ffmpeg:tldr:26962

This command is using the FFmpeg software to convert a video file from avi format to mp4 format. Let's break down the command:

• ffmpeg is the command used to invoke the FFmpeg software.
• -i ${input_video}.avi specifies the input file. ${input_video} is a variable, so the actual input file name would be substituted in its place. It assumes that the input video file is in the avi format.
• -codec:a aac specifies the audio codec to be used for the output file. In this case, the Advanced Audio Codec (AAC) is chosen.
• -b:a 128k sets the audio bitrate to 128 kilobits per second. It determines the audio quality in the output file.
• -codec:v libx264 specifies the video codec to be used for the output file. Here, the libx264 codec is selected, which is a widely used and efficient video codec.
• -crf 23 sets the Constant Rate Factor (CRF) value. The CRF determines the video quality and compression level. A lower value results in better quality and larger file size, while a higher value decreases quality and reduces file size. CRF 23 is a moderate setting.
• ${output_video}.mp4 specifies the name and format of the output file. Again, ${output_video} is a variable, so the actual output file name would be substituted in its place. It assumes that the output video file should be in the mp4 format.