Re: USB audio on RPi

Ronny Julian <k4rjjradio@...>

Total beginner here but I want to help get this going.

I have a USB 2.0 headset (2 different models/brands) I can try along with a few generic USB sound cards.  I also have a powered 2.0 hub I got last night.  
Want to share info off list?  


On Sat, Jan 19, 2013 at 4:20 AM, Kristoff Bonne <kristoff@...> wrote:


As has been discussed and published a number of times on the net, there
seams to be a pretty serious problem with USB on the RPi, which has its
effects on using an USB audio-dongle on it.
From what I have found, it seams to be related to using a USB 1.1
device on the (USB 2.0) HUB of the Pi.

This has been my experience sofar:
- When I just plug in a USB audiofob on the RPi, I seams to be loseing
audio-frames during audio-capturing. The number of frames dropped per
second does differ quite a lot per device. On some devices (like a USB
headset), I only have 17 to 18 audio-frames of 40 ms per second (instead
of 25).

- One trick seams to be to boot the Pi with the option set to limit the
USB speed to USB 1.1).

However, this seams to have a number of issues:
- in some cases, USB does not work anymore. E.g. my USB keyboard does
not work anymore.
- I had rapports of people where there are problems with the video
- When I use this trick and have 2 audio-devices active (both running at
48 Kbps full-duplex) at the same time, I have problems that the devices
says it does not have sufficient bandwidth for both sessions.
I find this a bit odd as USB 1.1 is -as far as I know- 12 Mbps and even
if you take the worse-case senario (2 * full-duplex stereo, 48 Khz
sampling, 16 bits/sample), I only have 3 Mbps / second

I use my RPi for developing the the c2_gmsk modem (codec2-based GMSK
modem for VHF and UHF), so I do need two audio-connections (one for the
headset for the user and one for the GMSK modem connection to the radio).

What is the experience of people on this group about this?

Some question:
- is there somebody who has a revision 2.0 version of the RPi. Does it
also have this USB issue?

- Has somebody ever tried this with a USB 2.0 audio-device? As far as I
read, the problem with the USB-bus is related to using a USB 1.1 device
on the USB 2.0 bus. So does using a USB 2.0 device help?

Kristoff - ON1ARF

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