[LAU] Raspberry Pi and real-time, low-latency audio

Nicola nicola.di.marzo at vodafone.it
Thu Apr 18 12:59:16 UTC 2013


Hi, thanks for sharing.
The idea is simply brilliant and it works quite smoothly following the 
wiki[1] (Thanks again Jeremy!), i've got a UA25EX[2] and a Terratec 
Aureon dual-usb[3].
Just a couple of things i noticed:

1)Using the nexus7 power adaptor everything works fine, it's a 5w 2.0A.
2)if you run jack with following command as the wiki suggested "jackd 
-P70 -p16 -t2000 -dalsa -dhw:UA25 -p128 -n3 -r44100 -s" make sure to add 
the background "&" at the end of the line, without this the sound was 
lousy and glitchy, at least for my UA25EX.
3)Using this usb wireless adapter[4], so in a headless fashion, i had 
many jack's disconnection no matter what frames/periods i choose.Any 
suggestion to improve it?
4)I really love the tubescreamer in guitarix, it sounds GREAT!
5)I've got my PI amp now saved in a separate sd card, now i'm able to 
switch my pi from a server into an amp by just replacing the sd card, 
how lovely it is!?

p.s. I was thinking to install Ubuntu on my nexus7 to control Guitarix 
(headless through ssh -X) with the touch screen!!!

[1]http://wiki.linuxaudio.org/wiki/raspberrypi
[2]http://www.rolandus.com/products/details/970
[3]http://www.amazon.co.uk/Terratec-Aureon-Dual-USB-Notebook/dp/B000WL23KC/ref=sr_1_1?ie=UTF8&qid=1366289839&sr=8-1&keywords=terratec+aureon+dual+usb
[4]http://www.edimax.co.uk/en/produce_detail.php?pd_id=328&pl1_id=1&pl2_id=44

Nicola

On 04/18/2013 01:12 PM, Carlos sanchiavedraz wrote:
> 2013/4/17 Jeremy Jongepier <jeremy at autostatic.com>:
>> On 04/17/2013 09:49 AM, Carlos sanchiavedraz wrote:
>>> 2013/4/15 Jeremy Jongepier <jeremy at autostatic.com>:
>>>> On 04/15/2013 10:39 AM, Carlos sanchiavedraz wrote:
>>>>>
>>>>> Just a USB cable from RPi to an A/C to USB adapter, and UA25EX
>>>>> connected direct to the USB on RPi.
>>>>
>>>>
>>>> Check the current of the adapter, if it's somewhere around 1A you might
>>>> need
>>>> a more powerful adapter as the RPi already draws 700mA IIRC.
>>>
>>> The adapter is the same as that ones to charge mobile phones, just an
>>> adapter from USB to a switch. I thought it would be enough to plug the
>>> UA to the RPi and not having to plug it to an USB powered hub, because
>>> then it may occur problems with other devices plugged in it, and this
>>> would probably increase problems with audio latency and such.
>>>
>> I haven't had any problems with audio latency and using a powered hub.
>>
>>
> Good to know. I've had some problems before testing some other touch
> device with USB, but maybe it had to do with the hub was not powered.
>
>>>>
>>>>> IIRC, when configuring using raspi-config, the Modest preset for
>>>>> overclocking just increases the CPU freq from 700MHz to 800MHz. I
>>>>> didn't want to risk my SD because I red that issue you mention, but it
>>>>> seems that anyway I've left without my SD.
>>>>>
>>>> What kind of SD are you using? I've used different SD cards with
>>>> different
>>>> results. I'm now using a cheap OEM class 10 SD card that does get
>>>> corrupted
>>>> quickly but performance is better than other SD cards I've used. Whenever
>>>> I
>>>> change something I make a backup now.
>>>
>>> I'm using a SanDisk 2GB microSD on a SD adapter for the RPi slot. I
>>> never had any problem until now.
>>>
>> And that while SanDisk SD's are being recommended for use with the RPi. What
>> core_freq are you using?
> I chose the Modest preset, so it should be just 800MHz and with no
> other modification on other freqs.
>
>>
>>> Do you still can use yours once it is corrupted? I plug it, you can
>>> see the two partitions  mounted for a moment but then it unmount
>>> itself. I made a backup copy with dd once I configured some
>>> parameters. I've and tried several times to transfer it to the SD with
>>> dd again but at about 840MB transfered it stops with a corruption
>>> error; I only can modify the scripts and config on the first partition
>>> (boot partition) when it stays mounted for some time.
>>
>> First thing I do when a SD becomes corrupted is wipe all partitions and then
>> restore an image with dd.
> I tried it, but when I try to wipe partitions with gparted or any
> other it unmount itself or say that it's not possible.
>
>> If you run into corruption errors the SD might be
>> defective?
> At least not until now, never had a problem. I wonder if the reboot
> cause a physical damage on the SD, but in a reboot it shouldn't happen
> a peak of voltage to cause that.
>
>>
>>> This could allow me to maybe boot a system in a USB stick, but then I
>>> waste one USB slot, and I'm afraid that if I buy another SD card it
>>> could be corrupted again and then it would be wasted money.
>>
>> You can boot from an USB stick connected to a hub. I've tested this when
>> trying to run a RT kernel on the RPi. But either my USB stick or the RPi
>> itself has issues with the throughput because I had the idea the RPi was a
>> lot less responsive and audio was completely distorted.
>>
> In worst case, I could plug a USB stick on one slot and in the other
> the USB hub with the UA and mouse/keyboard/midi-usb..., but I would
> like to control what happen with SDs cards and when they get
> unusable/broken because of some corruption.
>
>> Jeremy
>>
>> _______________________________________________
>> Linux-audio-user mailing list
>> Linux-audio-user at lists.linuxaudio.org
>> http://lists.linuxaudio.org/listinfo/linux-audio-user
>
>



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