In this paper, the parallelization of the H.261 video coding algorithm on t
he IBM SP2(R) multiprocessor system is described. The effect of parallelizi
ng computations and communications in the spatial, temporal, and both spati
al-temporal domains are considered through the study of frame rate, speedup
, and implementation efficiency, which are modeled and measured with respec
t to the number of nodes (n) and parallel methods used. Four parallel algor
ithms were developed, of which the first two exploited the spatial parallel
ism in each frame, and the last two exploited both the temporal and spatial
parallelism over a sequence of frames, The two spatial algorithms differ i
n that one utilizes a single communication master, while the other attempts
to distribute communications across three masters. On the other hand, the
spatial-temporal algorithms use a pipeline structure for exploiting the tem
poral parallelism together with either a single master or multiple masters.
The best median speedup (frame rate) achieved was close to 15 [15 frames p
er second (fps)] for 552 x 240 video on 24 nodes, and 13 (37 fps) for QCIF
video, by the spatial algorithm with distributed communications. For n < 10
, the single-master spatial algorithm performs better with efficiency up to
90%, while the multiple-master spatial algorithm is superior for n > 10, w
ith efficiency up to 70%. The spatial-temporal algorithms achieved average
speedup performance, but are most scalable for large n.