Re: Multichannel audio playback
On Wed 28 Apr 2021 at 18:21:27 (+0000), Rodolfo Medina wrote:
> Now it works:
>
> $ ecasound -a:1,2,3 -i:sndfile,3canali.wav -o alsaplugin,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.
> (audioio_sndfile) Using libsndfile to open file "3canali.wav" for reading.
> (eca-chainsetup) NOTE: using existing audio parameters -f:s16_le,3,48000
> ... for object 'sndfile' (tried to open with -f:s16_le,2,44100).
> (eca-chainsetup) Opened input "sndfile", mode "read". Format: s16_le,
> ... channels 3, srate 48000, interleaved (locked params).
> (eca-chainsetup) Opened output "alsaplugin", mode "write". Format: s16_le,
> ... channels 2, srate 48000, interleaved.
> - [ Connected chainsetup: "untitled-chainsetup" ] ------------------------
> - [ Controller/Starting batch processing ] -------------------------------
> - [ Engine - Driver start ] ----------------------------------------------
>
> - [ Engine - Processing finished ] ---------------------------------------
> - [ Controller/Batch processing finished (0) ] ---------------------------
> - [ Controller/Processing stopped (cond) ] -------------------------------
> - [ Engine exiting ] -----------------------------------------------------
> (eca-control-objects) Disconnecting chainsetup: "untitled-chainsetup".
> Let's try to go to problem 2).
It's difficult to know what you've actually done from this description.
I know nothing about the UMC404HD apart from the two downloaded PDFs,
8849567252510.pdf and download_259085.pdf. I know nothing about Ecasound.
Let me first reveal my ignorance by asking: does Ecasound run on your
computer, or on the Behringer?
I'm going to assume the former, that you're playing a file on the
computer in Ecasound, which then enters the Behringer via the USB
connection.
> The above command properly sends channel 1 to
> loudspeaker 1 and channel 2 to loudspeaker 2, but it doesn't manage to send
> channel 3 into loudspeaker 3.
How are these loudspeakers connected to the Behringer: which type of
connectors are used, in which sockets, and what's the pinout at each
end of the cables? What type of input do these loudspeakers expect
to be driven by: presumably not an unbalanced 50W into 8Ω!
> Actually, the Behringer seems to behave in
> stereo mode.
Do you mean that all three channels have been mixed into two channels,
and this is what you hear on your loudspeakers 1 and 2?
Isn't that what these lines might indicate:
> (eca-chainsetup) Opened input "sndfile", mode "read". Format: s16_le,
> ... channels 3, srate 48000, interleaved (locked params).
↑
> (eca-chainsetup) Opened output "alsaplugin", mode "write". Format: s16_le,
> ... channels 2, srate 48000, interleaved.
↑
Then the two channels exit the computer through:
2 [U192k ]: USB-Audio - UMC404HD 192k
BEHRINGER UMC404HD 192k at usb-0000:00:12.0-1.2, high speed
as channels 1 and 2.
(I told you I was ignorant.)
> But the strange thing is that outputs `B' (i.e. 3 and 4) do not
> work at all and seems to be dead. So please help: how can I - if ever possible
> - send channel 3 to loudspeaker 3? And, more in general: is it possible, even
> with some other device, to achive what I want?
I can only guess, because I know so little about the Behringer.
Here are questions I'd want to find the answers to by experimentation.
Your sound source is the computer?
Do the three channels become "inputs", controlled by those Gain knobs,
or do those only function with instruments/microphones (plugged in).
Do any of the SIG LEDs light up?
What's the effect of the Stereo/Mono button on your sound channels?
What's the effect of rotating the Mix (IN/PB) knob?
Are you also monitoring through the headphones? If so, what's the
effect of MONITOR A/B?
I won't ask about the Inserts, unless you say you're using them.
OK, my guess is that you're feeding the Behringer with two sound
channels, mixed by Ecasound on your computer, into its 1 and 2,
and that's what you're hearing played. Your feedback might
completely change my mind.
BTW would it help to see what the output of
$ amixer -c 2 scontents
shows, ie the capabilities of the USB sound card. It sould be more
informative than cat /proc/asound/cards.
Cheers,
David.
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