  Video transcoding is the process of converting a video to the format
supported by the viewer's device. Video transcoding requires huge storage and
computational resources, thus, many video stream providers choose to carry it
out on the cloud. Video streaming providers generally need to prepare several
formats of the same video (termed pre-transcoding) and stream the appropriate
format to the viewer. However, pre-transcoding requires enormous storage space
and imposes a significant cost to the stream provider. More importantly,
pre-transcoding proven to be inefficient due to the long-tail access pattern to
video streams in a repository. To reduce the incurred cost, in this research,
we propose a method to partially pre-transcode video streams and re-transcode
the rest of it in an on-demand manner. We will develop a method to strike a
trade-off between pre-transcoding and on-demand transcoding of video streams to
reduce the overall cost. Experimental results show the efficiency of our
approach, particularly, when a high percentage of videos are accessed
frequently. In such repositories, the proposed approach reduces the incurred
cost by up to 70\%.
