[libav-tools] need help defining audio stream inputs to avconv

Dave davestechshop at gmail.com
Wed Aug 28 08:29:58 CEST 2013


see below


On Wed, Aug 28, 2013 at 2:04 AM, Luca Barbato <lu_zero at gentoo.org> wrote:

> On 28/08/13 07:14, Dave wrote:
> > This is almost working. However, the recorded audio is garbled and there
> is
> > only one track. My goal was to record each of these two sources to its
> own
> > channel (like left & right in a stereo audio file).
>
>
>
> > I'm not sure what the problem is because I'm new to everything related to
> > audio.
> >
> > #!/bin/bash
> >
> > pacmd list-cards | grep -qi -e
> > "alsa_output.usb-Focusrite_Scarlett_2i2_USB-00-USB.analog-stereo.monitor"
> > if [ $? -ne 0 ]; then
> >     echo "there seems to be a problem with the Focusrite_Scarlett_2i2..."
> >     exit 1
> > fi
> >
> > OUTPUT="/path/audio_`date +%Y-%m-%d_%H%M`.flac"
> > ffmpeg \
>
> If you are using ffmpeg I'm not sure how I can help you, I have no idea
> how this command line is parsed.
>
> > -ac 1 -f pulse -i
> > alsa_input.usb-Focusrite_Scarlett_2i2_USB-00-USB.analog-stereo -name
> > localmic \
>
> -ac 1 looks wrong to me.
>
> > -ac 1 -f pulse -i
> > alsa_output.usb-Focusrite_Scarlett_2i2_USB-00-USB.analog-stereo.monitor
> > -name remote \
> > -map 0:0 -map 1:0 \
> > -c:a flac \
> > -threads 0 \
> > -y $OUTPUT
> > exit 0
>
> You are recording an input and the monitor of that input?
>

Yes.

*My mic* is recorded by this source:
    alsa_input.usb-Focusrite_Scarlett_2i2_USB-00-USB.analog-stereo

*The remote person* (the person I'm interviewing via VoIP) is recorded by
this source:
    alsa_output.usb-Focusrite_Scarlett_2i2_USB-00-USB.analog-stereo.monitor


Based on your example, I tried this:

OUTPUT="/path/audio_`date +%Y-%m-%d_%H%M`.flac"
avconv \
-ac 1 -f pulse -i
alsa_input.usb-Focusrite_Scarlett_2i2_USB-00-USB.analog-stereo \
-ac 1 -f pulse -i
alsa_output.usb-Focusrite_Scarlett_2i2_USB-00-USB.analog-stereo.monitor \
-map 0:a \
-map 1:a \
-c:a flac \
-threads 0 \
-y $OUTPUT
exit 0

I end up with a single channel in the output file and the audio is garbled.

If I record either of those inputs alone, it works as expected. Combining
them is the problem. The way I would like to combine them is like the left
and right channels of a stereo recording. Each input if mono, of course.

Thanks for your help!




> lu
>
>
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