POSTS

🎥ffmpeg howto/examples

By Philip

FFMPEG is a video and audio manipulation library and cli program.

  • ffmpeg is the main tool
  • ffplay is a simple graphical viewer.
  • ffprobe will only probe input data (file, stream, … )

A short explanation how the ffmpeg cli accepts parameters:

 ffmpeg <globaloptins> <format> <inputfile_options> <input> <output_option> <output>

show info

the ffmpeg cli has alot of options, this will give you a good starting point to find info about them:

get info about available input formats

ffplay -formats

get available filter info

ffmpeg -filters

get available codecs

ffmpeg -codecs

is hardware en/decode available?

ffmpeg -hwaccels

get system devices (audio, video, other hardware)

ffmpeg -devices

what options has a specific encoder?

# h264 software en/decoder
ffmpeg -h encoder=h264

# nvidia hardware encoder
ffmpeg -h encoder=h264_nvenc

The ffmpeg website has good documentation section:

http://ffmpeg.org/documentation.html

example snippets

next are some command line’s i use, with a small explanation how they work or what his needed

re/encode a video file

most basic encode to h264 (default encoder):

ffmpeg -i input.avi output.mp4

without audio, and lower quality

ffmpeg -i input.avi -an -crf 30 output.mp4

explantion:

  • ffmpeg command
  • -i input.avi |the input file
  • -an: audio none, this will strip the audio
  • -crf 30: encoder qualtity (a higher number lowers the quality) the default encoder is x264 and the default crf (qualtiy factor) is 23
  • output.mp4: the name of the output file

hardware assisted encoding

ffmeg is able to use hardware to accelerate the processing of video data. Be aware that you need certain hardware. I only tested this with nvidia hardware but amd/ati will also be able to proffit from hardware assist.

ffmpeg -i input.avi -c:v h264_nvenc -crf 20 output.mp4
  • -c:v h264_nvenc select the h264 nvidia codec for video
  • -crf 20 encoder quality (higher numbers,lower the quality). The hardware encoder default uses a lower quality, I want more quality that is why i up it a little here.

encode ‘analog’ video

I use this to recompress analog fpv video’s

ffmpeg -i input.avi -vf deband,deflicker,hqdn3d -crf 25 output.mp4

explained:

  • ffmpeg: command
  • -i input.avi: the input file
  • -vf deband,deflicker,hqdn3d: videofilter
    • deband: remove’s banding artifacts
    • deflicker: remove’s flickering
    • hqdn3d: remove’s video noise.
      if you need the best quality denoiser you should use nlmeans, wich is a bit better but takes 10x the time to denoise
  • -crf 25: lower the quality a little (default is 23), this gives smaller files and the video quality isn’t noticable for me
  • output.mp4: the name of the output file

stabilize shaky video

a 2 step process to create a stabilized, smoother video. for example: an old gopro’s video. note:

  • output video will be a bit cropped, zoomed in
  • underwater video’s near the surface can act wierd because the stabilizer try’s to stabilize the water mirror

step 1: analyse the source video

  ffmpeg -i input.avi -vf vidstabdetect dummy.mp4

explained:

  • -i input.avi the input file
  • -vf vidstabdetect analyze input video motion
  • dummy.mp4 a dummy output file, can safely be deleted after the analyzing step

step 2 : stabilize the video

ffmpeg -i input.avi -vf vidstabtransform,unsharp output.mp4

explained:

  • -i input.avi the input file
  • -vf vidstabtransform,unsharp
    • vidstabtransform transform the video to smooth it out
    • unsharp needed for the vidstabtransform to work
  • output.mp4 output video, wich is stabilized

more info: http://public.hronopik.de/vid.stab/

screen record

windows

ffmpeg.exe -f gdigrab -i desktop output.mp4
  • -f gdigrab the format is gdigrab, a windows screen api
  • -i desktop select the desktop as gdigrab input

linux

ffmpeg -f x11grab -i :0.0 output.mp4
  • -f x11grab the format is x11grab, X11 screen api
  • -i :0.0 select screen 0 as x11grab input

screen record with hardware encode

windows

for this you need an nvidia card This is tested on 1920x1600, for higher screen resolutions you need to adjust the b:v and maxrate:v

ffmpeg.exe -f gdigrab -i desktop -c:v h264_nvenc -b:v 6M -maxrate:v 10M -rc:v vbr_hq output.mp4
  • -f gdigrab the format is gdigrab, a windows screen api
  • -i desktop select the desktop as gdigrab input
  • -c:v h264_nvenc select the hardware h264 nvidia codec for video
  • -b:v 6M set video rate at 6M (for higher quality) note: you need to adjust this higher is you use a higher desktop resoloution.
  • -maxrate:v 10M set maximum burst rate to 10M. same note as previous
  • -rc:v vbr_hq set rate control to variable bit rate and high quality

for more info and options: ffmpeg -h encoder=h264_nvenc

references: nvidia website and stackoverflow

audio record

windows

fist you need to list the available audio devices

ffmpeg -list_devices true -f dshow -i dummy

see the ability’s of the input device

ffmpeg -f dshow -list_options true -i audio="Microfoon (High Definition Audio-apparaat)"

record audio

ffmpeg -f dshow -i audio="Microfoon (Realtek High Definition Audio)" output.ogg

linux

TODO

ffmpeg documentation & reference