low latency for embedded processing

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low latency for embedded processing

Postby davefollmers » Tue Feb 06, 2018 5:35 am

Hello all,

I'm looking for an economic solution for having low latency audio i/o with a single board computer, such as Raspberry Pi 2, BeagleBone Black, or Udoo Quad. My ultimate goal is to incorporate one of these into a (probably LM3886 based) amplifier, running a stripped-down linux, JACK, and Guitarix for emulation.

Now, I've achieved reasonable latency doing this with my 8 year old Dell PC's on-board connectors, but like I said, I want an embedded solution. It seems like the audio cape for BBB is not currently available, and I'm not entirely up for creating a custom-built interface using an I2S codec right now.

Any thoughts on the on-board sound for Udoo Quad? I've heard mixed things about the quality of sound, but this could just be people with poorly implemented software. I'm thinking an on-board solution *could* give me the option for a lower buffer size.

Then, there is USB audio. It seems in most cases that buffer sizes are limited to 64 bits at the smallest for many USB solutions. I'm wondering, has anyone had good luck running JACK with a USB device to achieve very low latency, economically? I want Guitarix to have <=5ms. Also, since budget is an issue (the rest of this project is not cheap), I'm looking for USB devices that are under $100, preferably under $60. Bitrate isn't a huge issue, 16 bit is OK. Also input for a high impedence source isn't a problem, I will take care of that externally.

Modules or small devices are better than large box solutions, as all this will be housed inside a chassis.

Any thoughts on what I/O device to use?
Thank you

I did not find the right solution from the internet
References :

http://www.diyaudio.com/forums/digital- ... ssing.html


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Re: low latency for embedded processing

Postby fho » Wed Feb 07, 2018 10:40 am

Read the rest of the forum :D

From what I gathered around, a RPi3 is capable of running Guitarix only lacking in memory. You might want to look in the upper tier OrangePi boards which host 2gb of memory (compared to 1gb on the RPi3).

As for USB any USB card with a HighZ input and USB Audio 2.0 profile (not to be confused with USB 2.0 or 3.0) should be fine.

Be aware that you are entering uncharted territory here. Several people on the forum have build rigs based on cheap embedded computers, with varying levels of success. There is no "use this, be happy" solution.
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Re: low latency for embedded processing

Postby arre525 » Sat Feb 24, 2018 5:23 pm

Hi,

I am pretty pleased with running guitarix on my embedded orange pi zero.
Please check out my post (I'll put a link here once it is approved by a moderator), or just have a look at http://arre234.blogspot.be/2018/02/linux-portable-wifi-guitar-amp-on.html

Kind regards,
Arnout
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Re: low latency for embedded processing

Postby FFFF » Sat Mar 10, 2018 3:02 pm

Just my 2 cents from previous experiences:

I have not yet found a more economical/better soundcard solution than existing USB devices.. with those u should be able to achieve latency under 5ms.. But it will depend on what you want, the behringer UCA is ok but only has line in & out so u need to upu your guitar signal to line level. the behringer UCG has instrument in but only headphone out..

the interfacing with an embedded solution can be done in several ways, for instance midi or using a touch screen.

The kind of board u use Beaglebone, RPI, Udoo should not matter that much, the config of your linux does. If u plan to use an ethernet connection with an usb audio device the RPI may not be the best sioluton. Although more RAM is always better if u use a midi device, not to much plugins and dont run a desktop environment u can get away with as little as 512mb RAM.

With all my boards RPI2, Olimex A20 lime, PINE64, Upboard and a behringer audio card i was able to make a workable (<5ms) embedded setup.. although I dont recommend the PINE board, it was a real pain in the @ss
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