FFMPEG Cheatsheet
Contents
FFMPEG Cheatsheet¶
Compiled from commands I find myself using frequently.
Generic niave trial is just to use
ffmpeg -i input.ext1 output.ext2
and if it fails, tinker. Below are some common tinkers to fix common problems.
For HTTP proxies, use the -http_proxy [addr] flag.
Table of Contents¶
Converting video¶
For .mp4 to .mp3 with correct time-stamping
ffmpeg -i video.mp4 -b:a 192K -vn audio.mp3
# -b:a is audio bit rate
# -vn blocks all video streams from being selected
For .mp4 to .wav
ffmpeg -i video.mp4 -ab 160k -ac 2 -ar 44100 -vn audio.wav
# -ac is audio channels
# -ar is audio sample rate
Converting streams¶
Downloading from .m3u8 files
ffmpeg -i [url to m3u8 file] -c copy -bsf:a aac_adtstoasc output.mp4
Can also include comma seperated string list of headers using the -headers flag.
The -map flag¶
Different streams from input files can be mux’d together into the output file. To do this, we first need to identify the audio and video streams available in the input:
ffmpeg -i s0q0.m4s -i s1q1.m4s
which outputs
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 's0q0.m4s':
Metadata:
major_brand : iso5
minor_version : 512
compatible_brands: iso6mp41
encoder : Lavf58.29.100
Duration: 02:40:07.65, start: 0.000000, bitrate: 65 kb/s
Stream #0:0(eng): Audio: aac (LC) (mp4a / 0x6134706D), 44100 Hz, mono, fltp, 63 kb/s (default)
Metadata:
handler_name : #Mainconcept MP4 Sound Media Handler
Input #1, mov,mp4,m4a,3gp,3g2,mj2, from 's1q1.m4s':
Metadata:
major_brand : iso5
minor_version : 512
compatible_brands: iso6mp41
encoder : Lavf58.29.100
Duration: 02:40:07.80, start: 0.160000, bitrate: 201 kb/s
Stream #1:0(eng): Video: h264 (High) (avc1 / 0x31637661), yuv420p, 1730x1080 [SAR 1:1 DAR 173:108], 199 kb/s, SAR 17820:17819 DAR 165:103, 25 fps, 25 tbr, 12800 tbn, 50 tbc (default)
Metadata:
handler_name : ?Mainconcept Video Media Handler
We can index the audio and videos using the formatter [inputID]:{a|v}:[streamID]. So for the above example, we can merge audio from s0q0.m4s and video from s1q1.m4s with the command
ffmpeg -i s0q0.m4s -i s1q1.m4s -c copy -map 0:a:0 -map 1:v:0 -shortest out.mp4
The -shortest flag ensures that if the timestamps for the two inputs are slightly different, we reduce the output to the length of the shortest.
Embedding subtitles¶
For a given .srt file, the subtitles can be embedded into an .mp4 using
ffmpeg -i [videos].mp4 -i [subtitles].srt -c:v copy -c:a copy -c:s mov_text -metadata:s:s:0 language=eng out.mp4
Here we are copying the video and audio channels from the input video, and copying subtitles with -c:s mov_text. We also use the metadata mapper to change the subtitle stream (:s:s:0, c.f. e.g. audio :s:a:1) language to eng.
Concatenation¶
Concatenating videos¶
To concatenate videos, create a file containing an ordered list of videos to be concatenated
file 'part1.mp4'
file 'part2.mp4'
...
Then pass this file to ffmpeg with
ffmpeg -f concat -safe 0 -i infile.txt output.mp4
The safe options is disable the unsafe filename error. From the docs:
safe If set to 1, reject unsafe file paths. A file path is considered safe if it does not contain a protocol specification and is relative and all components only contain characters from the portable character set (letters, digits, period, underscore and hyphen) and have no period at the beginning of a component.
If set to 0, any file name is accepted.
Concatenating images into videos¶
There are many commands that can achieve this result. For the problem I was solving, I wanted to concatenate PNG images, numbered 1.png, 2.png, ..., into a .mp4 video at a specific frame rate
ffmpeg -f image2 -r [framerate] -i %d.png -vcodec mpeg4 -y out.mp4
Splicing files¶
To extract media from a given time stamp
ffmpeg -i source.mp4 -ss START_TIME -t DURATION output.mp4