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I was using a PCI audio interface M-audio DELTA 1010LT, which had 8 input channels and it allowed me to record 4 independent inputs pairs, this is, the software recognized 4 sources (Line 1/2, Line 3/4, etc). This interface was too old and needed a new interface for a new PC, so I got the Behringer UMC404HD, thinking I could do the same with its 4 input channels. expecting 2 input sources (Line 1/2, Line 3/4). But using the same method for recording, the software which listed 4 sources with 2 channels each, just displays 1 input source with 4 channels for the UMC404HD.

For my application, I require to start the recording for each source independently of each other.

What specification determines this feature in an audio interface? Is this even determined by the hardware or is this a software feature?

EDIT:

I am using Ubuntu as OS and I am recording the audio using sounddevice Python package in a custom application. My application objective is to control the start and stop of recording from different audio sources independently based on messages received from another application.

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    It's a driver design choice (possibly forced by the OS version). You could try a third-party driver like Asio4All, but it may not work (fully). To be certain that a device works exactly as you want it to, you'd have to check the manual before buying. – Your Uncle Bob May 1 '19 at 13:29
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    Sounds like it could also be an Ubuntu/Python programming question; you could try asking on SO or AskUbuntu; there are questions about the interface there: askubuntu.com/questions/1017130/… – Your Uncle Bob May 1 '19 at 13:57
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    Yes it has a programming component, but as I solved it before with another interface, I wondered if there was a specific parameter in audio interfaces that define the recording scheme. I even found that some interfaces highlight their feature of recording simultaneously N channels, but in my case I need the opposite. I'm not sure if this is a common need in the audio/recording industry, I'm totally new in this stuff. – gustavovelascoh May 1 '19 at 14:05
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    I’m 99% sure this is a software question, not a hardware question. For example, I think Ableton Live can do this with any compatible interface. I don’t know much about Linux, but in the Mac and Windows worlds, this would depend on the API (i.e., CoreAudio, DirectX, or ASIO) and whether the interface is compatible with that API. – Todd Wilcox May 1 '19 at 14:23
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    Hi guys, you are right. This is dependant on the driver. I just tested the interface in a Windows machine and it lists different sources for each pair of inputs. I will answer my own question if that's ok. – gustavovelascoh May 1 '19 at 14:59
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TL;DR

It is up to the driver implementation (as stated by @your-uncle-bob and @todd-wilcox). In Windows using ASIO/WDM I got these entries in the list for the UMC404HD:

  ...
   1 UMC ASIO Driver, ASIO (4 in, 4 out)
  ...
  16 IN 1-2 (IN 1-2), Windows WDM-KS (2 in, 0 out)
  17 IN 3-4 (IN 3-4), Windows WDM-KS (2 in, 0 out)
  18 OUT 1-2 (OUT 1-2), Windows WDM-KS (0 in, 2 out)
  19 OUT 3-4 (OUT 3-4), Windows WDM-KS (0 in, 2 out)

But in Ubuntu, using ALSA I got just one entry:

  ...
   7 UMC404HD 192k: USB Audio (hw:2,0), ALSA (4 in, 4 out)
  ...

After testing the interface in a Windows machine, I obtained what I expected:

>>> import sounddevice as sd; sd.query_devices()
*  0 M-Audio Delta ASIO, ASIO (12 in, 10 out)
   1 UMC ASIO Driver, ASIO (4 in, 4 out)
   2 Line 1/2 (Delta 1010LT 1/2), Windows WDM-KS (0 in, 2 out)
   3 Line 1/2 (Delta 1010LT 1/2), Windows WDM-KS (2 in, 0 out)
   4 Line 3/4 (Delta 1010LT 3/4), Windows WDM-KS (0 in, 2 out)
   5 Line 3/4 (Delta 1010LT 3/4), Windows WDM-KS (2 in, 0 out)
   6 Line 5/6 (Delta 1010LT 5/6), Windows WDM-KS (0 in, 2 out)
   7 Line 5/6 (Delta 1010LT 5/6), Windows WDM-KS (2 in, 0 out)
   8 Line 7/8 (Delta 1010LT 7/8), Windows WDM-KS (0 in, 2 out)
   9 Line 7/8 (Delta 1010LT 7/8), Windows WDM-KS (2 in, 0 out)
  10 Monitor (Delta 1010LT Monitor), Windows WDM-KS (2 in, 0 out)
  11 Multichannel (Delta 1010LT Multi), Windows WDM-KS (0 in, 10 out)
  12 Multichannel (Delta 1010LT Multi), Windows WDM-KS (12 in, 0 out)
  13 S/PDIF 1 (Delta 1010LT SPDIF), Windows WDM-KS (0 in, 2 out)
  14 S/PDIF 2 (Delta 1010LT SPDIF), Windows WDM-KS (0 in, 2 out)
  15 S/PDIF (Delta 1010LT SPDIF), Windows WDM-KS (2 in, 0 out)
  16 IN 1-2 (IN 1-2), Windows WDM-KS (2 in, 0 out)
  17 IN 3-4 (IN 3-4), Windows WDM-KS (2 in, 0 out)
  18 OUT 1-2 (OUT 1-2), Windows WDM-KS (0 in, 2 out)
  19 OUT 3-4 (OUT 3-4), Windows WDM-KS (0 in, 2 out)

In Ubuntu I got this:

>>> import sounddevice as sd; sd.query_devices()
   0 HDA Intel PCH: ALC3246 Analog (hw:0,0), ALSA (2 in, 2 out)
   1 HDA Intel PCH: HDMI 0 (hw:0,3), ALSA (0 in, 8 out)
   2 HDA Intel PCH: HDMI 1 (hw:0,7), ALSA (0 in, 8 out)
   3 HDA Intel PCH: HDMI 2 (hw:0,8), ALSA (0 in, 8 out)
   4 HDA Intel PCH: HDMI 3 (hw:0,9), ALSA (0 in, 8 out)
   5 HDA Intel PCH: HDMI 4 (hw:0,10), ALSA (0 in, 8 out)
   6 HDA NVidia: HDMI 0 (hw:1,3), ALSA (0 in, 8 out)
   7 UMC404HD 192k: USB Audio (hw:2,0), ALSA (4 in, 4 out)
   8 sysdefault, ALSA (128 in, 128 out)
   9 front, ALSA (0 in, 2 out)
  10 surround40, ALSA (0 in, 2 out)
  11 surround51, ALSA (0 in, 2 out)
  12 surround71, ALSA (0 in, 2 out)
  13 hdmi, ALSA (0 in, 8 out)
  14 pulse, ALSA (32 in, 32 out)
  15 dmix, ALSA (0 in, 2 out)
* 16 default, ALSA (32 in, 32 out)
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