Common ffmpeg parameters

Friday, 24 June 2011 - 4 minutes to read

Argument	Description

Information
-codecs	Display codecs
-formats	Display formats

General
-f fmt	Force format "fmt"
-i filename	Set input file name
-y	Overwrite output file
-n	Never overwrite output files
-t secs	Force duration to specific length (`hh:mm:ss[.xxx]`)
-fs limit	Set file size limit (for 2-pass encoding)
-ss secs	Seek to given time position (`hh:mm:ss[.xxx]`)

Video
-r fps	Set frame rate (default 25)
-s WxH	Set frame size (default same as source)
-vf scale=W:H	Rescale video (use <=1 to scale, e.g. "640:-1" means resize height to scale, "640:-2" means same but maintain even /2 count)
-vf transpose=n	Rotate video (0 = 90° counterclockwise and vertical flip; 1 = 90° clockwise; 2 = 90° counterclockwise; 3 = 90° clockwise and vertical flip)
-aspect aspect	Set aspect ratio (4:3, 16:9 etc)
-vn	Disable video
-pass n	Multipass rendering (1 or 2)
-c:v	Force video codec (e.g. "libx265", "h264", "copy")
-crf nn	Constant Rate Factor (0=lossless, 23=default, 17-28=acceptable, every +6 means half the file size roughly)

Audio
-ar freq	Audio frequency (default 44100 Hz)
-ab bitrate	Audio bitrate in bps (default 64k)
-ac channels	Audio channels (ac=2 to downmix 5.1 to stereo)
-an	Disable audio
-c:a	Force audio codec ("aac", "mp3", "copy")
-q:a n	VBR quality: mp3=0-9, 0=~240kbit/s, 2=~190kbit/s (standard), 4=160kbit/s (medium)

Subtitles
-scodec	Force subtitle codec ("copy" to copy stream)
-sn	Disable subtitles

Misc
-map_metadata -1	Strip ID3 (or any kind of) metadata from input files (-1 is a dummy stream specifier)

Good default converter command:

ffmpeg -y -i infile.mp4 -c:v h264 -c:a aac -ac 2 -sn -crf 23 -r 24 -vf scale=-2:480 \
    -pix_fmt yuv420p out\outfile.mp4

Parameter	Explanation
`-y`	Always overwrite (hence the subfolder in the output path)
`-c:v h264`	Forces h264 encoder (h265 works too, but it's slooow)
`-c:a aac`	Forces AAC encoder
`-ac 2`	Downsample to two channels if 5.1
`-sn`	Ditch the subtitles, they suck anyway (get .srt subtitles)
`-crf 23`	Not bad video compression
`-r 24`	Force 24 fps (sometimes they can be weird, like >= 60)
`-vf scale=-2:480`	set 480 pixels high, scale width to even pixels
`-pix_fmt yuv420p`	force 8-bit YUV420 pixels (downsample from 10-bit)

Dump information to JSON format:

ffprobe "file.mkv" -v quiet -print_format json \
    -show_streams \
    -show_format \
    -show_programs \
    -show_chapters \
    -show_private_data \
    -show_error

Select specific track

ffmpeg -i movie1.avi -map 0:0 -map 0:2 movie1.m4v

Select the 0:0 video stream, and the 0:2 audio stream (supposedly 0:0 is the video, and 0:1 and 0:2 are audio streams).

Concatenate two videos two one:

ffmpeg -i movie1.avi -i movie2.avi \
    -filter_complex "[0:v:0][0:a:0][1:v:0][1:a:0]concat=n=2:v=1:a=1[outv][outa]" \
    -map "[outv]" -map "[outa]" result.m4v

[0:v:0][0:a:0][1:v:0][1:a:0] means "input 0 video stream 0; input 0 audio stream 0; input 1 video stream 0; input 2 video stream 0"
concat=n=2:v=1:a=1 means concatenate filter, two streams, one stream per video and one stream per audio
[outv][outa] means map to two result streams, outv and outa
-map is used to map streams to output instead of the input streams

Cut part of video out

Generate a video file containing two minutes of video, one 60-second clip from the start and another 60-second clip from 5 minutes into the video.

ffmpeg -i input.mp4 -filter_complex "\
    [0:v] trim=0:60, setpts=PTS-STARTPTS [v1]; \
    [0:a] atrim=0:60, asetpts=PTS-STARTPTS [a1]; \
    [0:v] trim=300:360, setpts=PTS-STARTPTS [v2]; \
    [0:a] atrim=300:360, asetpts=PTS-STARTPTS [a2]; \
    [v1][a1][v2][a2] concat=n=2:a=1:v=1 [outv][outa]" \
    -map "[outv]" -map "[outa]" result.m4v