A20 Android - 8kHz audio not good

[kbro]

I've been doing some experimentation with audio on my A20 Android board using EasyVoiceRecorder from the Google Play Store - https://play.google.com/store/apps/details?id=com.coffeebeanventures.easyvoicerecorder.

Audio recorded at 44.1 kHz sampling 16bpp PCM sounds very good; 16kHz sampling is still acceptable.  When I drop to 8kHz sampling I get very noticeable sibilance (try saying "Supercalifracilisticexpealidocious" or "She sells sea shell on the sea shore"!); and when I use AMR (which starts off as 8kHz PCM before it gets compressed) it's very poor indeed.

It appears to me that Android on the A20 (and the A10S - I've got one of those too) has problems with audio quality at lower sampling rates.  Has anyone else come across this problem?  Any suggestions on how to fix it?  Thanks!

[busyarmbox]

Hi,

i tried it with debian image. in 8kHz, captured auido is so bad. I am using now 48000Hz.
it is ok. When 48000Hz.

[MBR]

All audio has problem on lower sampling rates, because the sampling theorem (a.k.a. Nyquist–Shannon(-Kotelnikov and/or -Whittaker) theorem, see Wiki http://en.wikipedia.org/wiki/Nyquist%E2%80%93Shannon_sampling_theorem). To record frequency f, you need sampling rate at least 2f, so if you record at 8kHz, all frequencies above 4kHz are removed.

[kbro]

Hi MBR, I understand that 8kHz audio isn't going to be as good as 16kHz or 44.1kHz.  My problem is that on the A20 and A10S it is considerably worse that on other Android devices I've used.  For example, the VIA VAB-600 http://www.viaspringboard.com/via-vab-600-springboard-kit.html does 8kHz audio very nicely, using exactly the same software that doesn't work well on the A20.  I've had similar good experiences on other WonderMedia-based devices.  So is it something to do with the codec block in the AllWinner SoC, or something in the Android image (4.0.3 on the VAB, 4.1 on A10S, 4.2 on A20), or something else ...