[alsa-devel] Record stereo from one input on the soundcard

[Tomas Nordin]

Hello List again

Trying a ping on this. Might not be possible to give a good answer on
the post but then maybe somebody can give me some sort of hints or
pointer to some documentation or something.

Best regards
--
Tomas

Tomas Nordin <tomasn at posteo.net> writes:

> Hello List
>
> I sent this question first to the alsa-user list but somebody
> recommended somebody to send to this list instead when the user-list
> don't get much attention.
>
> I have an external USB soundcard called Audiobox from Presonus,
> https://www.presonus.com/products/AudioBox-USB. Somewhere I read that
> this is a class compliant USB sound card.
>
> I use this card to record audio from a drum module (e-drums). I take the
> audio signal from the head phones out socket on the module, and plug it
> into input 1 on the card. The card has 2 inputs, for the moment I don't
> use the second input but I consider it busy. For a minimum of hassle I
> want to make my recording using arecord (want to use a command line
> program).
>
> So the card is a kind of bedroom musician type of card that might have 2
> inputs, 4 inputs or 12 or whatever, to record a number of instruments at
> the same time. But as I said, this card has two inputs.
>
> The audio signal from the headphones out socket (on the drum module) is
> stereo. The card support routing that stereo sound from one input, in so
> far that it can be heard in stereo from the cards head phones out.
>
> The following command lets me record audio from the card,
>
> $ arecord -c 2 -d 60 -f S24_3LE -r 48000 -D hw:1,0 s3.wav
>
> The resulting wav file has all hearable audio in the left speaker when
> listening.
>
> Do you think it is possible to get that stereo signal from one input on
> the card into a stereo sound file. Or somehow else get left and right
> audio separately from that input 1 on the card. My guess on what's
> happening now is that the stereo signal gets merged as mono into one
> channel.
>
> Here are some listings:
>
> $ uname -a
> Linux raspberrypi 4.14.79+ #1159 Sun Nov 4 17:28:08 GMT 2018 armv6l GNU/Linux
>
> $ arecord -l
> **** List of CAPTURE Hardware Devices ****
> card 1: USB [AudioBox USB], device 0: USB Audio [USB Audio]
>   Subdevices: 1/1
>   Subdevice #0: subdevice #0
>
> $ arecord --dump-hw-params -D hw:1,0 
> Recording WAVE 'stdin' : Unsigned 8 bit, Rate 8000 Hz, Mono
> HW Params of device "hw:1,0":
> --------------------
> ACCESS:  MMAP_INTERLEAVED RW_INTERLEAVED
> FORMAT:  S24_3LE
> SUBFORMAT:  STD
> SAMPLE_BITS: 24
> FRAME_BITS: 48
> CHANNELS: 2
> RATE: [44100 48000]
> PERIOD_TIME: [1000 1981429)
> PERIOD_SIZE: [45 87381]
> PERIOD_BYTES: [270 524286]
> PERIODS: [2 1024]
> BUFFER_TIME: [1875 3962858)
> BUFFER_SIZE: [90 174762]
> BUFFER_BYTES: [540 1048572]
> TICK_TIME: ALL
> --------------------
> arecord: set_params:1299: Sample format non available
> Available formats:
> - S24_3LE
>
> Any ideas anyone?
>
> Best regards
> --
> Tomas
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