ffpresent

This commandline tool combines videos/images of arbitrary formats/resolutions into a single video.

How it works:

• Uses ffmpeg to convert all desired images/videos into individual videos of the same format, and then merges everything into a single video (see advanced usage to specify the output format), and adds padding as needed so the final video is 1920x1080 (allowing you to combine videos of different resolutions).
  • (I selected these output codecs because they always works with the Davinci Resolve video editing software).

How to use:

1. Create the config file project.ffpres:

# run with no arguments, and follow the interactive prompts:
./ffgenerate.sh

• Note that project.ffpres defines a list of pictures/video files to be combined in the order they appear in the file (initially ordered by increasing date).
  • After generating this file you can remove files from the list by adding a # symbol to the start of a line or by deleting the line entirely.
  • for image files, you can optionally edit the duration field from NA to a number like 5 or 1.2 to set the duration the image will be shown for in the outputted video. If you don't change this value, the default will be used (as defined by IMG_DUR at the top of ffpresent.sh).

2. Now generate the combined video defined by project.ffpres:

./ffpresent.sh project.ffpres .
# the program expects 2 arguments of the form:
./ffpresent.sh /path/to/project.ffpres /path/to/desired/output/dir

• after running, the combined video out-combined.mp4 will appear in the folder combined_output/ within the provided output_dir
  • you can also view log-ffmpeg.txt in the output directory to troubleshoot if anything went wrong.

Advanced usage:

• choose your desired output video format: mp4, mov, webm are supported (default is mp4)

# specify the desired output format (mp4, mov, and webm)
./ffpresent.sh project.ffpres . --mp4
./ffpresent.sh project.ffpres . --mov
./ffpresent.sh project.ffpres . --webm

• mov (video codec: dnxhd, audio: pcm_s16le) will be higher quality, but the video filesize will be much larger. (However this format works well with Davinci Resolve for video editing).

• other ways to generate project.ffpres:

# run with arguments instead of interactive mode:
./ffgenerate.sh "<folder_with_videos>" <ext1> <ext2> <ext3> <...>
# for example:
./ffgenerate.sh "/media/dan/My Passport/CALI/" mov MOV mp4 MP4 jpg
#
# or if you have a list of filenames (one per line) you can also generate project.ffpres with:
./ffgenerate.sh -g list.txt

---

Known limitations:

• Note that drives formatted with the FAT32 filesystem dont't support storing mp4 files above 4GB. This can lead to the error "av_interleaved_write_frame() file too large" more info.
• file names containing a comma will mess up the scripts?
• file names containing an apostrophe will mess up the combination process (I will fix this soon)
• The script is kind of slow (best to leave running overnight when combining many videos). In the future I will experiment further with parallel processing.

---

Future Ideas:

• add option to blend in a list of music files
  • adjust audio to max during for image portions
  • and use an optional flag in the video config file to specify if the audio there is "important" (so it knows to lower the music to say 20% audio there)
    • (and blend the volume changes in audio during transitions)

---

ffmpeg notes:

• filtergraph defined (read definition/options for each filter to understand):

  • scale filter
  • pad filter

• useful filters to consider in future:

  • afade: apply fad-in/out effect to input audio
  • apad: pad the end of an audio stream with silence
  • aresample: stretch/squeeze the audio data to make it match the timestamps or to inject silence / cut out audio to make it match the timestamps

• view the time_base of files (this is important):

  • ls *.mov | xargs -L 1 ffprobe -select_streams a -show_entries stream=time_base -of compact=p=0 2>/dev/null| grep -i "time_base"
  • what is a timebase?
    • (a defined unit of time to serve as a unit representing one tick of a clock)
    • PTS (Presentation Time Stamps) are denominated in terms of this timebase.
    • "tbn" (in ffmpeg readout) = Timescale = 1 / timebase

• working example for converting all vertical videos to horizontal with padding:

ffmpeg -hide_banner -y -i iphone/VER_2.MOV -c:v dnxhd -vf "scale=-1:1080,pad=1920:1080:(ow-iw)/2:color=AliceBlue,fps=30000/1001,format=yuv422p" -b:v 45M -c:a pcm_s16le /tmp/converted_vids/iphone_ver2.mov

---

Useful Commands to know:

• replacing a video's audio with a provided audio file:

# (also seemed to drastically lower the file size of my slideshow video without much noticeable quality drop):
fmpeg -i combined_output/out-combined.mov -i ../source_music/combined_music/combined-music.mp3 -map 0:v:0 -map 1:a:0 -shortest  combined_output/v4-with_music.mov

• convert mp3 files to wav for Davinci Resolve:

ls *.mp3 | xargs -L 1 -I@ bash -c "ffmpeg -i \"@\" \"`dirname @`/wav/@.wav\""

• listing files:

  • get list of all file extensions inside a folder: reference

  find . -type f -name '*.*' | sed 's|.*\.||' | sort -u

  • list all files in order by date:

  find -printf "%TY-%Tm-%Td %TT,%p\n" | sort -n | cut -d',' -f 2

  • get all files matching a list of extensions: reference

  find /path/to -type f -regex ".*\.\(jpg\|gif\|png\|jpeg\)"