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

Luca Barbato lu_zero at gentoo.org
Tue Aug 27 23:48:23 CEST 2013


On 25/08/13 18:09, Dave wrote:
> Hi. The command `pacmd list-cards` lists two sources on audio card 1. They
> are shown below.
> 
> I need help defining these two sources as inputs to avconv.
> 
>    1. alsa_output.usb-Focusrite_Scarlett_2i2_USB-00-USB.analog-stereo.monitor/#2:
>    Monitor of Scarlett 2i2 USB Analog Stereo
>    2. alsa_input.usb-Focusrite_Scarlett_2i2_USB-00-USB.analog-stereo/#3:
>    Scarlett 2i2 USB Analog Stereo
> 
> My goals is to create a single audio file that contains the stream from
> these two sources where they remain synced and one source is one track
> (e.g., left) and the other source is the other track (e.g., right). (I'm
> recording interviews for podcasting; one side of the conversation is more
> important than the other so separate tracks can help editing.)
> 
> My first *guess* about how to do this is this simple script:
> 
> #!/bin/bash
> OUTPUT="audio_`date +%Y-%m-%d_%H%M`"
> avconv \
> -f alsa -ac 2 -i
> <alsa_output.usb-Focusrite_Scarlett_2i2_USB-00-USB.analog-stereo.monitor>
> \
> -f alsa -ac 1 -i
> <alsa_input.usb-Focusrite_Scarlett_2i2_USB-00-USB.analog-stereo> \
> -map 0:0 -map 1:0 \
> -acodec flac \
> -threads 0 \
> -y $OUTPUT
> 
> 
> I assume I need to replace what is in angle brackets with the correct
> notation. I have no idea if the rest of the above script is even close...

If you are using pulseaudio, you can use the pulseaudio capture and use
those names verbatim. The rest doesn't look wrong beside an acodec that
could be a -c:a

lu


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