Re: [gentoo-user] [OT] ffmpeg video+audio capture question

[Walter Dnes]

On Wed, Sep 18, 2019 at 09:14:44PM +0100, Mick wrote

> Yes, you only have one card 0.  The first device (default) is the analogue.
>
> What does 'arecord -l' show?

**** List of CAPTURE Hardware Devices ****
card 0: PCH [HDA Intel PCH], device 0: CX20641 Analog [CX20641 Analog]
  Subdevices: 1/1
  Subdevice #0: subdevice #0
card 0: PCH [HDA Intel PCH], device 2: CX20641 Alt Analog [CX20641 Alt Analog]
  Subdevices: 1/1
  Subdevice #0: subdevice #0

> Let's try something else, specifying a sub-device.  What happens with:
>
> -i hw:0,1
>
> or
>
> -i hw:0,0,1

  Both fail with No such file or directory.


> The ffmpeg output seems noisy and you're getting alsa buffer
> over/under runs.  Try this:
>
>  -f alsa -thread_queue_size 2048

  That gets rid of the warnings and Alsa xrun messages.  But still no
help.  I did some further digging.  It appears that the instructions I
followed are for capture devices (USB microphones, etc).  According to
https://trac.ffmpeg.org/wiki/Capture/ALSA if I want to record from a
running application, I need to load the "snd_aloop" module and mention
it in a local .asoundrc.  According to the linux kernel config help...

CONFIG_SND_ALOOP:

| Say 'Y' or 'M' to include support for the PCM loopback device.      |
| This module returns played samples back to the user space using     |
| the standard ALSA PCM device                                        |

  Oh well, there is a new kernel, so I'll build it with the module, and
get back later to see how things work.

-- 
Walter Dnes <waltdnes@××××××××.org>
I don't run "desktop environments"; I run useful applications