ffmpeg commands that I need to remember

ffmpeg.txt

# This is for converting a ripped movie to a 480p size so my kids can watch it on their tablets in the car.
# I'm cropping off 276 pixels from the top and bottom, which means it's a 3840x2160 image with a 2.39:1 letterboxed video.
# The width can vary based on the aspect ratio, but the height should always be 480px.
# I'm hard-coding it to use H.264 and yuv420p and to downmix surround sound to regular stereo channels.
# On some movies, I had to use -map 0:2 to get the 5.1 audio stream if the 7.1 was truehd and ffmpeg didn't like that.
ffmpeg -i "4k.mkv" -vf "crop=iw:ih-552:0:276,scale=1146:480" -c:v libx264 -c:a copy -ac 2 -sn -pix_fmt yuv420p -map 0:0 -map 0:2 -crf 18 -map_chapters -1 "480p.mp4"

# After getting the resolution right, follow this process to reduce the size of the video: https://trac.ffmpeg.org/wiki/Encode/H.264#twopass
ffmpeg -y -i original.mp4 -c:v libx264 -b:v 1000k -pass 1 -an -f null NULL && ffmpeg -i original.mp4 -c:v libx264 -b:v 1000k -pass 2 -c:a aac -b:a 128k shrink.mp4

# I have to do this all of the time to clip a portion of a video clip from our live stream on social media.
ffmpeg -i "live.mp4" -ss 00:01:23 -to 00:04:56 -c copy "clip.mp4"

# Occasionally I may have to splice several clips together. This requires a text file, such as concat.txt:
file 'clip1.mp4'
file 'clip2.mp4'
file 'clip3.mp4'
# Then, it is a simple operation to create a single video file:
ffmpeg -safe 0 -f concat -i concat.txt -c copy full.mp4