[Interest] I am having problems reading multichannel data from usb soundboards using QAudioInput and QAudioInfo

val and leslie vveirs at coloradocollege.edu
Thu Aug 15 23:05:30 CEST 2013

Part two,

I compiled my 2 channel version of the Audio Input example program on a 
Windows XP computer with Qt 5.0  and here the two channels are distinct 
as they are supposed to be.  It seems then that the problem is in the 
Linux side of Qt.  I am more and more confident that the problem is not 
in ALSA as I found that Audacity can open my USB soundboards just fine 
and all their channels stay where they are supposed to be.

On 08/15/2013 01:08 PM, val and leslie wrote:
> Greetings,
> I am brand new to this mailing list so bear with me as I learn how you
> operate.
> I have found that the Audio Input example that comes with QT 5.0.1
> running under Ubuntu 12.03 and 13.04 does not return correct
> multichannel data. I modified the example for two channels and I find
> that data from channel 1 shows up in channel 1 and also in channel 2. I
> have checked this with two different USB soundboards (Griffen iMic and
> Lexicon Omega). I also have checked that the Ubuntu ALSA driver works
> for the USB soundboard (arecord -v -c 2 -f cd -t wav -D hw:CARD=system
> test1.wav records a proper two channel file with the proper channel
> separation).
> So, it seems to me that AudioInput or AudioInfo is not working properly.
> If I interrogate the devices via
> AudioInfo via foreach(const QAudioDeviceInfo &deviceInfo,
> QAudioDeviceInfo::availableDevices(QAudio::AudioInput))
> qDebug() << “Device name: “ << deviceInfo.deviceName();
> I find that the iMic shows up only as mono:
> Device name:
> “alsa_input.usb-Griffin_Technology__Inc_iMic_USB_audio_system-00-system.analog-mono”
> Interestingly, the Lexicon which is a 4 channel A/D shows up as stereo
> Device name:
> “alsa_input.usb-Lexicon_Lexicon_Omega_Lex1.00-00-Omega.analog-stereo”
> When reading 4 channel data with a signal in channel 1 and zero signal
> on the other channels, the signal comes in on channel 1 but various
> seemingly random portions show up in the other channels.
> I wonder if others have found a solution to getting multichannel audio
> data into Qt using QAudioInput?
> Thanks for any suggestions.
> Val
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