Hi Umakant,
If you install the Matterhorn ingest and processing scripts for BigBlueButton 0.80, you need to install ffmpeg, as described in
ffmpeg is not needed by BigBlueButton to record videos (webcams and desktop sharing). It is needed by the ingest and processing scripts to process the videos.
When you install the Matterhorn ingest and processing scripts on BigBlueButton, the scripts use ffmpeg to process the raw webcam and desktop videos recorded by BigBlueButton into a format that can be processed by Matterhorn. The scripts then send the processed videos to the separate Matterhorn server (via scp).