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Filtering white noise in vs1063a

Posted: Sun 2018-01-07 0:01
by demonoR
Good day,

Is it possible to filter that white noise which is from mic?

Can you check it please for me, i created a little sample.

I use this settings:

LoadPlugin(venc1063_patch, 1613);
WriteRegister16(SCIR_AICTRL0, 16000);
WriteRegister16(SCIR_AICTRL1, 0);
WriteRegister16(SCIR_AICTRL2, 10 * 0x0400);
WriteRegister16(SCIR_AICTRL3, (audio_format));
WriteRegister16(SCIR_WRAMADDR, 0xE0C0);
WriteRegister16(SCIR_MODE, SM_ENCODE | SM_SDINEW | ReadRegister(SCIR_MODE));
WriteRegister16(SCIR_AIADDR, 0x0050); /* Activate recording! */

Thank you,

Re: Filtering white noise in vs1063a

Posted: Tue 2018-01-09 11:31
by Henrik
Hello!

From your code it isn't clear if you use the line input or microphone input, although it sounds like you are using the microphone input.

If you are using the microphone input (SM_LINE1 = 0 in register SCI_MODE), then this amount of background noise is normal, especially with your 20 dB digital amplification (SCI_AICTRL2 = 10*0x400 = +20 dB digital gain). You may get lower background noise if you preamplify your signal by 20 dB using a low-noise op-amp, then removing the software gain (SCI_AICTRL2 = 0x400).

Kind regards,
- Henrik

Re: Filtering white noise in vs1063a

Posted: Tue 2018-01-09 16:53
by demonoR
Good day Henrik,

Thank you, for your answer, yes I am using microphone input.

I know that this is normal.

1. You said i can use some low noise op amp, do you have some schematic, or which one you prefer?

2. Is it possible to filter some noise with some plugin for vs1063a?

I can filter some noise in PCM, but for OGG or other compressed format it is not possible.

Thank you!

Re: Filtering white noise in vs1063a

Posted: Thu 2018-01-18 12:49
by Henrik
Hello!
demonoR wrote:
Tue 2018-01-09 16:53
1. You said i can use some low noise op amp, do you have some schematic, or which one you prefer?
Some time ago we did this one which worked quite well for dynamic microphones:
http://www.vlsi.fi/fileadmin/evaluation ... 20_sch.pdf
Note that this is purely for dynamic microphones which invariably come with XLR connectors (even though the schematic shows a 6.5mm stereo plug; we adapted the mic connectors ourselves at the time).
2. Is it possible to filter some noise with some plugin for vs1063a?
I've had an adaptive multi-band filter in mind for quite a while, but I'm afraid it will not be operable any time soon. But, because of your interest in it, I'll see if I can resuscitate that side project. I'll let everyone know here at the forum when I get that done.
I can filter some noise in PCM, but for OGG or other compressed format it is not possible.
Quite true. Well, actually, it would be possible to do adaptive post-filtering by playing using the floor curves off Ogg Vorbis files, so recompression would not be strictly required. Nevertheless, quite honestly, that would require very deep information of the format and would be very involved.

Kind regards,
- Henrik