F. Jitters
By “Jitters”, we mean the discontinuous video playback
experienced by mobile users who have to wait for segments
to be buffered, due to the dynamically varying download
bandwidths.
Following the same experiment settings as in
Section V-E, we emulate a highly unstable 3G cellular network
and measure the occurrence and stall duration of jitters when a
mobile client is viewing the movie.
We examine the download
completion time for each segment: if this time is later than
the playback deadline of the segment, a jitter is captured and
the stall duration is estimated as the difference between the
two.
Fig. 12 compares the results of CloudMoV and the case
where the movie is directly streamed to the mobile user without
dynamic transcoding nor burst transmission mechanisms, i.e.,
the case of “Normal Streaming”. A line segment is plotted
when a jitter happens at the corresponding time in the axis,
and the length of the line segment represents the stall duration.
We can see that CloudMoV incurs no jitter while “Normal
Streaming” suffers a total of 716 seconds of playback stall. This
again verifies the excellent streaming playback performance of
CloudMov clients.