On Dec 13, 9:56 am, Patrick Noffke <[email protected]> wrote:
> I'm not aware how the electronics work in the devices. What device(s) are > you using? Maybe the 8kHz sampling is actually sampled at 44.1 kHz, and > there is digital filtering/down-sampling to 8kHz. Right idea, but the initial on-chip sample rate is probably a multiple of that and and then downsampled/filtered to 44.1, 48, or 96 Ksps on chip. Most likely the data requested from the API with a lower sampling rate like 8 Ksps is further filtered as it's downsampled. Easy to test with an adjustable audio oscillator, since 4 KHz is well within the range of human hearing - start at 3 KHz and increase frequency. It should fade out, if it stays at full volume and the frequency of the output starts dropping as the input frequency is increased beyond 4 KHz, there's an aliasing problem. Also, when 8 Ksps data is played back an interpolation filter is needed on the upsampling before feeding to the DAC, but again that should hopefully be taken care of for you. -- You received this message because you are subscribed to the Google Groups "Android Developers" group. To post to this group, send email to [email protected] To unsubscribe from this group, send email to [email protected] For more options, visit this group at http://groups.google.com/group/android-developers?hl=en
