First, we need to know that the syntax of FFmpeg looks like this:
ffmpeg [global options] {[input file options] -i input_url_address} {[output file options] output_url_address}
Then, run the following Command to see which formats ffmpeg supports
ffmpeg -formats
1, convert video files to different formats
For example, we want to convert an MP4 file into an AVI file
ffmpeg -i video.mp4 video.avi
If you want to maintain your source video For the quality of the file, add -qscale 0
ffmpeg -i video.mp4 -qscale 0 video.avi
2, extract audio from video
ffmpeg -i input.mp4 -vn output.mp3
Of course, if you want to be more responsible, such as changing Audio conversion encoding or audio frequency, etc., will not be introduced here, anyway, it is almost useless.
3, remove audio from the video file
Su Su does not know why there is such a frenzied operation
ffmpeg -i input.mp4 -an output.mp4
4, change the resolution of the video file
For example, a certain video resolution is relatively large, We plan to compress to 640×480 size
ffmpeg -i input.mp4 -filter:v scale=640:480 -c:a copy output.mp4
You can also use the following shorthand
ffmpeg -i input.mp4 -s 640x480 -c :a copy output.mp4
5. Compressed video file size
There are two ways to compress video size, one is to compress audio, convert encoded audio to reduce the bit rate, but this effect is not obvious, and it is often reduced after a long time. A few megabytes is better than no compression, so the video quality is usually compressed. After compression, the definition of the video will decrease.
ffmpeg -i input.mp4 -vf scale=1280:-1 -c:v libx264 -preset veryslow -crf 24 output.mp4
If the video after crf 24 is too horrible, you can use a smaller number to make the video quality worse It would be so bad.
6. Crop video
is to crop a certain range in the video
ffmpeg -i input.mp4 -filter:v "crop=w:h:x:y" output.mp4
w-the width of the rectangle we want to crop from the source video.
h-the height of the rectangle.
x – The x coordinate of the rectangle we want to crop from the source video.
y-the y coordinate of the rectangle.
For example, if you want a video with a width of 640 pixels and a height of 480 pixels from the video position (200,150), the command should be:
ffmpeg -i input.mp4 -filter:v "crop=640:480:200: 150" output.mp4
7, split the video file into multiple parts
I believe this is a commonly used function for everyone, to be a video website, it is important to know how to slice
ffmpeg -i input.mp4 -t 00:00:30 -c copy part1.mp4 -ss 00:00:30 -codec copy part2.mp4
-t 00:00:30 means to create a part of the video from the beginning of the video to the 30th second of the video.
-ss 00:00:30 shows the start timestamp for the next part of the video. It means that Part 2 will start at the 30th second and will continue to the end of the original video file.
8. Merge multiple videos
After downloading the sliced videos, we need to merge them into one file. First prepare a txt file, assuming the file name is: join.txt, the content is probably the following
file /home/sk/myvideos/part1.mp4
file /home/sk/myvideos/part2.mp4
file /home/sk/myvideos/part3 .mp4
file /home/sk/myvideos/part4.mp4
Then, to merge these MP4s into one video, the command is
ffmpeg -f concat -safe 0 -i join.txt -c copy output.mp4
