ffmpeg
================

## Extract Audio From webm

Lookup format of audio stream with:

  ffmpeg -i in.webm

Then use that knowlege to extract that (audio) stream:

  ffmpeg -i in.webm -vn -acodec copy out.FORMAT_FROM_BEFORE



## Convert Formats

  ffmpeg -i in.opus out.wav


## Fine-tune audio codec

[See also](https://slhck.info/video/2017/02/24/vbr-settings.html)

Use  -codec:v copy  to keep video, or -codec:v no  for audio-only.

  -codec:a aac        -q:a 1.3   (min=0.1, good=1.3 max=2)
  -codec:a aac        -b:a 96k
  -codec:a libmp3lame -q:a 2
  -codec:a libopus
  -filter:a lowpass=f=16000


## Fix Loudness war, bring bass back

  -af "equalizer=f=200:w=200:t=h:g=-9,equalizer=f=400:w=600:t=h:g=-9,equalizer=f=2000:w=2000:t=h:g=-12,equalizer=f=4000:w=4000:t=h:g=-12,equalizer=f=10000:w=10000:t=h:g=-12,volume=+0.0dB"


## Audio trim

HINT: Repeat afade twice for log.

  -af "afade=t=in:d=500ms,afade=t=out:st=183427ms:d=500ms" \


## Record Desktop

  ffmpeg -f gdigrab -framerate 6 -probesize 10M -offset_x 0 -offset_y 0 \
      -video_size 1920x1200 -show_region 1 -i desktop -c:v h264_qsv \
      -pix_fmt yuv420p "output-$(date +%Y%m%d-%H%M%S).mp4"


## Trim video

  -i INFILE -ss <pos> -t <dur> OUTFILE
  -i INFILE -ss <pos> -to <pos> OUTFILE


## Concatenate

  && ffmpeg -i one.mkv -i two.mkv \
       -filter_complex '[0:v] [0:a] [1:v] [1:a] concat=n=2:v=1:a=1 [v] [a]' \
       -map "[v]" -map "[a]" out.mkv \


## Rotate Portrait

  -i INFILE -vf "transpose=2" OUTFILE



## Video to Gif

HINT: Use same filter for palette as for conversion.

  FILTERV=fps=6,scale=-1:600
  FILTERV=fps=6,scale=-1:480
  INPUTV=input.mp4

Create custom palette:
  ffmpeg -ss 4 -t 33 -i "$INPUTV" -vf "$FILTERV,palettegen=stats_mode=diff" palette.png

Use this palette:
  ffmpeg -ss 4 -t 33 -i "$INPUTV" -i palette.png -filter_complex "[0:v]$FILTERV[vid];[vid][1:v]paletteuse=dither=bayer:bayer_scale=5:diff_mode=rectangle" output.gif

Working example from web (but not optimized):
  ffmpeg -ss 0 -t 2.5 -i INPUT.mp4 -filter_complex "[0:v] fps=12,scale=-1:600,split [a][b];[a] palettegen=stats_mode=diff [p];[b][p] paletteuse=new=1" OUTPUT.gif


## Pictures to Video (eg Timelapse)

  -start_number 5619 -framerate 24 -i "input/IMG_%d.JPG" \
    -vf "scale=4096:-1,crop=4096:2160:0:0" \
    out.mkv