extract-frames

#!/bin/bash -e

fail() {
    echo $* 1>&2
    exit 1
}

[ $# -eq 3 ] || fail "Usage: $0 input-video timestamps-file output-dir"

input=$1
timestamps=( $(< $2) )
output=$3
count=${#timestamps[@]}

# Note: sometime '|| true' is needed below to prevent errexit from kicking.

mkdir -p $output

filter=''
for timestamp in ${timestamps[@]}
do
    if [ -n "$filter" ]
    then
        filter="$filter + "
    fi
    filter="${filter}lt(prev_pts*TB,$timestamp)*gte(pts*TB,$timestamp)"
done

quiet='-nostdin -y -loglevel warning'
tmp_format="$output/tmp-%03d.jpg"

ffmpeg $quiet -i $input -filter:v "select='$filter'" -vframes $count $tmp_format

i=1
for timestamp in ${timestamps[@]}
do
    tmp=$(printf $tmp_format $i)
    mv $tmp "$output/image-$timestamp.jpg"
    let i++ || true
done