[gst-devel] [PATCH] Make theoraenc expose the new "Speed level" property
Benjamin M. Schwartz
bmschwar at fas.harvard.edu
Wed Feb 18 22:11:06 CET 2009
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Donny Viszneki wrote:
> Do you think disabling motion vector calculation has a different
> effect on performance depending on what the video is like?
I'm no expert, but here are two ideas:
1. At fixed quality, removing the motion vectors makes the codec less
efficient if the scene has motion. My test did (some youtube music
video), and so, at fixed nominal quality, the bitrate increased by 25%.
That increase in bitrate means more bits to push into memory, which slows
things down. Non-moving scenes should not experience an increased
bitrate, and so potentially may be accelerated better.
2. The motion-vector search can be implemented many ways. A naive search
(I hear libtheora-1.0 has a fairly naive implementation) takes a similar
amount of time regardless of the underlying scene. A very advanced search
(I hear libtheora-1.1 will have a fancier motion search) might quickly
detect the lack of motion and stop searching. In any case, with
speedlevel=2 no search will be performed, and the speed gain depends on
how much time that search would have taken.
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