ffmpeg:tldr:95009

This command uses the FFmpeg tool to convert a video file (in .mp4 format) to a WebM video file (in .webm format), using the VP9 video codec and Opus audio codec. Here is a breakdown of the command:

• ffmpeg: This is the command to run the FFmpeg tool.
• -i ${input_video}.mp4: Specifies the input video file. ${input_video} represents a variable, so the command is expecting you to substitute it with the actual filename (without the extension) of your input video.
• -codec:v libvpx-vp9: Specifies the video codec to be used for encoding the video stream. libvpx-vp9 is the codec for VP9 video compression.
• -crf ${30}: Sets the Constant Rate Factor (CRF) for video compression. The value ${30} is again expecting a variable substitution, so it should be replaced with a specific value. A lower value results in better video quality but larger file size, while a higher value reduces quality but yields a smaller file size.
• -b:v 0: Sets the video bitrate to 0, which enables the VP9 codec to use variable bitrate mode (bitrate determined by CRF value).
• -codec:a libopus: Specifies the audio codec to be used for encoding the audio stream. libopus is the codec for Opus audio compression.
• -vbr on: Enables variable bitrate mode for audio encoding.
• -threads ${number_of_threads}: Sets the number of threads to use for video encoding. ${number_of_threads} is expecting a variable substitution representing the desired number of threads.
• ${output_video}.webm: Specifies the output video file. Similar to ${input_video}, ${output_video} expects a variable substitution. The resulting output video will be in .webm format.

To use this command, you need to replace ${input_video}, ${30}, ${number_of_threads}, and ${output_video} with the appropriate values for your specific case.