local-bin/bin/capturecard

#!/bin/sh
# This took me far too long to figure out how to do but 
# I think I've learned a lot from it. What a great exercise!
# These comments are for my future-self and whomever else.
# -- Siina, 2020.11.09
#
# Requirements:
# - alsa-utils
# - libv4l (brought in by USE=v4l)
# - mpv
#
# Tools I used to figure this shit out
# - arecord, aplay
# - ffmpeg
# - lspci
# - Lots of searching through ancient fragments of the 'net
#
# TODO:
# - Capture the exact PIDs of the launched mpv / alsaloop to prevent 
#   shutting down any other loops / mpv that happen to be open

# Set our device to 1080p otherwise it defaults to 480p
v4l2-ctl --set-fmt-video=width=1920,height=1080

# Connect to capture card and display captured images immediately
# Send to background so we can initiate the loop below
mpv --title="Capture Card"  av://v4l2:/dev/video0 --profile=low-latency --untimed &

# Run a loop for the capture card digital audio to be sent to my desktop audio
alsaloop -C hw:2,0 -P hw:1,0 &

# Watch for mpv to exit
while pgrep -f mpv >/dev/null; do
	continue
done

# Kill the alsaloop when mpv exits, then terminate this script
kill -9 $(pgrep -f alsaloop)
exit