Excellent news!
On Tue, Feb 9, 2016 at 6:24 PM, 'RLScott' via Android Developers < [email protected]> wrote: > Well if that don't beat all! It worked! I just replaced > MediaRecorder.AudioSource.MIC with > MediaRecorder.AudioSource.VOICE_RECOGNITION in my "new AudioRecord(...)" > and now the artifacts around 4000 Hz are gone. I can sweep a tone above > and below 4kHz and all I get is one nice peak in the FFT. Thanks a lot for > the suggestion. Now I just need to test and see if my app will suffer due > to the loss AGC. > > -Robert Scott > Hopkins, MN > > On Tuesday, February 9, 2016 at 5:29:00 PM UTC-6, Julian Bunn wrote: >> >> 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 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/924669ef-e48e-48a1-90f4-b069bfc029cb%40googlegroups.com > <https://groups.google.com/d/msgid/android-developers/924669ef-e48e-48a1-90f4-b069bfc029cb%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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