I've been working with android audio recording for a while. As far as I know the only guaranteed supported recording sample rate is 44100Hz which means up to 22KHz of bandwidth.
This should be a "real" sampling rate, no upsampling on most devices. Did you try to set AudioRecord with 44.100Hz as sampling rate? Regards. Il 23/dic/2015 17:20, "Robert Scott" <tunelab...@gmail.com> ha scritto: > There is an audio recording problem with some devices, even newer ones. > The native audio recording sample rate appears to be a puny 8000 Hz, which > means it can only render frequencies up to 4000 Hz. This is a problem for > my piano tuning app which must detect frequencies above 4000 Hz. to tune > the top few notes. > > So far I have only gotten reports of this problem on certain models of the > LG G3 and the Nexus 7 (Asus). The worst part is these devices do not > return an error when we try to set up an audio input stream and request a > sample rate of 22050 Hz. Instead they take their 8000 samples per second > and up-sample by duplicating each sample 2 or 3 times to give us audio that > appears to be sampled at 22050 samples per second as requested, but it > still cannot faithfully render frequencies above 4000 Hz, so our piano > tuning app gives very strange results for the top few notes on the piano. > > Does anyone here work with audio input apps and can you confirm this > problem on any other devices? You can test it out by sideloading our app > from > > www.tunelab-world.com/atl.html > > It will run in free-trial mode well enough to test this out. To test for > the sampling rate problem, tap on the large "A4" and select the note "B7" > by tapping on the "7" first. Then on a different device or computer, > generate a tone at 3950 Hz. One such on-line source is > > onlinetonegenerator.com/ > > If this tone produces just one peak in the spectrum display at 3950 Hz, > then everything is fine. But if this produces two peaks - one at 3950 and > the other at 4050, then you have a device that is sampling at 8000 Hz and > then up-sampling to feed our app a fake 22050 samples per second. > > -Robert Scott > Hopkins, MN > > -- > You received this message because you are subscribed to the Google Groups > "Android Developers" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to android-developers+unsubscr...@googlegroups.com. > To post to this group, send email to android-developers@googlegroups.com. > 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/5ab48a86-f5a9-4996-93e8-f7abb7855104%40googlegroups.com > <https://groups.google.com/d/msgid/android-developers/5ab48a86-f5a9-4996-93e8-f7abb7855104%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. To unsubscribe from this group and stop receiving emails from it, send an email to android-developers+unsubscr...@googlegroups.com. To post to this group, send email to android-developers@googlegroups.com. 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/CAMUXMhtFz6LvOcBQBa%3Dgz_BYUxnm5oNakFNc1T9mfOfhFaAirw%40mail.gmail.com. For more options, visit https://groups.google.com/d/optout.
