Native Development

[superdirt]

Are there any known issues with the microphone volume fluctuating on the device? My functions are sometimes reporting a wide range of amplitudes for ambient noise even though the actual noise levels are not changing significantly. I'm fairly confident my algorithms are correct and bug free.

Is this a known issue?

Scott

[cycletronic · Accepted solution]

I believe the microphone has AGC (automatic gain control).  A few months ago I took video with the playbook of a severe thunderstorm with heavy rain, and in the recording you could hear the rain, but when loud thunder came up, you could hear it just fine (no clipping), but you could not hear the rain.  As the thunder sound faded away, the "rain volume" came back up.  It's so good that I would think it's hardware rather than software AGC.

[superdirt]

AGC would certainly explain the issue.

[SliceAndDice]

I recorded a video with my speakers blasting music away and it recorded with no clipping (is it the same as sscratching). None at all and you could feel how loud it was, so yes, it does it pretty well, most likely hardware.

I believe the PlayBook microphones are the best in class.

[cycletronic]

I agree that the playbook mics are the best.  It's not just a glitzy feature either, it's actually extremely useful.  I walk along a busy street for several minutes on my way to work and with previous voice recorders it would clip out so I couldn't take any voice notes.  With the playbook I just have to talk loud and close to the mic and it all comes out perfectly clear.  So nice!

[superdirt]

It must be AGC then. Like you three, I was really impressed at its performance. I am operating at the other end of the spectrum and I'm looking at the low-volume noises and what it does to the AGC.

At night when ambient noise is quiet in my home, my application detects the AGC is bumping up the amplitude of the ambient noise by a factor of up to 5 over the daytime. The main ambient noises in the day are cars driving from 400 ft away (windows to my home are closed) and running water through the pipes in the wall. At night these noises are almost non-existent, not that they could easily be heard in the day time anyway. By ear it's hard to hear any difference from day time noise, but like I said my application shows the microphone bumping up the volume by 5 times at night, which is roughly the same volume detected for normal speaking during the daytime. The AGC is amazingly sensitive and responsive.

Thanks for the input. I've used my formulas on other platforms and the PB was the first to throw them off a little with such a sensitive AGC. Glad to know it's not a bug.

Scott