ffmpeg cheatsheet

ffmpeg is a powerful tool to process video and audio files. Let's create a cheat sheet of the commands I use from time to time!

#Remove audio from a video

ffmpeg -i input.mp4 -an -c:v copy output.mp4

• -i input.mp4: Input file
• -an: Remove audio stream
• -c:v copy: Copy the video stream without re-encoding

#Prepare a video for streaming

Remove metadata and move the moov atom to the beginning of the file for faster playback start.

ffmpeg -i input.mp4 -map_metadata -1 -movflags faststart output.mp4

• -i input.mp4: Input file
• -map_metadata -1: Remove all metadata
• -movflags faststart: Move the moov atom to the beginning of the file

#Encode a video by chunks

# Split the video into 10-minute chunks and remove audio
ffmpeg -i input.mp4 -c copy -an -map 0 -segment_time 600 -f segment chunk%03d.mp4
foreach ($file in Get-ChildItem -Filter "chunk*.mp4") {
    # Encode each chunk
    ffmpeg -i $file.FullName -c:v libx265 -preset medium -c:a aac -b:a 128k converted$($file.BaseName).mp4
}

# Concatenate the chunks into a single video
foreach($file in Get-ChildItem -Filter "converted*.mp4") {
    "file '$($file.FullName)'" | Out-File -Append -Encoding utf8 concat.txt
}
ffmpeg -f concat -safe 1 -i concat.txt -c copy concat.mp4

# Merge video and audio
ffmpeg -i concat.mp4 -i input.mp4 -c copy -map 0:v:0 -map 1:a:0  converted.mp4

# Remove temporary files
Remove-Item concat.txt
Remove-Item chunk*.mp4
Remove-Item converted*.mp4

• -segment_time 600: Split the video into chunks of 600 seconds (10 minutes)
• -f segment: Use the segment muxer to split the video
• -c:v libx265: Encode the video using the H.265 codec
• -preset medium: Use the medium preset for encoding (balance between speed and compression)
• -c:a aac: Encode the audio using the AAC codec
• -b:a 128k: Set the audio bitrate to 128 kbps
• -f concat: Use the concat demuxer to merge the chunks
• -safe 1: Prevent the use of unsafe file paths in the concat file
• -map 0:v:0: Select the first video stream from the first input file
• -map 1:a:0: Select the first audio stream from the second input file

#Merge video and subtitles

ffmpeg -i input.mp4 -i subtitles.srt -c copy -c:s mov_text output.mp4

• -i input.mp4: Input video file
• -i subtitles.srt: Input subtitle file
• -c copy: Copy video and audio streams
• -c:s mov_text: Convert subtitles to mov_text format (required for MP4 container)

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