Create timelapse with ffmpeg

gistfile1.txt

###################################################
# concatenate all mp4 files into one mkv input file

time ffmpeg -f concat -safe 0 -i <(for f in *.MP4; do echo "file '$PWD/$f'"; done) -c copy input.mkv

#############################################
# make 10x speed timelapse with 60 fps output

time ffmpeg -i input.mkv -an -r 60 -filter:v "setpts=0.10*PTS" timelapse-10x.mkv

# real	12m44.746s

#############################################
# make 20x speed timelapse with 60 fps output

time ffmpeg -i input.mkv -an -r 60 -filter:v "setpts=0.05*PTS" timelapse-20x.mkv

# real	8m4.926s

######################################
# Do it with pipe, no large temp files

ffmpeg -nostats -f concat -safe 0 -i <(for f in *.MP4; do echo "file '$PWD/$f'"; done) -c copy -an -f matroska - \
  | time ffmpeg -y -i - -r 60 -filter:v "setpts=0.05*PTS" pipetest-20x.mkv

##################################
# Use NVidia GPU & CUDA-enabled ffmpeg

ffmpeg -nostats -f concat -safe 0 -i <(for f in *.MP4; do echo "file '$PWD/$f'"; done) -c copy -an -f matroska - \
  | time /usr/local/bin/ffmpeg -y -hwaccel cuda -i - -r 60 -filter:v "setpts=0.1*PTS" -c:v h264_nvenc -b:v 150M \
  cuda-10x.mkv

# 2:06 elapsed

ffmpeg -nostats -f concat -safe 0 -i <(for f in *.MP4; do echo "file '$PWD/$f'"; done) -c copy -an -f matroska - \
  | time /usr/local/bin/ffmpeg -y -hwaccel cuda -i - -r 60 -filter:v "setpts=0.05*PTS" -c:v h264_nvenc -b:v 150M \
  cuda-20x.mkv

# 2:12 elapsed

gistfile2.txt

#!/bin/bash

BITRATE=100M

DEST=/store/sjm/timelapse
ffm=/usr/local/bin/ffmpeg

vlist=""
date=""
prevdate=""

process_files() {
  echo "### Processing: $vlist"
  $ffm -nostats -f concat -safe 0 -i <(for f in $vlist; do echo "file '$PWD/$f'"; done) \
    -c copy -an -f matroska - \
    | time $ffm -y -hwaccel cuda -i - \
    -r 60 -filter:v "setpts=0.1*PTS" -c:v h264_nvenc -b:v $BITRATE \
    $DEST/$prevdate.mkv
}

for v in *F.MP4
do
    date=$(echo $v | cut -d_ -f1)
    if [ -n "$vlist" -a "$date" != "$prevdate" ]
    then
	process_files
	vlist=""
    fi
    [ -s $v ] && vlist="$vlist $v"
    prevdate=$date
done
if [ -n "$vlist" ]
then
    process_files
fi

exit 0
# EOF