I think that you should perhaps use the VOICE_RECOGNITION stream which is *supposed* to be devoid of filtering and AGC etc..
http://developer.android.com/reference/android/media/MediaRecorder.AudioSource.html#VOICE_RECOGNITION It's possible to select which Mic is being used, too. (My app offers a choice between "FRONT" and "Main" mics - the Front one is typically next to the front facing camera lens, and makes sense for video ...) On Tue, Feb 9, 2016 at 1:19 PM, 'RLScott' via Android Developers < [email protected]> wrote: > No, I don't know anything about the "VOICE_RECOGNITION" mic stream. I am > just using the standard audio input stream set up with the code I posted > earlier. However someone in a DSP forum told me that the LG G3 has two > mics, one in front and one in back, and they do some DSP with those two > data streams to realize noise cancellation. This might be some artifact of > that operation. > > -Robert Scott > Hopkins, MN > > On Tuesday, February 9, 2016 at 1:20:12 PM UTC-6, Julian Bunn wrote: >> >> That is very curious! Are you using the "VOICE_RECOGNITION" mic stream? >> I'm wondering if there is some sort of odd DSP filtering being applied in >> the firmware. >> >> On Tue, Feb 9, 2016 at 8:59 AM, 'RLScott' via Android Developers < >> [email protected]> wrote: >> >>> OK, I finally got myself a cheap LG G3 from eBay and did some testing. >>> The situation is not exactly as I described before. Here is what is really >>> happening. I tested my app with a sine-wave tone generator. >>> >>> When the tone generator is below about 3700 Hz, the spectrum displayed >>> in my app shows just one peak at the desired frequency. As the frequency >>> of the tone generator increases toward 4000 Hz, a very tiny mirror image >>> peak begins to appear on the other side of 4000 Hz. It gradually gains in >>> amplitude until by 3958 Hz, the amplitude of the image peak is actually a >>> bit higher than the peak at the correct frequency. As the tone goes above >>> 4000 Hz, the image peak appears below 4000 Hz, and gradually decreases in >>> amplitude as the tone frequency increases. I ran the tone frequency up to >>> 4698 Hz and saw a single peak at 4698 Hz in the spectrum and no image >>> peak. This entirely destroys my supposition that this phone is initially >>> sampling at 8000 Hz and then up-sampling to 44100, because if it were, >>> there would be no way to show a single peak at 4698 Hz with no image peak, >>> right? I mean, the information that discriminates between 4698 and 3302 is >>> totally destroyed if the audio is initially sampled at 8000 Hz. >>> >>> But something is going on in the phone's audio system that introduces >>> this image around 4000 Hz. Could it be some sort of hetrodyning? I know >>> in single sideband radio there are ways to invert the audio spectrum if the >>> detection carrier is set on the wrong side of the signal. But why would >>> things return to normal for tones well away from 4000 Hz? >>> >>> -Robert Scott >>> Hopkins, MN >>> >>> >>> On Tuesday, February 2, 2016 at 12:41:32 PM UTC-6, Julian Bunn wrote: >>>> >>>> Perhaps you can post your code, and we can take a look to see if we see >>>> anything that might be causing this problem? Otherwise, if it really is a >>>> firmware "feature" in those two devices, I don't see any good alternatives >>>> other than a) marking your APK as incompatible with those devices in Google >>>> Play, or b) doing some DSP in your software to detect the condition and >>>> work around it somehow. If it were me, I would obtain a G3 and start >>>> testing ... >>>> >>>> >>>> >>>> On Tue, Feb 2, 2016 at 6:08 AM, 'RLScott' via Android Developers < >>>> [email protected]> wrote: >>>> >>>>> The theory says if the initial hardware sampling is done at 8000 >>>>> samples per second, the aliasing is already "frozen" into the sampled >>>>> data. >>>>> You can see that by observing that 4100 Hz and 3900 Hz look exactly the >>>>> same - produce exactly the same samples - after they are sampled at 8000 >>>>> samples per second. No amount of digital signal processing after that >>>>> point can distinguish the two cases, so the aliasing in the up-sampled FFT >>>>> is inevitable, with or without windowing. >>>>> >>>>> I may yet get a G3 on Ebay as you say, but I was hoping for some >>>>> independent confirmation of this problem with a codebase that had nothing >>>>> in common with my code, in case there is something I am doing in the code >>>>> that is making the difference. So if you have an app that processes sound >>>>> and can detect frequency content above 4000 Hz, just have someone with one >>>>> of these failing devices go to piano and play the highest "B". That is >>>>> usually about 4019 Hz. If the device is failing as I predict, there >>>>> should >>>>> also be an indication of a tone at 3981 Hz. >>>>> >>>>> Robert Scott >>>>> Hopkins, MN >>>>> >>>>> On Sunday, January 31, 2016 at 1:39:58 PM UTC-6, Julian Bunn wrote: >>>>> >>>>>> If you are only getting 8000 sps then even with interpolation to >>>>>> 44100 you would never see any signal above 4000Hz in an FFT, right? Are >>>>>> you >>>>>> windowing the FFT? >>>>>> >>>>>> If there are truly problems like this with the audio firmware on the >>>>>> LG G3 and Nexus 7, I haven't heard any reports from my users about them. >>>>>> That's not to say there can't be an issue, of course :-) If I were you, I >>>>>> would obtain a cheap used G3 on Ebay to test with. >>>>>> >>>>>> >>>>>> >>>>>> On Saturday, January 30, 2016 at 6:13:08 PM UTC-8, RLScott wrote: >>>>>>> >>>>>>> But are you sure you are getting the sample rate you asked for? How >>>>>>> would you know? As you can see from my very first posting, all the >>>>>>> checks >>>>>>> you are doing here work fine for me too, and I actually do get the >>>>>>> number >>>>>>> of samples per second I ask for. But they are not true samples. They >>>>>>> have >>>>>>> been faked by up-sampling. The system takes 8000 samples per second and >>>>>>> then duplicates each sample enough times to make up 44100 or 22050 or >>>>>>> whatever. But I know those samples are not true samples because I see >>>>>>> aliasing around 4000 Hz in the frequency spectrum. Unless you >>>>>>> specifically >>>>>>> look for this problem by testing with a pure tone above 4000 Hz and >>>>>>> analyze >>>>>>> with an FFT and look for aliasing below 4000 Hz, everything will appear >>>>>>> fine. Again this only happens on a very few models - specifically the >>>>>>> LG >>>>>>> G3 and the Asus Nexus 7. >>>>>>> >>>>>>> On Wednesday, January 27, 2016 at 10:57:45 AM UTC-6, Julian Bunn >>>>>>> wrote: >>>>>>>> >>>>>>>> Yes, that looks fine to me ... In case it helps, here is a snippet >>>>>>>> of what I do to check a samplerate is going to work: >>>>>>>> >>>>>>>> minBuffer = AudioRecord >>>>>>>> .getMinBufferSize(rate, config, encoding); >>>>>>>> if (minBuffer != AudioRecord.ERROR_BAD_VALUE >>>>>>>> && minBuffer != AudioRecord.ERROR) { >>>>>>>> boolean bGood = true; >>>>>>>> try { >>>>>>>> audio = new AudioRecord(audioSource, rate, config, >>>>>>>> encoding, minBuffer); >>>>>>>> int istate = audio.getState(); >>>>>>>> if (istate != AudioRecord.STATE_INITIALIZED) >>>>>>>> bGood = false; >>>>>>>> } catch (Exception e) { >>>>>>>> bGood = false; >>>>>>>> } >>>>>>>> audio.release(); >>>>>>>> audio = null; >>>>>>>> if (bGood) >>>>>>>> return rate; >>>>>>>> >>>>>>>> >>>>>>>> On Tuesday, January 26, 2016 at 12:49:46 PM UTC-8, RLScott wrote: >>>>>>>>> >>>>>>>>> I am calling >>>>>>>>> AudioRecord.getMinBufferSize(44100,AudioFormat.CHANNEL_IN_MONO,AudioFormat.ENCODING_PCM_16BIT) >>>>>>>>> and using the returned minAudioRecordBufSize in >>>>>>>>> >>>>>>>>> new AudioRecord(MediaRecorder.AudioSource.MIC, >>>>>>>>> 44100,AudioFormat.CHANNEL_IN_MONO, >>>>>>>>> AudioFormat.ENCODING_PCM_16BIT, >>>>>>>>> minAudioRecordBufSize); >>>>>>>>> >>>>>>>>> Is that sizing the buffers correctly? >>>>>>>>> >>>>>>>>> Thanks for the offer for the enumeration app, but I do not have a >>>>>>>>> failing device at my disposal. Only a few devices are failing, and >>>>>>>>> they >>>>>>>>> are all owned by my customers. I can't ask too much of them in the >>>>>>>>> way of >>>>>>>>> debugging help. >>>>>>>>> >>>>>>>>> >>>>>>>>> On Friday, January 15, 2016 at 1:34:15 AM UTC-6, Julian Bunn wrote: >>>>>>>>>> >>>>>>>>>> Make sure you are sizing the buffers correctly i.e. respecting >>>>>>>>>> the minimum recording buffer size (in bytes) required. If you don't >>>>>>>>>> then I >>>>>>>>>> believe the system will drop you down to 8kHz sample rate, which is >>>>>>>>>> what >>>>>>>>>> you are seeing (I think?). >>>>>>>>>> >>>>>>>>>> >>>>>>>>>> On Wednesday, December 23, 2015 at 9:52:37 AM UTC-8, Robert Scott >>>>>>>>>> wrote: >>>>>>>>>>> >>>>>>>>>>> I first call *AudioRecord.getMinBufferSize(22050...* If this >>>>>>>>>>> returns an error (<1) then I call >>>>>>>>>>> *AudioRecord.getMinBufferSize(44100...* Whichever one of these >>>>>>>>>>> calls succeeds, I use that rate in my call to "*new >>>>>>>>>>> AudioRecord(..,sampleRate..)*" >>>>>>>>>>> >>>>>>>>>>> I don't actually have one of these misbehaving devices, so my >>>>>>>>>>> experiments so far have been with the help of my customers. >>>>>>>>>>> >>>>>>>>>>> -Robert Scott >>>>>>>>>>> Hopkins, MN >>>>>>>>>>> >>>>>>>>>>> -- >>>>> You received this message because you are subscribed to a topic in the >>>>> Google Groups "Android Developers" group. >>>>> To unsubscribe from this topic, visit >>>>> https://groups.google.com/d/topic/android-developers/4yG4_Gw4Ilc/unsubscribe >>>>> . >>>>> To unsubscribe from this group and all its topics, send an email to >>>>> [email protected]. >>>>> To post to this group, send email to [email protected]. >>>>> Visit this group at https://groups.google.com/group/android-developers >>>>> . >>>>> To view this discussion on the web visit >>>>> https://groups.google.com/d/msgid/android-developers/6b7520f2-8376-4f1c-9f84-8f7f310846ae%40googlegroups.com >>>>> <https://groups.google.com/d/msgid/android-developers/6b7520f2-8376-4f1c-9f84-8f7f310846ae%40googlegroups.com?utm_medium=email&utm_source=footer> >>>>> . >>>>> >>>>> For more options, visit https://groups.google.com/d/optout. >>>>> >>>> >>>> -- >>> You received this message because you are subscribed to a topic in the >>> Google Groups "Android Developers" group. >>> To unsubscribe from this topic, visit >>> https://groups.google.com/d/topic/android-developers/4yG4_Gw4Ilc/unsubscribe >>> . >>> To unsubscribe from this group and all its topics, send an email to >>> [email protected]. >>> To post to this group, send email to [email protected]. >>> Visit this group at https://groups.google.com/group/android-developers. >>> To view this discussion on the web visit >>> https://groups.google.com/d/msgid/android-developers/ecdce8c1-e5a8-463d-a9f6-6852749e6c34%40googlegroups.com >>> <https://groups.google.com/d/msgid/android-developers/ecdce8c1-e5a8-463d-a9f6-6852749e6c34%40googlegroups.com?utm_medium=email&utm_source=footer> >>> . >>> For more options, visit https://groups.google.com/d/optout. >>> >> >> -- > You received this message because you are subscribed to a topic in the > Google Groups "Android Developers" group. > To unsubscribe from this topic, visit > https://groups.google.com/d/topic/android-developers/4yG4_Gw4Ilc/unsubscribe > . > To unsubscribe from this group and all its topics, send an email to > [email protected]. > To post to this group, send email to [email protected]. > Visit this group at https://groups.google.com/group/android-developers. > To view this discussion on the web visit > https://groups.google.com/d/msgid/android-developers/c5530388-6a11-4e52-890e-94ae55dd7a78%40googlegroups.com > <https://groups.google.com/d/msgid/android-developers/c5530388-6a11-4e52-890e-94ae55dd7a78%40googlegroups.com?utm_medium=email&utm_source=footer> > . > > For more options, visit https://groups.google.com/d/optout. > -- You received this message because you are subscribed to the Google Groups "Android Developers" group. 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