR_WB support above 34kHz or not? (I'm don't know AMR,
sorry for this :) )
Good Luck!
Libin Luo
On 3月13日, 下午4时06分, Aledis <[email protected]> wrote:
> Hello,
>
> I need to record frequencies about 17kHz. I'm using MediaRecorder like
> this:
>
> recorder = new MediaRecorder();
> recorder.setAudioSource(MediaRecorder.AudioSource.MIC);
>
> recorder.setOutputFormat(MediaRecorder.OutputFormat.THREE_GPP);
> recorder.setAudioEncoder(MediaRecorder.AudioEncoder.AMR_WB);
>
> When I analyze the recorded sound, 17kHz frequencies aren't there, its
> like the phone has a low pass filter that eliminates these
> frequencies. I think is not a problem of the frequency response of the
> microphone. Anybody knows how can I record these high frequencies??
> How can I 'deactivate' the filters or whatever that cuts off high
> frequencies??
>
> Note that there is a project called Zoosh (http://venturebeat.com/
> 2011/06/19/narattes-zoosh-enables-nfc-with-just-a-speaker-and-
> microphone/) where any two mobile phones can comunicate via
> ultrasounds, so I'm supposing any mobile phone can record ultrasounds.
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