Several FFmpeg examples

Posted on 2020-08-14 Edited on 2023-12-27 Word count in article: 2k Reading time ≈ 2 mins.

In this article, several FFmpeg examples that I used are listed.

Convert flv to mp3

1	$ ffmpeg -i video.flv -vn -acodec libmp3lame -ab 128k audio.mp3

Convert all mp3 files in a directory to opus

1	$ for f in *.mp3; do ffmpeg -i "$f" -c:a libopus -b:a 64k "${f%.mp3}.opus"; done

Batch converting mkv to mp4

1	$ for f in *.mkv; do ffmpeg -i "$f" -c copy "${f%.mkv}.mp4"; done

Convert animated gif to mp4

1	$ ffmpeg -i animated.gif -movflags faststart -pix_fmt yuv420p -vf "scale=trunc(iw/2)2:trunc(ih/2)2" video.mp4

Burn subtitles into a video

1	$ ffmpeg -i video.avi -vf subtitles=subtitle.srt out.avi

If the subtitles is embedded in the container video.mkv

1	$ ffmpeg -i video.mkv -vf subtitles=video.mkv out.avi

More complex, if the video has several sound tracks and subtitles, and the subtitles use different resolution than the video:

1	$ ffmpeg -i in.mkv -filter_complex "[0:s]scale=1280:-1[sub];[0:v][sub]overlay[v]" -map "[v]" -map 0:a -c:a copy out.mp4

Clip video

The -ss option specifies a start timestamp, the -t option specifies the encoding duration, the -to option specifies the timestamp to which you want to cut. For example:

1 2	$ ffmpeg -ss 00:00:30.0 -i input.wmv -c copy -t 00:00:10.0 output.wmv $ ffmpeg -ss 00:00:30.0 -i input.wmv -c copy -to 00:00:40.0 output.wmv

Split video in chunks with same length

1	$ ffmpeg -i input.mp4 -c copy -map 0 -segment_time 00:20:00 -f segment output%03d.mp4

Split video in chunks with different lengths

1
2
3

$ ffmpeg -i source.m4v -ss 0 -t 593.3 -c copy part1.m4v
$ ffmpeg -i source.m4v -ss 593.3 -t 551.64 -c copy part2.m4v
$ ffmpeg -i source.m4v -ss 1144.94 -t 581.25 -c copy part3.m4v

Compression the video using libx265

1	$ ffmpeg -i input.mp4 -vcodec libx264 -crf 20 output.mp4

Vary the CRF between around 18 and 24 — the lower, the higher the bitrate

Simple rescaling

1	$ ffmpeg -i input.avi -vf scale=320:240 output.avi

Keeping the aspect radio

1	$ ffmpeg -i input.jpg -vf scale=320:-1 output_320.png

Speeding up/down audio

1	$ ffmpeg -i input.mkv -filter:a "atempo=2.0" -vn output.mkv

Broadcasting video through Bilibili direct-sending

1	$ ffmpeg -re -i "1.mp4" -vcodec copy -acodec aac -b:a 192k -f flv "rtmp://dl.live-send.acg.tv/live-dl/your_direct_sending_id_number"