Re: [Alsa-user] Capturing stereo signals into files

[Vincent G. <vin...@gm...>]

Hi Bill,

Sorry for the delay in response. Here's the output:

[root@audio-capture ~]# ls /dev/snd
by-path  controlC0  controlC1  hwC0D2  hwC1D0  midiC1D0  midiC1D1  pcmC0D0c
 pcmC0D0p  pcmC1D0c  pcmC1D0p  seq  timer
[root@audio-capture ~]# ls /proc/asound/
card0  card1  cards  default  devices  hwdep  Intel  modules  oss  pcm  seq
 timers  version

TIA.



On Fri, May 3, 2013 at 4:29 PM, Bill Unruh <un...@ph...> wrote:

> On Fri, 3 May 2013, Vincent Gulinao wrote:
>
>  Thanks Bill,
>>
>> The signals I need to record will come from multiple sources (radio
>> stations) that outputs stereo format, so I guess it means I'd need a "-c
>> 2"
>> parameter in each of my arecord command then? In what cases is "-c 18" in
>> your example applicable?
>>
>
> Because my impression was that your soundcard had a large number (I chose
> 18
> as an example) of input channels. And that there is no way for the
> computer to
> know which of those were paired together. All of my choices were
> illustrative
> only to point out to you what to look for.
> As I said, I have absolutely no idea about your soundcard, how it works,
> how
> the driver for it works, etc. Maybe it puts out 16 different pairs and
> looks
> to alsa like 16 different sound cards each with a stereo output. In which
> case
> you would need a separate line for each. Or maybe it looks like one card
> with
> 32 channels. Or whatever.
>
>>
>> More noob questions: how would arecord determine which channels exactly to
>> get its signals? This card supports up to 64 input channels, I assume not
>>
>
> OK, change 16 and 32 above for  32 and 64. I have no idea. I have never
> seen such a card nor do I know anything about it.
>
>
>  all of them will be used at least in the beginning. Is this where the
>> asoundrc and/or "-D hw:.." comes into picture?
>>
>
> Maybe.
>
> You say you have installed the card and have a driver for it. What do you
> get
> when you do ls /dev/snd?
> ls /proc/asound?
>
>
>
>
>> / Vincent
>>
>>
>> On Thu, May 2, 2013 at 7:52 PM, Bill Unruh <un...@ph...> wrote:
>>
>>  On Thu, 2 May 2013, Vincent Gulinao wrote:
>>>
>>>  Hi everyone,
>>>
>>>>
>>>> I have a task to setup a system that will continuously capture multiple
>>>> stereo signals using a MADI audio card (RME HDSPe MADI) and write them
>>>> into
>>>> files (perhaps in 1 hour chunks). Few checks I've learned while googling
>>>> on
>>>> the topic looks like that my linux setup seem to recognize the card at
>>>> least.
>>>>
>>>>
>>> "Multiple Stereo signals" means what? I have no idea about the MADi
>>> interface
>>> or how alsa supports it. But if it does, it may be as simple as arecord
>>> -Dhw:0 -c 18 -r 48000 -f SB24_LE output.wav
>>>
>>> which would keep recording forever into output.wav. You could also use
>>> the
>>> -d 3600 to tell it to record for exactly an hour. You
>>> would then have to have a script to restart it to a different output
>>> file,
>>> but
>>> would miss a bit of the stream because of the time to stop and restart. I
>>> vaguely recall a recording program that will automatically dump into a
>>> new
>>> file every x secods, presumably not missing anything, but cannot remember
>>> it
>>> now.
>>>
>>> (Note the above tells arecord to use the hardware input, not put it
>>> through a
>>> filter like rate changing etc, tells it you want 18 channels, a rate of
>>> 48000
>>> samples per sec on each channel, and the input is in 24 bit format with
>>> Low
>>> Order byte order.
>>>
>>>
>>>
>>>  I'm a total noob in ALSA and audio concepts in general. I've read many
>>>> docs
>>>>
>>>>
>>> If you told us what you were trying to do, someone could probably offer
>>> better
>>> advice.
>>>
>>> Note that the above assumes that you alsa does support the card without
>>> problems and the card is card 0 on your system.
>>>
>>>
>>>  and forums (e.g. arecord, asoundrc, pulseaudio, jack, etc.) here and
>>>
>>>> there.
>>>> But while I wait all those info settle in my mind, can somebody pitch
>>>> here
>>>> some high-level hints on what things I need to know, or what sort of
>>>> questions should I be asking, to accomplish this task and make sure I'm
>>>> on
>>>> the right direction?
>>>>
>>>> Thanks in advance!
>>>>
>>>>
>>>>  --
>>> William G. Unruh   |  Canadian Institute for|     Tel: +1(604)822-3273
>>> Physics&Astronomy  |     Advanced Research  |     Fax: +1(604)822-5324
>>> UBC, Vancouver,BC  |   Program in Cosmology |     un...@ph...
>>> Canada V6T 1Z1     |      and Gravity       |
>>> www.theory.physics.ubc.ca/
>>>
>>>
>>
> --
> William G. Unruh   |  Canadian Institute for|     Tel: +1(604)822-3273
> Physics&Astronomy  |     Advanced Research  |     Fax: +1(604)822-5324
> UBC, Vancouver,BC  |   Program in Cosmology |     un...@ph...
> Canada V6T 1Z1     |      and Gravity       |  www.theory.physics.ubc.ca/
>