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Re: Ultramic on Android tablet

Subject: Re: Ultramic on Android tablet
From: "Pelix" ipelicella
Date: Tue Mar 26, 2013 11:29 am ((PDT))
> Given the specifications of the microphones and pre-amps, what is the poi=
nt of recording on a portable device at greater than 96KHz? Or even greater=
 than 44.1KHz? All you get are bigger files, less recording time, slower pr=
ocessing, and possibly more battery drain.

there are many bottleneck on portable devices:
- microcontroller speed
- DMA capability
on storage:
- SD card WRITING!!!! speed
- SD card communication protocol (4wire or SPI)
- SD bus communication speed.
I have done many test and the writing speed on sd card I could reach are: 1=
50 ~200 Kbytes/s in spi mode and 4.6 megabytes/s in 4wire mode.
With these speeds I could record 400khz 16bit 4 simultaneous channels or 25=
0khz 16 bit 8 simultaneous channels.
Connecting an SSD on usb High speed probably it's possible to reach higher =
writing speed but I have not tested it.
Linux OS are easy to use but limited in "normal" use not suited for this so=
 high transfer rate combined with many other tasks.
The file dimentions are proportional to the sampling rate and channels numb=
er.
But it's possible to have more useful files enabling a trigger on incoming =
sound so empty recordings are eliminated and the storage is high enought fo=
r the greatest part of applications.
There are some compression algorithms that can be used but I don't know if =
it's the better choise, much more better is to increase the SD card number.
Tonight I hope to do some test increasing the speed of ultramic up to 400kh=
z
Ivano










"While a picture is worth a thousand words, a
sound is worth a thousand pictures." R. Murray Schafer via Bernie Krause.



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