==== Ffmpeg - various notes ====

==== general exploration ====

[[https://ffmpeg.lav.io/|FFmpeg Explorer]] is a tool to help you explore FFmpeg filters.

==== add audio track to a video ====

''ffmpeg -i input.mkv -i audio.mp3 -c copy output.mkv''

====extract audio from mp4 as mp3====

''ffmpeg -i input.mp4 -b:a 320K -vn output-audio.mp3''

====avoid audio/video reencode====

options '-c:a copy' and '-c:v copy'

====slo-mo video transcode (e.g. iphone)====

transcode from 240 to 30 fps w/out dropping frames

''ffmpeg -i IMG_0707\ \(203fps\).MOV -filter "setpts=6.0*PTS" -r 30 -an output.mp4'' (note -an removes audio)

...all files in a folder

''for file in `/bin/ls -1`; do ffmpeg -i $file -filter "setpts=6.0*PTS" -r 30 -an $file.30fps.mp4 ; done''

====video → image sequence====

...timelapsed (1 frame every 4 seconds)

''ffmpeg -i IMG_4566.MOV -r 0.25 IMG_4566_seq/output_%05d.png''

====image sequence  → video====

''ffmpeg -i %05d.jpg -c:v libx265 -r 25 out.mkv''
==== concat ====

create a list of files (e.g. named files.txt)\\
''file 'dust_and_shadow_28min.mp4' ''\\
''file 'dust_and_shadow_black.mp4' ''\\

then...\\
''ffmpeg -f concat -i files.txt -c copy dust_and_shadow_30min.mp4''

alternatively, partial automation...\\
''ls *.mp4 | while read each; do echo "file '$each'" >> files.txt; done\\
ffmpeg -f concat -i files.txt -c copy 000-qualia-RN101.mkv''

also -> https://stackoverflow.com/questions/7333232/how-to-concatenate-two-mp4-files-using-ffmpeg
====ffmpeg filters  ====

  * docs -> http://ffmpeg.org/ffmpeg-filters.html
  * introduction -> http://ffmpeg.org/ffmpeg-filters.html#Filtering-Introduction

[[http://ffmpeg.org/ffmpeg-filters.html#minterpolate|10.122 minterpolate]] / interpolate missing frames...

''ffmpeg -i IMG_0707\ \(203fps\).MOV -filter "setpts=9.0*PTS;minterpolate='fps=300'" -r 30 -an IMG_0707\ \(30fps\).MOV'' 

''ffmpeg -i IMG_0707\ \(203fps\).MOV -filter "minterpolate='fps=600'" -filter "setpts=10.0*PTS"  -r 30 -an IMG_0707\ \(minterp600-30fps\).mp4''

''ffmpeg -i IMG_0707\ \(203fps\).MOV -filter "minterpolate='fps=600':mci:mc_mode=aobmc:scd_threshold=0.1" -filter "setpts=9.0*PTS"  -r 30 -an IMG_0707\ \(minterp00-aobmc\).mp4''


  * 10.164 sab - Apply Shape Adaptive Blur
  * 10.168 selectivecolor
  * 10.175 shuffleframes  (...and then interpolate)
  * 10.133 ocv - Apply a video transform using libopencv 

====displacement====

''ffmpeg -i INPUT -f lavfi -i nullsrc=s=hd720,lutrgb=128:128:128 -f lavfi -i nullsrc=s=hd720,geq='r=128+30*sin(2*PI*X/400+T):g=128+30*sin(2*PI*X/400+T):b=128+30*sin(2*PI*X/400+T)' -lavfi '[0][1][2]displace' OUTPUT''

''ffmpeg -i "IMG_0707 (8m03).mp4"  -f lavfi -i IMG_0705.MOV -f lavfi -i IMG_0706.MOV -lavfi '[0][1][2]displace' displaced.mp4''

'''[0][1][2]displace=edge=mirror' overlooked-forest-disp.mp4'' 

====colour treatment / grading / etc====

  * 10.138 palettegen - Generate one palette for a whole video stream. 
  * 10.139 paletteuse - Use a palette to downsample an input video stream. 
  * split toning -> normalize w. black & whitepoints set to color (e.g. "normalize=blackpt=red:whitept=cyan" ) 
  * color syntax -> http://ffmpeg.org/ffmpeg-utils.html#color-syntax 
 
====subtitles -> hard subs====

1-step
''ffmpeg -i Gomorra.S04E04.mp4 -vf subtitles=Gomorra.S04E04.srt Gomorra.S04E04.hardsubs.mp4''

2-step
''ffmpeg -i Gomorra.S04E04.srt Gomorra.S04E04.ass && ffmpeg -i Gomorra.S04E04.mp4 -vf ass=Gomorra.S04E04.ass Gomorra.S04E04.hardsubs.mp4''

see also -> https://stackoverflow.com/questions/8672809/use-ffmpeg-to-add-text-subtitles and/or https://trac.ffmpeg.org/wiki/HowToBurnSubtitlesIntoVideo

====rotate 90 clockwise====

metadata only

''ffmpeg -i input.m4v -map_metadata 0 -metadata:s:v rotate="90" -codec copy output.m4v''

pixelwise

''ffmpeg -i in.mp4 -vf "transpose=1" out.mmp4''

  For the transpose parameter you can pass

  0 = 90CounterCLockwise and Vertical Flip (default)
  1 = 90Clockwise
  2 = 90CounterClockwise
  3 = 90Clockwise and Vertical Flip

====motion vectors====

''ffmpeg -flags2 +export_mvs -i input.mp4 -vf codecview=mv=pf+bf+bb output.mp4''

''ffmpeg -debug vis_mb_type -i input.mp4 output.mp4''

  * https://trac.ffmpeg.org/wiki/Debug/MacroblocksAndMotionVectors
  * https://oioiiooixiii.blogspot.com/2016/09/ffmpeg-create-video-composite-of.html

====video stabilisation====

Example Stabilization Commands (via https://scottlinux.com/2016/09/17/video-stabilization-using-vidstab-and-ffmpeg-on-linux/  and/or https://gist.github.com/maxogden/43219d6dcb9006042849 ) 

https://ffmpeg.org/ffmpeg-filters.html#vidstabdetect-1

  Option A: Stabilize a video using default settings for a quick fix:

  ffmpeg -i input.mp4 -vf vidstabtransform,unsharp=5:5:0.8:3:3:0.4 output.mp4

  Option B: (Better) 

  First let FFmpeg analyze the video (No changes are made- this just makes a file called transform.trf)

  1. Analyze with default values:

  ffmpeg -i input.mp4 -vf vidstabdetect -f null -

  Or analyze a very shaky video, on a scale of 1-10:

  ffmpeg -i input.mp4 -vf vidstabdetect=shakiness=10:accuracy=15 -f null -

  2. Next, use that generated file transform.trf to help better stabilize the video:

  ffmpeg -i input.mp4 -vf vidstabtransform=smoothing=30:input="transforms.trf" output.mp4

  Done.


Make a side by side video with:

''ffmpeg -i video1.mp4 -i video2.mp4 -filter_complex "[0:v]setpts=PTS-STARTPTS, pad=iw*2:ih[bg]; [1:v]setpts=PTS-STARTPTS[fg]; [bg][fg]overlay=w" side_by_side.mp4''

etc

  set VID "sourcevideo.m4v"
  set VIDST "$VID-stablized.mov"; ffmpeg -i $VID -vf vidstabdetect -f null -; ffmpeg -i $VID -vf vidstabtransform=smoothing=5 $VIDST; ffmpeg -i $VID -i $VIDST -filter_complex "[0:v:0]pad=iw*2:ih[bg]; [bg][1:v:0]overlay=w" "$VID-merged.mov"

side-by-side (horizontally stacked)

''ffmpeg -i clip.mov -i clip2.mov  -filter_complex hstack merged.mov''

vertically stacked

''ffmpeg -i clip.mov -i clip2.mov  -filter_complex vstack merged.mov''


====blending===

  * 38.11 blend, tblend (time blend) filter takes two consecutive frames from one single stream, and outputs the result obtained by blending the new frame on top of the old frame. 


====etc====
  * tuning x265 output -> http://forum.doom9.org/showthread.php?t=172458
  * further examples -> https://hhsprings.bitbucket.io/docs/programming/examples/ffmpeg/index.html
  * An ffmpeg and SDL Tutorial or How to Write a Video Player in Less Than 1000 Lines (2015) http://dranger.com/ffmpeg/
  * various examples -> https://oioiiooixiii.blogspot.com/