"21122mp4" appears to be a specific file name or a technical code combining a date and a video format. In digital asset management, this typically decodes as (21-11-22) followed by the MP4 file extension.
Understanding Digital Video: A Deep Dive into the "21122mp4" Framework 21122mp4
What is 4:4:4 color and why should I care? - a clearone blog "21122mp4" appears to be a specific file name
Typically AAC or MP3, allowing for multi-channel sound. allowing for multi-channel sound.