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Re: Multichannel audio playback (was: Multichannel audio listening)

Le 27/04/2021 à 17:30, Rodolfo Medina a écrit :

Joel Roth <joelz@pobox.com> writes:


On Mon, Mar 05, 2018 at 10:39:19AM +0100, Rodolfo Medina wrote:

Hi all.

After learning, some months ago, thanks to listers' help, how to live record
into a multi channel audio file, I was wondering about the reverse problem:
now I have my multi channel audio file, e.g. composed by three different
channels.  Is it possibile (I guess it is), and how?, to send each of the
three outputs into a different loud speaker and so listen to the song...?



Hi Rodolfo,

Ecasound is pretty convenient for routing audio.

If you connect three powered speakers to the first three
channels of a (sufficiently capable) soundcard and you're
using ALSA (the default low-level linux audio API), it's
pretty simple:

For example,

ecasound -i:3ch.wav -f:16,3,44100 -o:alsa,default



Four years ago this interesting thread.  Now I've purchased a Behringer
UMC404HD 4-channels audio interface and finally want to do my experiment.  Now
I have a 3-channel .wav file and 3 loudspeakers connected to Behringer's
output: I want to playback each channel to a different speaker.  I get error:

$ ecasound -i 3canali.wav -f:16,3,44100 -o alsahw,2,0
**************************************************************************
*        ecasound v2.9.1 (C) 1997-2014 Kai Vehmanen and others
**************************************************************************
(eca-chainsetup) Chainsetup "untitled-chainsetup"
(eca-chainsetup) NOTE: Real-time configuration, but insufficient privileges
... to utilize real-time scheduling (SCHED_FIFO). With small buffersizes,
... this may cause audible glitches during processing.
(eca-chainsetup) "rt" buffering mode selected.
ERROR:  Connecting chainsetup failed: "Enabling chainsetup: AUDIOIO-WAVE:
... Only WAVE_FORMAT_PCM and WAVE_FORMAT_IEEE_FLOAT are supported."

Please help whoever can.

One more thing: on the back of Behringer there are two groups of `playback
outputs': group A and group B.  Each of the two groups has 4 holes: 2 black
6.35mm, one red RCA and one white RCA.  Please help also to understand how to
use them for my special purpose.  Besides, on Behringer's back there is one
more group of outputs called `Main Out' and including two 6.35mm and two XLR.

Thanks in advance for any help,

Rodolfo



Hello Rodolfo,
I might be wrong (I don't mix nor record) but I think there are two distinct problems:
a) the wav file you generated is not supported by ecasound because its type (codec) is neither (L)PCM nor IEEE_FLOAT 
https://en.wikipedia.org/wiki/WAV
So, either you produce a wav file encoded in LPCM to use ecasound, or you use another tool than ecasound that supports the codec you used to produce your wav file 

b) https://mediadl.musictribe.com/media/sys_master/h7e/hfb/8849567252510.pdf
your audio interface is a stereo one: it has only two channels (Left +Right) as outputs. Even if there are 3 groups of output, they all play the same thing, a stereo signal. Basically, I imagine that a typical situation would be to have a mixer or a Public Address (PA) system on MAIN, and 2 different paris of active monitors on A and B. If you want a 3 channels output, you need tou use a multichannel hardware, or tinker with 2 stereo interfaces
As a sidenote: are we speaking of the same thing? Inputs are called tracks. You could for example have 4 mono tracks for a rock band (1:singer, 2:guitar, 3:bass, 4:drums) and each of these tracks are mixed and panned to 2 outputs (Left and right) that are called channels.
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