[Galaxy S III Android Development] Meltus:
I've been looking into this recently, you beat me to it :P

This is what I've found (I'm not saying I'm right or anything, these are just my conclusions from research).

"AIF1ADC1 HPF" is indeed a High-Pass filter but would disabling the High-Pass filter be a good idea for audio recording?

Well, we have no idea what the current cut-off frequency is for the HPF (but we can take an educated guess, see below) and indeed, as 'dagrim1' pointed out, whether the cut-off frequency changes depending on the mode set. I've been unable to find a technical specification of the Galaxy S III's microphone but I'm guessing it wont be very good at handling the lower frequencies. Another reason is the majority of time we want the audio from a video recording it's when we are recording people. The recording of voices certainly wouldn't benefit from the extra bass frequencies that are being recorded from disabling the high-pass filter as the human voice is around 85Hz to 255Hz (including both male and female range - I've chosen this range because it is, roughly, what I was taught. There are people who claim different but it doesn't really matter that much).

If we look at the HPF modes (that dagrim1 pointed out), we can see there are 3 modes in use; 0, 1 and 2. Now 1 seems only to be used in the telephony sections ("Communication" modifiers in the file) whilst 2 is used for pretty much everything else (apart from where it isn't used at all, '0'. Although, '0' could itself be another HPF mode and whether it's on or off could be controlled entirely by the switch). The standard Frequency Band used for telephones is, approximately, 300hz to 3400hz (NOTE: this could just be for landline telephones and not mobiles, I'm not entirely sure), so we can logically assume the cut-off frequency of mode 1 is around the 300hz mark. Judging by the fact that telephone frequencies need to be quite heavily limited, I'm guessing that Band 1 will have a lower cut-off point (maybe around 50-100hz or so?), allowing more bass frequencies through.

So, you could remove the low-pass filter entirely and capture the whole range of sounds (no idea how the microphone will cope with this as I can't find any technical information about it), you could set it to the standard '2' or you can set the HPF to mode '1', limiting the available frequency range even further but potentially improving the clarity of the recording (it will probably sound tinny as hell too!).

That being said, with the 2 recordings 'radeonxt' made, the one with the disabled HPF did sound much better. It could sound worse in certain situations but it could also be an improvement across the board.

I see you also added in "AIF1ADC1L Mixer ADC/DMIC Switch". This seems to be a special modifier reserved for In-Call recording. I haven't had much luck adding extra parameters into this file (it seems to be quite strict) but I have no idea whether this will affect the sound or not. In theory, as the microphone on the SGSIII is indeed stereo (I think it is anyway, or am I just making that up?) it could enable both channels if they are not enabled by default. But, if both channels are already used and are simply controlled by 1 HPF and not 2, then this line could just do the same as "AIF1ADC1 HPF Switch".

There's also 2 separate sections for the camcorder microphone recording; "built-in mic", the normal one, I'm guessing, and the "back mic". Now I have absolutely no idea what the "back mic" is referring to, unless it means the secondary "noise cancelling mic" but it's not really on the "back" of the device.

EDIT: It seems the "back mic" records the right signal and the "built-in mic" records the left.

Of course, for any of this to actually be relevant completely depends on whether any of it is actually correct. I guess we'll just have to do some more testing :cool:

TL;DR version: Does disabling the HPF improve video recording audio? Dunno, lol. Depending upon the situation, perhaps. :D

You can either reboot or do "adb killall mediaserver" (or just "killall mediaserver" from a terminal) to re-load all the audio files :)