Tag: mencoder

Commands to create (time lapse) videos from individual frames

12 Feb 2022 – Ronny Errmann

Some of the time lapses can be found on youtube: Youtube Channel Ronny Errmann, for example an 8 hour time lapse of the night sky over La Palma. If you modify your images before creating a video, creating a working directory and copying the images into that will safe you from accidentally destroying the originals.

Create a Video from images:

mencoder mf://*.jpg -mf fps=24:type=jpg -noskip -vf scale=1156:868 -of lavf -lavfopts format=mp4 -ovc x264 -sws 9 -x264encopts nocabac:level_idc=30:bframes=0:bitrate=16384:threads=auto:turbo=1:global_header:threads=auto:subq=5:frameref=6:partitions=all:trellis=1:chroma_me:me=umh -o output.mp4

The following settings should be adapted to your images:

  • fps=24 : if the framerate of the pictures is not high enough a lower number might be better
  • scale=1156:868 : The pictures of my camera are 3 times bigger along each dimension than the values here, be sure to downsize your images without stretching one axis
  • bitrate=16384 : That bitrate gives reasonable results for my time lapses, however, you might consider larger values (better quality) or smaller values (less storage space needed)

Modify images before creating a video from them:

mogrify -resize 1156x868 IMG_20220212*.jpg

Rotate the images:

mogrify -rotate 90 -background black *.jpg

Crop the images:

To remove useless bits from the image, the values are the new size + start positions

mogrify -crop 3515x2541+142+199 *.jpg

Add exif information to the image, e.g. the time:

Sometimes it’s nice to see the real time running in the time lapse, for this the exif information can be used. In the example the modified images will be copied into “prefix_<original name>”

for img in *jpg; do convert "$img" -gravity SouthEast -pointsize 70 -fill white -annotate +30+30  %[exif:DateTimeOriginal] "prefix_""$img"; done

The following options can be changed:

  • gravity : this gives the corner in which the text should appear. Use geography, e.g. Northwest, South
  • pointsize : size of the text, probably worth to test on a subset of images first (copy images into a subfolder)
  • fill : text colour
  • annotate : distance from the chosen corner

Increase the brightness of the images:

For example, when taking night images and the video is too dark.

mogrify -modulate 200 *.jpg

Batch convert between different image types

for file in *.png; do convert $file -quality 95 ${file%.png}.jpg; done

Video modification for time lapse videos

6 Feb 2022 – Ronny Errmann – last modified on 31 March 2022

Some useful bits which helped me to make the time lapse videos I recorded ready to be published on youtube: Youtube Channel Ronny Errmann

Rotate an mp4 video:

For when the phone was upside down during the recording.

ffmpeg -i input.mp4 -c copy -metadata:s:v rotate="180" output.mp4

Crop an mp4 video:

When personal information is in an area of the video.

1. Get the video resolution:

ffprobe -v error -select_streams v:0 -show_entries stream=width,height -of csv=s=x:p=0 input.mp4

2. Modify the video:

ffmpeg -i input.mp4 -filter:v "crop=1280:600:0:120" output.mp4

Cut an mp4 video:

To keep 00:00:00 to 00:01:22, because afterwards only night was recorded as work had to be finished first.

ffmpeg -i input.mp4 -ss 00:00:00 -to 00:01:22 -c copy output.mp4

Merge/concatenate mp4 videos:

When you notice at the end of a time lapse that the sky is still amazing and you recorded a second one.

Version 1 with the concat protocoll (https://trac.ffmpeg.org/wiki/Concatenate)

Several lines of shell script, run with sh:

for f in $(ls input*.mp4); do
ffmpeg -i $f -c copy -bsf:v h264_mp4toannexb -f mpegts $f.ts
done
CONCAT=$(echo $(ls *.ts) | sed -e "s/ /|/g")
ffmpeg -i "concat:$CONCAT" -c copy -bsf:a aac_adtstoasc output.mp4
rm *.ts

Use Version 2 if this fails with:

Codec 'mpeg4' (12) is not supported by the bitstream filter 'h264_mp4toannexb'

Version 2 with the concat demuxer (https://trac.ffmpeg.org/wiki/Concatenate)

rm -f mylist.txt; for f in input*.mp4; do echo "file '$f'" >> mylist.txt; done
ffmpeg -f concat -safe 0 -i mylist.txt -c copy output.mp4
rm mylist.txt

Change the speed of mp4 videos:

You took a time lapse, but the viewers are bored, because changes are too small. Time to speed the video up.

ffmpeg -i input.mp4 -r 16 -filter:v "setpts=0.50*PTS" output.mp4

0.5*PTS mean twice the speed, 0.1*PTS would mean ten times the speed, and 2*PTS would mean half the speed; -r 16 means a frame rate of 16 fps (frames per second).

Change of resolution of mp4 videos:

ffmpeg -y -i input.mp4 -vf scale=480:-2,setsar=1:1 -c:v libx264 -c:a copy output.mp4

The 480 gives the horizontal resultion and the heigh is calculated by keeping the same aspect ratio.

Extract images from mp4 videos:

ffmpeg -i input.mp4 out-%05d.jpg

With above settings the output files will be of format out-12345.jpg. To get slightly better image quality png can be used instead of jpg. Images will require much more space than the video (about 10 times). Different commands can also be combined, e.g. to get only frames for a 8 second stretch:

ffmpeg -i input.mp4 -ss 00:00:27 -to 00:00:35 out-%03d.png

(I couldn’t get it to work to only get every x-th frame in the same command line)

Batch convert audio files to mp3

The line below will convert wav audio files to mp3s using 44.1 kHz sampling frequency, 2 audio channels, 192 kilobit per second bitrate. -vn makes sure no video is used

for ffile in *.wav; do ffmpeg -i "$ffile" -vn -ar 44100 -ac 2 -b:a 192k "${ffile%.wav}".mp3; done

Input can be any audio type (wma, mp3,…).