Solution I needed to use the -nostdin argument to ffmpeg. Thanks to TwilightKiddy for the answer.
I'm running this in a backgrounded container to convert level 5.2 h264 files down to level 5.1. It's working as expected in terms of all the checks for when to convert or not. But after the first file it comes across to convert, it performs the conversion, writes the final converted -> ... messages, and then exits the loop with the finished run message. I run the container again it dutifully finds the next file and converts it and cleanly exits again. I've done loads of other shell script looping over files using the while read do <<< $(find ...) pattern (to handle file paths/names with spaces and never had this issue.
container command:
docker run -d --rm --name ffmpeg -v ${HOME}/.local/bin:/scripts -v /volume1/media:/media --entrypoint /scripts/reduce_level.sh linuxserver/ffmpeg:latest -s /media/Movies -l /media/reduce_level.log
script
#!/usr/bin/env bash
# Find all .mp4 and .mkv files with h264 video streams whose level > 5.1 (ffprobe reports levels like 51 or 5.1)
# and re-encode the video to level 5.1 keeping the same profile (if available).
# Audio and subtitle streams are passed through (copied).
#
# Usage:
# ./reduce_level.sh # actually convert
# ./reduce_level.sh --dry-run # show the ffmpeg commands without running them
#
# Requirements: ffprobe and ffmpeg in PATH.
set -euo pipefail
log() {
local log_level=$1 # A string representing the log level provided by the user when calling the function
local message=$2 # A string representing the message provided by the user when calling the function
local script_name=$(basename $0) # The name of the script that is running
local timestamp=$(date +"%Y-%m-%d %H:%M:%S") # The current date and time at the time the function is called
if (( VERBOSE )); then
echo -e "$timestamp [$log_level] [$script_name] $message" | tee -a "${LOGFILE}"
else
echo -e "$timestamp [$log_level] [$script_name] $message" >> "${LOGFILE}"
fi
}
PARSED_ARGS=$(getopt -o dl:s:v --long dry-run,log-file:,start-dir:,verbose -- "$@")
eval set -- "${PARSED_ARGS}"
# Will be overwridden if arguments provided
DRY_RUN=0
VERBOSE=0
while true; do
case "$1" in
-d | --dry-run )
DRY_RUN=1
shift
;;
-l | --log-file )
LOGFILE="$(realpath "$2")"
shift 2
;;
-s | --start-dir )
START_DIR="$(realpath "$2")"
shift 2
;;
-v | --verbose )
VERBOSE=1
shift
;;
-- )
shift
break
;;
* )
log ERROR "Unsupported argument $1"
exit 1
;;
esac
done
# Defaults if arguments not provided
START_DIR="${START_DIR:-$(pwd)}"
LOGFILE="${LOGFILE:-${START_DIR}/$(basename "${0/.sh/.log}")}"
# Verify inputs
[[ ! -d "${START_DIR}" ]] && { log ERROR "Could not find starting directory \"${START_DIR}\""; exit 1; }
[[ ! -d "$(dirname "${LOGFILE}")" ]] && { log ERROR "Could not find log file directory \"$(dirname "${LOGFILE}")\""; exit 1; }
log INFO "\n\n---------------- Starting run ----------------\n\n"
while read f; do {
log INFO "Checking: $f"
# Get codec_name, profile and level for each video stream as separate lines (triplets)
probe_output=$(ffprobe -v error -show_format -show_streams -select_streams v -of json "$f")
if [[ "{}" == "$(jq -r '.' <<< ${probe_output})" ]]; then
log INFO " no video streams found or ffprobe failed"
continue
fi
if [[ 1 -lt $(jq -r '.streams | length' <<< ${probe_output}) ]]; then
log WARN " more than one video stream found, skipping"
continue
fi
need_convert=0
picked_profile=""
# Iterate over the probe output three lines at a time (codec, profile, level)
# We use a here-string so the loop runs in the current shell (no subshell) and doesn't need mapfile/readarray.
bit_rate_bps=$(jq -r '.format.bit_rate' <<< ${probe_output})
bit_rate_mbps=$(awk -v br=${bit_rate_bps} 'BEGIN{printf("%2.2f", br/1000000)}')
codec=$(jq -r '.streams[0].codec_name' <<< ${probe_output})
height=$(jq -r '.streams[0].height' <<< ${probe_output})
level_raw=$(jq -r '.streams[0].level' <<< ${probe_output})
profile=$(jq -r '.streams[0].profile' <<< ${probe_output})
width=$(jq -r '.streams[0].width' <<< ${probe_output})
# skip if codec not h264
if [[ "$codec" != "h264" && "$codec" != "libx264" ]]; then
log INFO " video streams found are not h264/libx264"
continue
fi
# Only process 4k files
if [[ ${width} -gt ${height} ]]; then
resolution=${height}
else
resolution=${width}
fi
if [[ ${resolution} -lt 2160 ]]; then
log INFO " ok (video resolution is under 4k)"
continue
fi
# normalize level:
# ffprobe may return "51" or "5.1"; convert "5.1" -> 51 (integer) for comparison.
if [[ -z "$level_raw" ]]; then
level_int=0
elif [[ "$level_raw" == *.* ]]; then
# multiply by 10 and floor
level_int=$(awk -v l="$level_raw" 'BEGIN{printf("%d", l*10)}')
else
# ensure base-10 integer
level_int=$((10#$level_raw)) 2>/dev/null || level_int=0
fi
if (( level_int > 51 )); then
# look for othe files of same name root, but with different bit rate
froot=$(sed -r "s,(.*)\[[0-9\.]+ Mbps\]\.${f##*.},\1," <<< $f)
fcount=$(/bin/ls -1 "${froot}"*.${f##*.} | wc -l)
if [[ 2 -le $fcount ]]; then
log INFO " Found other files with same name root and different bitrate, skipping"
continue
fi
need_convert=1
# prefer first non-empty profile we find
if [[ -z "$picked_profile" && -n "$profile" ]]; then
picked_profile="$profile"
fi
fi
if (( need_convert )); then
log INFO " will convert (found h264 level > 5.1). profile='${picked_profile:-(none)}'"
# create a unique temporary file in the same directory
out="${f%.*}.level51"
tmpdir="$(dirname "${out}.${f##*.}")"
tmptmpl="$(basename "${out}").tmp.XXXXXX"
tmpfile="$(mktemp "$tmpdir/$tmptmpl")" || { log WARN " failed to create temp file"; continue; }
rm -f -- "$tmpfile" # remove placeholder so ffmpeg can create it with correct container ext
tmp="${tmpfile}.${f##*.}"
if [[ -n "$picked_profile" ]]; then
ffargs=( -i "$f" -v error -map 0 -c:a copy -c:s copy -c:v libx264 -profile:v "$picked_profile" -level 5.1 -preset slow -crf 18 -y "$tmp" )
else
ffargs=( -i "$f" -v error -map 0 -c:a copy -c:s copy -c:v libx264 -level 5.1 -preset slow -crf 18 -y "$tmp" )
fi
if (( DRY_RUN )); then
log INFO " DRY RUN -- Running: ffmpeg ${ffargs[*]}"
continue
fi
log INFO " Running: ffmpeg ${ffargs[*]}"
if ffmpeg "${ffargs[@]}"; then
bit_rate_reduced=$(ffprobe -v error -of json -show_format -show_entries format=bit_rate "$tmp" | jq -r '.format.bit_rate')
bit_rate_reduced_mbps=$(awk -v br=${bit_rate_reduced} 'BEGIN{printf("%2.2f", br/1000000)}')
mv -v -- "$f" "${f%.*}.[${bit_rate_mbps} Mbps].${f##*.}"
mv -v -- "$tmp" "${f%.*}.[${bit_rate_reduced_mbps} Mbps].${f##*.}"
log INFO " converted -> $f"
else
log WARN " ffmpeg failed for $f" >&2
rm -f -- "$tmp"
fi
else
log INFO " ok (no h264 stream with level > 5.1)"
fi
} done <<< $(find "${START_DIR}" -type f -iname '*.mp4' -o -iname '*.mkv')
log INFO "\n\n---------------- Finished run ----------------\n\n"
