ates the compressed video combined with extra data
to allow the fast scalable coding of the sequence. As
shown in the last column of the table, the overhead of
the extra data is quite large, almost doubling the size
of the compressed video.
Figure 3 shows the speed of the scalable coding
process. The required time to encode the sequences
is at most 140 ms at the highest bit rates. Regardless
the preprocessing step, which is performed only once
and can be considered as an offline process, the pro-
posed method is much faster than directly encoding
the video with x264.
The scalable coding algorithm is limited only by
how fast the data can be read and written since the
total transcoding time is linearly correlated with the
target rate. Figure 4 shows that the rate control is pre-
cise, achieving the desired constraint with a negligible
error.
5 CONCLUSIONS
The proposed approach can rapidly transcode a pre-
processed video sequence into a large range of differ-
ent bit rates with extreme fine control of the resulting
rate. It employs a fast fractal encoding method using
volumetric range and domain blocks matched against
each other using a generalization of a fast fractal en-
coder to three dimensions.
It is important to mention that the proposed rate
control and the transcoding heuristic could be applied
to other encoding methods that are not based on frac-
tals but are still adaptive. The near-optimal behavior
of the transcoding algorithm, combined with better
block encoding methods, could result in viable alter-
native to the current commonly used video encoders.
ACKNOWLEDGMENTS
The authors are thankful to the Minas Gerais Re-
search Foundation (FAPEMIG), S
˜
ao Paulo Research
Foundation (FAPESP grants #2015/03156-7 and
#2015/12228-1) and Brazilian National Council for
Scientific and Technological Development (CNPq
grant #305169/2015-7) for their financial support.
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