Handy FFmpeg commands

ffmpeg.txt

# Build ffmpeg on MacOs
# https://trac.ffmpeg.org/wiki/CompilationGuide/MacOSX
> brew install ffmpeg --with-fdk-aac --with-ffplay --with-freetype --with-libass --with-libquvi --with-libvorbis --with-libvpx --with-opus --with-x265


# Conversion to WEBM format:
# http://trac.ffmpeg.org/wiki/Encode/VP8
> ffmpeg -i input-file.mp4 -c:v libvpx -crf 10 -b:v 1M -c:a libvorbis output-file.webm


# Video quality reduction
# (Vary the CRF between around 18 and 24 — the lower, the higher the bitrate)
> ffmpeg -i input.mp4 -vcodec libx264 -crf 20 output.mp4


# Change video container (no encoding)
> ffmpeg -i video.mkv -vcodec copy -acodec copy video.mp4


# Video Scaling
> ffmpeg -i input.avi -vf scale=320:240 output.avi


# Convert container of all videos in a folder
> OIFS="$IFS"; IFS=$'\n'; for i in $(ls *.mkv); do ffmpeg -i $i -vcodec copy -acodec copy $i.mp4; done; IFS="$OIFS";

# Audio normalization

    # 1) Get max_volume
    > ffmpeg -i audio.mp3 -af "volumedetect" -f null /dev/null

        [Parsed_volumedetect_0 @ 0x7f899a40dc40] n_samples: 14162782
        [Parsed_volumedetect_0 @ 0x7f899a40dc40] mean_volume: -16.7 dB
        [Parsed_volumedetect_0 @ 0x7f899a40dc40] max_volume: -2.4 dB

    # 2) if max_volume < 0
    > ffmpeg -i audio.mp3 -af "volume=2.4dB" audio-normalized.mp3


# Partial video extraction
# -ss : initial offset
# -t  : seconds from offset to extract
> ffmpeg -i <video.avi> -ss 00:00:00 -t 10 -codec copy <video-copy.avi>


# Frame sequence
# (http://linuxers.org/tutorial/how-extract-images-video-using-ffmpeg)
# -q:v 2 : quality
> ffmpeg -i video/video.mp4 -r 25 -s hd480 -f image2 -q:v 2 frames/frame-%4d.jpg


# Merge subs in a video
> ffmpeg -i subtitle.srt subtitle.ass
> ffmpeg -i video.avi -vf "ass=subtitle.ass" out.avi