The FFmpeg command converts an input .mp4 video file to an output .webm file using VP9 video codec, Opus audio codec, and a constant rate factor of 30, with an automatically determined video bitrate and a fixed 128k audio bitrate.

To convert an input video file to a .webm file, the FFmpeg command is used with the following parameters: ffmpeg -i input.mp4 -c:v libvpx-vp9 -crf 30 -b:v 0 -b:a 128k -c:a libopus output.webm. This command uses the VP9 video codec, Opus audio codec, and a constant rate factor of 30 to control the video quality.

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ffmpeg -i input.mp4 -c:v libvpx-vp9 -crf 30 -b:v 0 -b:a 128k -c:a libopus output.webm

ffmpeg -i ${input_file} -c:v libvpx-vp9 -crf ${quality} -b:v 0 -b:a ${bitrate} -c:a libopus ${output_file}

FFmpeg Command Breakdown

Command

ffmpeg

• The FFmpeg command-line tool for processing audio and video.

Input

-i input.mp4

• Specify the input file, which is a .mp4 video file named input.mp4.

Encoding

-c:v libvpx-vp9

• Set the video codec to libvpx-vp9, a VP9 video codec.

Video Quality

-crf 30

• Set the constant rate factor (CRF) to 30, which controls video quality.

Audio Bitrate

-b:v 0

• Set the video bitrate to 0, which means the bitrate will be automatically determined by the encoder.

Audio Bitrate

-b:a 128k

• Set the audio bitrate to 128 kilobits per second (kbps).

Audio Codec

-c:a libopus

• Set the audio codec to libopus, an Opus audio codec.

Output

output.webm

• Specify the output file, which will be a .webm video file named output.webm.