play yt livestreaming from Terminal

ytlive.sh

#!/usr/bin/env bash
# play yt livestreaming from Terminal;
#   and/or workaround of mpv HLS buffer secs to empty BUG
# @version  2017.4.8.0
# @author   noromanba
# @license  https://opensource.org/licenses/MIT

# https://www.shellcheck.net/

set -euC

MY_NAME=$(basename "${0}")

# TODO player-options
if [ $# -lt 1 ]; then
  echo "usage: $MY_NAME {YT_URL} [quality]"
  exit 1
fi

# TODO handle channel w/ multi stream
STREAM_URL="${1}"
# quality e.g.
# Available streams: 144p (worst), 240p, 360p, 480p, 720p, 1080p (best)
# 360p> same audio quality ~128kbps
RESOLUTION="${2:-360p}"
CHANNEL_NAME=$(GET "$STREAM_URL" | grep -P -o '"name":\s*"\K[^"]+')
# --restrict-filenames can not apply to stream title
#TITLE=$(youtube-dl --get-title "$STREAM_URL" | tr -d "'")
# c.f.
# https://gist.github.com/noromanba/34b7ba05dbccb4fa844c18a88ff38d89#title
# TODO completely replace of numeric/number character entity/reference
# "'" :  single quote "'"
TITLE=$(GET "$STREAM_URL" | grep -o -P '<title>\K.+(?=</title>)' | sed 's/&#39;//')

# stdin method; can not use key-input from Terminal {{{
# stdout workaround due to `-p` complex escaping " and ' within $TITLE
# $ streamlink -p "mpv -title "$TITLE" ..."
# https://streamlink.github.io/cli.html#cmdoption-stdout
streamlink --verbose-player "$STREAM_URL" "$RESOLUTION" --stdout | \
    mpv -volume 50 -cache-initial 1000 -title "$TITLE - $CHANNEL_NAME" - #"${@:3}"
# TODO
# M3U heredoc
# arguments for player
# }}}

# available key-input method {{{
# XXX unstable buffer same as use mpv only
#mpv -volume 50 -cache-initial 1000 -cache-secs 20 -title "$TITLE - $CHANNEL_NAME" \
# REMOVE_THIS_PREFIX_WHEN_ENABLE_BELOW_shellcheck disable=2016
# https://github.com/koalaman/shellcheck/wiki/SC2016
#    -term-playing-msg '${title}' \
#    "$(streamlink --stream-url "$STREAM_URL" "$RESOLUTION")"
#
# }}}

# DBG
# -msg-level 'all=v'
# https://mpv.io/manual/master/#options-msg-level
#   no     complete silence
#   fatal  fatal messages only
#   error  error messages
#   warn   warning messages
#   info   informational messages
#   status status messages (default)
#   v      verbose messages
#   debug  debug messages
#   trace  very noisy debug messages
#   Example
#       mpv --msg-level=ao/sndio=no
#   Completely silences the output of ao_sndio, which uses the log prefix [ao/sndio].
#       mpv --msg-level=all=warn,ao/alsa=error
#   Only show warnings or worse, and let the ao_alsa output show errors only.